conclusion and discussion in research

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• How to Write Discussions and Conclusions

The discussion section contains the results and outcomes of a study. An effective discussion informs readers what can be learned from your experiment and provides context for the results.

What makes an effective discussion?

When you’re ready to write your discussion, you’ve already introduced the purpose of your study and provided an in-depth description of the methodology. The discussion informs readers about the larger implications of your study based on the results. Highlighting these implications while not overstating the findings can be challenging, especially when you’re submitting to a journal that selects articles based on novelty or potential impact. Regardless of what journal you are submitting to, the discussion section always serves the same purpose: concluding what your study results actually mean.

A successful discussion section puts your findings in context. It should include:

• the results of your research,
• a discussion of related research, and
• a comparison between your results and initial hypothesis.

Tip: Not all journals share the same naming conventions.

You can apply the advice in this article to the conclusion, results or discussion sections of your manuscript.

Our Early Career Researcher community tells us that the conclusion is often considered the most difficult aspect of a manuscript to write. To help, this guide provides questions to ask yourself, a basic structure to model your discussion off of and examples from published manuscripts. 

Questions to ask yourself:

• Was my hypothesis correct?
• If my hypothesis is partially correct or entirely different, what can be learned from the results? 
• How do the conclusions reshape or add onto the existing knowledge in the field? What does previous research say about the topic? 
• Why are the results important or relevant to your audience? Do they add further evidence to a scientific consensus or disprove prior studies? 
• How can future research build on these observations? What are the key experiments that must be done? 
• What is the “take-home” message you want your reader to leave with?

How to structure a discussion

Trying to fit a complete discussion into a single paragraph can add unnecessary stress to the writing process. If possible, you’ll want to give yourself two or three paragraphs to give the reader a comprehensive understanding of your study as a whole. Here’s one way to structure an effective discussion:

Writing Tips

While the above sections can help you brainstorm and structure your discussion, there are many common mistakes that writers revert to when having difficulties with their paper. Writing a discussion can be a delicate balance between summarizing your results, providing proper context for your research and avoiding introducing new information. Remember that your paper should be both confident and honest about the results! 

• Read the journal’s guidelines on the discussion and conclusion sections. If possible, learn about the guidelines before writing the discussion to ensure you’re writing to meet their expectations. 
• Begin with a clear statement of the principal findings. This will reinforce the main take-away for the reader and set up the rest of the discussion. 
• Explain why the outcomes of your study are important to the reader. Discuss the implications of your findings realistically based on previous literature, highlighting both the strengths and limitations of the research. 
• State whether the results prove or disprove your hypothesis. If your hypothesis was disproved, what might be the reasons? 
• Introduce new or expanded ways to think about the research question. Indicate what next steps can be taken to further pursue any unresolved questions. 
• If dealing with a contemporary or ongoing problem, such as climate change, discuss possible consequences if the problem is avoided. 
• Be concise. Adding unnecessary detail can distract from the main findings. 

Don’t

• Rewrite your abstract. Statements with “we investigated” or “we studied” generally do not belong in the discussion. 
• Include new arguments or evidence not previously discussed. Necessary information and evidence should be introduced in the main body of the paper. 
• Apologize. Even if your research contains significant limitations, don’t undermine your authority by including statements that doubt your methodology or execution. 
• Shy away from speaking on limitations or negative results. Including limitations and negative results will give readers a complete understanding of the presented research. Potential limitations include sources of potential bias, threats to internal or external validity, barriers to implementing an intervention and other issues inherent to the study design. 
• Overstate the importance of your findings. Making grand statements about how a study will fully resolve large questions can lead readers to doubt the success of the research. 

Snippets of Effective Discussions:

Consumer-based actions to reduce plastic pollution in rivers: A multi-criteria decision analysis approach

Identifying reliable indicators of fitness in polar bears

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Discussion and Conclusions

Your Discussion and Conclusions sections should answer the question: What do your results mean?

In other words, the majority of the Discussion and Conclusions sections should be an interpretation of your results. You should:

• Discuss your conclusions in order of  most to least important.
• Compare  your results with those from other studies: Are they consistent? If not, discuss possible reasons for the difference.
• Mention any  inconclusive results  and explain them as best you can. You may suggest additional experiments needed to clarify your results.
• Briefly describe the  limitations  of your study to show reviewers and readers that you have considered your experiment’s weaknesses. Many researchers are hesitant to do this as they feel it highlights the weaknesses in their research to the editor and reviewer. However doing this actually makes a positive impression of your paper as it makes it clear that you have an in depth understanding of your topic and can think objectively of your research.
• Discuss  what your results may mean  for researchers in the same field as you, researchers in other fields, and the general public. How could your findings be applied?
• State how your results  extend the findings  of previous studies.
• If your findings are preliminary, suggest  future studies  that need to be carried out.
• At the end of your Discussion and Conclusions sections,  state your main conclusions once again .

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The conclusion is intended to help the reader understand why your research should matter to them after they have finished reading the paper. A conclusion is not merely a summary of the main topics covered or a re-statement of your research problem, but a synthesis of key points derived from the findings of your study and, if applicable, where you recommend new areas for future research. For most college-level research papers, two or three well-developed paragraphs is sufficient for a conclusion, although in some cases, more paragraphs may be required in describing the key findings and their significance.

Conclusions. The Writing Center. University of North Carolina; Conclusions. The Writing Lab and The OWL. Purdue University.

Importance of a Good Conclusion

A well-written conclusion provides you with important opportunities to demonstrate to the reader your understanding of the research problem. These include:

• Presenting the last word on the issues you raised in your paper . Just as the introduction gives a first impression to your reader, the conclusion offers a chance to leave a lasting impression. Do this, for example, by highlighting key findings in your analysis that advance new understanding about the research problem, that are unusual or unexpected, or that have important implications applied to practice.
• Summarizing your thoughts and conveying the larger significance of your study . The conclusion is an opportunity to succinctly re-emphasize  your answer to the "So What?" question by placing the study within the context of how your research advances past research about the topic.
• Identifying how a gap in the literature has been addressed . The conclusion can be where you describe how a previously identified gap in the literature [first identified in your literature review section] has been addressed by your research and why this contribution is significant.
• Demonstrating the importance of your ideas . Don't be shy. The conclusion offers an opportunity to elaborate on the impact and significance of your findings. This is particularly important if your study approached examining the research problem from an unusual or innovative perspective.
• Introducing possible new or expanded ways of thinking about the research problem . This does not refer to introducing new information [which should be avoided], but to offer new insight and creative approaches for framing or contextualizing the research problem based on the results of your study.

Bunton, David. “The Structure of PhD Conclusion Chapters.” Journal of English for Academic Purposes 4 (July 2005): 207–224; Conclusions. The Writing Center. University of North Carolina; Kretchmer, Paul. Twelve Steps to Writing an Effective Conclusion. San Francisco Edit, 2003-2008; Conclusions. The Writing Lab and The OWL. Purdue University; Assan, Joseph. "Writing the Conclusion Chapter: The Good, the Bad and the Missing." Liverpool: Development Studies Association (2009): 1-8.

Structure and Writing Style

I.  General Rules

The general function of your paper's conclusion is to restate the main argument . It reminds the reader of the strengths of your main argument(s) and reiterates the most important evidence supporting those argument(s). Do this by clearly summarizing the context, background, and necessity of pursuing the research problem you investigated in relation to an issue, controversy, or a gap found in the literature. However, make sure that your conclusion is not simply a repetitive summary of the findings. This reduces the impact of the argument(s) you have developed in your paper.

When writing the conclusion to your paper, follow these general rules:

• Present your conclusions in clear, concise language. Re-state the purpose of your study, then describe how your findings differ or support those of other studies and why [i.e., what were the unique, new, or crucial contributions your study made to the overall research about your topic?].
• Do not simply reiterate your findings or the discussion of your results. Provide a synthesis of arguments presented in the paper to show how these converge to address the research problem and the overall objectives of your study.
• Indicate opportunities for future research if you haven't already done so in the discussion section of your paper. Highlighting the need for further research provides the reader with evidence that you have an in-depth awareness of the research problem but that further investigations should take place beyond the scope of your investigation.

Consider the following points to help ensure your conclusion is presented well:

• If the argument or purpose of your paper is complex, you may need to summarize the argument for your reader.
• If, prior to your conclusion, you have not yet explained the significance of your findings or if you are proceeding inductively, use the end of your paper to describe your main points and explain their significance.
• Move from a detailed to a general level of consideration that returns the topic to the context provided by the introduction or within a new context that emerges from the data [this is opposite of the introduction, which begins with general discussion of the context and ends with a detailed description of the research problem]. 

The conclusion also provides a place for you to persuasively and succinctly restate the research problem, given that the reader has now been presented with all the information about the topic . Depending on the discipline you are writing in, the concluding paragraph may contain your reflections on the evidence presented. However, the nature of being introspective about the research you have conducted will depend on the topic and whether your professor wants you to express your observations in this way. If asked to think introspectively about the topics, do not delve into idle speculation. Being introspective means looking within yourself as an author to try and understand an issue more deeply, not to guess at possible outcomes or make up scenarios not supported by the evidence.

II.  Developing a Compelling Conclusion

Although an effective conclusion needs to be clear and succinct, it does not need to be written passively or lack a compelling narrative. Strategies to help you move beyond merely summarizing the key points of your research paper may include any of the following:

• If your essay deals with a critical, contemporary problem, warn readers of the possible consequences of not attending to the problem proactively.
• Recommend a specific course or courses of action that, if adopted, could address a specific problem in practice or in the development of new knowledge leading to positive change.
• Cite a relevant quotation or expert opinion already noted in your paper in order to lend authority and support to the conclusion(s) you have reached [a good source would be from your literature review].
• Explain the consequences of your research in a way that elicits action or demonstrates urgency in seeking change.
• Restate a key statistic, fact, or visual image to emphasize the most important finding of your paper.
• If your discipline encourages personal reflection, illustrate your concluding point by drawing from your own life experiences.
• Return to an anecdote, an example, or a quotation that you presented in your introduction, but add further insight derived from the findings of your study; use your interpretation of results from your study to recast it in new or important ways.
• Provide a "take-home" message in the form of a succinct, declarative statement that you want the reader to remember about your study.

III. Problems to Avoid

Failure to be concise Your conclusion section should be concise and to the point. Conclusions that are too lengthy often have unnecessary information in them. The conclusion is not the place for details about your methodology or results. Although you should give a summary of what was learned from your research, this summary should be relatively brief, since the emphasis in the conclusion is on the implications, evaluations, insights, and other forms of analysis that you make. Strategies for writing concisely can be found here .

Failure to comment on larger, more significant issues In the introduction, your task was to move from the general [the field of study] to the specific [the research problem]. However, in the conclusion, your task is to move from a specific discussion [your research problem] back to a general discussion framed around the implications and significance of your findings [i.e., how your research contributes new understanding or fills an important gap in the literature]. In short, the conclusion is where you should place your research within a larger context [visualize your paper as an hourglass--start with a broad introduction and review of the literature, move to the specific analysis and discussion, conclude with a broad summary of the study's implications and significance].

Failure to reveal problems and negative results Negative aspects of the research process should never be ignored. These are problems, deficiencies, or challenges encountered during your study. They should be summarized as a way of qualifying your overall conclusions. If you encountered negative or unintended results [i.e., findings that are validated outside the research context in which they were generated], you must report them in the results section and discuss their implications in the discussion section of your paper. In the conclusion, use negative results as an opportunity to explain their possible significance and/or how they may form the basis for future research.

Failure to provide a clear summary of what was learned In order to be able to discuss how your research fits within your field of study [and possibly the world at large], you need to summarize briefly and succinctly how it contributes to new knowledge or a new understanding about the research problem. This element of your conclusion may be only a few sentences long.

Failure to match the objectives of your research Often research objectives in the social and behavioral sciences change while the research is being carried out. This is not a problem unless you forget to go back and refine the original objectives in your introduction. As these changes emerge they must be documented so that they accurately reflect what you were trying to accomplish in your research [not what you thought you might accomplish when you began].

Resist the urge to apologize If you've immersed yourself in studying the research problem, you presumably should know a good deal about it [perhaps even more than your professor!]. Nevertheless, by the time you have finished writing, you may be having some doubts about what you have produced. Repress those doubts! Don't undermine your authority as a researcher by saying something like, "This is just one approach to examining this problem; there may be other, much better approaches that...." The overall tone of your conclusion should convey confidence to the reader about the study's validity and realiability.

Assan, Joseph. "Writing the Conclusion Chapter: The Good, the Bad and the Missing." Liverpool: Development Studies Association (2009): 1-8; Concluding Paragraphs. College Writing Center at Meramec. St. Louis Community College; Conclusions. The Writing Center. University of North Carolina; Conclusions. The Writing Lab and The OWL. Purdue University; Freedman, Leora  and Jerry Plotnick. Introductions and Conclusions. The Lab Report. University College Writing Centre. University of Toronto; Leibensperger, Summer. Draft Your Conclusion. Academic Center, the University of Houston-Victoria, 2003; Make Your Last Words Count. The Writer’s Handbook. Writing Center. University of Wisconsin Madison; Miquel, Fuster-Marquez and Carmen Gregori-Signes. “Chapter Six: ‘Last but Not Least:’ Writing the Conclusion of Your Paper.” In Writing an Applied Linguistics Thesis or Dissertation: A Guide to Presenting Empirical Research . John Bitchener, editor. (Basingstoke,UK: Palgrave Macmillan, 2010), pp. 93-105; Tips for Writing a Good Conclusion. Writing@CSU. Colorado State University; Kretchmer, Paul. Twelve Steps to Writing an Effective Conclusion. San Francisco Edit, 2003-2008; Writing Conclusions. Writing Tutorial Services, Center for Innovative Teaching and Learning. Indiana University; Writing: Considering Structure and Organization. Institute for Writing Rhetoric. Dartmouth College.

Writing Tip

Don't Belabor the Obvious!

Avoid phrases like "in conclusion...," "in summary...," or "in closing...." These phrases can be useful, even welcome, in oral presentations. But readers can see by the tell-tale section heading and number of pages remaining that they are reaching the end of your paper. You'll irritate your readers if you belabor the obvious.

Assan, Joseph. "Writing the Conclusion Chapter: The Good, the Bad and the Missing." Liverpool: Development Studies Association (2009): 1-8.

Another Writing Tip

New Insight, Not New Information!

Don't surprise the reader with new information in your conclusion that was never referenced anywhere else in the paper. This why the conclusion rarely has citations to sources. If you have new information to present, add it to the discussion or other appropriate section of the paper. Note that, although no new information is introduced, the conclusion, along with the discussion section, is where you offer your most "original" contributions in the paper; the conclusion is where you describe the value of your research, demonstrate that you understand the material that you’ve presented, and position your findings within the larger context of scholarship on the topic, including describing how your research contributes new insights to that scholarship.

Assan, Joseph. "Writing the Conclusion Chapter: The Good, the Bad and the Missing." Liverpool: Development Studies Association (2009): 1-8; Conclusions. The Writing Center. University of North Carolina.

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The Conclusion: How to End a Scientific Report in Style

• First Online: 26 April 2023

Cite this chapter

• Siew Mei Wu 3 ,
• Kooi Cheng Lee 3 &
• Eric Chun Yong Chan 4  

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Sometimes students have the mistaken belief that the conclusion of a scientific report is just a perfunctory ending that repeats what was presented in the main sections of the report. However, impactful conclusions fulfill a rhetorical function. Besides giving a closing summary, the conclusion reflects the significance of what has been uncovered and how this is connected to a broader issue. At the very least, the conclusion of a scientific report should leave the reader with a new perspective of the research area and something to think about.

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Goh, Z.-H., Tee, J. K., &amp; Ho, H. K. (2020). An Evaluation of the in vitro roles and mechanisms of silibinin in reducing pyrazinamide and isoniazid-induced hepatocellular damage. International Journal of Molecular Sciences, 21 , 3714–3734. https://doi.org/10.3390/ijms21103714

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Swales, J. M., &amp; Feak, C. B. (2012). Academic writing for graduate students (3rd ed.). University of Michigan Press.

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Appendix 1: Tutorial Notes for Conclusion Activity

1.1 learning outcomes.

At the end of the tutorial, you should be able to:

Identify and demonstrate understanding of the roles of Conclusion section of research reports

Analyze the rhetorical moves of Conclusion and apply them effectively in research reports

1.2 Introduction

The Conclusion of a paper is a closing summary of what the report is about. The key role of a Conclusion is to provide a reflection on what has been uncovered during the course of the study and to reflect on the significance of what has been learned (Craswell &amp; Poore, 2012). It should show the readers why all the analysis and information matters.

Besides having a final say on the issues in the report, a Conclusion allows the writer to do the following:

Demonstrate the importance of ideas presented through a synthesis of thoughts

Consider broader issues, make new connections, and elaborate on the significance of the findings

Propel the reader to a new view of the subject

Make a good final impression

End the paper on a positive note

(University of North Carolina at Chapel Hill, 2019)

In other words, a Conclusion gives the readers something to take away that will help them see things differently or appreciate the topic in new ways. It can suggest broader implications that will not only interest the readers, but also enrich their knowledge (Craswell &amp; Poore, 2012), and leave them with something interesting to think about (University of North Carolina at Chapel Hill, 2019).

1.3 About the Conclusion Section

In most universities, undergraduate students, especially those in the last year of their programs, are required to document their research work in the form of a research report. The process of taking what you have done in the lab or from systematic review, and writing it for your academic colleagues is a highly structured activity that stretches and challenges the mind. Overall, a research paper should appeal to the academic community for whom you are writing and should cause the reader to want to know more about your research.

As an undergraduate student in your discipline, you have the advantage of being engaged in a niche area of research. As such, your research is current and will most likely be of interest to scholars in your community.

A typical research paper has the following main sections: introduction, methods, results, discussion, and conclusion. The other front and back matters of a research paper are the title, abstract, acknowledgments, and reference list. This structure is commonly adopted and accepted in the scientific fields. The research report starts with a general idea. The report then leads the reader to a discussion on a specific research area. It then ends with applicability to a bigger area. The last section, Conclusion, is the focus of this lesson.

The rhetorical moves of a Conclusion reflect its roles (see Fig. 54.1 ). It starts by reminding the reader of what is presented in the Introduction. For example, if a problem is described in the Introduction, that same problem can be revisited in the Conclusion to provide evidence that the report is helpful in creating a new understanding of the problem. The writer can also refer to the Introduction by using keywords or parallel concepts that were presented there.

Rhetorical moves of Conclusion (the University of North Carolina at Chapel Hill Writing Center,2019)

Next is a synthesis and not a summary of the outcomes of the study. Ideas should not simply be repeated as they were in the earlier parts of the report. The writer must show how the points made, and the support and examples that were given, fit together.

In terms of limitations, if it is not already mentioned in the Discussion section, the writer should acknowledge the weaknesses and shortcomings in the design and/or conduct of the study.

Finally, in connecting to the wider context, the writer should propose a course of action, a solution to an issue, or pose questions for further study. This can redirect readers’ thoughts and help them apply the information and ideas in the study to their own research context or to see the broader implications of the study.

1.4 Linguistic Features of the Conclusion Section

In terms of linguistic features, the use of tense in the Conclusion section is primarily present where the writer’s voice, position, and interpretation are prominent. This is followed by the use of the future tense in sharing what is ahead and some use of past when referring to the study that was done. As summarized by Swales and Feak (2012), Table 54.1 presents the frequency of use of the present tense and past tense in a research report.

1.5 Writing the Conclusion Section

Often, writing a Conclusion is not as easy as it first seems. Using the Question and Answer approach, below is a description of what is usually included in the Conclusion section.

How long should the Conclusion be?

One or two paragraphs comprising 1 sentence summarizing what the paper was about

Two to three sentences summarizing and synthesizing the key findings related to the thesis or objectives of the study

One sentence on limitations (if not in Discussion)

One to two sentences highlighting the significance and implications

One sentence on potential directions for further research

Should the objective be referred to in a Conclusion?

An effective Conclusion reiterates the issue or problem the hypothesis or objective(s) set out to solve. It is important to remind the readers what the hypothesis or objective(s) of the report are and to what extent they are addressed

How far should the Conclusion reflect the Introduction?

Referring to points made in the Introduction in the conclusion ties the paper together and provides readers with a sense of closure.

How much summarizing should there be in a Conclusion?

The conclusion can loosely follow the organization of your paper to parallel, but the focus should be on the paper’s analysis rather than on the organization.

Should newly found information be added to a Conclusion?

Well-written conclusions do not bring in new information or analysis; instead, they sum up what is already contained in the paper.

(Bahamani et al., 2017; Markowsky, 2010)

1.6 Task: Analysing a Conclusion Section

Consider Examples 1 to 4. How do the writers communicate the following information?

Restatement of objective(s)

Refection of outcome(s)

Acknowledgment of limitations, if any

Connection to wider context

“According to this study, the use of educational models, such as a Precaution Adoption Process Model (PAPM) that most people are associated with the process of decision-making in higher education will be beneficial. Moreover, in the preparation, development and implementation of training programs, factors like increased perceived susceptibility, and perceived benefits should be dealt with and some facilities should be provided to facilitate or resolve the barriers of doing the Pap smear test as much as possible.”

(Bahamani et al., 2016)

“Community pharmacists perceived the NMS service as being of benefit to patients by providing advice and reassurance. Implementation of NMS was variable and pharmacists’ perceptions of its feasibility and operationalisation were mixed. Some found the logistics of arranging and conducting the necessary follow-ups challenging, as were service targets. Patient awareness and understanding of NMS was reported to be low and there was a perceived need for publicity about the service. NMS appeared to have strengthened existing good relationships between pharmacists and GPs. Some pharmacists’ concerns about possible overlap of NMS with GP and nurse input may have impacted on their motivation. Overall, our findings indicate that NMS provides an opportunity for patient benefit (patient interaction and medicines management) and the development of contemporary pharmacy practice.”

(Lucas &amp; Blenkinsopp, 2015)

“In this review, we discussed several strategies for the engineering of RiPP pathways to produce artificial pep-tides bearing non-proteinogenic structures characteristic of peptidic natural products. In the RiPP pathways, the structures of the final products are defined by the primary sequences of the precursor genes. Moreover, only a small number of modifying enzymes are involved, and the enzymes function modularly. These features have greatly facilitated both in vivo and in vitro engineering of the pathways, leading to a wide variety of artificial derivatives of naturally occurring RiPPs. In principle, the engineering strategies introduced here can be interchangeably applied for other classes of RiPP enzymes/pathways. Post-biosynthetic chemical modification of RiPPs would be an alternative approach to further increase the structural variation of the products [48–50]. Given that new classes of RiPP enzymes have been frequently reported, and that genetic information of putative RiPP enzymes continues to arise, the array of molecules feasible by RiPP engineering will be further expanded. Some of the artificial RiPP derivatives exhibited elevated bioactivities or different selectivities as compared with their wild type RiPPs. Although these precedents have demonstrated the pharmaceutical relevance of RiPP ana-logs, the next important step in RiPP engineering is the development of novel RiPP derivatives with artificial bioactivities. In more recent reports [51 __,52 __,53 __], the integration of combinatorial lanthipeptide biosynthesis with in vitro selection or bacterial reverse two-hybrid screening methods have successfully obtained artificial ligands specific to certain target proteins. Such approaches, including other strategies under investigation in laboratories in this field, for constructing and screening vast RiPP libraries would lead to the creation of artificial bioactive peptides with non-proteinogenic structures in the near feature.”

(Goto &amp; Suga, 2018)

“Our study is the first to assess and characterise silibinin’s various roles as an adjuvant in protecting against PZA- and INH-induced hepatotoxicity. Most promisingly, we demonstrated silibinin’s safety and efficacy as a rescue adjuvant in vitro , both of which are fundamental considerations in the use of any drug. We also identified silibinin’s potential utility as a rescue hepatoprotectant, shed important mechanistic insights on its hepatoprotective effect, and identified novel antioxidant targets in ameliorating ATT-induced hepatotoxicity. The proof-of-concept demonstrated in this project forms the ethical and scientific foundation to justify and inform subsequent in vivo preclinical studies and clinical trials. Given the lack of alternative treatments in tuberculosis, the need to preserve our remaining antibiotics is paramount. The high stakes involved necessitate future efforts to support our preliminary work in making silibinin clinically relevant to patients and healthcare professionals alike.”

(Goh, 2018)

1.7 In Summary

To recap, in drafting the Conclusion section, you should keep in mind that final remarks can leave the readers with a long-lasting impression of the report especially on the key point(s) that the writer intends to convey. Therefore, you should be careful in crafting this last section of your report.

1.8 References

Bahamani, A. et al. (2017). The Effect of Training Based on Precaution Adoption Process Model (PAPM) on Rural Females’ Participation in Pap smear. BJPR, 16 , 6. Retrieved from http://www.journalrepository.org/media/journals/BJPR_14/2017/May/Bahmani1662017BJPR32965.pdf

Craswell G., &amp; Poore, M. (2012). Writing for Academic Success, 2nd. London: Sage.

Goh, Z-H. (2018). An Evaluation of the Roles and Mechanisms of Silibinin in Reducing Pyrazinamide- and Isoniazid-Induced Hepatotoxicity . Unpublished Final Year Project. National University of Singapore: Department of Pharmacy.

Goto, Y., &amp; Suga, H. (2018). Engineering of RiPP pathways for the production of artificial peptides bearing various non-proteinogenic structures. Current Opinion in Chemical Biology , 46 , 82–90.

Lucas, B., &amp; Blenkinsopp, A. (2015). Community pharmacists’ experience and perceptions of the New Medicines Serves (NMS). IJPP , 23 , 6. Retrieved from http://onlinelibrary.wiley.com/doi/10.1111/ijpp.12180/full

Markowski (2010). WPPD Evaluation form for capstone paper . Retrieved from https://cop-main.sites.medinfo.ufl.edu/files/2010/12/Capstone-Paper-Checklist-and-Reviewer-Evaluation-Form.pdf

Swales, J.M., &amp; Feak, C.B. (2012). Academic writing for graduate students , 3 rd ed. Michigan: University of Michigan Press.

University of North Carolina at Chapel Hill, The Writing Center. (2019). Conclusions . Retrieved from https://writingcenter.unc.edu/tips-and-tools/conclusions/

Appendix 2: Quiz for Conclusion Activity

Instructions

There are 6 questions in this quiz. Choose the most appropriate answer among the options provided.

What does the Conclusion section of a scientific report do?

It provides a recap of report, with reference to the objective(s).

It gives a closure to what has been discussed in relation to the topic.

It shares future direction(s) and in doing so connects to a wider context.

It propels the reader to have an enhanced understanding of the topic.

i, ii, and iii

i, ii and iv

ii, iii and iv

i, ii, iii and iv

The first rhetorical move of the Conclusion section is restatement of objective(s). It …

reminds the reader the objective(s) of the report.

restates reason(s) of each objective of the report.

revisits issue(s) presented requiring investigation.

reiterates the importance of the research project.

The second rhetorical move of the Conclusion section is reflection of outcome(s). It …

summarizes all the findings of the research project.

synthesizes outcomes of the research project.

is a repeat of important ideas mentioned in the report.

shows how key points, evidence, and support fit together.

In connecting to a wider context, the authors …

remind the reader of the importance of the topic.

propose a course of action for the reader.

pose a question to the reader for further research.

direct the reader to certain direction(s).

Following is the Conclusion section of a published article.

“In summary, we have assessed and characterised silibinin’s various roles as an adjuvant in protecting against PZA- and INH-induced hepatotoxicity. Our in vitro experiments suggest that silibinin may be safe and efficacious as a rescue adjuvant, both fundamental considerations in the use of any drug. Further optimisation of our in vitro model may also enhance silibinin’s hepatoprotective effect in rescue, prophylaxis, and recovery. Using this model, we have gleaned important mechanistic insights into its hepatoprotective effect and identified novel antioxidant targets in ameliorating HRZE-induced hepatotoxicity. Future directions will involve exploring the two main mechanisms by which silibinin may ameliorate hepatotoxicity; the proof-of-concept demonstrated in this project will inform subsequent in vitro and in vivo preclinical studies. Given the lack of alternative treatments in tuberculosis, the need to preserve our remaining antibiotics is paramount. These high stakes necessitate future efforts to support our preliminary work, making silibinin more clinically relevant to patients and healthcare professionals alike.” (Goh et al., 2020)

This excerpt of the Conclusion section…

restates objectives of the research.

synthesizes outcomes of the research.

acknowledges limitations of the research

connects the reader to a wider context.

i, ii and iii

What can one observe about the use of tenses in the Conclusion section? The frequency of use of present and future tenses …

demonstrates the importance results being synthesized.

is ungrammatical as the past tense should be used to state the outcomes.

propels the reader to think of future research.

suggests an encouraging tone to end the report.

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About this chapter

Wu, S.M., Lee, K.C., Chan, E.C.Y. (2023). The Conclusion: How to End a Scientific Report in Style. In: Rowland, S., Kuchel, L. (eds) Teaching Science Students to Communicate: A Practical Guide. Springer, Cham. https://doi.org/10.1007/978-3-030-91628-2_54

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How to Write a Conclusion for Research Papers (with Examples)

The conclusion of a research paper is a crucial section that plays a significant role in the overall impact and effectiveness of your research paper. However, this is also the section that typically receives less attention compared to the introduction and the body of the paper. The conclusion serves to provide a concise summary of the key findings, their significance, their implications, and a sense of closure to the study. Discussing how can the findings be applied in real-world scenarios or inform policy, practice, or decision-making is especially valuable to practitioners and policymakers. The research paper conclusion also provides researchers with clear insights and valuable information for their own work, which they can then build on and contribute to the advancement of knowledge in the field.

The research paper conclusion should explain the significance of your findings within the broader context of your field. It restates how your results contribute to the existing body of knowledge and whether they confirm or challenge existing theories or hypotheses. Also, by identifying unanswered questions or areas requiring further investigation, your awareness of the broader research landscape can be demonstrated.

Remember to tailor the research paper conclusion to the specific needs and interests of your intended audience, which may include researchers, practitioners, policymakers, or a combination of these.

Table of Contents

What is a conclusion in a research paper, summarizing conclusion, editorial conclusion, externalizing conclusion, importance of a good research paper conclusion, how to write a conclusion for your research paper, research paper conclusion examples.

• How to write a research paper conclusion with Paperpal? 

Frequently Asked Questions

A conclusion in a research paper is the final section where you summarize and wrap up your research, presenting the key findings and insights derived from your study. The research paper conclusion is not the place to introduce new information or data that was not discussed in the main body of the paper. When working on how to conclude a research paper, remember to stick to summarizing and interpreting existing content. The research paper conclusion serves the following purposes: 1

• Warn readers of the possible consequences of not attending to the problem.
• Recommend specific course(s) of action.
• Restate key ideas to drive home the ultimate point of your research paper.
• Provide a “take-home” message that you want the readers to remember about your study.

Types of conclusions for research papers

In research papers, the conclusion provides closure to the reader. The type of research paper conclusion you choose depends on the nature of your study, your goals, and your target audience. I provide you with three common types of conclusions:

A summarizing conclusion is the most common type of conclusion in research papers. It involves summarizing the main points, reiterating the research question, and restating the significance of the findings. This common type of research paper conclusion is used across different disciplines.

An editorial conclusion is less common but can be used in research papers that are focused on proposing or advocating for a particular viewpoint or policy. It involves presenting a strong editorial or opinion based on the research findings and offering recommendations or calls to action.

An externalizing conclusion is a type of conclusion that extends the research beyond the scope of the paper by suggesting potential future research directions or discussing the broader implications of the findings. This type of conclusion is often used in more theoretical or exploratory research papers.

Align your conclusion’s tone with the rest of your research paper. Start Writing with Paperpal Now!  

The conclusion in a research paper serves several important purposes:

• Offers Implications and Recommendations : Your research paper conclusion is an excellent place to discuss the broader implications of your research and suggest potential areas for further study. It’s also an opportunity to offer practical recommendations based on your findings.
• Provides Closure : A good research paper conclusion provides a sense of closure to your paper. It should leave the reader with a feeling that they have reached the end of a well-structured and thought-provoking research project.
• Leaves a Lasting Impression : Writing a well-crafted research paper conclusion leaves a lasting impression on your readers. It’s your final opportunity to leave them with a new idea, a call to action, or a memorable quote.

Writing a strong conclusion for your research paper is essential to leave a lasting impression on your readers. Here’s a step-by-step process to help you create and know what to put in the conclusion of a research paper: 2

• Research Statement : Begin your research paper conclusion by restating your research statement. This reminds the reader of the main point you’ve been trying to prove throughout your paper. Keep it concise and clear.
• Key Points : Summarize the main arguments and key points you’ve made in your paper. Avoid introducing new information in the research paper conclusion. Instead, provide a concise overview of what you’ve discussed in the body of your paper.
• Address the Research Questions : If your research paper is based on specific research questions or hypotheses, briefly address whether you’ve answered them or achieved your research goals. Discuss the significance of your findings in this context.
• Significance : Highlight the importance of your research and its relevance in the broader context. Explain why your findings matter and how they contribute to the existing knowledge in your field.
• Implications : Explore the practical or theoretical implications of your research. How might your findings impact future research, policy, or real-world applications? Consider the “so what?” question.
• Future Research : Offer suggestions for future research in your area. What questions or aspects remain unanswered or warrant further investigation? This shows that your work opens the door for future exploration.
• Closing Thought : Conclude your research paper conclusion with a thought-provoking or memorable statement. This can leave a lasting impression on your readers and wrap up your paper effectively. Avoid introducing new information or arguments here.
• Proofread and Revise : Carefully proofread your conclusion for grammar, spelling, and clarity. Ensure that your ideas flow smoothly and that your conclusion is coherent and well-structured.

Write your research paper conclusion 2x faster with Paperpal. Try it now!

Remember that a well-crafted research paper conclusion is a reflection of the strength of your research and your ability to communicate its significance effectively. It should leave a lasting impression on your readers and tie together all the threads of your paper. Now you know how to start the conclusion of a research paper and what elements to include to make it impactful, let’s look at a research paper conclusion sample.

How to write a research paper conclusion with Paperpal?

A research paper conclusion is not just a summary of your study, but a synthesis of the key findings that ties the research together and places it in a broader context. A research paper conclusion should be concise, typically around one paragraph in length. However, some complex topics may require a longer conclusion to ensure the reader is left with a clear understanding of the study’s significance. Paperpal, an AI writing assistant trusted by over 800,000 academics globally, can help you write a well-structured conclusion for your research paper. 

• Sign Up or Log In: Create a new Paperpal account or login with your details.  
• Navigate to Features : Once logged in, head over to the features’ side navigation pane. Click on Templates and you’ll find a suite of generative AI features to help you write better, faster.  
• Generate an outline: Under Templates, select ‘Outlines’. Choose ‘Research article’ as your document type.  
• Select your section: Since you’re focusing on the conclusion, select this section when prompted.  
• Choose your field of study: Identifying your field of study allows Paperpal to provide more targeted suggestions, ensuring the relevance of your conclusion to your specific area of research. 
• Provide a brief description of your study: Enter details about your research topic and findings. This information helps Paperpal generate a tailored outline that aligns with your paper’s content. 
• Generate the conclusion outline: After entering all necessary details, click on ‘generate’. Paperpal will then create a structured outline for your conclusion, to help you start writing and build upon the outline.  
• Write your conclusion: Use the generated outline to build your conclusion. The outline serves as a guide, ensuring you cover all critical aspects of a strong conclusion, from summarizing key findings to highlighting the research’s implications. 
• Refine and enhance: Paperpal’s ‘Make Academic’ feature can be particularly useful in the final stages. Select any paragraph of your conclusion and use this feature to elevate the academic tone, ensuring your writing is aligned to the academic journal standards. 

By following these steps, Paperpal not only simplifies the process of writing a research paper conclusion but also ensures it is impactful, concise, and aligned with academic standards. Sign up with Paperpal today and write your research paper conclusion 2x faster .  

The research paper conclusion is a crucial part of your paper as it provides the final opportunity to leave a strong impression on your readers. In the research paper conclusion, summarize the main points of your research paper by restating your research statement, highlighting the most important findings, addressing the research questions or objectives, explaining the broader context of the study, discussing the significance of your findings, providing recommendations if applicable, and emphasizing the takeaway message. The main purpose of the conclusion is to remind the reader of the main point or argument of your paper and to provide a clear and concise summary of the key findings and their implications. All these elements should feature on your list of what to put in the conclusion of a research paper to create a strong final statement for your work.

A strong conclusion is a critical component of a research paper, as it provides an opportunity to wrap up your arguments, reiterate your main points, and leave a lasting impression on your readers. Here are the key elements of a strong research paper conclusion: 1. Conciseness : A research paper conclusion should be concise and to the point. It should not introduce new information or ideas that were not discussed in the body of the paper. 2. Summarization : The research paper conclusion should be comprehensive enough to give the reader a clear understanding of the research’s main contributions. 3 . Relevance : Ensure that the information included in the research paper conclusion is directly relevant to the research paper’s main topic and objectives; avoid unnecessary details. 4 . Connection to the Introduction : A well-structured research paper conclusion often revisits the key points made in the introduction and shows how the research has addressed the initial questions or objectives. 5. Emphasis : Highlight the significance and implications of your research. Why is your study important? What are the broader implications or applications of your findings? 6 . Call to Action : Include a call to action or a recommendation for future research or action based on your findings.

The length of a research paper conclusion can vary depending on several factors, including the overall length of the paper, the complexity of the research, and the specific journal requirements. While there is no strict rule for the length of a conclusion, but it’s generally advisable to keep it relatively short. A typical research paper conclusion might be around 5-10% of the paper’s total length. For example, if your paper is 10 pages long, the conclusion might be roughly half a page to one page in length.

In general, you do not need to include citations in the research paper conclusion. Citations are typically reserved for the body of the paper to support your arguments and provide evidence for your claims. However, there may be some exceptions to this rule: 1. If you are drawing a direct quote or paraphrasing a specific source in your research paper conclusion, you should include a citation to give proper credit to the original author. 2. If your conclusion refers to or discusses specific research, data, or sources that are crucial to the overall argument, citations can be included to reinforce your conclusion’s validity.

The conclusion of a research paper serves several important purposes: 1. Summarize the Key Points 2. Reinforce the Main Argument 3. Provide Closure 4. Offer Insights or Implications 5. Engage the Reader. 6. Reflect on Limitations

Remember that the primary purpose of the research paper conclusion is to leave a lasting impression on the reader, reinforcing the key points and providing closure to your research. It’s often the last part of the paper that the reader will see, so it should be strong and well-crafted.

• Makar, G., Foltz, C., Lendner, M., & Vaccaro, A. R. (2018). How to write effective discussion and conclusion sections. Clinical spine surgery, 31(8), 345-346.
• Bunton, D. (2005). The structure of PhD conclusion chapters.  Journal of English for academic purposes ,  4 (3), 207-224.

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Discussion Vs. Conclusion: Know the Difference Before Drafting Manuscripts

The discussion section of your manuscript can be one of the hardest to write as it requires you to think about the meaning of the research you have done. An effective discussion section tells the reader what your study means and why it is important. In this article, we will cover some pointers for writing clear/well-organized discussion and conclusion sections and discuss what should NOT be a part of these sections.

What Should be in the Discussion Section?

Your discussion is, in short, the answer to the question “what do my results mean?” The discussion section of the manuscript should come after the methods and results section and before the conclusion. It should relate back directly to the questions posed in your introduction, and contextualize your results within the literature you have covered in your literature review . In order to make your discussion section engaging, you should include the following information:

• The major findings of your study
• The meaning of those findings
• How these findings relate to what others have done
• Limitations of your findings
• An explanation for any surprising, unexpected, or inconclusive results
• Suggestions for further research

Your discussion should NOT include any of the following information:

• New results or data not presented previously in the paper
• Unwarranted speculation
• Tangential issues
• Conclusions not supported by your data

Related: Avoid outright rejection with a well-structured manuscript. Check out these resources and improve your manuscript now!

How to Make the Discussion Section Effective?

There are several ways to make the discussion section of your manuscript effective, interesting, and relevant. Hear from one of our experts on how to structure your discussion section and distinguish it from the results section:

Now that we have listened to how to approach writing a discussion section, let’s delve deeper into some essential tips with a few examples:

• Most writing guides recommend listing the findings of your study in decreasing order of their importance. You would not want your reader to lose sight of the key results that you found. Therefore, put the most important finding front and center. Example: Imagine that you conduct a study aimed at evaluating the effectiveness of stent placement in patients with partially blocked arteries. You find that despite this being a common first-line treatment, stents are not effective for patients with partially blocked arteries. The study also discovers that patients treated with a stent tend to develop asthma at slightly higher rates than those who receive no such treatment.

Which sentence would you choose to begin your discussion? Our findings suggest that patients who had partially blocked arteries and were treated with a stent as the first line of intervention had no better outcomes than patients who were not given any surgical treatments.   Our findings noted that patients who received stents demonstrated slightly higher rates of asthma than those who did not. In addition, the placement of a stent did not impact their rates of cardiac events in a statistically significant way.

If you chose the first example, you are correct!

• If you are not sure which results are the most important, go back to your research question and start from there. The most important result is the one that answers your research question.
• It is also necessary to contextualize the meaning of your findings for the reader. What does previous literature say, and do your results agree? Do your results elaborate on previous findings, or differ significantly?
• In our stent example, if previous literature found that stents were an effective line of treatment for patients with partially blocked arteries, you should explore why your interpretation seems different in the discussion section. Did your methodology differ? Was your study broader in scope and larger in scale than the previous studies? Were there any limitations to previous studies that your study overcame? Alternatively, is it possible that your own study could be incorrect because of some difficulties you had in carrying it out? The discussion section should narrate a coherent story to the target audience.
• Finally, remember not to introduce new ideas/data, or speculate wildly on the possible future implications of your study in the discussion section. However, considering alternative explanations for your results is encouraged.

Avoiding Confusion in your Conclusion!

Many writers confuse the information they should include in their discussion with the information they should place in their conclusion. One easy way to avoid this confusion is to think of your conclusion as a summary of everything that you have said thus far. In the conclusion section, you remind the reader of what they have just read. Your conclusion should:

• Restate your hypothesis or research question
• Restate your major findings
• Tell the reader what contribution your study has made to the existing literature
• Highlight any limitations of your study
• State future directions for research/recommendations

Your conclusion should NOT:

• Introduce new arguments
• Introduce new data
• Fail to include your research question
• Fail to state your major results

An appropriate conclusion to our hypothetical stent study might read as follows:

In this study, we examined the effectiveness of stent placement. We compared the patients with partially blocked arteries to those with non-surgical interventions. After examining the five-year medical outcomes of 19,457 patients in the Greater Dallas area, our statistical analysis concluded that the placement of a stent resulted in outcomes that were no better than non-surgical interventions such as diet and exercise. Although previous findings indicated that stent placement improved patient outcomes, our study followed a greater number of patients than those in major studies conducted previously. It is possible that outcomes would vary if measured over a ten or fifteen year period. Future researchers should consider investigating the impact of stent placement in these patients over a longer period (five years or longer). Regardless, our results point to the need for medical practitioners to reconsider the placement of a stent as the first line of treatment as non-surgical interventions may have equally positive outcomes for patients.

Did you find the tips in this article relevant? What is the most challenging portion of a research paper for you to write? Let us know in the comments section below!

This is the most stunning and self-instructional site I have come across. Thank you so much for your updates! I will help me work on my dissertation.

Thank you so much!! It helps a lot!

very helpful, thank you

thanks a lot …

this is one of a kind! awesome, straight to the point and easy to understand! Thanks a lot

Thank you so much for this, I never comment on these types of sites but I just had too here as I’ve never seen an article that has answered everyone of the questions I wanted when I searched on Google. Certainly not to the extent and clear clarity that you have presented. Thanks so much for this it has put my mind to ease a bit with my terrible dissertation haha.

Have a nice day.

Helped massively with writing a good conclusion!

Extremely well explained all details in simple and applicable manner, Thank you very much for outstanding article. It really made life easy. Ravi, India.

Thanks a lot for such a nicely explained difference of discussion and conclusion. now got some basic idea to write what.

Thanks for clearing the great confusion. It gave real clarity to me!

Clarified my confusion. Thank you for this article

This website certainly has all of the information I wanted concerning this subject and didn’t know who to ask.

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How to Write the Discussion Section of a Research Paper

The discussion section of a research paper analyzes and interprets the findings, provides context, compares them with previous studies, identifies limitations, and suggests future research directions.

Updated on September 15, 2023

Structure your discussion section right, and you’ll be cited more often while doing a greater service to the scientific community. So, what actually goes into the discussion section? And how do you write it?

The discussion section of your research paper is where you let the reader know how your study is positioned in the literature, what to take away from your paper, and how your work helps them. It can also include your conclusions and suggestions for future studies.

First, we’ll define all the parts of your discussion paper, and then look into how to write a strong, effective discussion section for your paper or manuscript.

Discussion section: what is it, what it does

The discussion section comes later in your paper, following the introduction, methods, and results. The discussion sets up your study’s conclusions. Its main goals are to present, interpret, and provide a context for your results.

What is it?

The discussion section provides an analysis and interpretation of the findings, compares them with previous studies, identifies limitations, and suggests future directions for research.

This section combines information from the preceding parts of your paper into a coherent story. By this point, the reader already knows why you did your study (introduction), how you did it (methods), and what happened (results). In the discussion, you’ll help the reader connect the ideas from these sections.

Why is it necessary?

The discussion provides context and interpretations for the results. It also answers the questions posed in the introduction. While the results section describes your findings, the discussion explains what they say. This is also where you can describe the impact or implications of your research.

Adds context for your results

Most research studies aim to answer a question, replicate a finding, or address limitations in the literature. These goals are first described in the introduction. However, in the discussion section, the author can refer back to them to explain how the study's objective was achieved. 

Shows what your results actually mean and real-world implications

The discussion can also describe the effect of your findings on research or practice. How are your results significant for readers, other researchers, or policymakers?

What to include in your discussion (in the correct order)

A complete and effective discussion section should at least touch on the points described below.

Summary of key findings

The discussion should begin with a brief factual summary of the results. Concisely overview the main results you obtained.

Begin with key findings with supporting evidence

Your results section described a list of findings, but what message do they send when you look at them all together?

Your findings were detailed in the results section, so there’s no need to repeat them here, but do provide at least a few highlights. This will help refresh the reader’s memory and help them focus on the big picture.

Read the first paragraph of the discussion section in this article (PDF) for an example of how to start this part of your paper. Notice how the authors break down their results and follow each description sentence with an explanation of why each finding is relevant. 

State clearly and concisely

Following a clear and direct writing style is especially important in the discussion section. After all, this is where you will make some of the most impactful points in your paper. While the results section often contains technical vocabulary, such as statistical terms, the discussion section lets you describe your findings more clearly. 

Interpretation of results

Once you’ve given your reader an overview of your results, you need to interpret those results. In other words, what do your results mean? Discuss the findings’ implications and significance in relation to your research question or hypothesis.

Analyze and interpret your findings

Look into your findings and explore what’s behind them or what may have caused them. If your introduction cited theories or studies that could explain your findings, use these sources as a basis to discuss your results.

For example, look at the second paragraph in the discussion section of this article on waggling honey bees. Here, the authors explore their results based on information from the literature.

Unexpected or contradictory results

Sometimes, your findings are not what you expect. Here’s where you describe this and try to find a reason for it. Could it be because of the method you used? Does it have something to do with the variables analyzed? Comparing your methods with those of other similar studies can help with this task.

Context and comparison with previous work

Refer to related studies to place your research in a larger context and the literature. Compare and contrast your findings with existing literature, highlighting similarities, differences, and/or contradictions.

How your work compares or contrasts with previous work

Studies with similar findings to yours can be cited to show the strength of your findings. Information from these studies can also be used to help explain your results. Differences between your findings and others in the literature can also be discussed here. 

How to divide this section into subsections

If you have more than one objective in your study or many key findings, you can dedicate a separate section to each of these. Here’s an example of this approach. You can see that the discussion section is divided into topics and even has a separate heading for each of them. 

Limitations

Many journals require you to include the limitations of your study in the discussion. Even if they don’t, there are good reasons to mention these in your paper.

Why limitations don’t have a negative connotation

A study’s limitations are points to be improved upon in future research. While some of these may be flaws in your method, many may be due to factors you couldn’t predict.

Examples include time constraints or small sample sizes. Pointing this out will help future researchers avoid or address these issues. This part of the discussion can also include any attempts you have made to reduce the impact of these limitations, as in this study .

How limitations add to a researcher's credibility

Pointing out the limitations of your study demonstrates transparency. It also shows that you know your methods well and can conduct a critical assessment of them.  

Implications and significance

The final paragraph of the discussion section should contain the take-home messages for your study. It can also cite the “strong points” of your study, to contrast with the limitations section.

Restate your hypothesis

Remind the reader what your hypothesis was before you conducted the study. 

How was it proven or disproven?

Identify your main findings and describe how they relate to your hypothesis.

How your results contribute to the literature

Were you able to answer your research question? Or address a gap in the literature?

Future implications of your research

Describe the impact that your results may have on the topic of study. Your results may show, for instance, that there are still limitations in the literature for future studies to address. There may be a need for studies that extend your findings in a specific way. You also may need additional research to corroborate your findings. 

Sample discussion section

This fictitious example covers all the aspects discussed above. Your actual discussion section will probably be much longer, but you can read this to get an idea of everything your discussion should cover.

Our results showed that the presence of cats in a household is associated with higher levels of perceived happiness by its human occupants. These findings support our hypothesis and demonstrate the association between pet ownership and well-being. 

The present findings align with those of Bao and Schreer (2016) and Hardie et al. (2023), who observed greater life satisfaction in pet owners relative to non-owners. Although the present study did not directly evaluate life satisfaction, this factor may explain the association between happiness and cat ownership observed in our sample.

Our findings must be interpreted in light of some limitations, such as the focus on cat ownership only rather than pets as a whole. This may limit the generalizability of our results.

Nevertheless, this study had several strengths. These include its strict exclusion criteria and use of a standardized assessment instrument to investigate the relationships between pets and owners. These attributes bolster the accuracy of our results and reduce the influence of confounding factors, increasing the strength of our conclusions. Future studies may examine the factors that mediate the association between pet ownership and happiness to better comprehend this phenomenon.

This brief discussion begins with a quick summary of the results and hypothesis. The next paragraph cites previous research and compares its findings to those of this study. Information from previous studies is also used to help interpret the findings. After discussing the results of the study, some limitations are pointed out. The paper also explains why these limitations may influence the interpretation of results. Then, final conclusions are drawn based on the study, and directions for future research are suggested.

How to make your discussion flow naturally

If you find writing in scientific English challenging, the discussion and conclusions are often the hardest parts of the paper to write. That’s because you’re not just listing up studies, methods, and outcomes. You’re actually expressing your thoughts and interpretations in words.

• How formal should it be?
• What words should you use, or not use?
• How do you meet strict word limits, or make it longer and more informative?

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Home » Research Paper Conclusion – Writing Guide and Examples

Research Paper Conclusion – Writing Guide and Examples

Table of Contents

Research Paper Conclusion

Definition:

A research paper conclusion is the final section of a research paper that summarizes the key findings, significance, and implications of the research. It is the writer’s opportunity to synthesize the information presented in the paper, draw conclusions, and make recommendations for future research or actions.

The conclusion should provide a clear and concise summary of the research paper, reiterating the research question or problem, the main results, and the significance of the findings. It should also discuss the limitations of the study and suggest areas for further research.

Parts of Research Paper Conclusion

The parts of a research paper conclusion typically include:

Restatement of the Thesis

The conclusion should begin by restating the thesis statement from the introduction in a different way. This helps to remind the reader of the main argument or purpose of the research.

Summary of Key Findings

The conclusion should summarize the main findings of the research, highlighting the most important results and conclusions. This section should be brief and to the point.

Implications and Significance

In this section, the researcher should explain the implications and significance of the research findings. This may include discussing the potential impact on the field or industry, highlighting new insights or knowledge gained, or pointing out areas for future research.

Limitations and Recommendations

It is important to acknowledge any limitations or weaknesses of the research and to make recommendations for how these could be addressed in future studies. This shows that the researcher is aware of the potential limitations of their work and is committed to improving the quality of research in their field.

Concluding Statement

The conclusion should end with a strong concluding statement that leaves a lasting impression on the reader. This could be a call to action, a recommendation for further research, or a final thought on the topic.

How to Write Research Paper Conclusion

Here are some steps you can follow to write an effective research paper conclusion:

• Restate the research problem or question: Begin by restating the research problem or question that you aimed to answer in your research. This will remind the reader of the purpose of your study.
• Summarize the main points: Summarize the key findings and results of your research. This can be done by highlighting the most important aspects of your research and the evidence that supports them.
• Discuss the implications: Discuss the implications of your findings for the research area and any potential applications of your research. You should also mention any limitations of your research that may affect the interpretation of your findings.
• Provide a conclusion : Provide a concise conclusion that summarizes the main points of your paper and emphasizes the significance of your research. This should be a strong and clear statement that leaves a lasting impression on the reader.
• Offer suggestions for future research: Lastly, offer suggestions for future research that could build on your findings and contribute to further advancements in the field.

Remember that the conclusion should be brief and to the point, while still effectively summarizing the key findings and implications of your research.

Example of Research Paper Conclusion

Here’s an example of a research paper conclusion:

Conclusion :

In conclusion, our study aimed to investigate the relationship between social media use and mental health among college students. Our findings suggest that there is a significant association between social media use and increased levels of anxiety and depression among college students. This highlights the need for increased awareness and education about the potential negative effects of social media use on mental health, particularly among college students.

Despite the limitations of our study, such as the small sample size and self-reported data, our findings have important implications for future research and practice. Future studies should aim to replicate our findings in larger, more diverse samples, and investigate the potential mechanisms underlying the association between social media use and mental health. In addition, interventions should be developed to promote healthy social media use among college students, such as mindfulness-based approaches and social media detox programs.

Overall, our study contributes to the growing body of research on the impact of social media on mental health, and highlights the importance of addressing this issue in the context of higher education. By raising awareness and promoting healthy social media use among college students, we can help to reduce the negative impact of social media on mental health and improve the well-being of young adults.

Purpose of Research Paper Conclusion

The purpose of a research paper conclusion is to provide a summary and synthesis of the key findings, significance, and implications of the research presented in the paper. The conclusion serves as the final opportunity for the writer to convey their message and leave a lasting impression on the reader.

The conclusion should restate the research problem or question, summarize the main results of the research, and explain their significance. It should also acknowledge the limitations of the study and suggest areas for future research or action.

Overall, the purpose of the conclusion is to provide a sense of closure to the research paper and to emphasize the importance of the research and its potential impact. It should leave the reader with a clear understanding of the main findings and why they matter. The conclusion serves as the writer’s opportunity to showcase their contribution to the field and to inspire further research and action.

When to Write Research Paper Conclusion

The conclusion of a research paper should be written after the body of the paper has been completed. It should not be written until the writer has thoroughly analyzed and interpreted their findings and has written a complete and cohesive discussion of the research.

Before writing the conclusion, the writer should review their research paper and consider the key points that they want to convey to the reader. They should also review the research question, hypotheses, and methodology to ensure that they have addressed all of the necessary components of the research.

Once the writer has a clear understanding of the main findings and their significance, they can begin writing the conclusion. The conclusion should be written in a clear and concise manner, and should reiterate the main points of the research while also providing insights and recommendations for future research or action.

Characteristics of Research Paper Conclusion

The characteristics of a research paper conclusion include:

• Clear and concise: The conclusion should be written in a clear and concise manner, summarizing the key findings and their significance.
• Comprehensive: The conclusion should address all of the main points of the research paper, including the research question or problem, the methodology, the main results, and their implications.
• Future-oriented : The conclusion should provide insights and recommendations for future research or action, based on the findings of the research.
• Impressive : The conclusion should leave a lasting impression on the reader, emphasizing the importance of the research and its potential impact.
• Objective : The conclusion should be based on the evidence presented in the research paper, and should avoid personal biases or opinions.
• Unique : The conclusion should be unique to the research paper and should not simply repeat information from the introduction or body of the paper.

Advantages of Research Paper Conclusion

The advantages of a research paper conclusion include:

• Summarizing the key findings : The conclusion provides a summary of the main findings of the research, making it easier for the reader to understand the key points of the study.
• Emphasizing the significance of the research: The conclusion emphasizes the importance of the research and its potential impact, making it more likely that readers will take the research seriously and consider its implications.
• Providing recommendations for future research or action : The conclusion suggests practical recommendations for future research or action, based on the findings of the study.
• Providing closure to the research paper : The conclusion provides a sense of closure to the research paper, tying together the different sections of the paper and leaving a lasting impression on the reader.
• Demonstrating the writer’s contribution to the field : The conclusion provides the writer with an opportunity to showcase their contribution to the field and to inspire further research and action.

Limitations of Research Paper Conclusion

While the conclusion of a research paper has many advantages, it also has some limitations that should be considered, including:

• I nability to address all aspects of the research: Due to the limited space available in the conclusion, it may not be possible to address all aspects of the research in detail.
• Subjectivity : While the conclusion should be objective, it may be influenced by the writer’s personal biases or opinions.
• Lack of new information: The conclusion should not introduce new information that has not been discussed in the body of the research paper.
• Lack of generalizability: The conclusions drawn from the research may not be applicable to other contexts or populations, limiting the generalizability of the study.
• Misinterpretation by the reader: The reader may misinterpret the conclusions drawn from the research, leading to a misunderstanding of the findings.

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How To Write The Conclusion Chapter

A Simple Explainer With Examples + Free Template

By: Jenna Crossley (PhD) | Reviewed By: Dr. Eunice Rautenbach | September 2021

So, you’ve wrapped up your results and discussion chapters, and you’re finally on the home stretch – the conclusion chapter . In this post, we’ll discuss everything you need to know to craft a high-quality conclusion chapter for your dissertation or thesis project.

Overview: The Conclusion Chapter

• What the thesis/dissertation conclusion chapter is
• What to include in your conclusion
• How to structure and write up your conclusion
• A few tips  to help you ace the chapter
• FREE conclusion template

What is the conclusion chapter?

The conclusion chapter is typically the final major chapter of a dissertation or thesis. As such, it serves as a concluding summary of your research findings and wraps up the document. While some publications such as journal articles and research reports combine the discussion and conclusion sections, these are typically separate chapters in a dissertation or thesis. As always, be sure to check what your university’s structural preference is before you start writing up these chapters.

So, what’s the difference between the discussion and the conclusion chapter?

Well, the two chapters are quite similar , as they both discuss the key findings of the study. However, the conclusion chapter is typically more general and high-level in nature. In your discussion chapter, you’ll typically discuss the intricate details of your study, but in your conclusion chapter, you’ll take a   broader perspective, reporting on the main research outcomes and how these addressed your research aim (or aims) .

A core function of the conclusion chapter is to synthesise all major points covered in your study and to tell the reader what they should take away from your work. Basically, you need to tell them what you found , why it’s valuable , how it can be applied , and what further research can be done.

Whatever you do, don’t just copy and paste what you’ve written in your discussion chapter! The conclusion chapter should not be a simple rehash of the discussion chapter. While the two chapters are similar, they have distinctly different functions.  

What should I include in the conclusion chapter?

To understand what needs to go into your conclusion chapter, it’s useful to understand what the chapter needs to achieve. In general, a good dissertation conclusion chapter should achieve the following:

• Summarise the key findings of the study
• Explicitly answer the research question(s) and address the research aims
• Inform the reader of the study’s main contributions
• Discuss any limitations or weaknesses of the study
• Present recommendations for future research

Therefore, your conclusion chapter needs to cover these core components. Importantly, you need to be careful not to include any new findings or data points. Your conclusion chapter should be based purely on data and analysis findings that you’ve already presented in the earlier chapters. If there’s a new point you want to introduce, you’ll need to go back to your results and discussion chapters to weave the foundation in there.

In many cases, readers will jump from the introduction chapter directly to the conclusions chapter to get a quick overview of the study’s purpose and key findings. Therefore, when you write up your conclusion chapter, it’s useful to assume that the reader hasn’t consumed the inner chapters of your dissertation or thesis. In other words, craft your conclusion chapter such that there’s a strong connection and smooth flow between the introduction and conclusion chapters, even though they’re on opposite ends of your document.

Need a helping hand?

How to write the conclusion chapter

Now that you have a clearer view of what the conclusion chapter is about, let’s break down the structure of this chapter so that you can get writing. Keep in mind that this is merely a typical structure – it’s not set in stone or universal. Some universities will prefer that you cover some of these points in the discussion chapter , or that you cover the points at different levels in different chapters.

Step 1: Craft a brief introduction section

As with all chapters in your dissertation or thesis, the conclusions chapter needs to start with a brief introduction. In this introductory section, you’ll want to tell the reader what they can expect to find in the chapter, and in what order . Here’s an example of what this might look like:

This chapter will conclude the study by summarising the key research findings in relation to the research aims and questions and discussing the value and contribution thereof. It will also review the limitations of the study and propose opportunities for future research.

Importantly, the objective here is just to give the reader a taste of what’s to come (a roadmap of sorts), not a summary of the chapter. So, keep it short and sweet – a paragraph or two should be ample.

Step 2: Discuss the overall findings in relation to the research aims

The next step in writing your conclusions chapter is to discuss the overall findings of your study , as they relate to the research aims and research questions . You would have likely covered similar ground in the discussion chapter, so it’s important to zoom out a little bit here and focus on the broader findings – specifically, how these help address the research aims .

In practical terms, it’s useful to start this section by reminding your reader of your research aims and research questions, so that the findings are well contextualised. In this section, phrases such as, “This study aimed to…” and “the results indicate that…” will likely come in handy. For example, you could say something like the following:

This study aimed to investigate the feeding habits of the naked mole-rat. The results indicate that naked mole rats feed on underground roots and tubers. Further findings show that these creatures eat only a part of the plant, leaving essential parts to ensure long-term food stability.

Be careful not to make overly bold claims here. Avoid claims such as “this study proves that” or “the findings disprove existing the existing theory”. It’s seldom the case that a single study can prove or disprove something. Typically, this is achieved by a broader body of research, not a single study – especially not a dissertation or thesis which will inherently have significant  limitations . We’ll discuss those limitations a little later.

Step 3: Discuss how your study contributes to the field

Next, you’ll need to discuss how your research has contributed to the field – both in terms of theory and practice . This involves talking about what you achieved in your study, highlighting why this is important and valuable, and how it can be used or applied.

In this section you’ll want to:

• Mention any research outputs created as a result of your study (e.g., articles, publications, etc.)
• Inform the reader on just how your research solves your research problem , and why that matters
• Reflect on gaps in the existing research and discuss how your study contributes towards addressing these gaps
• Discuss your study in relation to relevant theories . For example, does it confirm these theories or constructively challenge them?
• Discuss how your research findings can be applied in the real world . For example, what specific actions can practitioners take, based on your findings?

Be careful to strike a careful balance between being firm but humble in your arguments here. It’s unlikely that your one study will fundamentally change paradigms or shake up the discipline, so making claims to this effect will be frowned upon . At the same time though, you need to present your arguments with confidence, firmly asserting the contribution your research has made, however small that contribution may be. Simply put, you need to keep it balanced .

Step 4: Reflect on the limitations of your study

Now that you’ve pumped your research up, the next step is to critically reflect on the limitations and potential shortcomings of your study. You may have already covered this in the discussion chapter, depending on your university’s structural preferences, so be careful not to repeat yourself unnecessarily.

There are many potential limitations that can apply to any given study. Some common ones include:

• Sampling issues that reduce the generalisability of the findings (e.g., non-probability sampling )
• Insufficient sample size (e.g., not getting enough survey responses ) or limited data access
• Low-resolution data collection or analysis techniques
• Researcher bias or lack of experience
• Lack of access to research equipment
• Time constraints that limit the methodology (e.g. cross-sectional vs longitudinal time horizon)
• Budget constraints that limit various aspects of the study

Discussing the limitations of your research may feel self-defeating (no one wants to highlight their weaknesses, right), but it’s a critical component of high-quality research. It’s important to appreciate that all studies have limitations (even well-funded studies by expert researchers) – therefore acknowledging these limitations adds credibility to your research by showing that you understand the limitations of your research design .

That being said, keep an eye on your wording and make sure that you don’t undermine your research . It’s important to strike a balance between recognising the limitations, but also highlighting the value of your research despite those limitations. Show the reader that you understand the limitations, that these were justified given your constraints, and that you know how they can be improved upon – this will get you marks.

Next, you’ll need to make recommendations for future studies. This will largely be built on the limitations you just discussed. For example, if one of your study’s weaknesses was related to a specific data collection or analysis method, you can make a recommendation that future researchers undertake similar research using a more sophisticated method.

Another potential source of future research recommendations is any data points or analysis findings that were interesting or surprising , but not directly related to your study’s research aims and research questions. So, if you observed anything that “stood out” in your analysis, but you didn’t explore it in your discussion (due to a lack of relevance to your research aims), you can earmark that for further exploration in this section.

Essentially, this section is an opportunity to outline how other researchers can build on your study to take the research further and help develop the body of knowledge. So, think carefully about the new questions that your study has raised, and clearly outline these for future researchers to pick up on.

Step 6: Wrap up with a closing summary

Tips for a top-notch conclusion chapter

Now that we’ve covered the what , why and how of the conclusion chapter, here are some quick tips and suggestions to help you craft a rock-solid conclusion.

• Don’t ramble . The conclusion chapter usually consumes 5-7% of the total word count (although this will vary between universities), so you need to be concise. Edit this chapter thoroughly with a focus on brevity and clarity.
• Be very careful about the claims you make in terms of your study’s contribution. Nothing will make the marker’s eyes roll back faster than exaggerated or unfounded claims. Be humble but firm in your claim-making.
• Use clear and simple language that can be easily understood by an intelligent layman. Remember that not every reader will be an expert in your field, so it’s important to make your writing accessible. Bear in mind that no one knows your research better than you do, so it’s important to spell things out clearly for readers.

Hopefully, this post has given you some direction and confidence to take on the conclusion chapter of your dissertation or thesis with confidence. If you’re still feeling a little shaky and need a helping hand, consider booking a free initial consultation with a friendly Grad Coach to discuss how we can help you with hands-on, private coaching.

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17 Comments

Really you team are doing great!

Your guide on writing the concluding chapter of a research is really informative especially to the beginners who really do not know where to start. Im now ready to start. Keep it up guys

Really your team are doing great!

Very helpful guidelines, timely saved. Thanks so much for the tips.

This post was very helpful and informative. Thank you team.

A very enjoyable, understandable and crisp presentation on how to write a conclusion chapter. I thoroughly enjoyed it. Thanks Jenna.

This was a very helpful article which really gave me practical pointers for my concluding chapter. Keep doing what you are doing! It meant a lot to me to be able to have this guide. Thank you so much.

Nice content dealing with the conclusion chapter, it’s a relief after the streneous task of completing discussion part.Thanks for valuable guidance

Thanks for your guidance

I get all my doubts clarified regarding the conclusion chapter. It’s really amazing. Many thanks.

Very helpful tips. Thanks so much for the guidance

Thank you very much for this piece. It offers a very helpful starting point in writing the conclusion chapter of my thesis.

It’s awesome! Most useful and timely too. Thanks a million times

Bundle of thanks for your guidance. It was greatly helpful.

Wonderful, clear, practical guidance. So grateful to read this as I conclude my research. Thank you.

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• How to Write a Discussion Section | Tips & Examples

How to Write a Discussion Section | Tips & Examples

Published on 21 August 2022 by Shona McCombes . Revised on 25 October 2022.

The discussion section is where you delve into the meaning, importance, and relevance of your results .

It should focus on explaining and evaluating what you found, showing how it relates to your literature review , and making an argument in support of your overall conclusion . It should not be a second results section .

There are different ways to write this section, but you can focus your writing around these key elements:

• Summary: A brief recap of your key results
• Interpretations: What do your results mean?
• Implications: Why do your results matter?
• Limitations: What can’t your results tell us?
• Recommendations: Avenues for further studies or analyses

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Table of contents

What not to include in your discussion section, step 1: summarise your key findings, step 2: give your interpretations, step 3: discuss the implications, step 4: acknowledge the limitations, step 5: share your recommendations, discussion section example.

There are a few common mistakes to avoid when writing the discussion section of your paper.

• Don’t introduce new results: You should only discuss the data that you have already reported in your results section .
• Don’t make inflated claims: Avoid overinterpretation and speculation that isn’t directly supported by your data.
• Don’t undermine your research: The discussion of limitations should aim to strengthen your credibility, not emphasise weaknesses or failures.

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Start this section by reiterating your research problem  and concisely summarising your major findings. Don’t just repeat all the data you have already reported – aim for a clear statement of the overall result that directly answers your main  research question . This should be no more than one paragraph.

Many students struggle with the differences between a discussion section and a results section . The crux of the matter is that your results sections should present your results, and your discussion section should subjectively evaluate them. Try not to blend elements of these two sections, in order to keep your paper sharp.

• The results indicate that …
• The study demonstrates a correlation between …
• This analysis supports the theory that …
• The data suggest  that …

The meaning of your results may seem obvious to you, but it’s important to spell out their significance for your reader, showing exactly how they answer your research question.

The form of your interpretations will depend on the type of research, but some typical approaches to interpreting the data include:

• Identifying correlations , patterns, and relationships among the data
• Discussing whether the results met your expectations or supported your hypotheses
• Contextualising your findings within previous research and theory
• Explaining unexpected results and evaluating their significance
• Considering possible alternative explanations and making an argument for your position

You can organise your discussion around key themes, hypotheses, or research questions, following the same structure as your results section. Alternatively, you can also begin by highlighting the most significant or unexpected results.

• In line with the hypothesis …
• Contrary to the hypothesised association …
• The results contradict the claims of Smith (2007) that …
• The results might suggest that x . However, based on the findings of similar studies, a more plausible explanation is x .

As well as giving your own interpretations, make sure to relate your results back to the scholarly work that you surveyed in the literature review . The discussion should show how your findings fit with existing knowledge, what new insights they contribute, and what consequences they have for theory or practice.

Ask yourself these questions:

• Do your results support or challenge existing theories? If they support existing theories, what new information do they contribute? If they challenge existing theories, why do you think that is?
• Are there any practical implications?

Your overall aim is to show the reader exactly what your research has contributed, and why they should care.

• These results build on existing evidence of …
• The results do not fit with the theory that …
• The experiment provides a new insight into the relationship between …
• These results should be taken into account when considering how to …
• The data contribute a clearer understanding of …
• While previous research has focused on  x , these results demonstrate that y .

Even the best research has its limitations. Acknowledging these is important to demonstrate your credibility. Limitations aren’t about listing your errors, but about providing an accurate picture of what can and cannot be concluded from your study.

Limitations might be due to your overall research design, specific methodological choices , or unanticipated obstacles that emerged during your research process.

Here are a few common possibilities:

• If your sample size was small or limited to a specific group of people, explain how generalisability is limited.
• If you encountered problems when gathering or analysing data, explain how these influenced the results.
• If there are potential confounding variables that you were unable to control, acknowledge the effect these may have had.

After noting the limitations, you can reiterate why the results are nonetheless valid for the purpose of answering your research question.

• The generalisability of the results is limited by …
• The reliability of these data is impacted by …
• Due to the lack of data on x , the results cannot confirm …
• The methodological choices were constrained by …
• It is beyond the scope of this study to …

Based on the discussion of your results, you can make recommendations for practical implementation or further research. Sometimes, the recommendations are saved for the conclusion .

Suggestions for further research can lead directly from the limitations. Don’t just state that more studies should be done – give concrete ideas for how future work can build on areas that your own research was unable to address.

• Further research is needed to establish …
• Future studies should take into account …
• Avenues for future research include …

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Results, discussion, and conclusion, results/findings.

The Results (or Findings) section follows the Methods and precedes the Discussion section. This is where the authors provide the data collected during their study. That data can sometimes be difficult to understand because it is often quite technical. Do not let this intimidate you; you will discover the significance of the results next.

The Discussion section follows the Results and precedes the Conclusions and Recommendations section. It is here that the authors indicate the significance of their results. They answer the question, “Why did we get the results we did?” This section provides logical explanations for the results from the study. Those explanations are often reached by comparing and contrasting the results to prior studies’ findings, so citations to the studies discussed in the Literature Review generally reappear here. This section also usually discusses the limitations of the study and speculates on what the results say about the problem(s) identified in the research question(s). This section is very important because it is finally moving towards an argument. Since the researchers interpret their results according to theoretical underpinnings in this section, there is more room for difference of opinion. The way the authors interpret their results may be quite different from the way you would interpret them or the way another researcher would interpret them.

Note: Some articles collapse the Discussion and Conclusion sections together under a single heading (usually “Conclusion”). If you don’t see a separate Discussion section, don’t worry.  Instead, look in the nearby sections for the types of information described in the paragraph above.

When you first skim an article, it may be useful to go straight to the Conclusion and see if you can figure out what the thesis is since it is usually in this final section. The research gap identified in the introduction indicates what the researchers wanted to look at; what did they claim, ultimately, when they completed their research? What did it show them—and what are they showing us—about the topic? Did they get the results they expected? Why or why not? The thesis is not a sweeping proclamation; rather, it is likely a very reasonable and conditional claim.

Nearly every research article ends by inviting other scholars to continue the work by saying that more research needs to be done on the matter. However, do not mistake this directive for the thesis; it’s a convention. Often, the authors provide specific details about future possible studies that could or should be conducted in order to make more sense of their own study’s conclusions.

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Trikalinos TA, Dahabreh IJ, Lee J, et al. Defining an Optimal Format for Presenting Research Needs [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2011 Jun. (Methods Future Research Needs Reports, No. 3.)

Defining an Optimal Format for Presenting Research Needs [Internet].

Discussion and conclusions.

Future research needs recommendations are valuable inputs for researchers, funders, and advocates making decisions about avenues for future scientific exploration. We performed an empirical evaluation of the published literature to appreciate the variability in the presentation of information on future research needs. We found that most systematic reviews, meta-analyses, or economic analyses do not focus on future research needs, and any referral to future research is most often cursory. Systematic reviews and meta-analyses often call for additional randomized trials, while economic analyses are more diverse in their suggestions.

In qualitative discussions with experts, we identified a number of general themes. The discussions were quickly saturated, and while additional one-to-one interviews could have generated more themes, it is unclear whether these would have been of major importance for defining the optimal format for presenting future research needs. An unanticipated theme from the qualitative interviews was that specificity in the recommendations for future research is not universally and unconditionally viewed as a desirable attribute. The rationale is that specific descriptions could be perceived as too prescriptive or restrictive, and in the extreme they may have unintended consequences, such as opposing the paradigm of investigator-initiated research. Experts disagreed on the importance of this point. Nevertheless it is probably prudent to take this point into account when reporting assessments of future research needs, and all experts agreed that proper framing of the future research needs documents could address this concern. A survey of a large and representative sample of potential users of future research needs assessments would clarify whether such reactions are prevalent. If yes, it would be also interesting to understand why some users are prone to seeing even moderately specific recommendations with skepticism. Ideology, cultural norms, or professional self-interests may be explanations.

Several limitations need to be considered when interpreting our results. First, we only recruited four experts for our qualitative interviews; hence, our results should be considered hypothesis forming and not representative of all stakeholders. However, the purpose of the qualitative interviews was to identify general themes with respect to the way different stakeholders would approach a document presenting and discussing future research needs, and not necessarily to get a representative quantification of different opinions. The optimal research design to quantify the frequency of different opinions is a survey using a representative sampling scheme, rather than qualitative interviews or even focus groups.

Regarding our empirical assessment of secondary research manuscripts, we focused on high impact general journals (for systematic reviews) or highly specialized technical journals (for cost-effectiveness/utility analyses). Thus our empirical assessment of future research presentation is not be generalizable to all journals. If anything, because even in these “top-tier” journals the presentation of implications for future research was fairly cursory and informal, the situation is unlikely to be better in other research outlets. Further, determining future research needs is not the primary focus of systematic reviews and cost-effectiveness/utility analyses. Therefore it is doubtful that including a broader set of journals would change the essence of our conclusions.

The concept of a stand-alone document on future research needs is probably new to most of the individuals approached, and additional discussion is likely needed regarding potential uses prior to making very specific recommendations on the optimal presentation of future research needs documents. We outline the following preliminary recommendations for presenting future research needs documents, based on the results of the empirical assessment and the qualitative interviews:

• Provide succinct yet adequate description of methods and results, following guidelines for reporting of health care research (for example, reporting guidelines for qualitative research 8–11 and modeling 12–15 ). Aim for a level of detail similar to that found in papers addressed to a general medical audience.
• Be cognizant of the importance of the face validity of the process. Justify the selection of the stakeholders who participated in the identification or prioritization of research needs, and be clear about their degree of engagement.
• Consider reporting the results of the future research needs assessment at two levels of detail. A suggestion would be to first present general areas that merit future research without specifying research designs or specific details on, for example, PICO elements. A second set of results could elaborate further on potential research designs, details on PICO elements, or other details as applicable.
• Frame the more specific set of results as “examples” rather than strict recommendations.
• Avoid explicit prioritization of research needs when there are no clear differences in the perceived strength of alternative recommendations. A general prioritization of future research recommendations as of “high,” “medium,” or “low” importance may be more appropriate than an explicit numerical ranking. Consider a grouped presentation of future research needs by thematic entities.
• Clearly define how the feasibility of future research was assessed. It may be instructive to perform power analyses for specific research designs for a range of assumptions, and to compare the results with the size and type of existing studies in the field. For example, trials are typically more resource-intensive than secondary analyses of existing data.
• Cite this Page Trikalinos TA, Dahabreh IJ, Lee J, et al. Defining an Optimal Format for Presenting Research Needs [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2011 Jun. (Methods Future Research Needs Reports, No. 3.) Discussion and Conclusions.
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• Published: 18 May 2024

Genomic identification and evolutionary analysis of chemosensory receptor gene families in two Phthorimaea pest species: insights into chemical ecology and host adaptation

• Ruipeng Chen 1 ,
• Junjie Yan 1 ,
• Jacob D. Wickham 2 , 3 &
• Yulin Gao 1  

BMC Genomics volume  25 , Article number:  493 ( 2024 ) Cite this article

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Insects rely on sophisticated sensitive chemosensory systems to sense their complex chemical environment. This sensory process involves a combination of odorant receptors (ORs), gustatory receptors (GRs) and ionotropic receptors (IRs) in the chemosensory system. This study focused on the identification and characterization of these three types of chemosensory receptor genes in two closely related Phthorimaea pest species, Phthorimaea operculella (potato tuber moth) and Phthorimaea absoluta (tomato leaf miner).

Based on manual annotation of the genome, we identified a total of 349 chemoreceptor genes from the genome of P. operculella , including 93 OR , 206 GR and 50 IR genes, while for P. absoluta, we identified 72 OR , 122 GR and 46 IR genes. Through phylogenetic analysis, we observed minimal differences in the number and types of ORs and IRs between the potato tuber moth and tomato leaf miner. In addition, we found that compared with those of tomato leaf miners, the gustatory receptor branch of P. operculella has undergone a large expansion, which may be related to P. absoluta having a narrower host range than P. operculella . Through analysis of differentially expressed genes (DEGs) of male and female antennae, we uncovered 45 DEGs (including 32ORs, 9 GRs, and 4 IRs).

Conclusions

Our research provides a foundation for exploring the chemical ecology of these two pests and offers new insights into the dietary differentiation of lepidopteran insects, while simultaneously providing molecular targets for developing environmentally friendly pest control methods based on insect chemoreception.

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Introduction

Chemical sensing in insects relies on the participation of chemoreceptor organs, which are divided into two categories: olfactory receptors and gustatory receptors [ 1 ]. The process of insect olfaction recognition is complex and involves the participation of multiple chemical sensory genes. This process occurs at the level of the peripheral olfactory nervous system and involves chemosensory genes such as odorant receptors (ORs), ionotropic receptors (IRs), and gustatory receptors (GRs), along with other chemical sensory receptor proteins that recognize odorant molecules and deliver them to receptors [ 2 ]. The main organ involved in olfaction is the antennae, while the gustatory organs include the maxillary and labial palps, proboscis [ 3 ], legs [ 4 ], and ovipositors [ 5 ]. In addition, some insects also have gustatory receptor neurons distributed on the wing margins that can function as gustatory receptors to perceive taste [ 6 ]. Many substances, such as acids, carbon dioxide or carbonic acid, and even water, can be perceived through both taste (gustation) and smell (olfaction) [ 7 ]. Due to technical limitations, there is currently more research on the process of insect olfaction than on the signal transduction pathways of gustatory receptors [ 1 ].

The length of insect ORs is about 400–450 amino acids, consisting of 7 transmembrane domains [ 8 ]. Insect odorant receptors are structurally very different from mammalian odorant receptors, which belong to the G protein-coupled receptor (GPCR) gene family and have the typical characteristics of 7 transmembrane helical domains [ 9 ]. However, insect odorant receptors have opposite topologies, with their N-terminus located inside the cell and their C-terminus located outside the cell membrane [ 10 ]. Gustatory receptors (GRs) primarily function in taste perception. Insects use GRs to assess the quality of food and their environment, as well as to avoid toxic and harmful chemicals. Some of these GRs are crucial for insects to sense CO 2 . Taste receptors are expressed on neurons of taste organs and recognize non-volatile chemicals [ 11 ]. The first GRs in insects were identified in the genome of D. melanogaster [ 2 ]. With the completion of genome sequencing for various insects, research on taste receptors has revealed that the secondary structure of taste receptors is similar to that of odorant receptors, with multiple transmembrane domains and the same membrane topology as ORs [ 12 ]. According to the nature of ligands, insect taste receptors can be classified into bitter receptors, carbon dioxide (CO 2 ) receptors, and sugar receptors. Benton et al. identified the first ionotropic receptor gene family in insects from the genome of fruit flies [ 13 ]. Current studies on the function of ionotropic receptor genes in Drosophila melanogaster suggest that IRs are only expressed on olfactory sensory neurons (OSNs) in the olfactory cone sensilla and are involved in the detection of various amine and acid compounds. In addition to olfactory perception, IRs in fruit flies also participate in taste recognition, primarily perceiving compounds such as amino acids, amines, salts, and acids, which can indicate the nutritional value and quality of food to varying degrees. Gustatory receptor neurons (GRNs) responsible for taste perception exist in various taste organs, including the labellum, pharynx, legs, wing margins, and abdomen of fruit flies. IRs have been identified in all confirmed taste organs [ 14 ]. Furthermore, some studies suggest that IRs may also be involved in the perception of temperature and humidity in the environment [ 15 , 16 , 17 ].

The potato tuber moth, Phthorimaea operculella , belongs to the family Gelechiidae in the order Lepidoptera [ 18 ]. Phthorimaea operculella is primarily a pest of potatoes but also can be found in other solanaceous crops including tomato, tobacco, pepper and cape gooseberry [ 19 ]. It has been reported that P. operculella utilizes 60 alternate hosts of cultivated and wild plants and most of them belong to the Solanaceae family [ 20 ]. Phthorimaea operculella adults lay their eggs in leaves, stems, and tubers. The immature stages mine the leaves, resulting in foliar damage and burrow into tubers. Chemical signals play a crucial role in host selection, as the detection of plant odours could prompt the female to seek out the most suitable host for her offspring [ 19 ]. Numerous studies have found a direct correlation between the quantity of captured adults and the abundance of larvae on both the leaves and tubers [ 21 ]. The tomato leaf miner Phthorimaea absoluta belongs to same family Gelechiidae and order Lepidoptera and is also a significant insect pest that severely damages tomato crops. The pest was initially discovered in South America and quickly spread worldwide [ 22 ]. Solanaceous species are the main host plants for P. absoluta , with tomato, potato, and Solanum nigrum being the most preferable [ 23 ], but can also lay eggs and develop on various plants from the Amaranthaceae, Convolvulaceae, Fabaceae, and Malvaceae families [ 24 ]. Since the 1950s, P. absoluta has become a major pest of tomato crops in South America. Phthorimaea absoluta primarily damages host plants in their larval stage. The larvae create a narrow leaf mine by mining the leaf mesophyll when feeding and when populations are at high density, the larvae delve beneath sepals, mining through axillary buds in young stems and/or tomato fruits. When infesting potato plants, P. absoluta only feeds on the aboveground parts and does not damage the tubers and this can be a distinguishing characteristic from P. operculella [ 25 ].

Although high-quality genome data for P. operculella and P. absoluta have been published [ 26 ], our understanding of the chemosensory genes of these two insects remains limited. He et al. sequenced the antennal transcriptome of P. operculella and analyzed the function of the sex pheromone receptor PR in P. operculella [ 27 ]. Li et al. analyzed the types and functions of odorant-binding proteins (OBPs) in P. operculella , providing important insights for the study of the chemical ecology of P. operculella [ 28 ] . To further investigate the chemical ecological mechanisms of P. operculella and P. absoluta , comprehensive identification and analysis of their chemosensory genes are urgently needed and potentially of great significance.

In this study, a total of 93 ORs, 206 GRs, and 50 IRs were identified from the genome of P. operculella , while 72 ORs, 122 GRs, and 46 IRs were identified from the genome of P. absoluta . The gene structure and phylogenetic characteristics of these genes were analyzed. Transcriptional profiling of chemosensory receptor genes from P. operculella at different developmental stages and chemosensory organs was conducted. Through differential expressed genes (DEGs) analysis of male vs. female antennae, we found that 32 ORs, 9 GRs, and 4 IRs were DEGs. This study provides a foundation for further research on the chemosensory gene characteristics of P. operculella and P. absoluta .

Identification of chemosensory receptor genes

Candidate odorant receptors.

Genome analysis of P. operculella led to the identification of 93 OR genes containing one co-receptor PopeORco with 92 odorant receptors named PopeOR1 to PopeOR92. Through the combined analysis of the antennal transcriptome and genome, the ORs of the potato tuber moth were well annotated. The 93 odorant receptor genes we identified. Based on transcriptome information and comparative analysis with homologous receptor genes, 75 PopeORs have predicted full-length sequences, with the possibility of having 3–8 transmembrane helical domains. Using similar methods, we annotated 72 odorant receptor genes from the genome of P. absoluta through the homology annotation pipeline. These genes include one PabsORco gene and 71 odorant receptor genes named PabsOR71 ~ PabsOR72 (Additional file 2: Table S2).

We performed an approximate maximum likelihood phylogenetic analysis of the odorant receptors (ORs) identified in P. operculella and P. absoluta , along with other publicly available ORs from Lepidopteran species. We observed that 24 PopeORs (PopeOR18 ~ 22, PopeOR24 ~ 25, PopeOR30, PopeOR39, PopeOR55 ~ 62, PopeOR78 ~ 80, and PopeOR85 ~ 86, PopeOR91 ~ 92,) and 7 PabsORs (PabsOR8 ~ 13, PabsOR18) cluster together with the Lepidopteran pheromone receptors (PRs) clade (Table  1 , Fig.  1 ). Additionally, we found that PopeORs and PabsORs have a greater number of OR orthologs. Furthermore, they each exhibit at least one species-specific branch, indicating their distinct evolutionary trajectory (Fig.  1 ).

The phylogenetic tree of odorant receptors in Lepidoptera species. The gray dots denote > 70% bootstrap support values. Shaded colors indicate different kinds of ORs: Yellow (ORco clade), and light blue (PR clade). Asterisks represent DEGs in antennae, black asterisks indicate higher expression in females, while blue asterisks indicate differential expression in males

Candidate gustatory receptors

A total of 206 gustatory receptors (GRs) were identified from the genome of P. operculella , 194 of which have full-length ORFs ranging from 227 to 580 aa in length. Twelve of these 206 GR sequences are partial sequences. Transmembrane domain (TMD) prediction indicates that these full-length PopeGR genes have 4–9 TMDs (Additional file 2: Table S2). A total of 122 GRs were annotated from the genome of P. absoluta , and all had intact ORFs encoding protein lengths from 209 to 652 aa which have 4 ~ 9 TMDs. For the nomenclature of PopeGRs and PabsGRs , we numbered the genes according to their position information on chromosomes. All details about gene information and the structure of gustatory receptor genes are shown in Additional file 2: Table S2.

A phylogenetic analysis was performed by combining the gustatory receptor sequences from of P. operculella , P. absoluta , Bombyx mori , 69 sequences from Plutella xylostella , 45 sequences from Manduca sexta , and Heliconius melpomene. The ML tree showed that: 11 PopeGRs (PopeGR173 ~ 183) and 12 PabsGRs (PabsGR043 ~ 54) clustered to sugar receptors, 12 PopeGRs (PopeGR125 ~ 126) and 7 PabsGRs (PabsGR62 ~ 68) clustered with the fructose receptor, 4 PopeGRs (PopeGR001, PopeGR042, PopeGR104, and PopeGR107) and 4 PabsGRs (PabsGR002, PabsGR011, PabsGR016, and PabsGR026) clustered with the carbon dioxide receptors, and PopeGRs and PabsGRs clustered with the bitter receptor’s clade (Table  1 , Fig.  2 ).

The phylogenetic tree of gustatory receptors in Lepidoptera species. The gray dots denote > 70% bootstrap support values. The shaded colours indicate different types of GRs. Asterisks represent DEGs in antennae, black asterisks indicate higher expression in females, while blue asterisks indicate differential expression in males

Candidate ionotropic receptors

Overall, we have provided comprehensive descriptions of 50 and 46 IR genes in P. operculella and P. absoluta , respectively, through our annotations (Additional file 2: Table S2). The IR gene structure of P. operculella consisted of 1 to 20 exons, with 26 genes having no introns among the 50 IR genes. Eight genes had a higher number of introns (≥ 14). The average length of these PopeIRs was 659 amino acids (aa), and the length of individual gene models ranged from 389 to 1063 aa (Additional file 2: Table S2). We did not find any evidence of pseudogene or alternative splicing from the P. operculella genome and transcriptome data. All the annotated PopeIRs were full-length. The IR gene structure of P. absoluta consisted of 1 to 19 exons, with 23 genes having no introns among the 46 IR genes. Six genes had a higher number of introns (≥ 14). The average length of these PabsIRs was 649 aa, and the length of individual gene models ranged from 391 to 1000 aa (Additional file 2: Table S2). From the Pabs genome, we found that PabsIR93a.1 might be a pseudogene, while the remaining 45 PabsIR genes had complete ORFs (Additional file 2: Table S2).

Phylogenetic analysis and ionotropic receptors from Drosophila melanogaster [ 29 ] and three Lepidoptera species, including H. melpomene [ 30 , 31 , 32 ], B. mori [ 30 , 31 , 33 ], and S. litura [ 34 , 35 , 36 ]. The phylogenetic results showed that P. operculella and P. absoluta have conserved co-receptors IR8a, IR25a, IR76b, and IR93a; In P. operculella , 16 candidate PopeIRs were clustered with the “antennal IRs” clade, including PopeIR31a.1/2, PopeIR75p.1/2/3, PopeIR75q.1/2/3, PopeIR75d.1/2, PopeIR21a, PopeIR68a, PopeIR40a, PopeIR60a, PopeIR64a, PopeIR41a, while 25 PopeIRs (PopeIR100c ~ r, PopeIR7d.1/2a/2b/3/4, PopeIR85a, and PopeIR143.1/2/3) belong to the "divergent IRs" family (Fig.  3 ). The PopeIR1.1/2, PopeIR2, PopeIR100a, and PopeIR87a belong to "Lepidopteran-specific IRs ". In contrast, for P. absoluta , 22 PabsIRs were found to belong to the D-IRs branch, including PabsIR100c ~ q, PabsIR143.1/2, PabsIR85a, and PabsIR7d.1 ~ 4. Five PabsIRs (PabsIR1.1, PabsIR1.2, PabsIR100a, PabsIR2, and PabsIR87a) were classified as LS-IRs. Additionally, 15 PabsIRs (PabsIR21a, PabsIR31a.1/2, PabsIR40a, PabsIR41a.1, PabsIR60a, PabsIR64a, PabsIR68a, PabsIR75d, PabsIR75p.1/2/3, PabsIR75q.1/2/3) belong to the antennal IR clade (Fig.  3 ).

The phylogenetic relationships of ionotropic receptors between Lepidoptera and Diptera species. Gray dots denote > 70% bootstrap support values. Shaded colours indicate different types of IR genes: Divergent IRs (D-IRs clade), Antennal IRs (A-IRs clade), Lepidoptera-specific IRs (LS-IRs clade), Co-Receptor IR genes (IR25a/8a, andIR76b//93a clade)

Chromosomal distribution map of GRs

The gustatory receptor (GRs) genes of P. operculella were mapped on the chromosomes. The number of chromosomes in P. operculella was 29, and the 206 identified GR sequences were distributed on 23 different chromosomes and 8 scaffolds, which include chromosomes 1, 2, 3, 4, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 18, 19, 20, 21, 22, 23, 24, 25, 27, Scaffold00199, Scaffold00287, Scaffold00338, Scaffold00340, Scaffold00365, Scaffold00394, Scaffold00437, Scaffold00625 (Fig.  4 and Additional file 2: Table S2).

Chromosomal distribution map of PopeGR genes. The sugar receptors are marked in blue, fructose receptor is marked in red, and carbon dioxide receptors are marked in magenta

Overall, the distribution of GR genes in the genome of P. operculella is relatively discrete. The number of GR genes on chromosomes 3, 13 and 20 is significantly higher than on other chromosomes, and there is a taste receptor expansion phenomenon on these chromosomes, which is speculated to be produced by large-scale replication of genes. The distribution of sugar receptors in P. operculella is relatively concentrated: all are located on Chromosome 24. Fructose receptors are located on chromosome 20. PTM carbon dioxide receptor distribution is relatively scattered, with four carbon dioxide receptors distributed on chromosomes 1, 2, 14 and 15. The bitter taste receptor in the genome of P. operculella is also relatively scattered. There is a large-scale amplification phenomenon of bitter receptors on chromosomes 13 and 20, which corresponds to the results of systematic evolution analysis (Figs.  2 and  4 ).

The 122 identified gustatory receptor (GRs) genes of P. absoluta were mapped on chromosomes, and it was found that PabsGRs were distributed on the following 20 chromosomes: 1, 2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 19, 20, 21, 22, and 23 (Fig.  5 and Additional file 2: Table S2). Overall, the distribution of GR genes in the genome of P. absoluta is also relatively discrete. Among them, the number of GR genes on chromosomes 2, 3, 8 and 21 is significantly higher than on other chromosomes, and there is also an expansion of taste receptors on these chromosomes. The distribution of sugar receptors in P. absoluta is also relatively concentrated, but unlike P. operculella , all sugar receptors in P. absoluta are located on chromosome 2. However, the fructose receptor of P. absoluta is also located on chromosome 20. The distribution of carbon dioxide receptors in P. absoluta is relatively scattered, with four carbon dioxide receptors distributed on chromosomes 1, 11, 12 and 15 respectively. The bitter taste receptors in P. absoluta are also scattered in the genome, with large-scale amplification of bitter receptors on chromosomes 3 and 8 (Fig.  5 ).

Chromosomal distribution map of PabsGR genes. The sugar receptors are marked in blue, fructose receptor is marked in red, and carbon dioxide receptors are marked in magenta

Analysis of potato tuber moth chemosensory organs transcriptome

We collected and analyzed 11 chemical sensory organs of P. operculella , including larval head, adult female antennae, head, legs, and ovipositor, and adult male antennae and genitalia. Through transcriptome sequencing, we obtained a total of 1425.37 million raw reads. After the adapters and low-quality raw reads were filtered out, we obtained 1410.44 million clean reads. In addition, the average Q30 base percentage after filtering was 93.22% (see Additional file 3: Table S3). When the clean reads were aligned to the reference genome of P. operculella , the average alignment rate (percentage of aligned reads to clean reads) of the samples was 86% (Additional file 4: Table S4). The raw reads were deposited in the National Center for Biotechnology Information (NCBI) Sequence Read Archive (SRA) database with submission number PRJNA1074269. Gene expression levels of all chemosensory receptor genes based on the transcripts per million (TPM) value are represented in Table S5.

The expression level analysis of odorant receptor genes showed that almost all ORs were enriched in the antennae. Only one OR ( PopeOR85 ) was not detected in any tissue. PopeORco displayed the highest expression level in both male and female antennae, but no expression was detected in the legs. Two ORs ( PopeOR33 and PopeOR77 ) were expressed in all tissues, with PopeOR33 highly expressed in the head of mature larvae, and PopeOR77 highly expressed in the adult antennae (Fig.  6 A and Additional file 5: Table S5). The results of OR expression analysis also showed that 53 ORs were detected in the head of larvae, while 88 ORs were detected in the chemosensory tissues of adults. There were 49 ORs expressed throughout the entire larval and adult stages, 4 ORs ( PopeOR3 , PopeOR27 , PopeOR54 , PopeOR85 ) expressed only during the larval period, and 39 ORs expressed only during the adult period (Fig.  6 D and Additional file 5: Table S5). Through DEGs analysis, it was found that 12 PRs ( PopeOR18 - 20 , PopeOR25 , PopeOR30 , PopeOR39 , PopeOR61 - 62 , PopeOR78-80 , PopeOR91 ) had higher expression levels in the antennae of males than females. The remaining 12 PRs had no significant difference in expression levels between the two sexes. Thirteen ORs ( PopeOR15 , PopeOR16 , PopeOR31 , PopeOR37 , PopeOR45 , PopeOR47 , PopeOR67-68 , PopeOR75 , PopeOR84 , PopeOR87 - 88 , PopeOR90 ) had significantly higher expression levels in female antennae than males (Fig.  6 A and Additional file 6: Table S6).

Analysis of expression patterns of chemosensory receptor genes in Phthorimaea operculella . All expression values are represented as normalized TPM (Log10 (TPM + 0.001)), and the colour represents the expression level, with red representing high expression and dark green representing low expression. A Heat map of expression levels of odorant receptor genes in P. operculella ; B ) Heat map of expression levels of ionotropic receptor genes in P. operculella ; C ) Phylogenetic tree and heat map of gustatory receptor genes in P. operculella , with bootstrap values shown as numbers in the figure, using IQ-Tree, with 1000 bootstraps for tree construction; D ) Expression information of ORs in adult and larval stages; E ) Expression information of IRs in adult and larval stages; F Expression information of GRs in adult and larval stages: The abbreviations and names of each tissue are as follows: L1: first-instar larvae, L2H: second-instar larvae heads, L3H: third-instar larvae heads, L4H: fourth-instar larvae heads, LL4H: mature larvae heads, FAn: female adult antennae, Man: male adult antennae, FHe: female adult heads, FFo: female adult legs, FOv: female adult ovipositors, MGl: male adult reproductive organs

The expression analysis of ionotropic receptor genes showed that the main antennal IRs were enriched in the antennae, while the expression levels of divergent IRs, which are specific to Lepidoptera, did not show obvious tissue specificity. Interestingly, we found that some antennal IRs, including the PopeIR25a/76b clade, PopeIR75d clade, PopeIR64a clade, and divergent IRs (PopeIR7d.3), had high expression levels in all tissues (Fig.  6 B and Additional file 5: Table S5). The results of IR expression analysis also showed that 47 IRs were detected in the head of larvae, while 46 IRs were detected in the chemosensory tissues of adults. All IRs were expressed throughout the entire larval and adult stages, while 4 IRs expressed only during the larval period and 3 IRs expressed only during the adult period (Fig.  6 E and Additional file 5: Table S5). Six A-IRs (PopeIR75p.2, PopeIR31a.1, PopeIR31a.2, PopeIR75q.2, PopeIR60a) and three LS-IRs (PopeIR1.1, PopeIR1.2, PopeIR87a) were mainly expressed in adult tissues. Two LS-IRs (PopeIR100a PopeIR2) and seven D-IRs (PopeIR100g, PopeIR100n, PopeIR100m, PopeIR100r, PopeIR143.2, PopeIR100k, PopeIR7d.2b) were mainly expressed in larval tissues (Fig.  6 B). The analysis of DEGs in male and female antennae showed that four A-IRs (PopeIR40a, PopeIR75d.2, PopeIR75p.1, PopeIR75p.2) had significantly higher expression levels in female antennae than in male antennae (Table S6).

The results of GRs expression analysis also showed that 148 GRs were detected in the head of larvae, while 152 GRs were detected in the chemosensory tissues of adults. There were 182 GRs expressed throughout the entire larval and adult stages, 30 GRs expressed only during the larval period, and 34 GRs expressed only during the adult period (Fig.  6 C and F). Among these GRs, four carbon dioxide receptors in potato tuber moth were expressed in adult and larval tissues, of which PopeGR107 was only detected in the antennae of female adults and the heads of L1 ~ 4 larvae, while PopeGR042 was mainly expressed in adult tissues than in larvae. All sugar receptors had higher expression levels in adult tissues than in larvae. The sugar receptor PopeGR182 had higher expression levels in the heads of 1st instar larvae, 3rd instar larvae and female adults. The fructose receptor PopeGR127 was expressed in various tissues, with higher expression levels in the antennae of the adult and female heads (Fig.  6 C). The expression analysis of these bitter gustatory receptors revealed that four bitter taste receptors (PopeGR022, PopeGR024, PopeGE156, PopeGR161) had high expression levels in all tissues (Fig.  6 C). From Fig.  6 C, the constructing an evolutionary tree of 206 PopeGRs and labelling their expression information shows these bitter receptors cluster on one branch of the evolutionary tree and have similar expression patterns, such as the bitter taste receptor PopeGR015 ~ PopeGR019 branch all being highly expressed in adult tissues.

The analysis of DEGs in male and female antennae revealed distinct patterns. Female adults exhibited significantly higher expression levels of four sugar receptors PopeGRs (PopeGR173–175, PopeGR181) and fructose receptor PopeGR127 in their antennae compared to male adults. On the other hand, the sugar receptor PopeGR177 had significantly higher expression levels in the antennae of male adults compared to female adults. Additionally, among the bitter taste receptors, PopeGR027, PopeGR102 and PopeGR111 exhibited significantly higher expression levels in the antennae of female adults compared to male adults (Fig.  6 C and Table S6).

The development of sequencing technology has made it possible to study the size and evolutionary relationships of chemosensory gene families of different species [ 1 , 37 ], providing a good reference to annotate and study the evolution of chemosensory genes in two Phthorimaea pests. In this study, we conducted genome-based identification of chemosensory receptor genes in P. operculella and P. absoluta . Our objective was to investigate the numbers, types, and evolutionary relationships of chemosensory receptor-related genes in two closely related Phthorimaea pests with similar habits and evolutionary relationships. By manually annotating the genomes of these two insect species, we identified 349 (93 PopeORs , 206 PopeGRs , 50 PopeIRs ) and 240 (72 PabsORs , 122 PabsGRs , 46 PabsIRs ) candidate chemosensory receptor genes from the genomes of P. operculella and P. absoluta , respectively. These data allow exploration of the molecular mechanisms underlying their mutual adaptation and competition. Furthermore, we hope that this study will lay the foundation for further research in their chemical ecology and the development of environmentally friendly pest control techniques based on insect olfaction.

A complete annotation of odorant receptors in two Phthorimaea pests provides insights for inter-specific competition and host selection

Researchers have found that insect ORs are a highly variable family of receptor genes by comparing the sequences of various insect ORs. A total of 79 different ORs were discovered in the genome of Anopheles gambiae [ 38 , 39 ]. By comparing the OR families of D. melanogaster and A. gambiae , it was found that although both belong to Diptera, their OR sequences differ greatly, and there is gene expansion to varying degrees in each OR subfamily (Fig.  7 ) [ 39 ]. Some insects with complex environments, such as the red wood ant Pogonomyrmex barbatus , have up to 345 ORs. However, an exception was found in Tribolium castaneum , a storage pest that can complete its entire life cycle within a limited food range. Despite this, it has 245 ORs, suggesting that its environment may be relatively complex, and adults rely on a well-developed olfactory system to locate food resources [ 40 , 41 ]. These findings reflect that the number and sequence of ORs are generally adapted to the ecological needs of each species. Research on the number and phylogenetic analysis of insect ORs can provide valuable information on the evolution and functional differentiation of insect ORs [ 42 ]. From the number of ORs in P. operculella and P. absoluta , it can be seen that P. operculella (93 ORs) has a larger number of odorant receptor genes compared to B. mori (71 ORs) [ 30 , 33 ], H. melpomene (70 ORs) [ 30 ], and P. absoluta (72 ORs), and is comparable to the number of genes in P. xylostella (95 ORs ) [ 43 ]. Evolutionary analysis of these ORs revealed that the pheromone receptor branches in these lepidopteran insects are relatively conserved and clustered together, which is consistent with previous studies [ 44 ]. Among them, the PR branch of P. operculella showed species-specific expansion with a total of 24 branches, and the bootstrap values for these branches were all above 70%. Similar results were reported in P. xylostella , where Engsontia et al . identified many species-specific branch expansions in the PR. However, due to the lack of functional evidence, these branches were temporarily classified as putative PR branches [ 43 ]. For consideration for classification as candidate pheromone receptors, at least one of them should exhibit male-specific expression associated with hairy sensilla, according to the idea proposed by Koenig et al. [ 45 ]. Therefore, in this study, these ORs are also temporarily classified as PR branches, and further functional studies are needed to analyze the expression and functional characteristics of these putative PRs. However, in P. absoluta , we only identified seven PRs and uncovered evidence of a close evolutionary relationship between the two species in terms of PRs. In addition, the large number of expanded branches in PopePRs suggests that there are also large differences in the recognition of sex pheromone components between the two species. For example, Chang et al. studied the PRs of two Helicoverpa species and found that functional studies of the PRs of two closely related moths, Helicoverpa armigera and H. assulta , revealed that homologous PRs have maintained functional consistency during the evolutionary process, although most of the similar receptors have maintained functional consistency, however, there is also the possibility that species divergence events may have caused certain PR direct homologs to produce functional consistency [ 46 ].

Insect chemosensory receptors gene family statistics. The numbers indicate genes and numbers in parentheses indicate pseudogenes. ORs indicate olfactory receptors, GR indicates gustatory receptors, and IRs indicate ionotropic receptors

Through expression profile analysis of these PopePRs, we found that not all the predicted PRs exhibited male-biased expression in the male moths of the potato tuber moth, with only 12 PRs showing male-specific or highly expressed patterns. This indicates that these PRs may be involved in male perception of female sex pheromones. Other PRs did not show significant expression preferences. The study by Wan et al. on the codling moth demonstrated that the sex pheromone receptor branch of CpomOR3a and CpomOR3b exhibited female-biased expression, and these PRs were not only involved in sex pheromone perception but also the perception of host plant volatiles [ 47 ]. Therefore, it can be speculated that the function of these PopePRs is that they do not exhibit clear male-biased expression preferences. In addition to participating in the perception of sex pheromones, these PRs may also be involved in the perception of other chemical cues from sources such as host plant volatiles. In addition, in B. mori , studies have found that BmorOR19, BmorOR45, and BmorOR47 are receptors that show female-biased expression. They respond to aromatic volatile compounds such as linalool, benzoic acid, and benzaldehyde. It has been suggested that these receptors may be involved in regulating oviposition behaviour or detecting male sex pheromones [ 48 ]. According to DEGs analysis, we found 13 PopeORs that showed significantly higher expression levels in female antennae. It is speculated that these PopeORs may be involved in the oviposition behaviour of females. PopeOR77 is highly expressed throughout the growth and development stages. Interestingly, PopeOR77 and BmorOR66 cluster together on the same branch. BmorOR56 has a similar expression pattern in the silkworm and is highly sensitive to cis-jasmone and is involved in the chemo-attraction response to cis-jasmone [ 33 ]. This suggests that PopeOR77 in P. absoluta is likely to have similar biological functions as BmorOR77 in the silkworm.

The extensive expansion and expression pattern analysis of bitter taste receptors provide new insights into the mechanisms of host adaptation in oligophagous insect species

Insect GRs can detect non-volatile compounds in the environment through contact chemosensation of amino acids, sugars, bitter substances, and some plant secondary metabolites. Each species has a unique number of GRs. Engsontia et al. suggested that the expansion of Gr genes is mainly due to extensive gene duplications and relatively few gene losses [ 43 ]. In addition, it has been shown that the total number of GRs may be closely related to species behaviour and their ecological adaptation. For example, in model species such as fruit flies and mosquitoes ( D. melanogaster and Anopheles gambiae ), 60 and 76 Gr genes have been identified, respectively. In a human parasitic louse Pediculus humanus, only 6 GR genes were found, indicating a correlation between the low number of GRs and the simple environment needed for this insect to survive [ 49 ]. Helicoverpa armigera is currently reported to have the highest number of gustatory receptors, with 213 GRs identified (Fig.  7 ) [ 50 ]. In some lepidopteran species with narrower host range, such as B. mori , 76 GRs have been identified [ 51 ], while D. plexippus has 64 GRs [ 32 , 52 ], Heliconius melpomene has 70 GRs [ 30 ], and P. xylostella has 69 GRs [ 43 ]. Among these four species, the silkworm feeds exclusively on mulberry leaves [ 48 , 53 ], D. plexippus feeds only on plants of the Asclepiadaceae family [ 52 ], the Heliconius melpomene feeds exclusively on Passiflora oerstedii or P. menispermifolia [ 30 ], and P. xylostella only feeds on plants of the Brassicaceae family [ 54 ]. Therefore, the expansion of 213 GRs in the cotton bollworm may be related to its feeding habits, as the extensive expansion of GR branches may enhance its ability to perceive a wide range of host plant metabolites, facilitating its survival on various host species [ 50 ]. In our study, we found an interesting phenomenon: the number of GRs identified in the specialist herbivore P. operculella is much higher than those in the generalist herbivore P. absoluta . Phylogenetic analysis of their GRs revealed no significant differences in the number of carbon dioxide receptors, sugar receptors, and two types of gustatory receptors. Furthermore, through expression studies, it has been found that the differential expression of taste receptor genes on the antennae of the potato tuber moth is mainly related to sugar receptors and fructose receptors. It is speculated that this may be associated with the adult insects' need for increased sugar perception to supplement the energy required for mating, oviposition, and flight, especially in females. Interestingly, we observed that more than half of the female moths showed a preference for the expression of genes enriched in sugar receptors. In our analysis of fructose receptor expression in the potato tuber moth, we found that the PopeGR127 fructose receptor gene is expressed to varying degrees in chemosensory tissues at different developmental stages. Other putative fructose receptors are predominantly expressed in the heads of larvae, suggesting their possible involvement in regulating feeding-related behaviours. Further research is needed to investigate the expression and functional characteristics of these sugar receptors in the gut and other tissues. In addition, there is substantial evidence of expansion in the fructose receptor branch of the potato tuber moth, a conserved class of GRs found in almost all insects. Studies of fruit flies and cotton bollworms have shown that fructose receptors may function as internal nutrient sensors, playing important roles in regulating feeding behaviour [ 55 , 56 ].

Notably, P. operculella showed a significant expansion in the branches of fructose and bitter receptors. Phthorimaea operculella is a specialized herbivorous lepidopteran insect that exclusively feeds on plants of the Solanaceae family, such as potatoes and eggplants. It is speculated that the specific expansion of bitter taste receptor branches in P. operculella helps it better perceive the various glycoalkaloids commonly present in solanaceous plants [ 57 ], allowing it to select hosts that are beneficial for its survival. The potato tuber moth may adapt to solanaceous hosts by using a large expansion of bitter receptors to selectively feed on suitable hosts or parts of plants. Analysis of DEGs (differentially expressed genes) between the sexes of the potato tuber moth revealed that three bitter taste receptor genes were highly expressed in the female antennae. We speculate that this may be related to the female moth's perception and oviposition behaviour.

Identification of the complete set of ionotropic receptors in two Phthorimaea pests provides crucial insights into their physiological characteristics and management strategies

A total of 50 and 46 IRs were identified from P. operculella and P. absoluta . This is a higher number compared to other lepidopteran species B. mori , and D. plexippus (Fig.  7 ) [ 31 ]. Ionotropic receptor genes were first identified in fruit flies and are divided into A-IRs and D-IRs [ 13 ] based on their expression characteristics and evolutionary relationships. Studies on Lepidoptera have found that insects in the Family Noctuidae have a unique IR branch called LS-IRs [ 58 ]. Subsequent studies on ionotropic receptors in Lepidoptera have found that some LS-IRs are not exclusive to the noctuids, such as IR1 [ 45 ]. Similarly, we also identified the IR1 branch in P. operculella and P. absoluta . Like the silkworm, we did not identify the 100b branch of the LS-IR in P. operculella and P. absoluta , but Zhu et al. identified the IR100b branch in S. litura . By comparing the types of D-IR receptors in P. operculella and P. absoluta , we found that the number of ionotropic receptor genes in both species was the same, and no species-specific IR receptor branches were found. The differences between the two species are mainly due to the fact that the PabsIR100c branch has four additional gene copies (PabsIR100c.1 − 4) located close to each other on the chromosome, suggesting similar physiological functions. However, we did not observe an expansion of the PopeIR100c branch in P. operculella . We found three gene copies on the PopeIR143 branch, while only one gene copy was found on the PabsIR143 branch. The same phenomenon was found in the IR75d and IR7d branches. Analysis of exon and intron structures of these two species’ IR genes revealed that the gene structures of LS-IRs (except for IR1.1 and IR1.2) and D-IRs are relatively simpler than those of conserved A-IRs, showing fewer introns or single exon structures. For example, D-IR subfamilies (except for IR85a) lack introns, while A-IR subfamilies usually have multiple introns, like fruit fly IRs [ 59 ]. Interestingly, we found one intron in two D-IRs of PabsIR (PabsIR100c.1 and PabsIR143.2). Unlike dipterans, the IR85a branch in both species' D-IRs is a single exon gene. In A-IRs, we also found that the IR68 branch is a single exon gene similar to that in Spodoptera litura ; however, the structure of IR68a is more complex and different from that in Spodoptera litura [ 35 ].

Based on the expression profile analysis of ionotropic receptors (IRs) in the chemosensory tissues of P. operculella during developmental stages, we found some interesting expression patterns. For example, IR25a, IR76b, IR8a, IR64a and IR75d were enriched in the antennae of different developmental stages. Previous studies have shown that these receptors may be involved in the olfactory and gustatory perception of acids by various insects [ 60 , 61 , 62 ]. These acids may come from the products of microbial fermentation of sugars [ 63 ]. Therefore, the conserved expression characteristics of these antennal IRs suggest that they play an important role in the perception of acids throughout the entire development of P. operculella . PopeIR7d.4, which belongs to Divergent-IR, also shows a similar expression pattern. However, there is little research on the function of Divergent-IRs in Lepidoptera, and further study is needed to determine the function of this gene. The expression pattern analysis of other D-IRs also suggests that these IRs are not enriched in adult antennae, and some are only detected in the heads of larvae, suggesting that they may be related to feeding and olfaction functions. For example, D-IRs involved in the taste perception of some fatty acids have been found in fruit flies [ 64 ]. Further research is needed to fully understand the function of D-IRs. Different Pope LS-IRs show various expression patterns. We particularly note that PopeIR100a is expressed not only in the heads of larvae but also in the female antennae of adults, suggesting that it may be related to olfaction function. However, there is limited research on its function and further functional verification is needed. The diverse expression profiles of the potato tuber moth indicate different expression patterns, which may reflect different ecological adaptation strategies and behavioural characteristics. Current research indicates that ionotropic receptor genes in insects have multiple sensory functions, including olfaction, taste, temperature, and humidity perception [ 65 ]. Specifically, IRs play a role in the temperature and humidity perception of pests, for example, IR25a and IR93a are expressed in thermosensory neurons and humidity-sensing neurons in the antennae, participating in temperature and humidity perception [ 15 ]. Furthermore, some IRs, such as IR21a, are essential for temperature-based host-seeking behavior in mosquitoes [ 66 ], while other IRs are involved in the perception of specific chemicals in the environment, such as amino acids and organic acids [ 67 , 68 , 69 ]. Some organic acids provide insects with rich information. For example, the accumulation of large amounts of acids indicates severe food resource corruption, and at the same time, the accumulation of acids is disadvantageous to the survival of insects [ 70 , 71 ]. The perception of acids helps insects assess the suitability of food resources and help them to avoid eating toxic and harmful areas. Our study shows that the homology of the ionotropic receptor gene sequences of these two pests was close, and the specific expression patterns of some ionotropic receptor genes in different tissues and developmental stages reveal that these ionotropic receptors play important roles in olfaction, gustation, and the perception of temperature and humidity. These genes can serve as potential targets for interference with the host plant recognition of these two pests, providing sufficient data support and molecular targets for further research on the development of pest management strategies.

In this study, we investigated the chemosensory receptor-related genes of P. operculella and P. absoluta in terms of their similar habits and evolutionary relationships. In addition, the odorant receptor and ionotropic receptor genes of both insect species were identified, and the close homology of these chemosensory receptor genes revealed similarities in the functions of receptors between the two species. These two types of receptors are mainly involved in olfactory perception, which also suggests the possibility of intense interspecific competition in olfactory behaviour between the two species. Our research demonstrated that the potato tuber moth has more chemosensory receptor genes (349 genes) compared to the tomato leaf miner (240). We discovered extremely large expansions of bitter receptor genes in the P. operculella compared to the P. absoluta , which may be related to the broad adaptation to solanaceous hosts of P. operculella . These research findings lay the foundation for further studies on the chemical ecology of these pests and the development of environmentally friendly pest control technologies based on insect chemosensation.

Sample collection and sequencing

Phthorimaea operculella were collected from potato fields in QuJing, Yunnan Province, China, in 2014. In the laboratory, the rearing conditions in the climate controlled chamber were as follows: temperature, 26 ± 1°C; relative humidity, 60 ± 10%; photoperiod, 12 h light: 12 h dark. The larvae were reared using potatoes and placed together with the adults in nylon cages. The amount of head tissues used for each larval stage were as follows: L1 (whole head larvae, approximately 50 individuals), L2 larvae (approximately 90 heads dissected), L3 larvae (approximately 80 heads dissected), L4 larvae and mature larvae (approximately 50 heads dissected). The antennae (80 pairs of each sex), heads (40 females), legs (40 females), male genitalia (40 males), and female ovipositors (40 females) were separately excised from 2 − 3-day-old adults and immediately frozen in liquid nitrogen and stored at − 70 ℃ until use.

The total RNA of the tissues above was separately extracted using TRIzol reagent (Invitrogen, Carlsbad, CA, USA) following the manufacturer’s instructions. RNA integrity was determined with an Agilent Bioanalyzer 2100 system (Agilent Technologies Inc., CA, USA). RNA concentration and purity were measured by a Nanodrop ND2000 spectrophotometer (NanoDrop Technologies Inc., Wilmington, DE). One microgram of total RNA per sample was used for cDNA library construction. A cDNA library was prepared using the Optimal Dual-mode mRNA Library Prep Kit (BGI, Shenzhen, China) according to the manufacturer's instructions. The library was then sequenced on the BGI MGISEQ-2000 platform (BGI, Shenzhen, China), and paired-end (150 bp) reads were generated.

Identification chemosensory genes

Comparative genomic analysis was conducted between P. operculella and P. absoluta [ 18 , 72 ]. Chemosensory gene sequences were collected from various lepidopteran species with published genome and transcriptome data, including Bombyx mori [ 30 , 31 , 33 ], Plutella xylostella [ 73 ], Chilo suppressalis [ 74 , 75 ], Ostrinia furnacalis [ 74 , 76 ], Helicoverpa armigera [ 50 ], Helicoverpa zea [ 50 ], Galleria mellonella [ 74 , 77 ], Eogystia hippophaecolus [ 78 ], Spodoptera exigua [ 74 , 79 ], Peridroma saucia [ 80 ], Carposina sasakii [ 81 ], Mythimna separata [ 82 , 83 , 84 ], Manduca sexta [ 45 , 85 , 86 ], Loxostege sticticalis [ 87 ], Danaus plexippus [ 31 , 32 , 52 ], Heliconius melpomene [ 30 , 31 , 32 ], and Spodoptera litura [ 34 , 35 , 36 ] (Additional file 1: Table S1). Next, protein sequences were obtained from the National Center for Biotechnology Information ( https://www.ncbi.nlm.nih.gov ) based on published data and manually verified to construct a reliable reference dataset.

Subsequently, a local TBLASTN (v2.14.0) analysis was performed to search candidate chemosensory genes in the genomes of P. operculella and P. absoluta , with an E-value cutoff of e −5 [ 88 ]. Based on the Blast search results, the positional information of different chemosensory genes on chromosomes or scaffolds was manually determined. The genome sequence of these candidate receptor genes was extracted using a Python script, and the coding sequences of chemosensory genes from the genomes of the two species were identified using an online server Genewise ( https://www.ebi.ac.uk/Tools/psa/genewise/ ). Furthermore, after obtaining RNA-seq data of chemosensory tissues in the potato tuber moth, we aligned the clean reads to the reference genome of the potato tuber moth using the HISAT software (v2.10) [ 89 ]. Then, we assembled the aligned reads using StingTie (v1.0.4) to reconstruct transcript information. Based on the transcript information, we corrected the sequences of chemosensory genes annotated from the genome, resulting in nearly complete genes including exon–intron boundaries and their location in the potato tuber month. Furthermore, the conserved domains of these candidate genes were confirmed using the InterPro online server ( https://www.ebi.ac.uk/interpro/search/sequence/) [ 90 ].

Sequence and phylogenetic analysis

We used the ORF prediction component of the TBtools software (v2.034) to predict the open reading frames (ORFs) of chemosensory genes in species P. operculella and P. absoluta [ 91 ]. The transmembrane helical domains (TMDs) of chemosensory genes were predicted using the online server DeepTMHMM ( https://dtu.biolib.com/DeepTMHMM ). TBtools was used to visualize the chromosomal positions of gustatory receptor genes in P. operculella and P. absoluta [ 91 ].

All chemosensory gene sequence alignments were performed by the MAFFT software (v7.490). Then, we used ModelFinder to find the best amino acid substitution model for phylogenetic analysis. The phylogenetic trees for chemosensory genes were constructed using IQ-Tree software v.2.0.7) based on the best amino acid substitution model, with 1000 bootstraps. We used the OR dataset, including sequences from Bombyx mori [ 33 ], Ostrinia furnacalis [ 76 ], Manduca sexta [ 45 ], and Heliconius melpomene [ 30 ]. The GR phylogenetic trees included sequences from Bombyx mori [ 51 ], Plutella xylostella [ 43 ], Manduca sexta , and 73 from Heliconius melpomene [ 32 ]. The IR dataset included sequences from Drosophila melanogaster [ 29 ], Heliconius melpomene [ 31 ], Bombyx mori [ 31 ], and Spodoptera litura [ 35 ]. The sequences resource of each species was collected from genome or transcriptome data (see Additional file 1: Table S1 ). The ML tree was visualized using iTOL online tools (v. 5) [ 92 ].

P. operculella ’s chemosensory genes expression analysis

We conducted a study on the developmental stages and tissue expression profiles of chemosensory genes in the potato tuber moth. The raw reads were processed using SOAPnuke software (v1.6.5) to eliminate unknown (poly N) or low-quality and adaptor sequences, resulting in clean data. Quality metrics, including Q20, Q30, and GC-content levels, were calculated for the clean data. All subsequent analyses were performed using high-quality clean data. Subsequently, the clean reads were aligned to the reference genome using STAR (2.7.10b) [ 93 ]. Furthermore, we employed RSEM to calculate the gene expression levels in each tissue [ 94 ]. Finally, the expression levels of the chemosensory genes were visualized using the pHeatmap package (v1.0.12) in R (v4.1.2). For the differentially expressed gene (DEG) analysis, we used the R package DEseq2 to analyze the number of differentially expressed chemosensory genes between female and male antennae [ 95 ]. We set | Log2 (FoldChange) |> 1, FDR < 0.05 as the threshold for screening differentially expressed genes.

Availability of data and materials

No datasets were generated or analysed during the current study.

Abbreviations

Odorant receptors

Gustatory receptors

Ionotropic receptors

G protein-coupled receptor

Carbon dioxide

Olfactory sensory neurons

Gustatory receptor neurons

Odorant-binding proteins

Differential expressed genes

Transmembrane domain

Pheromone receptor

Divergent IRs

Lepidopteran-specific IRs

Antennal IRs

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Acknowledgements

We thank Dr. RunMao Lin for providing the additional genome information for the P. operculella in this study.

This work was supported by the National Natural Science Foundation of China (grants 32372535) and the Science and Technology Innovation Project of the Chinese Academy of Agricultural Sciences.

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State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China

Ruipeng Chen, Junjie Yan & Yulin Gao

A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, 119071, Russia

Jacob D. Wickham

Department of Entomology, Rutgers University, 93 Lipman Drive, New Brunswick, New Jersey, USA

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Contributions

Conceptualization: Yulin Gao. Formal analysis: Ruipeng Cheng, Junjie Yan. Funding acquisition: Yulin Gao. Investigation: Ruipeng Cheng, Junjie Yan. Supervision: Yulin Gao. Writing – original draft: Ruipeng Cheng, Junjie Yan, Yulin Gao. Writing – review & editing: Jacob D. Wickham, Yulin Gao.

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Correspondence to Yulin Gao .

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We hereby declare that all research involving animal tissues in this study was conducted following relevant ethical guidelines and principles. All necessary ethical approvals were obtained before the commencement of the research. The ethics committee responsible for approving the research is named the ethics committee of the State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, with the approval number SYXK (Beijing) 2008–008. Furthermore, during the animal experimentation process, it was ensured that the subjects were anesthetized and the dissection tools were sterilized. It is our commitment to fully respect and protect the welfare and rights of animals involved in the research. We have made every effort to minimize the number of animals used and to minimize any pain or discomfort caused to them during the experimentation process.

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Supplementary Information

12864_2024_10428_moesm1_esm.docx.

Additional file 1: Table S1. The information of reference chemosensory gene set used in gene annotation from other species.

Additional file 2: Table S2. The detail of identification of chemosensory receptor genes.

Additional file 3: table s3. quality statistics of clean reads., additional file 4: table s4. summary of genome mapping information., additional file 5: table s5 table. chemosensory gene expression data., 12864_2024_10428_moesm6_esm.xlsx.

Additional file 6: Table S6. DEGs information between FAn Vs MAn. Set FoldChang > 2, FDR < 0.05 as threads to filter DEGs.

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Chen, R., Yan, J., Wickham, J.D. et al. Genomic identification and evolutionary analysis of chemosensory receptor gene families in two Phthorimaea pest species: insights into chemical ecology and host adaptation. BMC Genomics 25 , 493 (2024). https://doi.org/10.1186/s12864-024-10428-6

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Published : 18 May 2024

DOI : https://doi.org/10.1186/s12864-024-10428-6

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• Phthorimaea operculella
• Phthorimaea absoluta
• Chemosensory receptors
• Transcriptome analysis
• Gene expression profiles

BMC Genomics

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Social Workers’ Perceived Barriers and Facilitators to Social Work Practice in Schools: A Scoping Review

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Sarah Binks, Lyndal Hickey, Airin Heath, Anna Bornemisza, Lauren Goulding, Arno Parolini, Social Workers’ Perceived Barriers and Facilitators to Social Work Practice in Schools: A Scoping Review, The British Journal of Social Work , 2024;, bcae046, https://doi.org/10.1093/bjsw/bcae046

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The aim of this scoping review was to establish the breadth of the academic literature regarding the barriers and facilitators to social work practice in schools as perceived by School Social Workers (SSWs). Following the PRISMA-ScR Scoping Review Framework, 42 articles were identified as meeting the inclusion criteria. Five interrelated themes related to the barriers and facilitators to SSW practice were identified: (1) Inadequacy of service delivery infrastructure; (2) SSWs’ role ambiguities and expectations; (3) SSWs’ competency, knowledge and support; (4) School climate and context; and (5) Cultivating relationships and engagement. This scoping review found that social workers perceive far greater barriers than facilitators when delivering services in school settings, with limited evidence related to the facilitators that enhance School Social Work (SSW) practice. Further research regarding the facilitators of SSW practice is needed, specifically in countries where research on this topic is emergent.

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