Genomic responses to mating signals

Lead Research Organisation: University of East Anglia
Department Name: Biological Sciences

Abstract

You may not know whether 'love changes everything', but, scientifically speaking, the act of mating certainly does. Research focussed on the varied and inventive mating habits of invertebrates reveals the astonishing ways in which males can remodel the behaviour and physiology of the females with which they mate. This includes the transfer during mating by males of chemicals that go deep into female brains and nervous systems to alter behaviour, and those that effectively take over the female reproductive system. Small wonder then that females are sometimes resistant to such manipulations. Our recent work reveals just how global and sophisticated are the changes wrought upon females by mating males. We examined the responses of female fruitflies that mated with males that either did or did not transfer during mating a single ejaculate 'sex peptide' known to affect female sexual receptivity and egg laying. We examined both how messenger RNAs (mRNAs, that make gene products), and microRNAs (miRs, which sit on mRNAs and block them or target them for destruction) changed in females following receipt of sex peptide. We found many alterations to mRNAs, but what was really striking was the number of miRs that were different. This is consistent with the emerging general view that miRs have extremely important and widespread roles in regulating how genes work, with 20-30% of all genes (roughly 13,000 genes in the fruitfly) estimated as targets for miRs. Hence sex peptide sets in train global effects on female genomes not only at the level of DNA to RNA synthesis (transcription), but also on the rate at which RNA is translated (i.e. made into proteins). We are interested in SP because it has a 'swiss army knife' of functions and can alter the reproductive performance of both males and females. Remarkably, SP can significantly benefit the reproductive performance of males at the expense of that of females. This shows that SP plays a role in the battle of the sexes, where males can gain by maximising their returns from each mating even if that results in a decrease in the longer term reproductive prospects of their mates. SP benefits males because it decreases female sexual receptivity for several days and increases egg-laying. Hence males that transfer SP father more offspring than males that lack SP. However, females that receive elevated levels of SP suffer adverse consequences in the long term. The effects of SP are dependent on female diet and can be significantly altered, abolished or even reversed in sign under poor and good quality food. This research puts us in a timely position to address the following two fundamental questions: (1) to find out how male sex peptide intervenes in the female genome - which are the key genes that are targeted by miRs following receipt of sex peptide? and secondly - given that female diet is key to determining how much females are able to respond to sex peptide - (2) to examine how female genomes respond to sex peptide following both short- and long-term (evolutionary) changes in diet. The research is important because this is the first example we have where we can investigate the co-ordinated changes in both mRNAs and miRs to an external stimulus like the sex peptide that underlies important reproductive functions in both sexes. The fact that diet is also an important part of how females respond to sex peptide is also crucial as it allows us to test at the level of the genome SP responses following both short- and long-term alterations to diet. Our research will also therefore show miRs that change under different dietary conditions, which is important because diet is also a crucial determinant of lifespan.

Technical Summary

Discovering the genomic basis of fundamentally important phenotypes is a major challenge. We have recently determined genome-level responses in female D. melanogaster fruitfies to the male 'sex peptide' (SP), a molecule delivered during mating that has striking effects on male and female fitness. This is the first example, to our knowledge, to report simultaneous differential expression of mRNAs and microRNAs (miRs) in response to an external stimulus. We have also documented dramatic differences in SP phenotypes following manipulation of adult female diet. Hence, we are in a timely position, using this system, to identify and characterise the key miRs involved in SP responses, and - given that adult nutrition is key to the magnitude of SP responses - to determine how the genomic profiles of SP responses alter following short- and long-term manipulation of nutrition. We have 2 specific major objectives: (1) to characterise miRs identified as important in the SP responses at the functional level, using both computational and experimental approaches, (2) to test the genomic and phenotypic SP responses of females to variation in short- and long-term nutrition. The proposal also offers a general test of an important hypothesis: that plastic, short-term responses are achieved by different mechanisms than long-term, evolved responses. This is based upon the premise that short-term responses are more likely through adjustments to existing mRNAs rather than via de novo mRNA synthesis that may be more characteristic of longer-term changes.

Planned Impact

The School of Biological Sciences (BIO) is committed to significant growth in engagement and enterprise. There are four main areas in which the research will have broad impact for a range of beneficiaries across the public, private sectors and general public: 1. Diet and Health. With the impact of diet on reproduction and ageing being of topical interest across the public, health and political domains, our results are anticipated to have broad impact, especially given that food lifestyles have changed dramatically in recent times in human populations, generally to detrimental effect. 2. Novel microRNAs. We plan to build upon what we think is the first example of genomic changes in mRNAs and small RNAs to an external stimulus. This is an exciting scientific development in a rapidly developing field. 3. The battle of the sexes. The interplay between males and females is especially powerful in evolutionary terms. There is intuitive appeal in the study of adaptations that are good for males and bad for females, and vice versa. There is also an applied context of this research in terms of the husbandry of insect pests that are mass reared for control. 4. Bioinformatics. Our datasets will be valuable for technological development of bioinformatics toolkits and prediction algorithms because there are scant data from profiles of mRNAs and miRs. Who will benefit from the research and how? Public sector: In the public sector, we aim to communicate to health professionals and ultimately through to policy makers. There is much interest in the prophylactic effects of food manipulations of age related pathologies, and our work will be relevant here. We have good links with the School of Medicine, Health Policy and Practice, and we have already co-ordinated bids for funding with them and with the Institute of Food Research. Private sector: In the private sector we will be using the research and enterprise office staff to develop CASEing for studentships to investigate the links between miRs that respond to food manipulations. The aim of doing this is to work towards future KE partnerships. We are already developing in the private sector the application of knowledge from the study of reproductive behaviour and post-mating paternity mechanisms in fruitfly pests in a CASE studentship together with Oxford insect technologies (Oxitec), and they are supporting a BBSRC research grant application made in January. General public: We are actively involved with the press office in highlighting research papers and grant successes at a local and national level. We wish to highlight our research findings to the engagement office so that the results can be directly cascaded through local schools to provide immediate impact. Should this grant be successful, we will press release it to disseminate the aims of our research. The UEA also has a series of open lectures and we plan to give one of these. Collaborations and partnerships The research team is a new collaboration and each member has distinct expertise which aids synergy. In relation to impact, we will collaborate fully on all activities listed here. Exploitation and Application We will be seeking to exploit the research. Specific partnership agreements are already in place for related projects. We will have 6 monthly meetings with our enterprise and engagement officer to discuss results and work up opportunities. To protect the research we will have IP and MTA agreements with new collaborators, drawn up by our research contracts office. Capability All personnel, and particularly the PDRAs will be expected to engage with the impact agenda. Other staff involved will be our web development officer, our media office who will advise and assist with press releases and our School enterprise and engagement staff. All investigators have a track record of such activities and have sought training from staff development programmes.

Publications

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Bretman A (2016) Effect of competitive cues on reproductive morphology and behavioral plasticity in male fruitflies. in Behavioral ecology : official journal of the International Society for Behavioral Ecology

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Chapman T (2018) Sexual Conflict: Mechanisms and Emerging Themes in Resistance Biology in The American Naturalist

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Dore AA (2021) Plastic male mating behavior evolves in response to the competitive environment. in Evolution; international journal of organic evolution

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Dore AA (2018) The role of complex cues in social and reproductive plasticity. in Behavioral ecology and sociobiology

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Edward DA (2011) Quantifying the life-history response to increased male exposure in female Drosophila melanogaster. in Evolution; international journal of organic evolution

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Edward DA (2010) Adaptations to sexual selection and sexual conflict: insights from experimental evolution and artificial selection. in Philosophical transactions of the Royal Society of London. Series B, Biological sciences

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Fricke C (2017) Variation in the post-mating fitness landscape in fruit flies. in Journal of evolutionary biology

 
Description Research focussed on the varied and inventive mating habits of invertebrates reveals the astonishing ways in which males can remodel the behaviour and physiology of the females with which they mate. This includes the transfer during mating by males of chemicals that go deep into female brains and nervous systems to alter behaviour, and those that effectively take over the female reproductive system.



In this project we have been examining the responses of female fruitflies that mate with males that either did or did not transfer during mating a single ejaculate 'sex peptide' known to affect female sexual receptivity and egg laying. We examined both how messenger RNAs (mRNAs, that make gene products), and microRNAs (miRs, which sit on mRNAs and block them or target them for destruction) changed in females following receipt of sex peptide (SP).



We are interested in SP because it has a 'swiss army knife' of functions. Remarkably, SP can significantly benefit the reproductive performance of males at the expense of that of females. This shows that SP plays a role in the battle of the sexes. SP benefits males because it decreases female sexual receptivity for several days and increases egg-laying. Hence males that transfer SP father more offspring than males that lack SP. However, females that receive elevated levels of SP suffer adverse consequences in the long term. The effects of SP are dependent on female diet and can be significantly altered, abolished or even reversed in sign under poor and good quality food.



The main aim of this research is to answer two fundamental questions: (1) to find out how male sex peptide intervenes in the female genome, and (2) to examine how female genomes respond to sex peptide following both short- and long-term (evolutionary) changes in diet.



With regard to the first aim, we have now published our first set of findings on changes in gene expression in females following receipt of sex peptide (Gioti et al 2012). This shows a dramatic set of changes over time and across different tissues. We have followed this up with a more in depth time series analysis which is now nearing completion, as well as an investigation of the associated changes in the expression of microRNAs. These data give a unparalleled insight into the profound changes in females following mating, and the first indication of what sexual conflict might 'look like' at the genomic level. Following completion of validation tests these data are to form a significant publication. Associated with this, we also showed that females lacking specific microRNAs have altered responses to receipt of SP, and we are currently finishing up a manuscript for submission to the journal Genetics. Towards the second aim, we initiated lines in which we successfully conducted experimental evolution on low and high adult nutrition. Our analyses show that these lines have evolved and diverged both in terms of how they utilise food, but also in terms of how females in them respond to receipt of sex peptide. We are now characterising those responses at the genomic level. These data will form two further significant publications. An important part of this second aim is to consider better the life history. Therefore we did a study in which we examined how costs and benefits of receipt of sex peptide change with female age. This work has been accepted for publication in Proceedings of the Royal Society B (Fricke et al 2013).



Overall, the research results are important because they represent a great example where we can investigate the co-ordinated changes in both genes and microRNAs to an external stimulus like the sex peptide that underlies important reproductive functions in both sexes. The fact that diet is also an important part of how females respond to sex peptide is also crucial, and allows us also to consider key life history traits such as lifespan.

The following publication arises from this work and is in press:

Fowler EK, Bradbury T, Moxon S, Chapman T. (2020) Sex-specific transcriptional responses to mating in D. melanogaster. Scientific Reports in press.
Exploitation Route In terms of non-academic impact, there is considerable public interest in understanding the battle of the sexes. Given the intersection of the work with diet and health, there is also much interest in understanding the effects of diet on traits such as lifespan via reproduction. The work therefore has the potential for use in the education domain. There is much interest in the prophylactic effects of food manipulations of age related pathologies, and our work

will also be relevant here. This is primarily a fundamental bioscience project. However, there are two potential sets of exploitation routes (i) diet, health and ageing-related impacts, and (ii) genetic insect pest control SMEs. Our research could inform the latter for example, via suggesting new husbandry techniques to alter the extent of deleterious effects of male-female interactions. It might also suggest novel modulators of insect behaviour.



For the former, we have been engaging with the strong research interests in diet and health at UEA School of Medicine, and at the Institute of Food Research within the Norwich Research Park. In terms of pest control links, we have expanded our work with Oxitec Ltd (Oxford

Insect technologies) through an additional CASE PhD award and also through Project Partnerships.



An additional exploitation route is through the analysis of novel, large genomic datasets for the development of bioinformatic algorithms and toolkits.
Sectors Environment

 
Description BBSRC DTP studentship to T Chapman and W Haerty on sexual detection - social responses in fruitflies
Amount £100,000 (GBP)
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 10/2019 
End 09/2023
 
Description measure for measure: female responses to the social and sexual environment.
Amount £430,886 (GBP)
Funding ID NE/R000891/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 09/2017 
End 09/2020
 
Description microRNAs as agents of sexual conflict and cooperation
Amount £200,000 (GBP)
Funding ID RPG-2018-078 
Organisation The Leverhulme Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 02/2019 
End 01/2022
 
Description media interviews - genomic responses paper 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact interviews led to many further interviews and interest in the science

sparked further interest
Year(s) Of Engagement Activity 2012