Control of seminal fluid protein expression via regulatory hubs in Drosophila melanogaster

Abstract

Highly precise, yet flexible and responsive coordination of expression across groups of genes underpins the integrity of many vital functions. However, our understanding of gene regulatory networks (GRNs) is often hampered by the lack of experimentally tractable systems, by significant computational challenges derived from the large number of genes involved or from difficulties in the accurate identification and characterization of gene interactions. Here we used a tractable experimental system in which to study GRNs: the genes encoding the seminal fluid proteins that are transferred along with sperm (the ‘transferome’) in Drosophila melanogaster fruit flies. The products of transferome genes are core determinants of reproductive success and, to date, only transcription factors have been implicated in the modulation of their expression. Hence, as yet, we know nothing about the post-transcriptional mechanisms underlying the tight, responsive and precise regulation of this important gene set. We investigated this omission in the current study. We first used bioinformatics to identify potential regulatory motifs that linked the transferome genes in a putative interaction network. This predicted the presence of putative microRNA (miRNA) ‘hubs’. We then tested this prediction, that post-transcriptional regulation is important for the control of transferome genes, by knocking down miRNA expression in adult males. This abolished the ability of males to respond adaptively to the threat of sexual competition, indicating a regulatory role for miRNAs in the regulation of transferome function. Further bioinformatics analysis then identified candidate miRNAs as putative regulatory hubs and evidence for variation in the strength of miRNA regulation across the transferome gene set. The results revealed regulatory mechanisms that can underpin robust, precise and flexible regulation of multiple fitness-related genes. They also help to explain how males can adaptively modulate ejaculate composition.

Sexual conflict drives male manipulation of female postmating responses inDrosophila melanogaster

“…When considering all SFP genes, M males showed on average 16.6% lower expression than P males. The breadth of this reduced investment in SFP gene expression in M males (113 of the 132 SFP genes show nominally lower expression) is consistent with the idea that these genes are tightly coregulated (81) and suggests that fine-tuned tailoring of the composition of the ejaculate may be to some extent evolutionarily constrained. The reduced investment in SFP gene expression in M males was confirmed by qPCR analyses for the five most well-characterized SFP genes ( Acp26Aa , Acp29AB , Acp36DE , Acp62F , and SP ) across an extended time course spanning the first 5 d post eclosion ( SI Appendix , Fig.…”

Divergent allocation of sperm and the seminal proteome along a competition gradient inDrosophila melanogaster

“…We also sought to understand the regulatory differences that underlie between-SFP variation in sensitivity to competition. Recent work has shown that groups of SFPs share putative binding sites for particular miRNAs (53). Thus, it may be that specific miRNAs are responsible for driving the changes in SFP expression that facilitate strategic changes in ejaculate composition.…”

TheDrosophilaseminal proteome and its role in postcopulatory sexual selection

“…Sfp gene expression can also change: reduced RNA levels of ovulin and Acp62F have been found in males exposed to rivals [94]. The latter data are difficult to reconcile with the results of studies that quantify Sfps at the protein level, but may reflect the existence of important posttranscriptional regulation [97][98][99], or they may simply reflect strain differences, or differences in experimental design. In any case, males display modulation of Sfp production and transfer in response to perceived PCSS, which may represent an adaptive strategy to maximize reproductive returns from costly ejaculate investment and/or result from constraints imposed by resource limitation [100].…”