TheDrosophilaseminal proteome and its role in postcopulatory sexual selection

Abstract

Postcopulatory sexual selection (PCSS), comprised of sperm competition and cryptic female choice, has emerged as a widespread evolutionary force among polyandrous animals. There is abundant evidence that PCSS can shape the evolution of sperm. However, sperm are not the whole story: they are accompanied by seminal fluid substances that play many roles, including influencing PCSS. Foremost among seminal fluid models is Drosophila melanogaster , which displays ubiquitous polyandry, and exhibits intraspecific variation in a number of seminal fluid proteins (Sfps) that appear to modulate paternity share. Here, we first consolidate current information on the identities of D. melanogaster Sfps. Comparing between D. melanogaster and human seminal proteomes, we find evidence of similarities between many protein classes and individual proteins, including some D. melanogaster Sfp genes linked to PCSS, suggesting evolutionary conservation of broad-scale functions. We then review experimental evidence for the functions of D. melanogaster Sfps in PCSS and sexual conflict. We identify gaps in our current knowledge and areas for future research, including an enhanced identification of PCSS-related Sfps, their interactions with rival sperm and with females, the role of qualitative changes in Sfps and mechanisms of ejaculate tailoring. This article is part of the theme issue ‘Fifty years of sperm competition’.

The role of female reproductive fluid in sperm competition

“…While research on seminal fluid continues apace [see 8,9], we know far less about the potential sexually selected roles of female reproductive fluid. For the purposes of the present review, we define female reproductive fluid (hereafter FRF) as the medium, arising from females, through which sperm must pass on © 2020 The Author(s) Published by the Royal Society.…”

How Soon Hath Time… A History of Two “Seminal” Publications

“…Understanding why sperm are small and numerous is no longer difficult [ 60 , 70 ], and theory has been successful in predicting relative testes size [ 71 , 72 , 73 ] and sperm economics [ 74 , 75 ], i.e., sperm numbers allocated under different biological conditions. Major advances have occurred in our understanding of how sperm competition influences seminal fluid proteins, and their manipulation of female reproductive biology [ 69 , 76 , 77 , 78 , 79 , 80 ]. One aspect not covered in the 1970 review was how sperm competition may modify sperm cell form and function, something proposed by John Sivinski at the influential meeting of the Florida Entomological Society in 1979 [ 53 ].…”

Research gaps and new insights in the intriguing evolution of Drosophila seminal proteins

“…Some of these candidates were already known as predicted or confirmed SFPs, while nine were novel discoveries (Sepil et al 2019). While we were concluding this report, Wigby et al (2020) combined data from these and other proteomic studies to provide a list of 292 D. melanogaster SFPs. However, the conditions they evaluated may have been too lax; according to modENCODE [implemented in FlyBase r2020_03 (Graveley et al 2010;Thurmond et al 2019)] and FlyAtlas2 (Leader et al 2018), some of the genes they proposed as novel candidates are not expressed in the male reproductive was not certified by peer review) is the author/funder.…”

“…The biochemical classes into which SFPs typically fall (e.g., proteases, protease inhibitors, lectins, lipases, and cysteine-rich secretory proteins) seem quite conserved among Diptera, even among animals from different classes (reviewed in, e.g., Avila et al 2016;Wigby et al 2020). This suggests that the functional spectrum of SFPs is adaptively restricted at the molecular level.…”