The Old and the New: Discovery Proteomics Identifies Putative Novel Seminal Fluid Proteins in Drosophila

Timothy L Karr,Helen Southern,Matthew A Rosenow,Toni I Gossmann,Rhonda R Snook

doi:10.1074/mcp.ra118.001098

Abstract

Seminal fluid proteins (SFPs), the nonsperm component of male ejaculates produced by male accessory glands, are viewed as central mediators of reproductive fitness. SFPs effect both male and female post-mating functions and show molecular signatures of rapid adaptive evolution. Although Drosophila melanogaster, is the dominant insect model for understanding SFP evolution, understanding of SFP evolutionary causes and consequences require additional comparative analyses of close and distantly related taxa. Although SFP identification was historically challenging, advances in label-free quantitative proteomics expands the scope of studying other systems to further advance the field. Focused studies of SFPs has so far overlooked the proteomes of male reproductive glands and their inherent complex protein networks for which there is little information on the overall signals of molecular evolution. Here we applied label-free quantitative proteomics to identify the accessory gland proteome and secretome in Drosophila pseudoobscura,, a close relative of D. melanogaster,, and use the dataset to identify both known and putative novel SFPs. Using this approach, we identified 163 putative SFPs, 32% of which overlapped with previously identified D. melanogaster, SFPs and show that SFPs with known extracellular annotation evolve more rapidly than other proteins produced by or contained within the accessory gland. Our results will further the understanding of the evolution of SFPs and the underlying male accessory gland proteins that mediate reproductive fitness of the sexes.

Highlights

Discovery proteomics identified Ͼ3000 proteins of the D. pseudoobscura accessory gland proteome. Identified 132 putative novel seminal fluid proteins in this species
Individual SFPs can rapidly evolve with signals of accelerated rates of adaptive molecular evolution found in studies of coding sequence and male-biased gene expression observed across different animal taxa (e.g. mammals [9, 10]; birds [11]; Drosophila [12,13,14])
Because a latter research goal is to quantify how sexual selection affects the production of proteins in the male accessory gland, here we present the overlap between proteins identified in the four replicates each of M and P selection lines

Summary

Introduction

Discovery proteomics identified Ͼ3000 proteins of the D. pseudoobscura accessory gland proteome. Identified 132 putative novel seminal fluid proteins in this species. Polyandry, where females mate with different males across a reproductive bout generating postcopulatory sexual selection, results in ejaculates that compete for fertilization of a limited supply of ova, and females may choose whose sperm will fertilize those limited ova [4]. Postcopulatory sexual selection operates between the male ejaculate that is transferred to and stored in the female reproductive tract [6]. SFP identification and their role in influencing fitness is dominated by work in D. melanogaster This species is relatively highly polyandrous [16] and studies identifying SFPs in species with different mating systems is necessary to un-. From the ‡Center for Mechanisms of Evolution, The Biodesign Institute, Arizona State University, Tempe, Arizona; §Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK; ¶Caris Life Sciences, Phoenix, Arizona; ʈDepartment of Zoology, Stockholm University, Stockholm, Sweden

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