Quantitative Proteomics Identification of Seminal Fluid Proteins in Male Drosophila melanogaster

Modulation of seminal fluid molecules by males and females

In insects, seminal fluid molecules (SFMs) influence female post-mating phenotypes that affect reproductive success including egg development, sperm use, mating behavior, attractiveness, and lifespan. Yet, the magnitude of these effects can be quite variable, even within inbred strains. This variation is important because it could impact post-copulatory reproductive success of both males and females. One likely cause of this variation is modulation by males or females of the quantities or qualities (e.g. stability or activity state) of SFMs, or, in the case of females, of their sensitivity to SFMs. Here, I review opportunities for SFM modulation by males and females and propose that these processes could provide mechanisms by which information received before and during copulation influences post-copulatory reproductive success.

Comparative proteomic analysis of sex-biased proteins in ovary and testis at different stages of Spodoptera litura

Sex-biased protein is thought to be able to drive the phenotypic differences in males and females in insects. In this study, 1385 and 1727 proteins were identified as differentially accumulated proteins (DAPs) by comparing the protein abundances at pupae stage with those at adult stage in ovary and testis of S.litura, respectively. And among which, 548 DAPs were showed to be expressed in both ovary and testis, and 837 and 1179 proteins were considered as ovary-specific and testis-specific DAPs, respectively. To further identify DAPs related to gonad development and sex dimorphism, a total of 320 DAPs were selected and defined as "proteins of specific interest" based on several selecting criteria. Sex dimorphism is a complex and dynamic developmental progress, and these identified DAPs were suggested to be involved in multiple functions such as organonitrogen compound catabolic process, glycosylation, proteasome, N-Glycan biosynthesis and other reproduction-related processes. Overall, our results highlighted these sexual-biased, gonad development related and sexual dimorphism related DAPs, and their abundance variations along with development were also examined, which could provide important information for their functional analysis in reproduction and potential biomarkers for developing useful strategies against S. litura and other orthologous pests. BIOLOGICAL SIGNIFICANCE: Sex dimorphism entails the differentiation of two sexual functions, resulting in sexually phenotypic differences and leading to the development of female and male morphologies and behaviors. However, sex dimorphism related proteins remain to be identified in many non-model insects. In this study, iTRAQ-based proteomic analysis was applied to examine the variations of protein abundances at pupae stage and adult stage in ovary and testis of S.litura, respectively. Reproduction and sex dimorphism related proteins were further identified as "proteins of specific interest". These identified candidate proteins provided valuable information for their further functional analysis in reproduction and could serve as potential biomarkers for developing useful strategies against S. litura and other orthologous pests.

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

Ejaculate quality plays an essential role in fertility, sperm competition, and offspring health. A key modulator of ejaculate quality is the social environment. Although males across taxa are known to strategically allocate sperm in response to rivals, how this applies to myriad other ejaculate components is poorly resolved. Here, we take a multilevel approach, from protein to fitness, to show that Drosophila melanogaster males divergently allocate sperm and seminal fluid proteins along a competition gradient. Using a combination of fluorescence-labeled sperm, quantitative proteomics, and multimating assays, we demonstrate that males are remarkably sensitive to the intensity of competition they perceive, show compositional change across and within portions of the ejaculate, and that this compositional change carries distinct costs and benefits.

Sperm competition favors large, costly ejaculates, and theory predicts the evolution of allocation strategies that enable males to plastically tailor ejaculate expenditure to sperm competition threat. While greater sperm transfer in response to a perceived increase in the risk of sperm competition is well-supported, we have a poor understanding of whether males (i) respond to changes in perceived intensity of sperm competition, (ii) use the same allocation rules for sperm and seminal fluid, and (iii) experience changes in current and future reproductive performance as a result of ejaculate compositional changes. Combining quantitative proteomics with fluorescent sperm labeling, we show that Drosophila melanogaster males exercise independent control over the transfer of sperm and seminal fluid proteins (SFPs) under different levels of male–male competition. While sperm transfer peaks at low competition, consistent with some theoretical predictions based on sperm competition intensity, the abundance of transferred SFPs generally increases at high competition levels. However, we find that clusters of SFPs vary in the directionality and sensitivity of their response to competition, promoting compositional change in seminal fluid. By tracking the degree of decline in male mating probability and offspring production across successive matings, we provide evidence that ejaculate compositional change represents an adaptive response to current sperm competition, but one that comes at a cost to future mating performance. Our work reveals a previously unknown divergence in ejaculate component allocation rules, exposes downstream costs of elevated ejaculate investment, and ultimately suggests a central role for ejaculate compositional plasticity in sexual selection.

USP32 regulates late endosomal transport and recycling through deubiquitylation of Rab7

The endosomal system is a highly dynamic multifunctional organelle, whose complexity is regulated in part by reversible ubiquitylation. Despite the wide-ranging influence of ubiquitin in endosomal processes, relatively few enzymes utilizing ubiquitin have been described to control endosome integrity and function. Here we reveal the deubiquitylating enzyme (DUB) ubiquitin-specific protease 32 (USP32) as a powerful player in this context. Loss of USP32 inhibits late endosome (LE) transport and recycling of LE cargos, resulting in dispersion and swelling of the late compartment. Using SILAC-based ubiquitome profiling we identify the small GTPase Rab7—the logistical centerpiece of LE biology—as a substrate of USP32. Mechanistic studies reveal that LE transport effector RILP prefers ubiquitylation-deficient Rab7, while retromer-mediated LE recycling benefits from an intact cycle of Rab7 ubiquitylation. Collectively, our observations suggest that reversible ubiquitylation helps switch Rab7 between its various functions, thereby maintaining global spatiotemporal order in the endosomal system.

Though ubiquitin is known to broadly influence endosomal trafficking, few ubiquitin-utilizing enzymes targeting endosomal regulators are known. Here, the authors find that the deubiquitylating enzyme (DUB) USP32 influences endosomal membrane dynamics by deubiquitinating Rab7.

Proteins, Transcripts, and Genetic Architecture of Seminal Fluid and Sperm in the Mosquito Aedes aegypti

The yellow fever mosquito, Aedes aegypti,, transmits several viruses causative of serious diseases, including dengue, Zika, and chikungunya. Some proposed efforts to control this vector involve manipulating reproduction to suppress wild populations or to replace them with disease-resistant mosquitoes. The design of such strategies requires an intimate knowledge of reproductive processes, yet our basic understanding of reproductive genetics in this vector remains largely incomplete. To accelerate future investigations, we have comprehensively catalogued sperm and seminal fluid proteins (SFPs) transferred to females in the ejaculate using tandem mass spectrometry. By excluding female-derived proteins using an isotopic labeling approach, we identified 870 sperm proteins and 280 SFPs. Functional composition analysis revealed parallels with known aspects of sperm biology and SFP function in other insects. To corroborate our proteome characterization, we also generated transcriptomes for testes and the male accessory glands-the primary contributors to Ae. aegypti, sperm and seminal fluid, respectively. Differential gene expression of accessory glands from virgin and mated males suggests that transcripts encoding proteins involved in protein translation are upregulated post-mating. Several SFP transcripts were also modulated after mating, but >90% remained unchanged. Finally, a significant enrichment of SFPs was observed on chromosome 1, which harbors the male sex determining locus in this species. Our study provides a comprehensive proteomic and transcriptomic characterization of ejaculate production and composition and thus provides a foundation for future investigations of Ae. aegypti, reproductive biology, from functional analysis of individual proteins to broader examination of reproductive processes.

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

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.