Seminal fluid protein divergence among populations exhibiting postmating prezygotic reproductive isolation

Abstract

Despite holding a central role in fertilization, reproductive traits often show elevated rates of evolution and diversification. The rapid evolution of seminal fluid proteins (Sfps) within populations is predicted to cause mis‐signalling between the male ejaculate and the female during and after mating resulting in postmating prezygotic (PMPZ) isolation between populations. Crosses between Drosophila montana populations show PMPZ isolation in the form of reduced fertilization success in both noncompetitive and competitive contexts. Here we test whether male ejaculate proteins produced in the accessory glands or ejaculatory bulb differ between populations using liquid chromatography tandem mass spectrometry. We find more than 150 differentially abundant proteins between populations that may contribute to PMPZ isolation, including a number of proteases, peptidases and several orthologues of Drosophila melanogaster Sfps known to mediate fertilization success. Males from the population that elicit the stronger PMPZ isolation after mating with foreign females typically produced greater quantities of Sfps. The accessory glands and ejaculatory bulb show enrichment for different gene ontology (GO) terms and the ejaculatory bulb contributes more differentially abundant proteins. Proteins with a predicted secretory signal evolve faster than nonsecretory proteins. Finally, we take advantage of quantitative proteomics data for three Drosophila species to determine shared and unique GO enrichments of Sfps between taxa and which potentially mediate PMPZ isolation. Our study provides the first high‐throughput quantitative proteomic evidence showing divergence of reproductive proteins between populations that exhibit PMPZ isolation.

Evolutionary quantitative proteomics of reproductive interactions in Drosophila

“…Ejaculate candidates with a signal peptide sequence showed elevated dN/dS ratios compared to the remaining ejaculate candidates (Mann-Whitney U test, p < 0.001 in all comparisons) and the genome average ( p < 0.006 in all comparisons), as expected for seminal fluid proteins (39, 42) (Fig. 3).…”

“…Heterospecific ejaculates may fair worse in postcopulatory sexual selection (34, 35), have reduced motility (15, 36), or elicit an abnormal postmating female response, which can cause impaired sperm use or reduced oviposition rates (16, 20, 37, 38). A growing body of literature has begun characterising the genomic, transcriptomic, and proteomic differences between taxa that may contribute to postmating prezygotic isolation (16,20, 33, 39–43).…”

“…The rapid molecular evolution of reproductive proteins poses a significant challenge for protein identification and quantitation with high throughput proteomics using liquid-chromatography tandem mass-spectrometry (LC-MS/MS) and data dependent acquisition (DDA). Most proteomics studies use a single query database to assign mass spectra to peptides and proteins, either using the proteome of one of the species of interest (40), the proteome of the closest available relative (39), or performing in silico predictions to generate a reference proteome (44). Using a single species query database for cross-species comparisons may suffer from problems akin to read mapping bias in short read RNA sequencing (RNA-Seq) analysis pipelines (45).…”

Adaptation and ecological speciation in seasonally varying environments at high latitudes: Drosophila virilis group

“…PMPZ isolation between Vancouver males and Colorado females is caused by the inability Vancouver males’ sperm to successfully fertilize Colorado females’ eggs [ 120 ], which could result from differences in male sperm length and female sperm storage organ morphology, interactions between sperm and egg cell surfaces and/or protein-level incompatibilities [ 18 ]. Interestingly, Garlovsky et al [ 122 ] identified more than 150 differentially abundant male ejaculate proteins between D. montana populations.…”

Discovering Novel Genes in Non-Model Fly Accessory Glands Using De Novo Nanopore Transcriptomics

“…Cystatins are also a large and diverse group of genes, that regulate the activity of cysteine and serine proteases. Although little is known about their speci c functions in male reproductive tissues, cystatins have been found in seminal uids and reproductive tissues of ies, atworms and ticks (Garlovsky et al, 2020;Geadkaew et al, 2014;Sonenshine et al, 2011). They are thought to be involved in spermatogenesis and fertilization (Geadkaew et al, 2014), and have been found to play a critical role in regulating programmed cell death during embryogenesis in plants (P. Zhao et al, 2014) Secretory Genes Eighty percent (32) of AG genes analysed in S. punctum were secretory in nature, i.e., they synthesize secretory proteins (Figure 4d).…”