Sexual selection rewires reproductive protein networks

Polyandry drives postcopulatory sexual selection (PCSS), resulting in rapid evolution of male ejaculate traits. Critical to male and female fitness, the ejaculate is known to contain rapidly evolving seminal fluid proteins (SFPs) produced by specialized male secretory accessory glands. The evidence that rapid evolution of some SFPs is driven by PCSS, however, is indirect, based on either plastic responses to changes in the sexual selection environment or correlative macroevolutionary patterns. Moreover, such studies focus on SFPs that represent but a small component of the accessory gland proteome. Neither how SFPs function with other reproductive proteins, nor how PCSS influences the underlying secretory tissue adaptations and content of the accessory gland, has been addressed at the level of the proteome. Here we directly test the hypothesis that PCSS results in rapid evolution of the entire male accessory gland proteome and protein networks by taking a system-level approach, combining divergent experimental evolution of PCSS in Drosophila pseudoobscura ( Dpse ) , high resolution mass spectrometry (MS) and proteomic discovery, bioinformatics and population genetic analyses. We demonstrate that PCSS influences the abundance of over 200 accessory gland proteins, including SFPs. A small but significant number of these proteins display molecular signatures of positive selection. Divergent PCSS also results in fundamental and remarkably compartmentalized evolution of accessory gland protein networks in which males subjected to strong PCSS invest in protein networks that serve to increase protein production whereas males subjected to relaxed PCSS alters protein networks involved in protein surveillance and quality. These results directly demonstrate that PCSS is a key evolutionary driver that shapes not only individual reproductive proteins, but rewires entire reproductive protein networks. The abbreviations used are: BLAST Basic Local Alignment Search Tool Dpse Drosophila pseudoobscura PCSS postcopulatory sexual selection SFPs seminal fluid proteins Dmel D. melanogaster SDS sodium dodecylsulfate SDS-PAGE sodium dodecylsulfate polyacrylamide gel electrophoresis MS mass spectrometry LC-MS/MS liquid chromatography-MS/MS AcgP accessory gland proteome FDRs False Discovery Rates AcgS accessory gland secretome exoP exoproteome LFQ label-free quantitation P polyandry M monandry GO gene ontology CC cellular component MF molecular function BP biological process STRING Search Tool for the Retrieval of Interacting Genes/Proteins DIOPT DRSC Integrative Ortholog Prediction Tools ER endoplasmic reticulum