Abdominal-B regulates the male seminal fluid transferome and new fecundity factors required for sperm sex peptide binding.

Seminal fluid proteins determine reproductive success in a wide range of animals. In the Drosophila male accessory gland, seminal fluid is mainly produced by two cell types, a majority of main cells and a small number of secondary cells that possess a specialized secretory apparatus with unusually enlarged dense core granule vesicles. Loss of Abdominal-B expression from secondary cells in the enhancer mutant iab-6cocu disrupts their transcriptional and secretory identity. Consequently, mutant males fail to induce the long-term post-mating response in females, which is characterized by a loss of receptivity and sustained egg laying. Here, we determine how secondary cells shape the seminal transferome and the female response by assessing iab-6cocu male accessory gland and female mate reproductive tract proteomes. We find downregulation of seminal fluid proteins that constitute a signaling network enabling sperm binding and the sustained action of the key regulator Sex Peptide. We identify two new Sex Peptide network proteins crucial for female fecundity, Cornutus (CG1701) and Hanrej (CG42564). Cornutus is required for mating dependent dense core granule vesicle release, providing a link between the products of these compartments and the female long-term post-mating response. Our data highlights the importance of secondary cell signaling and secretion for overall seminal fluid composition and Sex Peptide network function as well as the interdependence of main and secondary cells and their secretory products, advancing the general understanding of how seminal fluid signaling pathways modulate female physiology, sperm use and offspring production.