Proteome profiling reveals tissue-specific protein expression in male and female accessory glands of the silkworm, Bombyx mori

Male accessory gland (MAG) and female accessory gland (FAG) of the reproductive system are, respectively, responsible for producing seminal proteins and adhesive proteins during copulation and ovulation. Seminal proteins are ejaculated to female along with sperms, whereas adhesive proteins are excreted along with eggs. Proteins from the male and female reproductive organs are usually indicative of rapid adaptive evolution. Understanding the reproductive isolation and species divergence requires identifying reproduction-related proteins from many different species. Here, we present our proteomic analyses of male and female accessory glands of the silkworm, Bombyx mori. Using LC/MS-MS, we identified 2133 MAG proteins and 1872 FAG proteins. In total, 652 proteins were significant more abundant in the MAG than in the FAG, including growth factors, odorant-binding proteins, enzymes, and proteins of unknown function. Growth factors and odorant-binding proteins are potential signaling molecules, whereas most of proteins of unknown function were found to be Lepidoptera-specific proteins with high evolutionary rates. Microarray experiments and semi-quantitative RT-PCR validated that MAG-specific proteins were expressed exclusively in male moths. Totally, 192 proteins were considered as FAG-specific proteins, including protease inhibitors, enzymes, and other proteins. Protease inhibitors were found to be the most abundant FAG-specific proteins, which may protect eggs from infection by inhibiting pathogen-derived proteases. These results provide comprehensive insights into copulation and oviposition. Moreover, the newly identified Lepidoptera-specific MAG proteins provide useful data for future research on the evolution of reproductive proteins in insects.