Characterization of female reproductive proteases in a butterfly from functional and evolutionary perspectives

AbstractMolecules that mediate reproductive interactions are some of the most rapidly evolving traits. Researchers have often suggested that this is due to coevolution at key physiological interfaces. However, very few of these interfaces are well understood at the functional level. One such interface is the digestion of the spermatophore in Lepidoptera. Female Lepidoptera have a specialized reproductive organ called the bursa copulatrix that receives and processes the male spermatophore, a complex proteinaceous ejaculate. In the cabbage white butterfly, Pieris rapae, the bursa secretes a mixture of proteases hypothesized to digest the spermatophore. However, these proteases remain biochemically uncharacterized. Using a zymogram approach, we identified six proteases in bursal extracts at sufficiently high concentrations to characterize their in vitro activity. We assessed the modes of action of these bursal enzymes by quantifying their activity following exposure to diagnostic protease inhibitors. A serin...