Meeting Abstract
Reproductive traits provide extreme examples of diversity due to the rapid rate at which they evolve. This diversity has been heavily explored in relation to male reproductive traits. However, increasing evidence suggests that female reproductive traits are similarly diverse yet remain understudied. In order to fully understand the coevolution between male and female reproductive traits, both sexes must be considered. Butterflies provide an excellent system in which to explore the coevolution of reproductive traits. Female butterflies have a specialized reproductive organ, the bursa copulatrix, which receives and processes the male ejaculate or spermatophore. One bursal function is to digest spermatophore proteins, which are subsequently used to fund egg production. Our previous work uncovered a cocktail of proteases in the bursa of the Cabbage White butterfly, Pieris rapae, which are hypothesized to digest the spermatophore. However, although two of these proteases are predicted to have trypsin-like proteolytic activity, this mode of action remained uncharacterized. We assessed the specificity of these trypsin-like proteases using a modified zymogram technique. We found that while the bursa exhibits activity similar to that of trypsin, a trypsin specific inhibitor fails to inhibit activity of bursal enzymes. Predictive structural analysis indicates that the active sites of the bursal enzymes resemble that of trypsin, while the amino acids responsible for specificity share little similarity, potentially explaining the lack of inhibition. By characterizing the specificity and activity of bursal enzymes, the interaction between the bursa and spermatophore can be further studied in the light of coevolution.
