Role of Sex Peptide in Drosophila Males

Drosophila male sex peptide ACP70A is a small peptide mainly produced in the accessory glands. It elicits a high number of post-mating responses in mated females; yet its function in male physiology is not well known. Here, we explore its role in male sex behav- ior and pheromone biosynthesis, using males either mutant or RNAi knocked-down for Acp70A . Courtship was severely affected in both Acp70A mutants and Acp70A knocked- down males, with only 2% of the males succeeding copulation. Cuticular hydrocarbon amounts were moderately affected with 25% decrease in sp0 mutant (without Acp70A expression) and 10–22% increase in flies overexpressing Acp70A . Acp70A knock-down either ubiquitously or in the testes surprisingly resulted in an overproduction of hydro- carbons, whose amounts were double of the controls. We tested eight putative “off-target” genes but none of these led to an increase in hydrocarbon amounts. These results show that male courtship behavior is largely dependent on the presence of Acp70A and independent of cuticular hydrocarbons. The presence of potential “off-target” genes explain - ing the hydrocarbon phenotype is discussed.