Insulin-Producing Cells Regulate the Sexual Receptivity through the Painless TRP Channel in Drosophila Virgin Females

In a variety of animal species, females hold a leading position in evaluating potential mating partners. The decision of virgin females to accept or reject a courting male is one of the most critical steps for mating success. In the fruitfly Drosophila melanogaster, however, the molecular and neuronal mechanisms underlying female receptivity are still poorly understood, particularly for virgin females. The Drosophila painless (pain) gene encodes a transient receptor potential (TRP) ion channel. We previously demonstrated that mutations in pain significantly enhance the sexual receptivity of virgin females and that pain expression in pain(GAL4)-positive neurons is necessary and sufficient for pain-mediated regulation of the virgin receptivity. Among the pain(GAL4)-positive neurons in the adult female brain, here we have found that insulin-producing cells (IPCs), a neuronal subset in the pars intercerebralis, are essential in virgin females for the regulation of sexual receptivity through Pain TRP channels. IPC-specific knockdown of pain expression or IPC ablation strongly enhanced female sexual receptivity as was observed in pain mutant females. When pain expression or neuronal activity was conditionally suppressed in adult IPCs, female sexual receptivity was similarly enhanced. Furthermore, both pain mutations and the conditional knockdown of pain expression in IPCs depressed female rejection behaviors toward courting males. Taken together, our results indicate that the Pain TRP channel in IPCs plays an important role in controlling the sexual receptivity of Drosophila virgin females by positively regulating female rejection behaviors during courtship.