A Novel Function for Juvenile Hormone in Male Courtship Behavior of Drosophila melanogaster

Juvenile hormone is a significant insect hormone controlling development as well as reproduction, migration, and social behavior. Juvenile hormone-binding proteins of many insects are similar to Drosophila melanogaster ‘Takeout’, a protein preferentially expressed males that influences courtship behavior. This raises the possibility for a role for Juvenile hormone in male courtship behavior. This hypothesis was tested by creating flies with reduced Juvenile hormone levels and examining their mating behavior. To achieve a reduction in levels, a key enzyme of the Juvenile hormone synthesis pathway was targeted by RNA interference (RNAi). Juvenile Hormone Acid Methyl Transferase (JHAMT) catalyzes one of the last steps in the hormone’s synthesis in the Corpora allata, the organ of Juvenile hormone synthesis. A new Corpora allata-specific GAL4 driver line was created and used to direct JHAMT-RNAi to these cells. Courtship assays of the resulting males showed that RNAi against JHAMT results in a mutant courtship phenotype. Constitutive reduction as well as specific adult reduction reduced courtship. The same result was also obtained by conditional genetic ablation of the Corpora allata in adults. The courtship defects could be rescued by application of the Juvenile hormone analog Methoprene shortly before behavioral testing. Together, these results show that normal adult Juvenile hormone levels are physiologically required for normal male courtship behavior. It is unknown which protein(s) transport Juvenile hormone in Drosophila melanogaster. Since Takeout has many of the characteristics of JHBPs, we tested whether Takeout binds the hormone to act as a carrier for the hormone. No binding was observed between a Baculovirus produced Takeout protein and Juvenile hormone in an in vitro binding assay. The findings presented in this dissertation demonstrate a novel and important function for Juvenile hormone in the control of male courtship behavior in Drosophila melanogaster.