Ecdysone Receptor Acts in fruitless- Expressing Neurons to Mediate Drosophila Courtship Behaviors

Summary In Drosophila melanogaster, fruitless ( fru ) encodes male-specific transcription factors (FRU M ; encoded by fru P1 ) required for courtship behaviors (reviewed in [1]). However, downstream effectors of FRU M throughout development are largely unknown [2–5]. During metamorphosis the nervous system is remodeled for adult function, the timing of which is coordinated by the steroid hormone 20-hydroxyecdysone (ecdysone) through the ecdysone receptor, a heterodimer of the nuclear receptors EcR (isoforms are EcR-A, EcR-B1, or EcR-B2) and Ultraspiracle (USP) (reviewed in [6]). Here, we show that genes identified as regulated downstream of FRU M during metamorphosis are significantly overrepresented with genes known to be regulated in response to ecdysone or EcR . FRU M and EcR isoforms are coexpressed in neurons in the CNS during metamorphosis in an isoform-specific manner. Reduction of EcR-A levels in fru P1 -expressing neurons of males caused a significant increase in male-male courtship activity and significant reduction in size of two antennal lobe glomeruli. Additional genes were identified that are regulated downstream of EcR-A in fru P1 -expressing neurons. Thus, EcR-A is required in fru P1 -expressing neurons for wild-type male courtship behaviors and the establishment of male-specific neuronal architecture.