| Courtship and copulation behaviors in Drosophila melanogaster males are regulated by sex-specific products from the gene fruitless (fru). Male-specific FRU proteins (FRU M) are putative transcription factors of the BTB-ZnF family that likely act by controlling development and maintenance of the neural circuitry used during male sexual behavior. However, which neuronal characteristics are regulated by FRUM is mostly unknown and how FRUM neurons are grouped into circuits and the role that specific neuronal circuits play in sexual behavior has not been elucidated. I have identified a subset of FRUM neurons that co-express the transcription factor, Engrailed (En). After fruM-RNAi-induced targeted removal of FRUM proteins from FRUM/En neurons, males were impaired in their ability to initiate or maintain copulation. Further, I examined two characteristics, the initial projections and neurotransmitters used by FRUM/En neurons. Males and females showed a difference in the neurochemistry of FRUM/En neurons in the thoracic ganglia; this neurochemistry is disrupted in fru mutant males.; For one cohort of serotonergic neurons in the abdominal ganglion that were previously shown to be dependent on FRUM for expression of serotonin, I determined that FRUM works in conjunction with other sex-specific genes, TAKEOUT (TO) and DOUBLESEX (DSX), to induce of serotonin expression in males; in females serotonin expression is repressed by DSX and TO.; Finally, I performed a genetic screen for genes that interact with, or are downstream targets of, fru, dsx, or dissatisfaction (dsf). I assessed fertility, copulation success, and abdominal muscle development of EMS-mutagenized flies, resulting in one fly line in which homozygous mutant animals had a novel muscle phenotype. By genetic tests, the mutation was found to be allelic to string, which encodes a Cdc25-like phosphatase.; Taken together, my research demonstrates that subsets of FRUM neurons function in circumscribed circuits to regulate specific portions of sexual behavior, and that FRUM, along with other sex-specific genes, controls development of these neurons in part by determining neurochemistry. Further, FRUM likely directs multiple downstream targets, in different subsets of neurons in which it is expressed, which collectively provide correct development of neural circuits underlying courtship and copulation behavior. |
