Dissection of the control of sexual behavior by the fruitless gene. E. Reynaud , J. Hatzidakis , B. Baker. Dept. Biological Sciences. Stanford University. Stanford CA 94305-5020.

   The fruitless (fru) gene controls a branch of the sex determination pathway that regulates most, if not all, aspects of male sexual behavior in Drosophila melanogaster. The fru gene encodes a zinc finger transcription factors of the tram-track family. There are two kinds of fru transcripts: sex-specifically processed and non sex-specifically processed. The sex-specific transcripts control male sexual behavior and are the products of the P1 fru promoter. These transcripts are only expressed in a small fraction [ca. 1%] of the cells in the CNS. These neurons are mostly found in small groups and less often as isolated cells. We are interested in understanding the roles of these groups of neurons in the different stages of male sexual behavior. To address this question, we are currently isolating enhancers of fru to drive the expression of the GAL-4 protein to subsets of neurons that express the sex-specific forms of the fru protein. The fru transcriptional unit is complex and spans about 150kb. We have subcloned this entire region (as 26 fragments), into the enhancer testing Drosophila transformation vector pPT-GAL4 and generated several independent fly lines carrying each fragment (65 in total). We are currently testing these lines for their ability to drive the expression of UAS-GFP in subsets of neurons. Antibodies to the male-specific fru proteins are then used to identify the lines where enhancers drive the expression of UAS-GFP in subsets of the neurons in which fru's male-specific products are normally expressed. To study the behavioral roles of these subsets of cells we plan to inhibit the activity of the fru-GAL4 expressing neurons by driving the expression of toxins and cell death genes in these cells.