P-6

Bisexual courtship activity induced by ectopic expression of transformer and mini-white genes is suppressed by downstream actions of fruitless-satori.

Eric Nilsson, Zoltan Asztalos, Tamas Lukacsovich, Wakae Awano and Daisuke Yamamoto

（Yamamoto Behavior Genes Project, ERATO, Mitsubishi-kasei Institute for Life Sciences）

　Ectopic expression of both Transformer (Tra) protein and White protein in the brains of flies have been shown to induce bisexual courtship behavior in males. Models of sexual differentiation and development place the actions of trasformer (tra) upstream of fruitless (fru). Since the fru-sat mutation when homozygous completely suppresses courtship of females by males, and induces a low degree of homosexual courtship, it is possible to test behaviorally whether fru acts downstream of tra.

　The enhancer trap 53b-GAL4 was crossed into a fly line along with UAS-tra, to express Tra ectopically in male flies which were homozygous for the fru-sat allele. These flies were placed into courtship chambers along with either a male or female Canton-S fly acting as a sex object and the behavior of the fly pairs observed. Male flies having both 53b-GAL4 and UAS-tra in a fru-sat homozygous background were found to court females not at all, and to court males at a much reduced rate compared to flies having 53b-GAL4 and UAS-tra in a fru-sat heterozygous background. Similarly, flies with ectopic White protein expression were also found to court females not at all and males at a reduced rate in a fru-sat homozygous background.

　Thus the behavioral effects of ectopic Tra and White are abolished in the presence of homozygous fru-sat, supporting the conclusion that fru acts downstream in both these pathways controlling courtship behavior.