Functional analysis of fruitless gene expression by transgenic manipulations of Drosophila courtship

Abstract

A gal4-containing enhancer–trap called C309 was previously shown to cause subnormal courtship of Drosophila males toward females and courtship among males when driving a conditional disrupter of synaptic transmission (shi^TS). We extended these manipulations to analyze all features of male-specific behavior, including courtship song, which was almost eliminated by driving shi^TS at high temperature. In the context of singing defects and homosexual courtship affected by mutations in the fru gene, a tra-regulated component of the sex-determination hierarchy, we found a C309/tra^F combination also to induce high levels of courtship between pairs of males and “chaining” behavior in groups; however, these doubly transgenic males sang normally. Because production of male-specific FRU^M protein is regulated by TRA, we hypothesized that a fru-derived transgene encoding the male (M) form of an Inhibitory RNA (fru^MIR) would mimic the effects of tra^F; but C309/fru^MIR males exhibited no courtship chaining, although they courted other males in single-pair tests. Double-labeling of neurons in which GFP was driven by C309 revealed that 10 of the 20 CNS clusters containing FRU^M in wild-type males included coexpressing neurons. Histological analysis of the developing CNS could not rationalize the absence of tra^F or fru^MIR effects on courtship song, because we found C309 to be coexpressed with FRU^M within the same 10 neuronal clusters in pupae. Thus, we hypothesize that elimination of singing behavior by the C309/shi^TS combination involves neurons acting downstream of FRU^M cells

• reproductive behavior
• C309 enhancer trap
• shiTS transgene
• traF transgene
• inhibitory fru RNA transgene