Probably acts as a transcriptional regulator. Part of the somatic sex determination hierarchy; sex determination genes transformer (tra) and transformer-2 (tra-2) switch fru splicing from the male-specific pattern to the female-specific pattern through activation of the female-specific fru 5'-splice site. Vital for the development of males and females. Controls the development of the male specific abdominal muscle of Lawrence. Plays a role in male courtship behavior and sexual orientation. Enhances male-specific expression of takeout in brain-associated fat body. Sex specific splicing is controlled by tra and tra-2. Sex-specific repression of the translation of fru mRNA might be mediated by the binding of Tra to the fru mRNA in females. Expressed in parts of the adult male brain associated with the courtship song and steps of the male courtship. Also expressed in the larval and pupal male mushroom body and optic lobe. Expressed in pupal female optic lobe. Mutant males exhibit bisexual behavior; they court females but are behaviorally sterile so fail to mate and they exhibit vigorous courtship with other fru mutant males.