fruitless functions downstream of doublesex to promote sexual dimorphism of the gonad stem cell niche

Background: doublesex (dsx) and fruitless (fru) are the two downstream transcription factors that actuate Drosophila sex determination. While dsx assists fru to regulate sex-specific behavior, whether fru collaborates with dsx in regulating other aspects of sexual dimorphism remains unknown. One important aspect of sexual dimorphism is found in the gonad stem cell (GSC) niches, where male and female GSCs are regulated to create large numbers of sperm and eggs. Results: Here we report that Fru is expressed male-specifically in the GSC niche and plays important roles in the development and maintenance of these cells. Unlike previously studied regulation of sex-specific Fru expression, which is regulated by alternative splicing by Transformer (Tra), we show that male-specific expression of fru is regulated downstream of dsx, and is independent of Tra. Regulation of fru by dsx also occurs in the nervous system. fru genetically interacts with dsx to support maintenance of the hub throughout development. Ectopic expression of fru inhibited female niche formation and partially masculinized the ovary. fru is also required autonomously for cyst stem cell maintenance and cyst cell survival. Finally, we identified a conserved Dsx binding ...Continue Reading