Involvement of thedoublesexgene in body color masculinization of the blue-tailed damselfly,Ischnura senegalensis

AbstractOdonata (dragonflies and damselflies) display remarkable color pattern diversity including sexual dimorphism and intrasexual polymorphism. We previously found that expression of a sex-determining transcription factor, thedoublesex(dsx) gene, is associated with female color polymorphism (gynomorph for female-specific color and andromorph for male mimicking color) in the blue-tailed damselfly,Ischnura senegalensis. Here we investigate the function of dsx gene on thoracic coloration by electroporation-mediated RNA interference (RNAi). RNAi of thedsxcommon region changed color patterns of males and andromorphic females to patterns of gynomorphic females. Further, gynomorphic color pattern was not affected bydsxRNAi. The long isoform ofdsxRNAi produced no effects, suggesting that the short isoform ofdsxis important for body color masculinization in both males and andromorphic females. Expression pattern changes were also examined in five genes with different expression levels between sexes and female morphs. Among these genes are two melanin suppressing genes,blackandebony, that were upregulated in thedsx-RNAi region compared to a control region. Upregulation coincides with a gynomorphic orange color instead of the black stripe observed in males and andromorphic females.dsxmay regulate male color differentiation by suppressingblackandebonyin the thoracic region ofI. senegalensis.Results add to the understanding of molecular mechanisms underlying the evolution of female polymorphism in Odonata.