SRA

Purpose: Sexual dimorphisms fuel significant intraspecific variation and evolutionary diversification. Yet the developmental-genetic mechanisms underlying sex-specific development remain poorly understood. We focused on the conserved sex-determination gene doublesex (dsx) and the mechanisms by which it mediates sex-specific development in a species of horned beetle by combining systemic dsx knockdown, high-throughput sequencing of diverse tissues, and a genome-wide analysis of Dsx binding sites. We find that Dsx regulates sex-biased expression predominantly in males, that Dsx's target repertoires are highly sex- and tissue-specific, and that Dsx can exercise its regulatory role via two distinct mechanisms: as a sex-specific modulator by regulating strictly sex-specific targets, or as a switch by regulating the same genes in males and females in opposite directions. More generally, our results suggest Dsx can rapidly acquire new target gene repertoires to accommodate evolutionarily novel traits, evidenced by the large and unique repertoire identified in head horns, a recent morphological innovation. Overall design: Control and dsxRNAi individuals were collected within the first day after pupation. Six male and six female pupae from each group were sampled tissue for four distinct regions: the supraesophageal ganglion (brain), genitalia, thoracic horns, and head horns.