Transcriptomics Unveil <i>Dsx1</i> as a Critical Regulator in Sexual Dimorphism of Crustaceans

Sexually dimorphic traits are involved in reproductive competition and are specified during development through sex-biased gene expression programs. Here, we test this hypothesis using RNA-seq data from male and female T3 legs throughout the development of crustacean amphipods. Through comparative transcriptome, we found that Dsx1 shows male-biased expression during development of Morinoia aosen, and explored its phylogeny. Next, we performed RNA interference on amputated males, and found that knockdown of Dsx1 cause the feminization of the regenerated dactylus of T3 legs. Finally, to understand the genetic regulation of the embryonic development of sex differences, we conducted CRISPR-Cas9 knockout in crustacean model species Parhyale hawaiensis, to validate the feminization of T3 legs in male mutants. Together, phylogenetic analyses and gene knockout experiments identified homologous genes and revealed the conserved function of Dsx1 across different species. Our study provides insight into the causal relationship between sex-biased gene expression and sexually dimorphic traits.