Pf-Dmrt4, a potential factor in sexual development in the pearl oyster Pinctada fucata

The mechanisms of sex determination and sex differentiation in the pearl oyster Pinctada fucata are currently poorly understood. We therefore investigated the roles of orthologs of the Dmrt gene family, key players in male gonad differentiation in mammals, in P. fucata sex differentiation and sexual development. Pf-Dmrt4 exhibits features typical of the Dmrt family, and displays significant homologies to the DMRT4 cluster. Pf-Dmrt4 mRNA expression in the gonads during a gametogenic cycle, measured by quantitative polymerase chain reaction, was maximal in mature individuals. Pf-Dmrt4 expression, demonstrated by in situ hybridization, was localized in the spermatozoa, spermatids, oocytes and vitellogenic oocytes. Knockdown of Pf-Dmrt4 with double-stranded RNA resulted in decreased mRNA expression levels. And Pf-Dmrt4-dsRNA-injected groups showed spawning-stage male gonads, with ruptured follicles and released spermatozoa. Our results enhance the understanding of sex determination and differentiation in P.fucata and suggest that Pf-Dmrt4 could be involved in male gonadal development, and maintenance of male gonadal function.