Examination of the roles of Foxl2 and Dmrt1 in sex differentiation and gonadal development of oysters by using RNA interference

Abstract FOXL2 and DMRT1 are transcription factors that play critical roles in sex differentiation and gonadal development in model organisms for both vertebrates and invertebrates. However, studies on Foxl2 and Dmrt1 have been restricted to levels of gene expression and localization in adult molluscs because of limitations to experimental conditions. Here, non-invasive RNA interference was conducted in order to investigate the roles of Foxl2 and Dmrt1 in sex differentiation and gonadal development in the Pacific oyster Crassostrea gigas. The results showed that feeding oysters with dsRNA of Foxl2 could knockdown gene expression corresponding to Foxl2 by 62% - 82% and led to a decrease in gonadal coverage area, hindering development in female gonads. Similar knockdown results (58% - 70%) were obtained in male oysters subjected to Dmrt1 RNAi, causing 54% of the gonads to failing to differentiate. These findings for Foxl2 and Dmrt1 in C. gigas together with the regulation of Esr expression indicated that both genes are involved in gonadal development through an estrogen signaling pathway. The inhibitory effects of DMRT1 on Foxl2 supported a hypothesis of antagonism between Foxl2 and Dmrt1 in the sex-determining pathway in oysters. The results of this study have deepened the understanding of the Foxl2 and Dmrt1 functioning underlying bivalve gonadal development and sex differentiation, thus providing useful data for the control of sex in aquaculture.