Molecular characterization and potential function of Rxr? in gonadal differentiation of Chinese soft-shelled turtle (Pelodiscus sinensis)

Retinoid X receptor (RXR) is a member of the ligand-dependent nuclear receptor family. Previous studies revealed that RXRs are involved in reproduction in vertebrates. However, information on the function of RXRs in turtles is scarce. In this study, the Rxr? cDNA sequence of Pelodiscus sinensis was cloned and analyzed, and a polyclonal antibody was constructed. RXR? protein showed a positive signal in both mature and differentiated gonads of the turtle. Subsequently, the function of the Rxr? gene in gonadal differentiation was confirmed using short interfering RNA (RNAi). The full-length cDNA sequence of the Rxr? gene in P. sinensis was 2152 bp, encoding 407 amino acids and containing typical nuclear receptor family domains, including the DNA-binding domain (DBD), ligand-binding domain (LBD), and activation function 1 (AF1). Moreover, gonadal Ps-Rxr? showed sexual dimorphism expression patterns in differentiated gonads. Real-time quantitative PCR results revealed that the Rxr? gene was highly expressed in the turtle ovary. RNAi treatment increased the number of Sertoli cells in ZZ embryonic gonads. Furthermore, RNA interference upregulated Dmrt1 and Sox9 in ZZ and ZW embryonic gonads. However, Foxl2, Cyp19a1, Stra8, and Cyp26b1 were downregulated in embryonic gonads. The results indicated that Rxr? participated in gonadal differentiation and development in P. sinensis.