Molecular Characterization and Expression Profiling of ThreeTransformer-2Splice Isoforms in the Redclaw Crayfish,Cherax quadricarinatus

Sex determination/sex differentiation is determined by genetics, environmental factors, or the interactions of the two. TheTransformer-2(Tra-2) gene plays an important role in the sex determination cascade signal pathway in insects. In this study, theTra-2gene was isolated and characterized from the cDNA library of gonad tissues in the redclaw crayfish,Cherax quadricarinatus.Three splice variants were identified, designated asCqTra-2A, CqTra-2B, andCqTra-2C, and sequence analysis showed that they had a highly conserved RRM domain. Phylogenetic analysis was performed by the NJ method, and the results revealed that the Tra-2 protein of the redclaw crayfish was very closely related to those ofMacrobrachium rosenbergii,Fenneropenaeus chinensis, andMacrobrachium nipponense.Real-time PCR analysis showed that the three isoforms were predominantly expressed in the ovary and gradually increased with embryonic development. Additionally, the expression pattern ofCqTra-2at different developmental stages was analyzed by qPCR and revealed that the phase of having a body length of 3 cm may be the key period for the sex differentiation ofC. quadricarinatus.RNAi-targeting gene silencing further confirmed the function ofCqTra-2in sexual differentiation in redclaw crayfish. Our experimental data will contribute to understanding the mechanism of sex determination in crustaceans.