Identification, Expression and Evolution of Short-Chain Dehydrogenases/Reductases in Nile Tilapia ().

The short-chain dehydrogenases/reductases (SDR) superfamily is involved in multiple physiological processes. In this study, genome-wide identification and comprehensive analysis of superfamily were carried out in 29 animal species based on the latest genome databases. Overall, the number of genes in animals increased with whole genome duplication (WGD), suggesting the expansion of s during evolution, especially in 3R-WGD and polyploidization of teleosts. Phylogenetic analysis indicated that vertebrates SDRs were clustered into five categories: classical, extended, undefined, atypical, and complex. Moreover, tandem duplication of and was observed in teleosts analyzed. Additionally, tandem duplications of , , and were observed in all cichlids analyzed, and tandem duplication of was observed in tilapiines. Transcriptome analysis of adult fish revealed that 93 s were expressed in more than one tissue and 5 in one tissue only. Transcriptome analysis of gonads from different developmental stages showed that expression of 17 s were sexually dimorphic with 11 higher in ovary and 6 higher in testis. The sexually dimorphic expressions of these were confirmed by in situ hybridization () and qPCR, indicating their possible roles in steroidogenesis and gonadal differentiation. Taken together, the identification and the expression data obtained in this study contribute to a better understanding of SDR superfamily evolution and functions in teleosts.