Genome-Wide Identification, Evolutionary Analysis and Seasonal Expression Patterns of the Sox Gene Family in the Daurian Ground Squirrel (Spermophilus dauricus)

The Sox (SRY-related high-mobility group box) gene family encodes transcription factors characterized by a conserved high-mobility group (HMG) box DNA-binding domain and plays essential roles in metazoan development, including sex determination, embryogenesis, neurogenesis, organogenesis, and reproductive regulation. Seasonal breeders provide valuable models for investigating reproductive regulation. The Daurian ground squirrel (Spermophilus dauricus) is a typical species for studying seasonal reproductive adaptation. In this study, Sox genes were identified at the genome-wide level in the Daurian ground squirrel. A total of 11 genes were identified and classified into 5 subfamilies, SoxC (SdSox4, SdSox11), SoxD (SdSox5, SdSox6, SdSox13), SoxE (SdSox8, SdSox9, SdSox10), SoxF (SdSox17, SdSox18), SoxG (SdSox15). Structural and evolutionary analyses revealed conserved HMG domains along with diversification among subfamilies. The genetic homology of the Sox family between the Daurian ground squirrel and the Thirteen-lined ground squirrel (Ictidomys tridecemlineatus) was discovered through collinearity analysis. Furthermore, hematoxylin and eosin (HE) staining revealed seasonal morphological changes in the testes of the adult Daurian ground squirrel. The seasonal expression patterns of 7 reproduction-related Sox genes were analyzed in testicular tissues. All analyzed genes exhibited significantly higher expression levels in the breeding season than the non-breeding season. Notably, SdSox5, SdSox6, SdSox8, and SdSox13 showed pronounced seasonal differences in expression by the real-time quantitative polymerase chain reaction (RT-qPCR). This study provides new insights into the evolutionary characteristics and potential roles of Sox genes in seasonal reproductive regulation in mammals.