Comprehensive identification, phylogenetic analysis, and sex-biased expression of the Sox gene family in Spinibarbus hollandi.

The Sox gene family plays a fundamental role in vertebrate reproductive processes, including sex determination, gonadal development, and steroidogenesis. In this study, 42 Sox genes were systematically identified in the genome of Spinibarbus hollandi and categorized into seven subfamilies (B1, B2, C, D, E, F, and H) based on phylogenetic and conserved domain analyses.Comparative genomics and gene structure evaluations demonstrated high evolutionary conservation alongside functional diversification, likely driven by teleost-specific whole-genome duplication (TS-WGD). Quantitative real-time PCR (qRT-PCR) across eight adult tissues revealed distinct expression profiles: 14 genes exhibited brain-predominant expression, with eight of these being the most abundant across all tissues. Notably, significant sexual dimorphism was observed in the gonads; Sox-3 and Sox-11b were characterized as female-biased (ovary-enriched), while Sox-9a/9b and Sox-30 were identified as male-biased (testis-enriched). Masculinization experiments induced by 17α-methyltestosterone (MT) demonstrated that exogenous androgens suppress female-biased Sox genes and activate male-biased ones, facilitating ovarian transformation into testis-like tissue via an androgen receptor-mediated regulatory cascade. Interestingly, Sox-17 and Sox-10 maintained stable expression across different gonadal states, suggesting their involvement in cellular homeostasis independent of hormonal fluctuations. Collectively, these findings elucidate the functional plasticity and endocrine-regulatory roles of Sox genes in teleost gonadal differentiation, providing a molecular basis for understanding sex determination mechanisms and enhancing sex-control technologies in aquaculture.