Comprehensive characterization of transcriptional regulation during HCG-induced follicle maturation in mandarin fish...

Follicle maturation is critical for egg quality and fry production, yet its transcriptional regulation remains poorly defined. In this study, we employed comparative transcriptomics across five developmental stages (SCS1-SCS5) following HCG induction to resolve stage-specific transcriptional dynamics in mandarin fish (Siniperca chuatsi) follicle. A total of 15 libraries yielded high-quality data with mapping rates of 92.50-96.79 %, identifying 17,320 differentially expressed genes (DEGs), with a pronounced increase in later maturation stages. Functional enrichment highlighted stage-specific activation of key biological processes, including oocyte maturation, steroid biosynthesis, meiotic regulation, lysosomal proteolysis, fatty acid degradation, and immune responses. Notably, core cell-cycle regulators (CDC20, BUB1Bb, PKMYT1, YWHAE1) exhibited dynamic patterns consistent with meiotic resumption, indicating activation of the maturation-promoting factor (MPF) and APC/C pathways. Yolk hydrolysis was mediated by lysosomal proteases (CTSBa, CTSC) and ubiquitin-proteasome system genes (CDC34a), while lipid metabolism supported lipid droplet formation. Stage-specific immune activation further suggested complex immune-reproductive crosstalk. Co-expression network analysis further identified key hub genes positively (e.g., CDC20, BUB1Bb, SETD2) or negatively (e.g., MRPL4, RPS3) associated with maturation. Collectively, this study provides a comprehensive transcriptomic resource and reveals critical pathways and regulators, offering molecular insights to refine hormonal induction and selective breeding strategies in aquaculture.