Differential Expression and Alternative Splicing Pattern in Female and Male Groups Pelteobagrus ussuriensis with Different Growth Rate

Growth rate is a key trait influencing productivity in aquaculture species, and its regulation often differs between males and females. In this study, Nanopore full-length RNA sequencing was used to investigate sex-specific growth regulation in the liver and brain of <i>Pelteobagrus ussuriensis</i>. Male and female groups each included three fast-growing and three slow-growing individuals. In liver tissue, 332 differentially expressed genes were identified in males and 266 in females. Male-biased genes were mainly involved in lipid and cholesterol metabolism, including the peroxisome proliferator-activated receptor signaling pathway, whereas females showed broader metabolic regulation involving carbohydrate, amino acid, and lipid metabolism, as well as growth-related genes such as IGFBP1, ESR1, and PGR. In brain tissue, fewer growth-associated differences were observed, with 26 differentially expressed genes in males and 45 in females. Alternative splicing analysis revealed strong tissue specificity, with approximately 2903 events in liver and 7412 in brain, dominated by exon skipping in liver and alternative first exon usage in brain. Isoform-level analysis further identified transcript differences not detected at the gene level, highlighting the importance of transcript diversity in growth regulation.