Comparison of muscle structure and transcriptome analysis reveals the mechanism of growth variation in Yangtze sturgeon (Acipenser dabryanus)

Sturgeons display a slow growth rate and delayed initial sexual maturity, which extends the captive breeding and conservation processes. To date, few studies have revealed the molecular mechanism underlying the growth difference of sturgeons. In the present study, juvenile Yangtze sturgeons (Acipenser dabryanus) with different growth rates were selected from the same cultured pool for muscle structure, enzyme activity and comparative transcriptome analysis. Histological assays showed that the fiber diameter of the fast-growing group was significantly larger than that of the slow-growing group. The activities of four glycometabolism related enzymes, including two key rate-limiting enzymes hexokinase and pyruvate kinase, were significantly higher in fastgrowing group. RNA-Seq of muscle tissues identified 7408 differentially expressed genes (DEGs), which consisted of 3637 upregulated genes and 3771 downregulated genes, in the fast-growing group vs. the slow-growing group. In the brain, a total of 12,213 unigenes were differentially expressed (6050 upregulated unigenes and 6163 downregulated unigenes) between the two groups. The expression levels of IGF1 and IGF1-binding proteins (IGFBPs) in muscle were significantly higher in the fast-growing group and might be promising candidate biomarkers for measuring growth performance in Yangtze sturgeon. Two myogenic regulatory factors (myog and myf6) were significantly upregulated, which indicated that the growth variation in juvenile Yangtze sturgeon might be partly due to the difference in the differentiation of muscle cells. In addition, pathway enrichment analysis revealed that the glycolysis and cell cycle pathways were significantly enhanced in the fast-growing groups, suggesting that they might also play important roles in the improved growth performance of A. dabryanus. Furthermore, the WGCNA as well as hub gene network analyses supported that cell cycle and gluconeogenesis might be involved in the differential growth performance of A. dabryanus. The results of this study may contribute to our understanding of the underlying molecular mechanism of growth variation in fish.