Hepatic transcriptomic analysis reveals that Hif1α/ldha signal is involved in the regulation of hypoxia stress in black rockfish Sebastes schlegelii

Hypoxia has become a common problem for aquatic organisms due to the interaction of global climate change and human activity. Black rockfish inhabits rocky reefs in waters of Japan, Korea and China, whereas the limited hypoxia tolerance leads to mass mortality and great economic loss. In this study, high-throughput RNA-seq for transcriptomic analysis was used to investigate the hepatic response in black rockfish under hypoxia (critical oxygen tension, Pcrit; loss of equilibrium, LOE) and reoxygenation (recover normal dissolved oxygen 24 h, R24) to explore the mechanisms underlying hypoxia tolerance and adaptation. A total of 573,040,410 clean reads and 299 differentially expressed genes (DEGs) in total were obtained during hypoxia and reoxygenation. GO annotation and Kyoto Encyclopedia of Genes and Genomes analysis demonstrated that the DEGs are mainly enriched in the biochemical metabolic pathways and HIF-1 signaling pathways. Transcriptomic analysis also identified 18 DEGs associated with HIF-1 signaling pathway (hif1α, tf, epo, hmox, gult1, mknk2, ldha, pfkfb3, hkdc, aldoa) and biological process (hif2α, apoeb, bcl6, mr1, errfi1, slc38a4, igfbp1a, ap4m1) as further validated by quantitative real-time PCR. Moreover, hif1α was positively or negatively correlated with glucose (ldha, pfkfb3, hkdc, aldoa) and lipid (apoeb) metabolism-related genes. The mRNA level of hif1α was significantly up-regulated under acute hypoxia stress and obtained the higher values than hif2α. Meanwhile, hif1α recognized the hypoxia response element located in the promoter of ldha and directly bound to the promoter to transactivate ldha expression. These results indicated that black rockfish may mainly utilize glycolysis to maintain homeostasis, and hif1α facilities hypoxia tolerance by modulating ldha expression.