Integrated transcriptomic and metabolomic analyses reveal the molecular adaptive mechanisms of Schizopygopsis chengi baoxingensis under acute heat stress

Global warming alters aquatic habitats, challenging cold-water fish survival. Schizopygopsis chengi baoxingensis, a cold-water fish from the Qingyijiang River in China, is vulnerable to temperature changes. This study aimed to elucidate the molecular mechanisms underlying the response of S. c. baoxingensis to acute heat stress through an integrated approach of histopathological, transcriptomic, and metabolomic analyses. Histopathological results revealed significant tissue damage in both the liver and gills, with the liver showing pronounced hepatocellular vacuolization and nuclear displacement, and the gills exhibiting hyperplasia and partial lamellar necrosis. Transcriptomic analysis identified numerous differentially expressed genes (DEGs) in both tissues. In the liver, DEGs were enriched in pathways related to antioxidant stress, detoxification, and immune response. Notably, genes encoding glutathione S-transferase (GST) and UDP-glucuronosyltransferase (UGT) were upregulated, suggesting enhanced antioxidant and detoxification capabilities. Additionally, immune-related genes such as C2, C3, C4, C6, C9, CFB, CFH, and MASP2 were predominantly upregulated in the complement and coagulation cascades pathway. In the gills, DEGs including NPNT and NOS2 were significantly upregulated, suggesting enhanced respiratory function. Metabolomic profiling showed significant alterations in energy metabolism, with increased levels of NAD and NADH in the liver, indicating heightened energy demands under thermal stress. Our findings provide valuable insights into the molecular mechanisms underlying the heat stress response of S. c. baoxingensis and highlight potential targets for protecting this species under climate change.