Integrated analysis about the effects of heat stress on physiological responses and energy metabolism in Gymnocypris chilianensis.

The temperature of the rivers in the Qilian Mountains, China varies widely from day to night, and Gymnocypris chilianensis living in these rivers may experience a change of 10 °C to 20 °C within a day. To explore the mechanisms underlying G. chilianensis responses to heat stress, we conducted an acute temperature stress experiment. In response to heat stress, levels of antioxidant enzymes (SOD\CAT\MDA) first increased and then decreased with time, but T-AOC levels only decreased. The activities of key glycolytic enzymes HK and PFK in the liver also first increased and then decreased and transaminase (AST/ALT) activity increased significantly. We obtained 5350 significantly different genes through transcriptome sequencing with enrichment pathways including primarily glycine, serine and threonine metabolism, cysteine and methionine metabolism, tryptophan metabolism, fructose and mannose metabolism, steroid hormone biosynthesis, and fatty acid degradation. A total of 457 differential metabolites were identified in the liver under thermal stress, most of which are involved in biochemical pathways of amino acid metabolism. Biosynthesis of amino acids indicated that G. chilianensis maintained physiological homeostasis by enhancing glucose metabolism and regulating lipid and amino acid metabolism pathways under thermal stress. We also randomly selected 12 key response genes for validation using qRT-PCR. This is the first study describing the mechanisms underlying responses to thermal stress in G. chilianensis, and may also provide reference data for the study of environmental mutations in indigenous fish in the Qinghai-Tibet Plateau and Qilian Mountains.