Comprehensive analysis of growth performance, antioxidant capacity, digestive enzyme activity, and transcriptomics provides insights into the chronic high-temperature stress response of brass gudgeon (Coreius heterodon) in the Yangtze River.

Global warming poses a serious threat to both wild and farmed fish. The brass gudgeon (Coreius heterodon) is a unique species of the Yangtze River and has important scientific value for studies of the impact of climate change. In this study, brass gudgeon were cultured for 40 days at 22 °C as control group, and at 27°C and 32°C as mild and severe high-temperature groups, respectively. After 40 days, the growth performance, liver antioxidant capacity, and intestinal digestive enzyme activities of each group were compared. Then, transcriptome sequencing analysis of liver and kidney of the 22°C and 32°C groups was performed. The results showed temperatures of 27°C and 32°C influenced growth performance, especially at 32 °C. High temperature caused varying degrees of damage to liver antioxidant capacity and intestinal digestive enzyme activities in brass gudgeon. Transcriptome analysis identified 1953 and 6709 differentially expressed genes (DEGs) in liver and kidney, respectively. We identified three candidate pathways through KEGG analysis, namely, "protein process in the endoplasmic reticulum," "toll-like receptor signaling pathway," and "fatty acid degradation." DEGs involved in these pathways were mainly related to protein processing (HSP40, HSP70, and HSP90), immune system (TLR3, TLR8, IL1 β, and IL8), and lipid metabolism (FAD1, FADE, and ACAT), indicating that these functions might be adaptive regulatory mechanism of brass gudgeon in response to high-temperature stress. These results will help to elucidate the molecular mechanism of tolerance to high-temperature stress, enrich genetic resources, and provide reference data for large-scale artificial breeding of brass gudgeon.