High Temperature Adaptation Mechanisms of Common Carp (Cyprinus carpio) in Globally Important Agricultural Heritage System.

Domestication has profoundly transformed human production and lifestyles. The Qingtian rice-fish co-culture system is the first globally important agricultural heritage system (GIAHS). PF-carp are a key species in the Qingtian rice-fish system and have been domesticated in rice paddies for more than a millennium, yet the mechanisms of their tolerance to high temperature conditions remain unresolved. In this study, 28℃ as the control group (C0), and two heat stress groups were established at 38℃ for 0 h (H0) and 24 h (H24). Brain tissues were sampled for physiological index measurements and transcriptomic analysis. Physiological analyses showed that the activities of SOD, CAT, and GSH-Px increased initially and then declined, whereas MDA levels exhibited a continuous increase. Transcriptome profiling identified 9,825 differentially expressed genes (DEGs). KEGG enrichment analysis of DEGs indicated that immune responses and metabolic regulation were consistently involved throughout the thermal adaptation process. During acute warming phase, pathways such as protein processing in the endoplasmic reticulum, FoxO signaling pathway and glycerophospholipid metabolism were enriched. Under prolonged high temperature exposure, cytokine-cytokine receptor interaction, PPAR signaling pathway and TGF-β signaling pathway were prominently enriched. Within these pathways, genes including grp94, hsp70, bip, nef, il-1r, tlr8, cctgα6, ccr4, cxcr3, and il-10 were significantly up-regulated (p < 0.05). These results indicate that PF-carp exhibit coordinated brain physiological and transcriptomic responses to high temperature exposure, involving protein quality control, immune signaling, and metabolic regulation. Collectively, our findings provide new insights into the mechanisms by which PF-carp adapt to thermal exposure and provide theoretical support for the breeding of heat tolerant fish.