High-temperature stress response: Insights into the molecular regulation of American shad (Alosa sapidissima) using a multi-omics approach.

High temperature is an important abiotic stressor that limits the survival and growth of aquatic organisms. American shad (Alosa sapidissima), a migratory fish suitable for culturing at low temperatures, is known for its delicious taste and thus has high economic value. Studies concerning changes in A. sapidissima under high temperature are limited, especially at the gene expression and protein levels. High-temperature stress significantly reduced the survival rates and increased vacuolar degeneration and inflammatory infiltration in the gills and liver. High temperature increased the activities of SOD, CAT, and cortisol, with a trend of initial increase followed by decreases in MDA, ALP, and LDH, and irregular changes in T-AOC and Na-K-ATPase. Comprehensive analysis of the transcriptome, proteome, and metabolome of gills from fish treated with different culture temperatures (24, 27, and 30 °C) revealed that differentially expressed genes, proteins, and metabolites were highly enriched in pathways involved in protein digestion and absorption, protein processing in endoplasmic reticulum, metabolic pathways, and purine metabolism. Gene expression and protein profiles indicated that genes coding for antioxidants (i.e., cat and alpl) and members of the heat shock protein (i.e., HSP70, HSP90AA1, and HSP5) were significantly upregulated. Additionally, a conjoint analysis revealed that several key enzymes, including nucleoside diphosphate kinase 2, adenosine deaminase, and ectonucleoside triphosphate diphosphohydrolase 5/6 were altered, thereby affecting the metabolism of guanosine, guanine, and inosine. An interaction network further confirmed that levels of the essential amino acids DL-arginine and L-histidine were significantly reduced, and corticosterone levels were significantly increased, suggesting that A. sapidissima may be more dependent on amino acids for energy in vivo. Overall, this work suggests that living in a high-temperature environment leads to differential defense responses in fishes. The results provide novel perspectives for studying the molecular basis of adaptation to climate change in A. sapidissima and for genetic selection.