Molecular mechanisms underlying the maintenance of protein homeostasis in pearl gentian grouper under acute high-temperature stress.

Pearl gentian grouper (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂) is a key farmed marine fish along the southeastern coast of China known for its hybrid vigor and high economic value. However, high-temperature stress induced by frequent summer heatwaves and global warming in these aquaculture areas could disrupt protein homeostasis and intensify endoplasmic reticulum (ER) stress in this grouper, leading to cellular dysfunction and disease. Here, we employed RNA-Seq sequencing to analyze the gene expression changes and biological processes involved in protein homeostasis in the liver of pearl gentian grouper under temperature gradient stress (25 °C, 30 °C, 34 °C, 38 °C, and 38 °C sustained for 6 h). A total of 4144 differentially expressed genes, two significantly expressed gene profiles (Profile 0 and Profile 15), and two high-temperature-specific modules were identified. Based on gene function and pathway enrichment analyses, protein processing in the ER was emerged as a principal metabolic pathway in the response to acute high-temperature stress in pearl gentian grouper. Genes involved in protein sorting, transport, folding, and degradation within this pathway were consistently up-regulated at 25-38 °C, whereas most were down-regulated at 38 °C sustained for 6 h‌. Furthermore, 38 °C was identified as the critical temperature point for a protein homeostasis imbalance in this grouper. These findings provide new insights into the molecular basis for the maintenance of protein homeostasis in pearl gentian grouper under acute high-temperature stress and offer valuable scientific guidance for optimizing high-temperature aquaculture management.