Selection of Heat-Resistant Strains in Bohai Red Scallops and Their Transcriptomic Responses to Heat Stress

Abstract

Temperature has consistently been a critical environmental factor in the cultivation of scallops, and with global warming, marine animals will likely experience even more exposure to heat stress. Thus, it is necessary to select heat-resistant strains in scallops. The upper median lethal temperature (LT50) of Bohai Red scallops was initially determined. Subsequently, we selected heat-resistant scallops (elite group, EG) by exposing Bohai Red scallops to the determined LT50 (28.9°C). Heat-resistant F1 offspring (EGF1) were reproduced from the selected individuals in EG. Tolerance to heat stress was significantly increased in EGF1, as evidenced by the elevated LT50 and the activities of certain antioxidant enzymes. Transcriptomic analyses demonstrated that both EG and control group (CG), animals were capable of resisting heat stress and maintaining cellular homeostasis probably through the action of protein folding. A significant enhancement was observed in the activity of pathways related to energy metabolism and antioxidant mechanisms, particularly those involving glutathione and amino acid metabolism. Furthermore, the scallops in the EG group showed a strong immune profile, with immune-related DEGs enriched mainly in interleukin-1 receptor binding and Toll-like receptor pathways. Using Weighted gene co-expression network analysis (WGCNA), we discovered the module MM.darkolivegreen, which showing the strongest positive association with heat stress. Subsequent GO and KEGG enrichment analyses of this module highlighted pathways that aligned with those identified in differentially expressed genes, thereby providing mutual validation of the results. These results enhance our understanding of the molecular mechanisms driving heat stress adaptation in Bohai Red scallops and establish a theoretical foundation for the inheritance and evolution of heat-resistant traits.

Keywords: The scallop 'Bohai Red', heat-resistant selection, transcriptomics, antioxidant, immune system