Selection Of Cold-Resistant Scallop Strains and Their Transcriptomic Response to Cold Stress

Abstract

The Bohai Red scallop, an important aquaculture strain in China, has limited growth potential due to its low cold tolerance. This study aimed to develop a cold-resistant strain through selective breeding. Bohai Red scallops were stressed with LT50, Scallops that survived (EL group) were used as brood stocks to reproduce cold-resistant offspring (F1EL), and the unselected scallops (C group) were used to reproduced control offspring (F1C). The F2EL and F2C were similarly reproduced. Results showed that F1EL had significantly lower LT50 and higher survival rates than F1C, and F2EL had even further improved cold tolerance. The activities of CAT and SOD of F2EL were significantly higher than F2C, and MDA content of F2EL was significantly lower than F2C, suggesting enhanced ability to scavenge reactive oxygen species (ROS) and protect the organism from oxidative damage under cold stress in the selected offspring. In F2EL, the baseline expression level (0h) of the HSP90AB1 gene was higher than F2C, showing a “pre-activated” expression pattern.  RNA-seq was employed to analyze differentially expressed genes in the EL and C groups under cold stress. Enrichment analyses revealed that cold stress likely disrupts metabolic processes in Bohai Red scallops, inducing oxidative damage, activating apoptosis-related signaling pathways, and promoting interactions between molecular chaperone proteins. Additionally, the EL group exhibited higher metabolic activity than the C group, indicating a more efficient adaptation to cold stress by producing protective metabolites and maintaining energy supply. This study may provide a theoretical foundation for the selective breeding of cold-resistant scallop strains and a deeper understanding of the molecular responses to cold stress in Bohai Red scallops.

Keywords: Bohai Red scallop, Cold stress, selective breeding, RNA-seq, Stress memory