Comprehensive genome-wide identification, molecular characterisation, and expression profiling of HSP gene families in Bufo gargarizans.

Heat shock proteins (HSPs) play essential roles in cellular stress responses and development. However, these proteins have not been adequately characterised in the amphibian Bufo gargarizans. In this study, we performed genome-wide identification of the HSP family in B. gargarizans and investigated their expression dynamics under cold stress. A total of 56 BgaHSPs were identified, which were classified into six subfamilies (HSP10, HSP20, HSP40, HSP60, HSP70, and HSP90) and unevenly distributed across 10 chromosomes. Structure and motif analyses revealed family-specific conservation and divergence in gene architecture and motif composition. Transcriptome profiling of the heart over a time course of cold exposure (0-24 h) showed that cold modulates the expression of BgaHSPs. Weighted gene co-expression network analysis (WGCNA) identified the module that significantly correlated with the duration of cold stress; genes within this module were enriched in stress-related gene ontology terms (e.g., response to heat and unfolded protein binding). Notably, several genes, including BgaHSP90B1, BgaHSPA13, and BgaHSPA5, exhibited progressively increased expression upon prolonged cold exposure. This study provides the first comprehensive genome-wide characterisation of the HSP family in B. gargarizans and reveals temporal expression patterns of BgaHSPs under cold stress, establishing a foundation for understanding HSP-mediated stress adaptation in amphibians.