Identification and characterization of hsp70 gene family in Acrossocheilus fasciatus based on genome and full-length transcripts

Global warming and temperature extremes are increasingly recognized as critical environmental stressors for aquatic species, particularly stream fish, which are becoming more vulnerable due to fluctuating water temperatures and a scarcity of thermal refuges. The hsp70 gene family plays a crucial role in maintaining cellular homeostasis and mediating stress responses, especially under thermal stress. However, the evolutionary dynamics and functional diversity of this gene family remain relatively unexplored in stream fish. In this study, we investigated the hsp70 gene family in Acrossocheilus fasciatus, an economically important stream fish, by integrating full-length transcriptome data with genomic. Through the use of genomic and full-length transcriptome sequencing, we refined the genome annotation of A. fasciatus and identified 18 hsp70 family members, including six novel genes previously unannotated in the genome. Phylogenetic, domain, and motif analyses revealed significant structural variation among these genes. Chromosomal localization demonstrated their distribution across multiple chromosomes, while synteny analysis confirmed evolutionary conservation with A. fasciatus, Danio rerio and Onychostoma macrolepis. RNA-seq and qRT-PCR analyses revealed that hsp70 genes showed minimal differential expression in brain tissue under acute thermal stress and in muscle tissue under chronic thermal stress. qRT-PCR analysis revealed significant differential expression of hsp70 genes in muscle tissue under acute thermal stress, with hspa8b, hspa13, and hyou1 exhibited marked upregulation, whereas hspa14 was significantly downregulated. These genes could serve as potential biomarkers. The integration of full-length transcriptome data with genomic information improved the precision of gene identification and genome annotation. These findings carry significant and far-reaching implications for advancing our comprehension of thermal stress in aquatic organisms, potentially informing and enhancing conservation and breeding initiatives.