Heat shock protein 70 (Hsp70) and heat shock transcription factor (Hsf) gene families in Cynoglossus semilaevis: genome-wide identification and correlation analysis in response to low salinity stress

Genome-wide characterisation and correlation analysis between gene families and environmental stresses are important for understanding the adaptive evolution of marine animals to various environments. Heat shock protein 70 (Hsp70) and heat shock transcription factor (Hsf) are two important gene families that are associated with abiotic stresses and immune responses. In this study, the evolutionary history and function of Hsp70 and Hsf family genes were investigated in Cynoglossus semilaevis through an exhaustive search of all genomic resources. In addition, their regulatory mechanisms and cooperative relationship in marine fishes were investigated in response to various degrees of salinity stress. Gene structure, motif analysis and phylogenetic trees among various organisms provide references for biological and evolutionary studies of these genes. Most Hsp70 genes were upregulated under low salinity stress, especially heat shock protein family A member 5 (hspa5), whereas hsf1 and hsf2 were downregulated. The expression profile of Hsp70 genes under low salinity stress decreased the activity of hsf1 and hsf2, suggesting that transcriptional repression of Hsf occurs when a certain level of Hsp70 is reached. These findings may improve our understanding the regulatory mechanisms between Hsp70 and Hsf gene families in response to environmental stress and provide useful resources for future studies on these gene families.