Comparative analysis of hsp16 and hsp70 heat shock protein families in Caenorhabditis nematodes

The heat shock response (HSR), driven by molecular chaperons, is a key defense mechanism against proteotoxic stress. In nematodes, the hsp16 family and hsp70 family play central roles in the HSR, but their evolutionary conservation and expression patterns remain poorly understood. Here, we performed phylogenetic, genomic, and transcriptomic analyses of hsp16 and hsp70 genes in Caenorhabditis elegans and C. briggsae, and other related nematodes. Our findings show that hsp16 genes are rapidly evolving and often organized in clusters of closely spaced and oppositely oriented pairs. These genes show dynamic temporal expression in C. elegans and C. briggsae under basal, unstressed conditions. In contrast, hsp70 genes are more conserved across species and display stable expression. We also found that C. briggsae contains more orthologous HSP genes than C. elegans, and exhibits a higher proportion of constitutive expression, consistent with its greater thermal tolerance. These findings highlight the evolutionary diversification and functional organization of heat shock proteins in nematodes, offering insights into how genomic architecture and gene expression contribute to species-specific thermal adaptation.