Genome-wide identification and evolutionary characterization of predicted HSP70 proteins in the Cuban painted snail Polymita picta

Abstract

Climate change is expected to affect terrestrial ectotherms worldwide, including land snails, which are often characterized by limited dispersal capacity and high sensitivity to environmental fluctuations. Heat shock proteins of the 70 kDa family (HSP70) are highly conserved molecular chaperones involved in protein folding, cellular homeostasis and responses to environmental stress. Despite their biological importance, the diversity and evolution of HSP70 genes remain poorly explored in terrestrial gastropods. Here, we performed the first genome-based characterization of HSP70 genes in the Cuban painted snail Polymita picta , an endemic species of high conservation concern. Using sequence homology searches, conserved domain screening and comparative analyses, we identified ten non-redundant candidate HSP70 loci distributed across five genomic scaffolds, yielding ten predicted HSP70 protein sequences. The predicted proteins exhibited the characteristic physicochemical properties, conserved domains and motif architecture expected for cytosolic HSP70 proteins. Phylogenetic analyses grouped all P. picta sequences with cytosolic HSP70 homologues from other mollusks, whereas HSC70, HSP75 and HSP78 proteins formed distinct lineages. Pairwise sequence comparisons revealed high levels of amino acid conservation among paralogs, while Ka/Ks analyses indicated strong purifying selection across all sequence pairs. These results provide the first overview of the HSP70 repertoire currently identifiable in the P. picta genome and establish a molecular framework for future studies on stress physiology, gene expression and the evolutionary diversification of heat shock proteins in terrestrial mollusks.