Transcription dynamics and regulation of heat shock protein genes during stress and development in the estuarine cnidarian Nematostella vectensis

Heat shock proteins (HSPs) are molecular chaperones that function in protecting cells from proteotoxicity. Eukaryotes have multiple HSPs that localize in the cytoplasm, endoplasmic reticulum (ER), and mitochondria. In cnidarian species, where HSPs are often used as biomarkers of environmental stress, little is known about how particular HSPs vary in copy number, expression, inducibility, and regulation within a species. Here, we characterized the full repertoire of HSP70 and HSP90 genes in an emerging model cnidarian, Nematostella vectensis. We identified five HSP70 and three HSP90 genes, with at least one homolog from each family belonging to the three primary clades based on subcellular localization. Although transcriptional induction remained insignificant by a 10 °C temperature change, two cytosolic HSP70s and one cytosolic HSP90 were significantly upregulated with a 20 °C temperature increase. Most HSPs exhibited similar developmental expression patterns, with elevated expression during the early larval stage followed by reduced expression in the juvenile stage. HSPs showed evidence for differential expression across cell types, with multiple cytosolic and ER HSPs being highly expressed in neuronal and cnidocyte populations. Moreover, the putative promoters of N. vectensis HSPs differed in both the abundance and sequences of regulatory heat shock element motifs, providing a potential mechanism of functional diversification in response to temperature and development. By characterizing expression of all HSP70 and HSP90 genes in this cnidarian, we reveal distinct roles of these core chaperones in the proteostasis response, providing a foundation for future functional studies on contributions of HSPs to cnidarian life cycle and stress resilience.