Genome-wide identification, characterization and expression analysis of the HSP70 gene family in seagrass Zostera marina under abiotic stress

Seagrasses represent a distinctive clade of angiosperms adapted to marine ecosystems. As essential molecular chaperones, heat shock protein 70 (HSP70) plays a critical role in protein folding, stabilization, and maturation, thereby supporting plant growth and environmental stress adaptation. However, a systematic investigation of the HSP70 gene family in seagrass remains conspicuously absent. In this study, we conducted a genome-wide identification and comprehensive analysis of the HSP70 genes in seagrass Z. marina. A total of 21 ZmHSP70 genes were identified and classified into six subfamilies based on their phylogenetic relationships. These genes were distributed across all six chromosomes. ZmHSP70 proteins were predicted to be predominantly localized to the cytosol and cytoskeleton. Two pairs of tandem duplication events under strong purifying selection were identified within ZmHSP70 genes. Conserved motif compositions and exon-intron configurations were analyzed. Cis-element analysis showed high enrichment in light- and MeJA-responsive elements, implying their critical role in stress adaptation. Transcriptomic profiling revealed differential expression patterns of ZmHSP70 across various tissues. qRT-PCR analysis demonstrated that six selected ZmHSP70 genes exhibited a rapid upregulation in response to heat stress, whereas their expression showed a mild reaction under drought conditions, with significant upregulation after 12 h. Under cold treatment, the expression levels of most genes show a downward trend at 12 h. Under salt treatment, only two genes exhibited upregulated expression after 6 and 12 h of treatment. This study systematically identified and characterized the Hsp70 gene family in Z. marina. Our findings collectively demonstrate the involvement of ZmHSP70 genes in the abiotic stress response of Z. marina, thereby establishing a critical foundation for elucidating their role in the plant’s adaptation to the marine environment.