Genome-wide Identification and Bioinformatic Characterisation of the HSP70 Gene Family in Field Pea (Pisum sativum) under Heat Stress

Abstract

The HSP70 class comprises highly conserved molecular chaperones that help preserve cellular stability when plants encounter environmental stress. Using integrated bioinformatics resources together with available databases and software, we identified and characterised 87 PsHSP70 genes in the field pea genome. Phylogenetic reconstruction separated the PsHSP70 genes into six subfamilies (A-F); subfamily E was the largest (22 members), followed by subfamily A (20), group C (18), group D (15), group B (11), and subfamily F (one member). Mapping to the seven chromosomes showed an uneven distribution, with 31 genes on chromosome 3 and only three on chromosome 2. Eight genes (PsHSP70-2, PsHSP70-17, PsHSP70-68, PsHSP70-69, PsHSP70-70, PsHSP70-75, PsHSP70-80 and PsHSP70-83) were intronless, with their corresponding proteins classified as stable. Subcellular localisation analysis indicated that chloroplasts and nuclei were the principal predicted locations of PsHSP70 proteins. Other family members were predicted in the cytoplasm, mitochondria, extracellular space, and endomembrane system, indicating a broad cellular distribution in field pea. Promoter analysis identified 27 important cis-acting elements (CREs) related to biotic and abiotic stresses and phytohormone signalling. Important abiotic stress-related elements included LTR, ARE, and TC-rich repeat elements, while CAT-box and GCN4-motif elements functioned in growth and development regulation. Some cis-acting elements, including circadian, TCCC-motif, and A-box elements, were associated with light-responsive gene expression. The genome-wide analysis of the HSP70 gene family in field pea highlighted the potential roles of HSP70 genes in stress tolerance and adaptation to environmental stimuli.