The Stress of Suicide: Temporal and Spatial Expression of Putative Heat Shock Protein 70 Protect the Cells from Heat Injury in Wheat (Triticum aestivum)

Heat stress adversely affects growth, development, and yield of winter wheat (Triticum aestivum). Plants have, however, evolved mechanisms to adapt to such conditions mainly by the expression of stress-associated chaperones, the heat shock proteins (HSPs), for modulating the tolerance level. Here, we report cloning of cytosolic putative HSP70 of 1678 bp from a thermotolerant cultivar (C306) of wheat (T. aestivum). A BLASTn search showed maximum homology with the predicted HSP70 protein reported from Hordeum vulgare (accession no AK354795.1). In silico characterization showed the presence of a nucleotide-binding domain of the sugar kinase/HSP70/actin superfamily in the sequence. Putative HSP70 showed temporal and spatial variations in the expression under heat stress (HS). We observed the abundance of HSP70 protein, H2O2, proline, and guaiacol peroxidase activity during the seed-hardening stage under HS; accumulation was, however, higher in the thermotolerant C306 than in thermo-susceptible HD2329 cultivar. A gradual decrease in cell membrane stability (CMS) and an increase in total antioxidant capacity (TAC) were observed in both the cultivars at the different stages of growth. The expression of HSP70 showed a negative correlation with CMS and a positive correlation with TAC under HS; changes were less pronounced in C306 than in HD2329 at all the stages of growth studied. HSP70 seems to play diverse roles associated with thermotolerance, and partially protect wheat from terminal HS. Being the important member of family of the HSPs, HSP70 needs to be studied in detail, to be used for developing climate-smart wheat crops, through genetic engineering/breeding approaches.