Zinc oxide nanopriming elevates wheat drought tolerance by inducing stress-responsive genes and physio-biochemical changes

Zinc oxide nanoparticles (ZnO NPs) are currently being used in a number of applications, including agriculture. In agricultural regions all throughout the world, drought poses a serious danger to crop production and development. The outcome of this experiment showed that the treatment of 250 ppm ZnO NPs provides drought resistance by considerably improving physiological and biochemical traits, viz., shoot and root length, RWC, MSI, Zn content, total chlorophyll and protein content, biomass accumulation, osmolytes content, and antioxidant enzyme activities. Similar results were found by gene expression analysis. The expression of drought-responsive genes (DHN, DREB, P5CS, BADH, SOD, CAT, APX, bZIP and NAC) were highly upregulated in ZnO- treated plants compared with non-ZnO treated root and leaf tissues of plants under stress and non-stress conditions. The osmoregulation-related genes (P5CS and BADH) were highly expressed in ZnO treated plants over non-ZnO treated samples in both conditions (stress and control). However, the relative accumulation of these genes was higher root tissues compared to leaf tissues. According to the results, ZnO NPs caused an instantaneous rise in P5CS and BADH expression, which function as stress signaling molecules and trigger the production of genes that are responsive to drought. This results in the activation of the defense system and a greater ability to withstand stress. ZnO NPs in general may, under drought conditions, influence the expression of genes that are drought-inducible via both ABA-dependent and ABA-independent pathways.