Zinc Oxide Nanoparticles Enhance Drought Tolerance in Wheat via Physio-Biochemical Changes and Stress Genes Expression

Drought response in plants at molecular level, aiding them to overcome the adverse effects of drought, remarkably depends on the expression of a few regulator genes and signal transduction. For reducing the drought stress, nanoparticles show great promise compared to other commonly used methods, even though the underlying mechanisms are still unknown. This study was performed to investigate the expression analysis of genes involved in drought tolerance and the use of zinc oxide nanoparticles (ZnO NPs) to mitigate the undesirable effects of drought stress in wheat. A factorial experiment based on completely randomized design (CRD) was performed with three replicates. The experiment was carried out in the greenhouse of Mohaghegh Ardabili University, Ardabil, Iran in 2017. The factorial combination of stress levels of water supply (including 85%, 60%, and 35% fi eld capacity) and ZnO NPs (0, 0.5, and 1.0 g. L-1) were used on three wheat cultivars (Mihan, Heidari, and Gascogne). Three days after sprayingthe ZnO NPs in the three-leaf stage, drought stress was applied for ten days and physio-biochemical traits and gene expression of wheat cultivars were investigated. The expression of Wdhn13, DREB2, P5CS, and CAT1 genes in leaves were analyzed by real-time polymerase chain reaction (PCR). Generally, drought stress signifi cantly enhanced total protein and lysine, soluble sugars, chlorophyll, carotenoid contents, antioxidant enzymes activities, and proline accumulation in plants treated with ZnO NPs. Moreover, the ZnO NPs increased the expression of the genes involved in proline biosynthesis (i.e., P5CS), catalase activity (i.e., CAT1), and dehydration-responsive genes DREB2 and Wdhn13, which are known as drought-tolerance parameters. According to our results, ZnO NP-treated wheat induced drought-tolerance genes and effectively facilitated defi ciency tolerance. Therefore, under drought stress, we recommend spraying bread wheat with ZnO NPs (1 g. L-1) in the growing season, which can improve wheat grain yield under dry conditions.