Physiological, Biochemical, and Molecular Responses of Quinoa (Chenopodium quinoa Willd.) to Elicitors Under Drought Stress

Drought stress is one of the most important limiting factors in crop production, and it creates major challenges for the growth and development of plants in many parts of the world. Elicitors, as key messenger compounds, play an important modulatory role in plant responses to abiotic stresses, which leads to physiological changes and triggers the expression of stress-responsive genes by the synthesis of signaling molecules. A factorial experiment was conducted with two factors in a greenhouse at the University of Zabol, Iran, during 2021. The water supply applied at three levels including 100%, 75%, and 50% of crop water requirement (as control, mild, and severe water deficit stress, respectively). The foliar sprayings were applied at six levels: control, 70% ethanol, 0.5 and 1 mM SA, and 0.5 and 1 mM MeJA. The effect of elicitors on various physiological, biochemical parameters and expression of superoxide dismutase (SOD), MYB62, and NAM/ATAF1/2/CUC2 (NAC) genes under drought stress conditions was investigated by qRT-PCR. In final the target genes, correlation rate was calculated based on the co-expression and experimental parameters, and their expression network was plotted using Cytoscape software. The results of the physiological analysis revealed that with increasing water deficit stress intensity, the amount of Chl-a, Chl-b, and total chlorophyll content decreased significantly. The utilization of elicitors also increased the carotenoid content. The analysis of anti-oxidant enzyme activity showed that the activity of the guaiacol peroxidase (GPX) increased significantly under severe stress + 1 mM MeJA application. The highest catalase (CAT) activity was also observed under severe stress + 1 mM MeJA. The expression analysis of three genes SOD, MYB62, and NAC showed that with increasing water deficit stress, the expression of all three genes increased. Based on the present results, MeJA and SA had a positive effect on increasing the expression of MYB62, proline, and carbohydrate but greatly reduced the expression of NAC. Among the spraying treatments, 0.5 mM SA showed the highest positive impact on the expression of the studied genes, while the ethanol treatment had the most negative effect. The expression analysis of genes involved in drought tolerance under elicitor applications is necessary to elucidate the relationship between physiological and enzymatic changes (osmotic adjustment, pigments, and anti-oxidant enzymes) and gene expression patterns in quinoa.