Drought-Tolerant Enterobacter bugandensis WRS7 Induces Systemic Tolerance in Triticum aestivum L. (Wheat) Under Drought Conditions

Some plant growth-promoting bacteria (PGPR) can ameliorate abiotic stressors like drought stress and promote plant growth. The present study investigated various drought-tolerant mechanisms of Enterobacter bugandensis WRS7, a rhizospheric isolate, by which it alleviates the deleterious effects of drought stress in wheat plants (Triticum aestivum L). The isolate WRS7 showed different plant growth-promoting properties, including nitrogen fixation, phosphate solubilization, siderophore production, phytohormone (indole acetic acid and gibberellic acid) production, exopolysaccharide secretion, and ACC deaminase activity. Its inoculation to wheat plants improved plant growth in terms of root/shoot growth and chlorophyll content. Its inoculation also exhibited drought stress ameliorating properties, including increased osmolyte content (proline and total soluble sugar), relative water content, catalase and superoxide dismutase activity, and decreased lipid peroxidation compared to non-inoculated plants. Our biochemical data were coherent with gene expression analysis of WRS7-treated plants, which showed altered expression of genes encoding antioxidant enzymes (CAT, APX, and GPX), osmolyte synthesis (P5CS, P5CR, and TPS1), biosynthesis of stress hormone genes (NCED, WZE, SAMS, ACS1, and ACO encoding proteins for the biosynthesis of abscisic acid and ethylene), and calcium transporter (TPC1) in the wheat plant. The regulation of the ethylene biosynthesis gene and modulation of TPC1 gene expression by PGPR E. bugandensis WRS7 in wheat plants highlights its additional role in alleviating drought stress. The colonization study demonstrated the successful colonization of E. bugandensis WRS7 in wheat plants. Overall, the present study indicates that E. bugandensis WRS7 alleviates drought stress in wheat plants by differentially regulating various metabolic genes in treated plants.