Enhancement of Rice Growth Under Salinity Stress Triggered by Extracellular Polysaccharides from Pantoea alhagi Is Associated with Changes in Physiology and Root Proteomics

Soil salinization poses an escalating threat to global crop production. Extracellular polysaccharides (EPSs) secreted by plant growth-promoting rhizobacteria have the potential to improve the salt tolerance of crops. Here, we tested the effects of Pantoea alhagi NX-11 EPSs on the growth, physiological traits, and root proteomic profiles of rice under salt stress. We found that NX-11 EPSs effectively increased the salt tolerance of rice in soil, with 50 mg/kg EPS exhibiting the strongest plant growth-promoting effect. This effect was associated with increased the K+/Na+ ratio and soluble protein content in roots induced by NX-11 EPSs as well as reduced stomatal aperture and transpiration rate in leaves. Proteomic analyses revealed that NX-11 EPSs markedly changed the protein profiles of roots. Specifically, proteins associated with cyanoamino acid metabolism, glycolysis/gluconeogenesis, and fatty acid degradation were downregulated. Together, these results suggest that NX-11 EPSs improve rice performance under salt stress, accompanied by changes in physiological traits and root protein profiles.