Paraburkholderia sp. GD17 improves rice seedling tolerance to salinity

The plant growth promoting rhizobacteria have been extensively implicated in plant responses to changing environments. However, the action mechanisms still need to be elucidated. This study addressed the effect of Paraburkholderia sp. GD17 on rice seedlings in responses to salt stress. The experiment consisted of GD17-inoculated and non-inoculated plants, with or without NaCl treatment. Physiological and biochemical parameters, and gene expression were analyzed. GD17 efficiently colonized inside roots, and provided a protection against salt stress. Following exposure to 68 mM of NaCl for 48 h, although the accumulation of Na+ was not affected in GD17-inoculated (+ GD17) roots relative to non-inoculated ones, its concentration was substantially reduced in + GD17 shoots. The contents of K and other mineral elements were higher in + GD17 plants. The expression of Na+ and K+ transporter-encoding genes generally presented a higher level in + GD17 plants. The antioxidative defense especially related to the removal of H2O2 was more strongly activated in + GD17 plants. Correspondingly, salt-induced oxidative damage was significantly ameliorated. A substantial increase in proline content and gene expression was observed in + GD17 plants. Additionally, the cell wall invertase-encoding gene displayed a dramatically higher expression level in + GD17 plants. GD17 efficiently improved rice seedling tolerance to salt stress. The possible mechanisms might be associated with the absorption and redistribution of mineral elements, the vacuolar sequestration of Na+ as well as exclusion of Na+, antioxidative defense, the production of proline, and the sucrose catabolism in apoplast.