Endogenous salicylic acid levels in Arabidopsis impact the growth-promoting activity of the beneficial rhizobacterium Pseudomonas simiae WCS417r

Wild-type levels of SA limited Ps WCS417r-mediated plant growth, as the SA-deficient Arabidopsis mutant sid2-2 accumulated more biomass in response to Ps WCS417r treatment than did the wild-type plants in response to Ps WCS417r treatment, and the SA-overaccumulator cpr5 yielded less biomass than did the wild-type plants. Analysis of previously generated and publicly available plant gene expression datasets revealed modest downregulation of EPS1, a key gene that contributes to SA accumulation, in the roots of Arabidopsis wild-type plants treated with Ps WCS417r. These results suggest that SA accumulation strongly limits the potential of some plant growth-promoting rhizobacteria, potentially minimizing their effectiveness in ensuring sustainable agriculture that is less reliant on chemical fertilizers.