Effects of Sulfur Assimilation in SS101 on Growth, Defense, and Metabolome of Different .

Genome-wide analysis of plant-growth-promoting strain SS101 (SS101) followed by site-directed mutagenesis previously suggested that sulfur assimilation may play an important role in growth promotion and induced systemic resistance in . Here, we investigated the effects of sulfur metabolism in SS101 on growth, defense, and shoot metabolomes of and the Brassica crop, Broccoli. Root tips of seedlings of and two Broccoli cultivars were treated with SS101 or with a mutant disrupted in the adenylsulfate reductase , a key gene in cysteine and methionine biosynthesis. Phenotyping of plants treated with wild-type SS101 or its mutant revealed that sulfur assimilation in SS101 was associated with enhanced growth of but with a reduction in shoot biomass of two Broccoli cultivars. Untargeted metabolomics revealed that -mediated sulfur assimilation in SS101 had significant effects on shoot chemistry of , in particular on chain elongation of aliphatic glucosinolates (GLSs) and on indole metabolites, including camalexin and the growth hormone indole-3-acetic acid. In Broccoli, SS101 sulfur assimilation significantly upregulated the relative abundance of several shoot metabolites, in particular, indolic GLSs and phenylpropanoids. These metabolome changes in Broccoli plants coincided with SS101-mediated suppression of leaf infections by . Our study showed the metabolic interconnectedness of plants and their root-associated microbiota.