Vtc4-mediated changes in inositol exudation in the rhizosphere results in a smaller and less diverse microbial population impacting pseudomonads in particular

The plant microbiome plays a crucial role in maintaining plant health, and root exudates, including inositol, significantly influence microbial community composition in the rhizosphere. In this study, we explored how altered inositol exudation impacts rhizosphere microbial communities using a vtc4 mutant of Arabidopsis thaliana, deficient in myo-inositol production. By sampling different root compartments along a soil-root gradient, we assessed the rhizosphere effect and its influence on microbial community assembly. Our findings revealed that vtc4 plants exhibited a slightly reduced rhizosphere effect, particularly in the compartments closest to the roots. In these compartments, the vtc4 mutant hosted smaller and less diverse microbial populations with distinct community compositions compared to the wild type. Interestingly, well-known root colonizers such as Pseudomonas and Massilia showed reduced abundance on vtc4 roots, despite presumably lacking the iol locus necessary for inositol metabolism. This corroborates earlier evidence suggesting that inositol acts more as a signaling molecule than as a nutrient, influencing microbial colonization and motility. Overall, these results highlight the importance of root exudation patterns, particularly inositol, in shaping the rhizosphere microbiome and offer insights into plant-microbe interactions that could inform sustainable agricultural practices.