Pseudomonas volatiles shape the root transcriptome and microbiome to promote plant growth under drought

Volatile organic compounds (VOCs) emitted by soil bacteria influence interactions with other soil microbes and plants. While their potential as plant growth promoters is well recognized, their role in promoting plant resilience to abiotic stress and the underlying molecular mechanisms remain poorly understood. Here, we investigate the role of Pseudomonas VOCs in enhancing plant resilience to drought stress Arabidopsis seedlings were exposed to VOCs emitted by Pseudomonas strains under control and osmotic stress conditions. Plant biomass and root architecture were evaluated. Root transcriptomics analysis was performed and validated using Arabidopsis mutants and metabolomics. Volatile organic compounds effects were also tested on soil-grown Brassica oleracea and on its rhizosphere microbiome. Pseudomonas VOCs promoted plant growth under both axenic and soil conditions in A. thaliana and in B. oleracea, and under control and drought conditions. Transcriptomics, metabolomics, and functional analysis revealed interactions between Pseudomonas VOCs, glucosinolates, and ABA signalling, as well as a positive association between VOC exposure and coumarin biosynthesis. VOC treatment also reshaped the rhizosphere microbiome under drought, leading to a community composition more similar to that of well-watered plants. Overall, Pseudomonas VOCs promote plant growth under drought conditions, linked to root transcriptional reprogramming and direct or indirect microbiome modulation.