Natural genetic transformation of the wheat rhizosphere microbial community through DNA inoculations

Rhizosphere microorganisms are known to be able to modify the plants ability to resist abiotic stresses. It is, however, difficult to modify microbial communities to improve plant phenotypes. Here we tested if a rhizosphere microbial community from a water-stress naive soil could be modified by adding DNA extracted from soils with a water stress history. Six-week-old wheat plants growing under low or high-water availabilities were inoculated with DNA extracted from soils with contrasting long-term histories of water availability - one continuously and the other intermittently exposed to water deficit. The fate of the inoculated DNA in the rhizosphere microbial communities was assessed by shotgun metagenomics. Putatively transferred inoculum genes were disproportionately found in the Acidobacteria and Bacteroidetes and belonged to functional category such as antibiotics, biofilm, and carboxylates metabolism, among others. These functional categories were shared by pre-inoculation laterally transferred genes in the recipient soil, highlighting their usefulness for life in soil. The "continuous" inoculum reduced the stress levels of wheat under reduced soil water content, suggesting that the natural genetic transformation of the rhizosphere community can feedback to the plant. Altogether, we are providing evidence for an ecological mechanism that could be harnessed to modify plant-associated microbial communities and help plants sustain water stress.