Root hair developmental regulators orchestrate drought triggered microbiome changes and the interaction with beneficial Rhizobiaceae.

Drought is one of the most serious abiotic stresses, and emerging evidence suggest plant microbiome affects plant drought tolerance. However, there is a lack of genetic evidence regarding whether and how plants orchestrate the dynamic assembly of the microbiome upon drought. By utilizing mutants with enhanced or decreased root hair densities, we find that root hair regulators also affect drought induced root microbiome changes. Rhizobiaceae is a key biomarker taxa affected by root hair related mutants. We isolated and sequenced 1479 root associated microbes, and confirmed that several Rhizobium strains presented stress-alleviating activities. Metagenome, root transcriptome and root metabolome studies further reveal the multi-omic changes upon drought stress. We knocked out an ornithine cyclodeaminase (ocd) gene in Rhizobium sp. 4F10, which significantly dampens its stress alleviating ability. Our genetic and integrated multi-omics studies confirm the involvement of host genetic effects in reshaping a stress-alleviating root microbiome during drought, and provide mechanistic insights into Rhizobiaceae mediated abiotic stress protection.