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Microbial volatile metabolites can enhance plant growth, yet the mechanisms by which plants perceive and transduce these signals are unknown. Growth of Arabidopsis thaliana Col-0 seedlings was found to be stimulated by volatiles from the soil bacterium Streptomyces coelicolor. To investigate volatile-responding candidate signaling molecules and genes, cultivation of seedlings in gas-phase contact with S. coelicolor genotypes was combined with GC-MS and plant transcriptomics. Components potentially involved were further studied using pure compounds and A. thaliana T-DNA mutants. Application of volatiles from S. coelicolor enhanced the growth of A. thaliana seedlings primarily by stimulating lateral root growth rate and inhibiting primary root extension. Concurrently, a family-wide induction of the Kelch-repeat F-box gene family KISS ME DEADLY (KMD) was observed. A. thaliana genotypes with a loss of function for the KMD family or other alterations of auxin/cytokinin signaling homeostasis suppressed the root response to both S. coelicolor total volatiles and the common microbial volatile 3-octanone. The results reveal a novel function of KMDs in mediating plant growth stimulation in response to volatile stimulation that alters auxin/cytokinin signaling and emphasize rhizospheric microbials as potential indicators of soil status to plants.
Dotson et al. (Thu,) studied this question.