Speaker
Description
Leaf bacteria are critical for plant health, but little is known about how plant traits control their recruitment. Aliphatic glucosinolates (GLSs) are metabolites usually associated with defense that are present in leaves of Brassicaceae plants in genotypically-defined mixtures. Upon plant cell damage, they break down into products that deter herbivory and inhibit pathogens. We studied natural colonization of commensal leaf bacteria in the model A. thaliana genotype Col-0 which produces mainly 4-methylsulfinylbutyl-GLS and NG2, a genotype isolated from a local wild population, with mainly allyl-GLS. Comparing colonization in WT and GLSs-free mutants in both backgrounds showed that GLSs differentially affect leaf communities. In Col-0, GLSs had no measurable effect, but in NG2 they surprisingly enriched certain bacteria. Allyl-GLS likely functions as a resource, since similar leaf bacteria were enriched on it as a sole carbon source in-vitro, but not on 4MSOB-GLS. All enriched bacteria were fully dependent on a specialized Yersiniaceae strain that metabolized allyl-GLS and detoxified the resulting breakdown products. Further evidence supported GLS substrate specificity arising at the GLS hydrolysis step, catalyzed by myrosinase. Together, these results suggest that well-studied defense metabolites can have broader roles in the plant microverse, providing important insight into recruitment of bacterial symbionts.
