Rhizosphere microbiome mediates systemic root metabolite exudation ($) (PNAS)

Roots exude metabolites that affect the composition and activities of their microbiome. Korenblum et al. show that the microbiome in turn affects metabolite exudation, not only locally but also systemically (shown using a split-root system). They call this response SIREM: systemically induced root exudation of metabolites. For example, the presence of Bacillus bacteria triggers exudation of various acylsugars, the composition of which is influenced by the composition of the microbiome. The authors also show a role for azelaic acid (AzA) in systemic signaling. After coating roots with thin layers of agar, the authors used MALDI-MSI to localize exuded metabolites to specific portions of the root system, for example with some derived from root hairs and others from lateral root tips; this in turn might promote distinct patterns of microbial colonization. These finding shed light on the important trans-kingdom interactions between plants and their microbiome. (Summary by Mary Williams) Proc. Natl. Acad. USA 10.1073/pnas.1912130117