The plant microbiome at the intersection of metabolism and defense
C. HANEY (1), L. Shapiro (2), J. Bush (3), N. Pierce (2), F. Ausubel (3) (1) The University of British Columbia, Canada; (2) Harvard University, U.S.A.; (3) Massachusetts General Hospital, U.S.A.

Plant root-associated microbial communities (“rhizosphere microbiome”) influence plant growth and defense. Well-characterized bacteria within the rhizosphere microbiome can induce systemic resistance (ISR) against foliar pathogens. We report that novel strains of Pseudomonas spp., isolated from the roots of natural populations of Arabidopsis thaliana, actually induce systemic susceptibility (ISS) to bacterial foliar pathogens under conditions where well-characterized strains trigger ISR. Genome sequencing indicates that ISS strains include phylogenetically diverse strains of P. fluorescens, P. brassicacearum and P. simiae that are closely related to ISR strains. Pseudomonas strains that trigger ISS also promote Arabidopsis growth specifically under nitrogen-limiting conditions. We have found that increasing the nitrogen content of the soil is sufficient to induce susceptibility of Arabidopsis to bacterial foliar pathogens. This suggests that the microbiome may indirectly affect defenses by regulating plant nutrient status. Ongoing work is focused on identifying the mechanism by which Pseudomonas sp. promote plant nitrogen uptake and how microbiome bacteria trigger ISS. Collectively, this work will inform our understanding of how the plant microbiome coordinates plant metabolic status and immunity.

Abstract Number: C7-5, P1-10
Session Type: Concurrent