GNPS - Pseudomonas aeruginosa - Arabidopsis interaction

Seed germination irreversibly transforms the plant (highly resistant?) embryo into a fragile seedling. To anticipate potential seedling damage seeds block their germination under unfavorable conditions. Historically, studies focused on how seeds respond to abiotic stresses such as canopy light or high temperature. They uncovered the central role of gibberellic (GA) and abscisic acid (ABA) signaling to control germination. Seeds however are continuously exposed to rhizosphere organisms, such as bacteria, acting as potential pathogens or commensals. Singularly little is known about seed germination control responses to biotic factors. We found that Arabidopsis seeds repress their germination in presence of the plant pathogen Pseudomonas aeruginosa in their environment. We identify L-2-amino-4-methoxy-trans-3-butenoic acid (AMB), released by P. aeruginosa, as the biotic compound triggering germination arrest. AMB production is controlled by the quorum sensing system IQS governing bacterial behavior. We show that AMB stimulates the activity of the DELLA factor RGL2 to promote the accumulation of ABI5, an ABA response bZIP factor and repressor of germination. We provide evidence that an AMB-dependent germination arrest protects the plant by avoiding severe seedling developmental perturbations induced by AMB and potential exposure to a pathogen.