Age-Related Resistance in Arabidopsis thaliana Involves the MADS-Domain Transcription Factor SHORT VEGETATIVE PHASE and Direct Action of Salicylic Acid on Pseudomonas syringae

Abstract

Arabidopsis thaliana exhibits a developmentally regulated disease-resistance response known as age-related resistance (ARR), a process that requires intercellular accumulation of salicylic acid (SA), which is thought to act as an antimicrobial agent. ARR is characterized by enhanced resistance to some pathogens at the late adult-vegetative and reproductive stages. While the transition to flowering does not cause the onset of ARR, both processes involve the MADS-domain transcription factor SHORT VEGETATIVE PHASE (SVP). In this study, ARR-defective svp mutants were found to accumulate reduced levels of intercellular SA compared with wild type in response to Pseudomonas syringae pv. tomato. Double mutant and overexpression analyses suggest that SVP and SOC1 (SUPPRESSOR OF OVEREXPRESSION OF CO 1) act antagonistically, such that SVP is required for ARR to alleviate the negative effects of SOC1 on SA accumulation. In vitro, SA exhibited antibacterial and antibiofilm activity at concentrations similar to those measured in the intercellular space during ARR. In vivo, P. syringae pv. tomato formed biofilm-like aggregates in young susceptible plants, while this was drastically reduced in mature ARR-competent plants, which accumulate intercellular SA. Collectively, these results reveal a novel role for the floral regulators SVP and SOC1 in disease resistance and provide evidence that SA acts directly on pathogens as an antimicrobial agent. [Formula: see text] Copyright © 2017 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Actin depolymerization is able to increase plant resistance against pathogens via activation of salicylic acid signalling pathway

“…This could be due to SA antimicrobial activity, accompanied by the SA-induced production of antimicrobial compounds. These powerful SA properties have been nicely demonstrated in relationship to so-called age-related resistance 26–28 . Our study shows that SA pathway, specifically induced by actin depolymerization, is more powerful despite the missing actin dynamics.…”

Novel Salicylic Acid Analogs Induce a Potent Defense Response in Arabidopsis

“…Previous research has suggested that SA acts directly on P. syringae , acting as an anti-microbial agent and reducing biofilm formation [49]. In addition to their ability to induce plant defense, these SA analogs may also act directly to inhibit the growth of P. syringae and other pathogens.…”

Age-Dependent Abiotic Stress Resilience in Plants

“…This ARR mediation of SA defense is regulated by DEL1, a repressor of salicylic acid (SA) biosynthesis, which decreases in expression when leaves age [127]. Age-related SA accumulation can also be controlled by intercellular SA levels rather than by intracellular SA signaling, because apoplastic SA can have a direct antimicrobial effect on Pseudomonas syringae [128]. Similar to JA, there is an age-related shift in SA signaling-mediated defense toward a direct SA-mediated chemical defense.…”