Arabinoxylan-Oligosaccharides Act as Damage Associated Molecular Patterns in Plants Regulating Disease Resistance.

Hugo Mélida,Frédéric Brunner,Antonio Molina,Gemma López,Laura Bacete,Diego Rebaque,Irene Del Hierro,Fabian Pfrengle,Colin Ruprecht

doi:10.3389/fpls.2020.01210

Abstract

Immune responses in plants can be triggered by damage/microbe-associated molecular patterns (DAMPs/MAMPs) upon recognition by plant pattern recognition receptors (PRRs). DAMPs are signaling molecules synthesized by plants or released from host cellular structures (e.g., plant cell walls) upon pathogen infection or wounding. Despite the hypothesized important role of plant cell wall-derived DAMPs in plant-pathogen interactions, a very limited number of these DAMPs are well characterized. Recent work demonstrated that pectin-enriched cell wall fractions extracted from the cell wall mutant impaired in Arabidopsis Response Regulator 6 (arr6), that showed altered disease resistance to several pathogens, triggered more intense immune responses than those activated by similar cell wall fractions from wild-type plants. It was hypothesized that arr6 cell wall fractions could be differentially enriched in DAMPs. In this work, we describe the characterization of the previous immune-active fractions of arr6 showing the highest triggering capacities upon further fractionation by chromatographic means. These analyses pointed to a role of pentose-based oligosaccharides triggering plant immune responses. The characterization of several pentose-based oligosaccharide structures revealed that β-1,4-xylooligosaccharides of specific degrees of polymerization and carrying arabinose decorations are sensed as DAMPs by plants. Moreover, the pentasaccharide 33-α-L-arabinofuranosyl-xylotetraose (XA3XX) was found as a highly active DAMP structure triggering strong immune responses in Arabidopsis thaliana and enhancing crop disease resistance.

Highlights

Plants are sessile organisms that need to develop robust disease resistance mechanisms to efficiently defend from pathogens and pests
We hypothesized that the molecular basis of the differential disease resistance responses in the Arabidopsis arr6-3 mutant allele could be associated with the enhanced and differential presence of carbohydrate-based damageassociated molecular patterns (DAMPs) in the pectin-enriched fractions derived from their cell walls (Bacete et al, 2020)
We have showed that impairment of ARR6 gene in Arabidopsis affects cell wall composition, which may lead to the accumulation of DAMPs that would favor a “defense-ready” state, affecting plant-pathogen interactions (Bacete et al, 2020)

Summary

Introduction

Plants are sessile organisms that need to develop robust disease resistance mechanisms to efficiently defend from pathogens and pests. Activation of plant defense responses requires the perception of molecules from the pathogen (“non-self” signals) and from the plant (“damaged-self” signals) that trigger specific resistance responses through diverse molecular monitoring systems (Atkinson and Urwin, 2012). Among these monitoring mechanisms are pattern- and effector-triggered immunity (PTI and ETI) (Dodds and Rathjen, 2010). PTI is based in the recognition by pattern recognition receptors (PRRs) of microbe/pathogen-associated molecular patterns (MAMPs/ PAMPs) from microorganisms or of plant-derived damageassociated molecular patterns (DAMPs) (Boller and Felix, 2009). In comparison with the high number of MAMPs characterized so far, much less DAMPs derived from plants have been identified to date (Choi and Klessig, 2016; Duran-Flores and Heil, 2016; Bacete et al, 2018; De Lorenzo et al, 2018; Li et al, 2020)

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