The Cell Wall-Derived Xyloglucan Is a New DAMP Triggering Plant Immunity in Vitis vinifera and Arabidopsis thaliana

Abstract

Damage-associated molecular patterns (DAMPs) are endogenous molecules that can activate the plant innate immunity. DAMPs can derive from the plant cell wall, which is composed of a complex mixture of cellulose, hemicellulose, and pectin polysaccharides. Fragments of pectin, called oligogalacturonides (OG), can be released after wounding or by pathogen-encoded cell wall degrading enzymes (CWDEs) such as polygalacturonases (PGs). OG are known to induce innate immune responses, including the activation of mitogen-activated protein kinases (MAPKs), production of H₂O₂, defense gene activation, and callose deposition. Thus, we hypothesized that xyloglucans (Xh), derived from the plant cell wall hemicellulose, could also act as an endogenous elicitor and trigger a signaling cascade similar to OG. Our results indicate that purified Xh elicit MAPK activation and immune gene expression in grapevine (<i>Vitis vinifera</i>) and Arabidopsis (<i>Arabidopsis thaliana</i>) to trigger induced resistance against necrotrophic (<i>Botrytis cinerea</i>) or biotrophic (<i>Hyaloperonospora arabidopsidis</i>) pathogens. Xh also induce resveratrol production in grapevine cell suspension and callose deposition in Arabidopsis which depends on the callose synthase PMR4. In addition, we characterized some signaling components of Xh-induced immunity using Arabidopsis mutants. Our data suggest that Xh-induced resistance against <i>B. cinerea</i> is dependent on the phytoalexin, salicylate, jasmonate, and ethylene pathways.