Identification of the cell-wall derived xyloglucan as a new damage-associated molecular pattern (DAMP) eliciting plant immunity in Vitis vinifera and Arabidopsis thaliana and characterization of two chito-oligosaccharide pattern recognition receptors ; Identification du xyloglucane comme nouvel éliciteur oligosaccharidique stimulant l’immunité de Vitis vinifera et d’Arabidopsis thaliana et caractérisation de deux récepteurs aux chito-oligosaccharides chez la vigne (VvLYK1-1 et VvLYK1-2)

Activation of the plant immune responses requires recognition of common pathogen-associated molecular pattern (PAMP) by their cognate pattern recognition receptors (PRR). Chitin, a major component of fungal cell walls, is a well-known PAMP that triggers defense responses in several mammal and plant species.In the first part of this study, we show that two chitooligosaccharides, chitin and chitosan, act as PAMPs in grapevine (Vitis vinifera) as they elicit immune signaling events, defense gene expression, and resistance against pathogens. These two PAMPs are active in grapevine suggesting that at least one perception system exists. Phylogenetic analysis clearly distinguished three V. vinifera LysM Receptor Kinases (VvLYK1-1, -2, -3) located in the same clade as the Arabidopsis Chitin Elicitor Receptor Kinase 1 (AtCERK1), which mediates chitin-induced immune responses. Their functional characterization was achieved by complementation assays in the Atcerk1 mutant, impaired in chitin perception. Our results provide evidence that VvLYK1-1 and VvLYK1-2, but not VvLYK1-3, functionally complement the loss of AtCERK1 function by restoring chitooligosaccharide-induced MAPK activation and immune gene expression. Moreover, expression of VvLYK1-1 in Atcerk1 restored penetration resistance to the non-adapted grapevine powdery mildew (Erysiphe necator).The second part of this study focused on damaged-associated molecular patterns (DAMP), endogenous molecules that can be released from the plant cell wall during an attack and activate the plant innate immunity. Until now, the best characterized DAMPs are oligogalacturonides (OG) coming from pectin fragments that induce innate immune responses in various plant species, including MAPK activation, H2O2 production, defense gene expression and callose deposition. In this study, we showed that purified xyloglucans (Xh), derived from the plant cell wall hemicellulose, elicit MAPK activation and immune gene expression in grapevine (V. vinifera) and Arabidopsis to trigger induced ...