The grapevine LysM receptor-like kinase VvLYK5-1 mediates chitin-triggered immunity

Abstract

International audienceThe establishment of defense reactions to protect plants against invading pathogens first requiresthe recognition of Microbe-Associated Molecular Patterns (MAMPs), detected by plasmamembrane-bound Pattern Recognition Receptors (PRRs). These MAMPs, also termed elicitors, areused in several biocontrol products that are gradually developing to reduce the use of chemicalpesticides in agriculture. Chitin, the main component of fungal cell walls, as well as its deacetylatedderivative, chitosan, are two chitooligosaccharides (COS) that can be found in some of theseproducts. Unfortunately, the mechanism allowing the perception of these molecules is still poorlyunderstood in Vitis vinifera, sometimes hampering the improvement and the generalization ofthese emerging crop protection tools. On the contrary, chitin perception in the model plantArabidopsis thaliana is well described and relies on a tripartite complex formed by threemembrane-bound LysM Receptor-Like Kinases named AtLYK1/CERK1, AtLYK4 & AtLYK5, thelatter having the strongest affinity to chitin. In grapevine, COS perception has for the moment onlybeen demonstrated to rely on VvLYK1-1 & VvLYK1-2, two constitutively expressed genes that didnot specifically respond to pathogens according to genes expression analysis. In this context, weperformed experiments to complement the Arabidopsis lyk5 simple mutant and the lyk4/5 doublemutant, which showed altered response to COS, by overexpressing their grapevine orthologousgenes (VvLYK5-1/2). Our results revealed that MAPK activation and defense gene expression werepartially restored after chitin treatment by the complementation with VvLYK5-1 but not withVvLYK5-2. These preliminary results seem to indicate that VvLYK5-1 participates in the chitinrecognition in grapevine, together with VvLYK1-1 previously identified. Furthermore, as theperception of chitosan does not seem altered in the Atlyk5 mutant, it would also appear that theperception of chitin and chitosan does not involve the same receptors. FRET-FLIM experimentsinitiated with these co-receptors will soon provide additional information to better decipher themechanism of COS perception in grapevin