The establishment of defense reactions to protect plants against invading pathogens first requires the recognition of Microbe-Associated Molecular Patterns (MAMPs), detected by plasma membrane-bound Pattern Recognition Receptors (PRRs). These MAMPs, also termed elicitors, are used in several biocontrol products that are gradually developing to reduce the use of chemical pesticides in agriculture. Chitin, the main component of fungal cell walls, as well as its deacetylated derivative, chitosan, are two chitooligosaccharides (COS) that can be found in some of these products. Unfortunately, the mechanism allowing the perception of these molecules is still poorly understood in Vitis vinifera, sometimes hampering the improvement and the generalization of these emerging crop protection tools. On the contrary, chitin perception in the model plant Arabidopsis thaliana is well described and relies on a tripartite complex formed by three membrane-bound LysM Receptor-Like Kinases named AtLYK1/CERK1, AtLYK4 & AtLYK5, the latter having the strongest affinity to chitin. In grapevine, COS perception has for the moment only been demonstrated to rely on VvLYK1-1 & VvLYK1-2, two constitutively expressed genes that did not specifically respond to pathogens according to genes expression analysis. In this context, we performed experiments to complement the Arabidopsis lyk5 simple mutant and the lyk4/5 double mutant, which showed altered response to COS, by overexpressing their grapevine orthologous genes (VvLYK5-1/2). Our results revealed that MAPK activation and defense gene expression were partially restored after chitin treatment by the complementation with VvLYK5-1 but not with VvLYK5-2. These preliminary results seem to indicate that VvLYK5-1 participates in the chitin recognition in grapevine, together with VvLYK1-1 previously identified. Furthermore, as the perception of chitosan does not seem altered in the Atlyk5 mutant, it would also appear that the perception of chitin and chitosan does not involve the same receptors. FRET-FLIM experiments initiated with these co-receptors will soon provide additional information to better decipher the mechanism of COS perception in grapevine