The <i>Arabidopsis thaliana</i> LysM‐containing Receptor‐Like Kinase 2 is required for elicitor‐induced resistance to pathogens

<jats:title>Abstract</jats:title><jats:p>In <jats:italic>Arabidopsis thaliana</jats:italic>, perception of chitin from fungal cell walls is mediated by three LysM‐containing Receptor‐Like Kinases (LYKs): CERK1, which is absolutely required for chitin perception, and LYK4 and LYK5, which act redundantly. The role in plant innate immunity of a fourth LYK protein, LYK2, is currently not known. Here we show that CERK1, LYK2 and LYK5 are dispensable for basal susceptibility to <jats:italic>B. cinerea</jats:italic> but are necessary for chitin‐induced resistance to this pathogen. LYK2 is dispensable for chitin perception and early signalling events, though it contributes to callose deposition induced by this elicitor. Notably, <jats:italic>LYK2</jats:italic> is also necessary for enhanced resistance to <jats:italic>B. cinerea</jats:italic> and <jats:italic>Pseudomonas syringae</jats:italic> induced by flagellin and for elicitor‐induced priming of defence gene expression during fungal infection. Consistently, overexpression of <jats:italic>LYK2</jats:italic> enhances resistance to <jats:italic>B. cinerea</jats:italic> and <jats:italic>P. syringae</jats:italic> and results in increased expression of defence‐related genes during fungal infection. LYK2 appears to be required to establish a primed state in plants exposed to biotic elicitors, ensuring a robust resistance to subsequent pathogen infections.</jats:p>