Lysin motif (LysM) receptor kinase that functions as a cell surface receptor in chitin elicitor (chitooligosaccharides) signaling leading to innate immunity. Recognizes microbe-derived N-acetylglucosamine (NAG)-containing ligands. Involved in the resistance to the pathogenic fungus Alternaria brassicicola and to the bacterial pathogen the bacterial pathogen Pseudomonas syringae pv tomato DC3000, probably by sensing microbe-associated molecular pattern (MAMP) and pathogen-associated molecular patterns (PAMP). May play a role in detecting peptidoglycans (e.g. PGNs) during bacterial growth. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Homooligomer (By similarity). Binds to chitin oligosaccharide elicitors. Expressed in roots, stems, leaves (predominantly in hydathodes, apical meristems and stipules) and buds. Moderately induced by chitin oligomers (e.g. chitohexaose (6-mer) and chitooctaose (8-mer)) and flagellin (e.g. flg22). Autophosphorylated; induced by chitin and derivatives. Reduced induction of chitin-responsive genes and diminished chitin-induced cytosolic calcium elevation, accompanied by an enhanced susceptibility to both the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 and the fungal pathogen Alternaria brassicicola. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.