Required as a cell surface receptor for peptidoglycan (PGN) elicitor signaling leading to innate immunity. Plays an essential role in detecting PGNs and restricting bacterial growth (of Pseudomonas syringae pv. tomato DC3000 for example). Interacts with peptidoglycans. Impaired sensitivity to peptidoglycans (PGNs) leading to higher susceptibility to infection with virulent Pseudomonas syringae pv. tomato DC3000.