Recent Advances in PAMP-Triggered Immunity against Bacteria: Pattern Recognition Receptors Watch over and Raise the Alarm

Extract

In an environment rich in potentially harmful microbes, plant survival depends on efficient microbe perception and fast defense responses. Contrary to the mammalian immune system composed of cells specialized for defense (e.g. lymphocytes), plant immunity relies on the ability of each cell to recognize pathogens. A first level of microbe recognition is performed by membrane proteins termed pattern recognition receptors (PRRs), which perceive molecular signatures characteristic of a whole class of microbes, termed pathogen-associated (or microbe-associated) molecular patterns (PAMPs; Medzhitov and Janeway, 1997). Perception of PAMPs by PRRs is common to all multicellular organisms and leads to an array of defense responses and redeployment of cellular energy in a fast, efficient, and multiresponse manner, which prevents further pathogen ingress. PAMP recognition leads to a chain of signaling events, broadly referred to as general defense responses in plants. PAMP perception also results in plant systemic acquired resistance (Mishina and Zeier, 2007b).