The perception of environmental signals and the ability to react accordingly are essential for the survival of organisms. In plants, extracellular recognition of microbe- and host damage-associated molecular patterns leads to the first layer of inducible defenses, termed pattern-triggered immunity (PTI). Pattern recognition receptors (PRRs) can perceive pathogen/microbe-associated molecular patterns (P/MAMP) from different microbes such as bacteria, fungi, oomycetes or viruses. Danger-associated molecular patterns (DAMPs) correspond to cell wall fragments that can be released by the plant after wounding or pathogen attack. An important group of PRRs is the family of wall associated kinases (WAK) that perceives pathogens indirectly, via DAMPs, and activates oligogalacturonide-dependent defense responses. The present chapter will address the most important perception systems used by plants to perceive pathogen attack and initiate efficient defense responses.
Keywords: Bacterial flagellins, Damage Associated Molecular Patterns (DAMP), Pathogen-associated molecular pattern (PAMP), Pattern-Recognition Receptors (PRRs), PAMP-triggered immunity (PTI), Plant innate immunity, Plant lectin receptors, Wall-associated kinases (WAKs).