Pathogen-Associated Molecular Patterns and Their Perception in Plants

Abstract

In plants, innate immunity, the first line of microbial recognition leading to active defense responses, relies on the perception of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs). Pattern recognition receptors (PRRs) enable plants to sense non-self molecules exhibited by microbes and raise proper defense responses or establish symbiosis. This recognition leads to PAMP-triggered immunity (PTI). Despite the numerous PAMPs recognized by plants, only a handful of PRRs are characterized. Most of them correspond to the transmembrane proteins with a ligand-binding ectodomain. PRRs interact with additional transmembrane proteins that act as signaling adapters or amplifiers to achieve full functionality. The crucial role of PRRs in antimicrobial immunity is demonstrated by the direct targeting of PRRs and their associated proteins by pathogenic virulence effectors. In recent years the importance of PRR subcellular trafficking to plant immunity has become apparent. PRRs traffic through the endoplasmic reticulum (ER) and the Golgi apparatus to the plasma membrane, where they recognize their cognate ligands. At the plasma membrane, PRRs can be recycled or internalized via endocytic pathways. By using genetic and biochemical tools in combination with bio-imaging, the trafficking pathways and their role in PRR perception of microbial molecules are now being revealed.