Receptors in the induction of the plant innate immunity

Plants adjust amplitude and duration of immune responses via different strategies to maintain growth, development and resistance to pathogens. Pathogen-associated molecular patterns (PAMPs)-triggered immunity (PTI) and effector-triggered immunity (ETI) play vital roles. PRRs (pattern recognition receptors), comprising a large number of receptor-like protein kinases (RLKs) and receptor-like proteins (RLPs), recognize related ligands and trigger immunity. PTI is the first layer of the innate immune system, and it recognizes PAMPs at plasma membrane to prevent infection. However, pathogens exploit effector proteins to bypass or directly inhibit the PTI immune pathway. Consistently, plants have evolved intracellular nucleotide-binding domain and leucine-rich repeat-containing (NLR) proteins to detect pathogenic effectors and trigger a hypersensitive response to activate ETI. PTI and ETI work together to protect plants from infection of virus and other pathogens. Diverse receptors and the corresponding ligands, especially several pairs of well-studied receptors and ligands in PTI immunity, are reviewed to illustrate the dynamic process of PTI response here.