Advances in signal transduction of PAMP-triggered immunity in plants

Plant disease is one of the most important factors adversely affecting agricultural production. The resistance of plants to pathogens depends on the plant innate immunity system. The study on plant innate immunity will provide insight into the breeding of disease-resistant crops. Plant innate immunity is composed of two intertwined layers:PTI (PAMP-triggered immunity) and ETI (effector-triggered immunity). In recent years, a series of significance progress has been made in the study of PTI, which is triggered by PAMPs (pathogen-associated molecular patterns). Upon the perception of PAMPs by the cell surface-localized receptors, the immune signaling is transduced through receptor-like cytoplasmic kinase (RLCK) BIK1 (Botrytis-induced kinase 1), MAPK (mitogen-activated protein kinase) cascade, and CDPKs (calcium-dependent protein kinase), resulting in ROS (reactive oxygen species) burst, stomata closure, and expression of immune-related genes, which limit the colonization of infectious pathogens. Importantly, the innate immunity is regulated at different levels to ensure the optimal intensity and duration of immune responses. In this paper, we reviewed the advances in the molecular mechanisms and signal transduction of PTI in recent years, including the discoveries of FLS2 and other immune receptors, the functions of diverse components of innate immunity signal transduction pathway, the transcription factors involved in innate immunity, the regulation of immune signaling, and the application of innate immunity in the disease-resistance breeding. We also discussed future perspectives, and we thought that the studies on innate immunity signaling in crops and crop-fungi patho-system should be given the highest priority. Furthermore, the combination of the theories of plant innate immunity with the gene editing technologies would definitely provide new opportunities for crop disease-resistance breeding.