The secreted peptide PIP1 amplifies immunity through receptor-like kinase 7

• Published in: PLoS pathogens Vol. 10; no. 9; p. e1004331
• Main Authors: Hou, Shuguo, Wang, Xin, Chen, Donghua, Yang, Xue, Wang, Mei, Turrà, David, Di Pietro, Antonio, Zhang, Wei
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.09.2014; Public Library of Science (PLoS)
• Subjects: Amino Acid Sequence; Analysis; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - immunology; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; Biology and Life Sciences; Blotting, Western; Gene Expression Regulation, Plant; Genetic aspects; Health aspects; Immunity, Innate - immunology; Kinases; Molecular Sequence Data; Morphology; Pattern recognition; Peptide Fragments - immunology; Peptides; Phosphorylation; Physiological aspects; Plant cells and tissues; Plant Immunity - immunology; Plant Roots - growth & development; Plant Roots - immunology; Plant Roots - metabolism; Real-Time Polymerase Chain Reaction; Receptors, Pattern Recognition - immunology; Receptors, Pattern Recognition - metabolism; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; Seeds; Sequence Homology, Amino Acid; Signal Transduction; Stem cells; China
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1004331

In plants, innate immune responses are initiated by plasma membrane-located pattern recognition receptors (PRRs) upon recognition of elicitors, including exogenous pathogen-associated molecular patterns (PAMPs) and endogenous damage-associated molecular patterns (DAMPs). Arabidopsis thaliana produces more than 1000 secreted peptide candidates, but it has yet to be established whether any of these act as elicitors. Here we identified an A. thaliana gene family encoding precursors of PAMP-induced secreted peptides (prePIPs) through an in-silico approach. The expression of some members of the family, including prePIP1 and prePIP2, is induced by a variety of pathogens and elicitors. Subcellular localization and proteolytic processing analyses demonstrated that the prePIP1 product is secreted into extracellular spaces where it is cleaved at the C-terminus. Overexpression of prePIP1 and prePIP2, or exogenous application of PIP1 and PIP2 synthetic peptides corresponding to the C-terminal conserved regions in prePIP1 and prePIP2, enhanced immune responses and pathogen resistance in A. thaliana. Genetic and biochemical analyses suggested that the receptor-like kinase 7 (RLK7) functions as a receptor of PIP1. Once perceived by RLK7, PIP1 initiates overlapping and distinct immune signaling responses together with the DAMP PEP1. PIP1 and PEP1 cooperate in amplifying the immune responses triggered by the PAMP flagellin. Collectively, these studies provide significant insights into immune modulation by Arabidopsis endogenous secreted peptides.