title: A Pseudomonas syringae effector inactivates MAPKs to suppress PAMP-induced immunity in plants.
abstract: Pathogen-associated molecular patterns (PAMPs) elicit basal defense responses in plants, and, in turn, pathogens have evolved mechanisms to overcome these PAMP-induced defenses. To suppress immunity, the phytopathogenic bacterium Pseudomonas syringae secretes effector proteins, the biochemical function and virulence targets of which remain largely unknown. We show that HopAI1, an effector widely conserved in both plant and animal bacterial pathogens, inhibits the Arabidopsis mitogen-activated protein kinases (MAPKs) activated by exposure to PAMPs. HopAI1 inactivates MAPKs by removing the phosphate group from phosphothreonine through a unique phosphothreonine lyase activity, which is required for HopAI1 function. The inhibition of MAPKs by HopA1 suppresses two independent downstream events, namely the reinforcement of cell wall defense and transcriptional activation of PAMP response genes. The MAPKs MPK3 and MPK6 physically interact with HopAI1 indicating that they are direct targets of HopAI1. These findings uncover a mechanism by which Pseudomonas syringae overcomes host innate immunity to promote pathogenesis.
authors.affiliation: National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Feng
authors.initials: F
authors.lastname: Shao
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Haitao
authors.initials: H
authors.lastname: Cui
authors.forename: Linjie
authors.initials: L
authors.lastname: Chen
authors.forename: Hongtao
authors.initials: H
authors.lastname: Li
authors.forename: Yan
authors.initials: Y
authors.lastname: Zou
authors.forename: Chengzu
authors.initials: C
authors.lastname: Long
authors.forename: Lefu
authors.initials: L
authors.lastname: Lan
authors.forename: Jijie
authors.initials: J
authors.lastname: Chai
authors.forename: She
authors.initials: S
authors.lastname: Chen
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Tang
authors.forename: Jian-Min
authors.initials: JM
authors.lastname: Zhou
mesh_terms: D017360:Arabidopsis; D029681:Arabidopsis Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000276:immunology / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism; D010769:Phosphothreonine / Q000378:metabolism; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology*; D044224:Pseudomonas syringae / Q000276:immunology* / Q000378:metabolism; D037521:Virulence Factors / Q000276:immunology / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D037521:Virulence Factors; D010769:Phosphothreonine; D010758:Phosphorus; C458516:AtMPK3 protein, Arabidopsis; C436293:MPK6 protein, Arabidopsis; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases