title: A plant phosphoswitch platform repeatedly targeted by type III effector proteins regulates the output of both tiers of plant immune receptors.
abstract: Plants detect microbes via two functionally interconnected tiers of immune receptors. Immune detection is suppressed by equally complex pathogen mechanisms. The small plasma-membrane-tethered protein RIN4 negatively regulates microbe-associated molecular pattern (MAMP)-triggered responses, which are derepressed upon bacterial flagellin perception. We demonstrate that recognition of the flagellin peptide MAMP flg22 triggers accumulation of RIN4 phosphorylated at serine 141 (pS141) that mediates derepression of several immune outputs. RIN4 is targeted by four bacterial type III effector proteins, delivered temporally after flagellin perception. Of these, AvrB acts with a host kinase to increase levels of RIN4 phosphorylated at threonine 166 (pT166). RIN4 pT166 is epistatic to RIN4 pS141. Thus, AvrB contributes to virulence by enhancing "rerepression" of immune system outputs. Our results explain the evolution of independent effectors that antagonize accumulation of RIN4 pS141 and of a specific plant intracellular NLR protein, RPM1, which is activated by AvrB-mediated accumulation of RIN4 pT166.
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Eui-Hwan
authors.initials: EH
authors.lastname: Chung
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Farid
authors.initials: F
authors.lastname: El-Kasmi
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Yijian
authors.initials: Y
authors.lastname: He
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA.
authors.forename: Alex
authors.initials: A
authors.lastname: Loehr
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA; Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA; Carolina Center for Genome Sciences, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA; Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA; Howard Hughes Medical Institute, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599, USA. Electronic address: dangl@email.unc.edu.
authors.forename: Jeffery L
authors.initials: JL
authors.lastname: Dangl
mesh_terms: D017360:Arabidopsis / Q000276:immunology*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001419:Bacteria / Q000276:immunology; D002352:Carrier Proteins / Q000378:metabolism*; D005408:Flagellin / Q000276:immunology; D018506:Gene Expression Regulation, Plant; D047908:Intracellular Signaling Peptides and Proteins; D010766:Phosphorylation; D010940:Plant Proteins / Q000096:biosynthesis*; D011499:Protein Processing, Post-Translational; D011971:Receptors, Immunologic / Q000096:biosynthesis*
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D010940:Plant Proteins; C453279:RIN4 protein, Arabidopsis; D011971:Receptors, Immunologic; D005408:Flagellin