title: Phosphorylation of the Plant Immune Regulator RPM1-INTERACTING PROTEIN4 Enhances Plant Plasma Membrane H⁺-ATPase Activity and Inhibits Flagellin-Triggered Immune Responses in Arabidopsis.
abstract: The Pseudomonas syringae effector AvrB targets multiple host proteins during infection, including the plant immune regulator RPM1-INTERACTING PROTEIN4 (RIN4) and RPM1-INDUCED PROTEIN KINASE (RIPK). In the presence of AvrB, RIPK phosphorylates RIN4 at Thr-21, Ser-160, and Thr-166, leading to activation of the immune receptor RPM1. Here, we investigated the role of RIN4 phosphorylation in susceptible Arabidopsis thaliana genotypes. Using circular dichroism spectroscopy, we show that RIN4 is a disordered protein and phosphorylation affects protein flexibility. RIN4 T21D/S160D/T166D phosphomimetic mutants exhibited enhanced disease susceptibility upon surface inoculation with P. syringae, wider stomatal apertures, and enhanced plasma membrane H(+)-ATPase activity. The plasma membrane H(+)-ATPase AHA1 is highly expressed in guard cells, and its activation can induce stomatal opening. The ripk knockout also exhibited a strong defect in pathogen-induced stomatal opening. The basal level of RIN4 Thr-166 phosphorylation decreased in response to immune perception of bacterial flagellin. RIN4 Thr166D lines exhibited reduced flagellin-triggered immune responses. Flagellin perception did not lower RIN4 Thr-166 phosphorylation in the presence of strong ectopic expression of AvrB. Taken together, these results indicate that the AvrB effector targets RIN4 in order to enhance pathogen entry on the leaf surface as well as dampen responses to conserved microbial features.
authors.affiliation: Department of Plant Pathology, University of California, Davis, California 95616.
authors.forename: DongHyuk
authors.initials: D
authors.lastname: Lee
authors.affiliation: The Sainsbury Laboratory, Norwich NR4 7UH, United Kingdom.
authors.forename: Gildas
authors.initials: G
authors.lastname: Bourdais
authors.affiliation: Department of Plant Pathology, University of California, Davis, California 95616.
authors.forename: Gang
authors.initials: G
authors.lastname: Yu
authors.affiliation: The Sainsbury Laboratory, Norwich NR4 7UH, United Kingdom.
authors.forename: Silke
authors.initials: S
authors.lastname: Robatzek
authors.affiliation: Department of Plant Pathology, University of California, Davis, California 95616 glcoaker@ucdavis.edu.
authors.forename: Gitta
authors.identifier: http://orcid.org/0000-0003-0899-2449
authors.initials: G
authors.lastname: Coaker
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology*; D005408:Flagellin / Q000494:pharmacology; D055786:Gene Knockout Techniques; D007192:Indenes / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D064267:Intrinsically Disordered Proteins / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D000069452:Pathogen-Associated Molecular Pattern Molecules / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010769:Phosphothreonine / Q000378:metabolism; D010935:Plant Diseases / Q000382:microbiology; D057865:Plant Immunity / Q000187:drug effects*; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology; D011485:Protein Binding / Q000187:drug effects; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000302:isolation & purification
chemical_list: D000596:Amino Acids; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D007192:Indenes; D047908:Intracellular Signaling Peptides and Proteins; D064267:Intrinsically Disordered Proteins; D000069452:Pathogen-Associated Molecular Pattern Molecules; C453279:RIN4 protein, Arabidopsis; D011994:Recombinant Proteins; D010769:Phosphothreonine; D005408:Flagellin; C058487:coronatine; D006180:Proton-Translocating ATPases; C544444:AHA1 protein, Arabidopsis