title: Specific threonine phosphorylation of a host target by two unrelated type III effectors activates a host innate immune receptor in plants.
abstract: The Arabidopsis NB-LRR immune receptor RPM1 recognizes the Pseudomonas syringae type III effectors AvrB or AvrRpm1 to mount an immune response. Although neither effector is itself a kinase, AvrRpm1 and AvrB are known to target Arabidopsis RIN4, a negative regulator of basal plant defense, for phosphorylation. We show that RIN4 phosphorylation activates RPM1. RIN4(142-176) is necessary and, with appropriate localization sequences, sufficient to support effector-triggered RPM1 activation, with the threonine residue at position 166 being critical. Phosphomimic substitutions at T166 cause effector-independent RPM1 activation. RIN4 T166 is phosphorylated in vivo in the presence of AvrB or AvrRpm1. RIN4 mutants that lose interaction with AvrB cannot be coimmunoprecipitated with RPM1. This defines a common interaction platform required for RPM1 activation by phosphorylated RIN4 in response to pathogenic effectors. Conservation of an analogous threonine across all RIN4-like proteins suggests a key function for this residue beyond the regulation of RPM1.
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, 27599, USA.
authors.forename: Eui-Hwan
authors.initials: EH
authors.lastname: Chung
authors.forename: Luis
authors.initials: L
authors.lastname: da Cunha
authors.forename: Ai-Jiuan
authors.initials: AJ
authors.lastname: Wu
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Gao
authors.forename: Karen
authors.initials: K
authors.lastname: Cherkis
authors.forename: Ahmed J
authors.initials: AJ
authors.lastname: Afzal
authors.forename: David
authors.initials: D
authors.lastname: Mackey
authors.forename: Jeffery L
authors.initials: JL
authors.lastname: Dangl
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D047908:Intracellular Signaling Peptides and Proteins; D010766:Phosphorylation; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D044224:Pseudomonas syringae / Q000235:genetics / Q000378:metabolism*; D013912:Threonine / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C100931:AvrB protein, Pseudomonas syringae; C502082:AvrRpm1 protein, Pseudomonas syringae; D001426:Bacterial Proteins; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C453279:RIN4 protein, Arabidopsis; C095014:RPM1 protein, Arabidopsis; D013912:Threonine