title: Rice XB15, a protein phosphatase 2C, negatively regulates cell death and XA21-mediated innate immunity.
abstract: Perception of extracellular signals by cell surface receptors is of central importance to eukaryotic development and immunity. Kinases that are associated with the receptors or are part of the receptors themselves modulate signaling through phosphorylation events. The rice (Oryza sativa L.) XA21 receptor kinase is a key recognition and signaling determinant in the innate immune response. A yeast two-hybrid screen using the intracellular portion of XA21, including the juxtamembrane (JM) and kinase domain as bait, identified a protein phosphatase 2C (PP2C), called XA21 binding protein 15 (XB15). The interaction of XA21 and XB15 was confirmed in vitro and in vivo by glutathione-S-transferase (GST) pull-down and co-immunoprecipitation assays, respectively. XB15 fusion proteins purified from Escherichia coli and from transgenic rice carry PP2C activity. Autophosphorylated XA21 can be dephosphorylated by XB15 in a temporal- and dosage-dependent manner. A serine residue in the XA21 JM domain is required for XB15 binding. Xb15 mutants display a severe cell death phenotype, induction of pathogenesis-related genes, and enhanced XA21-mediated resistance. Overexpression of Xb15 in an XA21 rice line compromises resistance to the bacterial pathogen Xanthomonas oryzae pv. oryzae. These results demonstrate that Xb15 encodes a PP2C that negatively regulates the XA21-mediated innate immune response.
authors.affiliation: Department of Plant Pathology, University of California Davis, Davis, California, USA.
authors.forename: Chang-Jin
authors.initials: CJ
authors.lastname: Park
authors.forename: Ying
authors.initials: Y
authors.lastname: Peng
authors.forename: Xuewei
authors.initials: X
authors.lastname: Chen
authors.forename: Christopher
authors.initials: C
authors.lastname: Dardick
authors.forename: Deling
authors.initials: D
authors.lastname: Ruan
authors.forename: Rebecca
authors.initials: R
authors.lastname: Bart
authors.forename: Patrick E
authors.initials: PE
authors.lastname: Canlas
authors.forename: Pamela C
authors.initials: PC
authors.lastname: Ronald
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016923:Cell Death / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006801:Humans; D007113:Immunity, Innate; D008969:Molecular Sequence Data; D012275:Oryza / Q000201:enzymology* / Q000235:genetics; D010749:Phosphoprotein Phosphatases / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D010802:Phylogeny; D010940:Plant Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D000071636:Protein Phosphatase 2C; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D018626:Retroelements / Q000235:genetics; D016415:Sequence Alignment; D020798:Two-Hybrid System Techniques; D014974:Xanthomonas / Q000276:immunology / Q000472:pathogenicity
chemical_list: D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D018626:Retroelements; C097148:Xa21 protein, Oryza sativa; D017346:Protein Serine-Threonine Kinases; C000607456:PPM1A protein, human; C000607457:PPM1B protein, human; C000607460:PPM1G protein, human; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C