title: Arabidopsis TAO1 is a TIR-NB-LRR protein that contributes to disease resistance induced by the Pseudomonas syringae effector AvrB.
abstract: The type III effector protein encoded by avirulence gene B (AvrB) is delivered into plant cells by pathogenic strains of Pseudomonas syringae. There, it localizes to the plasma membrane and triggers immunity mediated by the Arabidopsis coiled-coil (CC)-nucleotide binding (NB)-leucine-rich repeat (LRR) disease resistance protein RPM1. The sequence unrelated type III effector avirulence protein encoded by avirulence gene Rpm1 (AvrRpm1) also activates RPM1. AvrB contributes to virulence after delivery from P. syringae in leaves of susceptible soybean plants, and AvrRpm1 does the same in Arabidopsis rpm1 plants. Conditional overexpression of AvrB in rpm1 plants results in leaf chlorosis. In a genetic screen for mutants that lack AvrB-dependent chlorosis in an rpm1 background, we isolated TAO1 (target of AvrB operation), which encodes a Toll-IL-1 receptor (TIR)-NB-LRR disease resistance protein. In rpm1 plants, TAO1 function results in the expression of the pathogenesis-related protein 1 (PR-1) gene, suggestive of a defense response. In RPM1 plants, TAO1 contributes to disease resistance in response to Pto (P. syringae pathovars tomato) DC3000(avrB), but not against Pto DC3000(avrRpm1). The tao1-5 mutant allele, a stop mutation in the LRR domain of TAO1, posttranscriptionally suppresses RPM1 accumulation. These data provide evidence of genetically separable disease resistance responses to AvrB and AvrRpm1 in Arabidopsis. AvrB activates both RPM1, a CC-NB-LRR protein, and TAO1, a TIR-NB-LRR protein. These NB-LRR proteins then act additively to generate a full disease resistance response to P. syringae expressing this type III effector.
authors.affiliation: Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Timothy K
authors.initials: TK
authors.lastname: Eitas
authors.forename: Zachary L
authors.initials: ZL
authors.lastname: Nimchuk
authors.forename: Jeffery L
authors.initials: JL
authors.lastname: Dangl
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000276:immunology* / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D007113:Immunity, Innate / Q000276:immunology; D000090263:Leucine-Rich Repeat Proteins; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010935:Plant Diseases / Q000276:immunology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D044224:Pseudomonas syringae / Q000502:physiology*; D051193:Toll-Like Receptors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins; C100931:AvrB protein, Pseudomonas syringae; D001426:Bacterial Proteins; D000090263:Leucine-Rich Repeat Proteins; D010940:Plant Proteins; D011506:Proteins; C095014:RPM1 protein, Arabidopsis; D051193:Toll-Like Receptors; C053376:pathogenesis-related proteins, plant; D002265:Carboxylic Ester Hydrolases; C400766:PAD4 protein, Arabidopsis