title: TIR-only protein RBA1 recognizes a pathogen effector to regulate cell death inArabidopsis.
abstract: Detection of pathogens by plants is mediated by intracellular nucleotide-binding site leucine-rich repeat (NLR) receptor proteins. NLR proteins are defined by their stereotypical multidomain structure: an N-terminal Toll-interleukin receptor (TIR) or coiled-coil (CC) domain, a central nucleotide-binding (NB) domain, and a C-terminal leucine-rich repeat (LRR). The plant innate immune system contains a limited NLR repertoire that functions to recognize all potential pathogens. We isolated Response to the bacterial type III effector protein HopBA1 (RBA1), a gene that encodes a TIR-only protein lacking all other canonical NLR domains. RBA1 is sufficient to trigger cell death in response to HopBA1. We generated a crystal structure for HopBA1 and found that it has similarity to a class of proteins that includes esterases, the heme-binding protein ChaN, and an uncharacterized domain ofPasteurella multocidatoxin. Self-association, coimmunoprecipitation with HopBA1, and function of RBA1 require two previously identified TIR-TIR dimerization interfaces. Although previously described as distinct in other TIR proteins, in RBA1 neither of these interfaces is sufficient when the other is disrupted. These data suggest that oligomerization of RBA1 is required for function. Our identification of RBA1 demonstrates that "truncated" NLRs can function as pathogen sensors, expanding our understanding of both receptor architecture and the mechanism of activation in the plant immune system.
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, NC 27599; marcusn@colostate.edu dangl@email.unc.edu.|Howard Hughes Medical Institute, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Marc T
authors.identifier: 0000-0003-4666-6900
authors.initials: MT
authors.lastname: Nishimura
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Ryan G
authors.initials: RG
authors.lastname: Anderson
authors.affiliation: Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Karen A
authors.initials: KA
authors.lastname: Cherkis
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, NC 27599.|Howard Hughes Medical Institute, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Terry F
authors.initials: TF
authors.lastname: Law
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Qingli L
authors.initials: QL
authors.lastname: Liu
authors.affiliation: Department of Pharmacology, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Mischa
authors.initials: M
authors.lastname: Machius
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Zachary L
authors.initials: ZL
authors.lastname: Nimchuk
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Li
authors.initials: L
authors.lastname: Yang
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, NC 27599.|Howard Hughes Medical Institute, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Eui-Hwan
authors.initials: EH
authors.lastname: Chung
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Farid
authors.initials: F
authors.lastname: El Kasmi
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Michael
authors.initials: M
authors.lastname: Hyunh
authors.affiliation: Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Erin
authors.identifier: 0000-0002-4313-4573
authors.initials: E
authors.lastname: Osborne Nishimura
authors.affiliation: Department of Pharmacology, University of North Carolina, Chapel Hill, NC 27599.|Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599.|Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: John E
authors.initials: JE
authors.lastname: Sondek
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, NC 27599; marcusn@colostate.edu dangl@email.unc.edu.|Howard Hughes Medical Institute, University of North Carolina, Chapel Hill, NC 27599.|Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599.|Carolina Center for Genome Sciences, University of North Carolina, Chapel Hill, NC 27599.|Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27599.
authors.forename: Jeffery L
authors.initials: JL
authors.lastname: Dangl
mesh_terms: D017360:Arabidopsis / Q000737:chemistry* / Q000235:genetics* / Q000276:immunology / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D001665:Binding Sites; D016923:Cell Death / Q000235:genetics / Q000276:immunology; D018360:Crystallography, X-Ray; D004885:Erwinia / Q000472:pathogenicity / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions; D008958:Models, Molecular; D009154:Mutation; D010935:Plant Diseases / Q000235:genetics* / Q000276:immunology / Q000382:microbiology; D057865:Plant Immunity / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary; D044224:Pseudomonas syringae / Q000472:pathogenicity / Q000502:physiology; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D015398:Signal Transduction; D014026:Nicotiana / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D000069296:Type III Secretion Systems / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D010940:Plant Proteins; D011994:Recombinant Proteins; D000069296:Type III Secretion Systems; C097421:rps4 protein, plant
keywords: NLR; Toll–interleukin-1 receptor homology domain; oligomerization; plant immunity; type III secretion