TIR-only protein RBA1 recognizes a pathogen effector to regulate cell death in Arabidopsis

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-bin...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2017-03, Vol.114 (10), p.E2053-E2062
Main Authors: Nishimura, Marc T., Anderson, Ryan G., Cherkis, Karen A., Law, Terry F., Liu, Qingli L., Machius, Mischa, Nimchuk, Zachary L., Yang, Li, Chung, Eui-Hwan, Kasmi, Farid El, Hyunh, Michael, Nishimura, Erin Osborne, Sondek, John E., Dangl, Jeffery L.
Format: Article
Language:English
Subjects:
Arabidopsis - chemistry
Arabidopsis - genetics
Arabidopsis - immunology
Arabidopsis - microbiology
Arabidopsis Proteins - chemistry
Arabidopsis Proteins - genetics
Arabidopsis Proteins - immunology
Bacteria
BASIC BIOLOGICAL SCIENCES
Binding Sites
Biological Sciences
Cell Death - genetics
Cell Death - immunology
Crystallography, X-Ray
Cytokines
Erwinia - pathogenicity
Erwinia - physiology
Gene Expression Regulation, Plant
Host-Pathogen Interactions
Immune system
Models, Molecular
Mutation
Nicotiana - genetics
Nicotiana - immunology
Nicotiana - microbiology
NLR
oligomerization
Plant Diseases - genetics
Plant Diseases - immunology
Plant Diseases - microbiology
plant immunity
Plant Immunity - genetics
Plant Proteins - chemistry
Plant Proteins - genetics
Plant Proteins - immunology
PNAS Plus
Protein Binding
Protein Interaction Domains and Motifs
Protein Structure, Secondary
Proteins
Pseudomonas syringae - pathogenicity
Pseudomonas syringae - physiology
Recombinant Proteins - chemistry
Recombinant Proteins - genetics
Recombinant Proteins - immunology
Signal Transduction
Toll–interleukin-1 receptor homology domain
type III secretion
Type III Secretion Systems - genetics
Type III Secretion Systems - metabolism
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Summary: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 of Pasteurella multocida toxin. Self-association, coimmunoprecipitationwith 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.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1620973114