Structural and functional analysis of a plant resistance protein TIR domain reveals interfaces for self-association, signaling, and autoregulation

The Toll/interleukin-1 receptor (TIR) domain occurs in animal and plant immune receptors. In the animal Toll-like receptors, homodimerization of the intracellular TIR domain is required for initiation of signaling cascades leading to innate immunity. By contrast, the role of the TIR domain in cytopl...

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Bibliographic Details
Published in:Cell host & microbe 2011-03, Vol.9 (3), p.200-211
Main Authors: Bernoux, Maud, Ve, Thomas, Williams, Simon, Warren, Christopher, Hatters, Danny, Valkov, Eugene, Zhang, Xiaoxiao, Ellis, Jeffrey G, Kobe, Bostjan, Dodds, Peter N
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Basidiomycota
Binding Sites
Computer Simulation
Crystallography, X-Ray
Flax - immunology
Flax - microbiology
Homeostasis
Models, Molecular
Molecular Sequence Data
Mutagenesis, Site-Directed
Plant Diseases - immunology
Plant Proteins - chemistry
Plant Proteins - genetics
Protein Interaction Domains and Motifs
Protein Multimerization
Protein Structure, Quaternary
Protein Structure, Secondary
Recombinant Fusion Proteins - chemistry
Recombinant Fusion Proteins - genetics
Sequence Alignment
Signal Transduction
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Summary:The Toll/interleukin-1 receptor (TIR) domain occurs in animal and plant immune receptors. In the animal Toll-like receptors, homodimerization of the intracellular TIR domain is required for initiation of signaling cascades leading to innate immunity. By contrast, the role of the TIR domain in cytoplasmic nucleotide-binding/leucine-rich repeat (NB-LRR) plant immune resistance proteins is poorly understood. L6 is a TIR-NB-LRR resistance protein from flax (Linum usitatissimum) that confers resistance to the flax rust phytopathogenic fungus (Melampsora lini). We determine the crystal structure of the L6 TIR domain and show that, although dispensable for pathogenic effector protein recognition, the TIR domain alone is both necessary and sufficient for L6 immune signaling. We demonstrate that the L6 TIR domain self-associates, most likely forming a homodimer. Analysis of the structure combined with site-directed mutagenesis suggests that self-association is a requirement for immune signaling and reveals distinct surface regions involved in self-association, signaling, and autoregulation.
ISSN:1931-3128
1934-6069
DOI:10.1016/j.chom.2011.02.009