Intramolecular interaction influences binding of the flax L5 and L6 resistance proteins to their AvrL567 ligands

Ravensdale, Michael, Bernoux, Maud, Ve, Thomas, Kobe, Bostjan, Thrall, Peter H., Ellis, Jeffrey G. and Dodds, Peter N. (2012) Intramolecular interaction influences binding of the flax L5 and L6 resistance proteins to their AvrL567 ligands. PloS Pathogens, 8 11: . doi:10.1371/journal.ppat.1003004


Author Ravensdale, Michael
Bernoux, Maud
Ve, Thomas
Kobe, Bostjan
Thrall, Peter H.
Ellis, Jeffrey G.
Dodds, Peter N.
Title Intramolecular interaction influences binding of the flax L5 and L6 resistance proteins to their AvrL567 ligands
Journal name PloS Pathogens   Check publisher's open access policy
ISSN 1553-7374
1553-7366
Publication date 2012-11-01
Year available 2012
Sub-type Article (original research)
DOI 10.1371/journal.ppat.1003004
Open Access Status DOI
Volume 8
Issue 11
Total pages 15
Place of publication San Francisco, United States
Publisher Public Library of Science
Language eng
Subject 2404 Microbiology
2405 Parasitology
2406 Virology
2403 Immunology
1311 Genetics
1312 Molecular Biology
Abstract L locus resistance (R) proteins are nucleotide binding (NB-ARC) leucine-rich repeat (LRR) proteins from flax (Linum usitatissimum) that provide race-specific resistance to the causal agent of flax rust disease, Melampsora lini. L5 and L6 are two alleles of the L locus that directly recognize variants of the fungal effector AvrL567. In this study, we have investigated the molecular details of this recognition by site-directed mutagenesis of AvrL567 and construction of chimeric L proteins. Single, double and triple mutations of polymorphic residues in a variety of AvrL567 variants showed additive effects on recognition strength, suggesting that multiple contact points are involved in recognition. Domain-swap experiments between L5 and L6 show that specificity differences are determined by their corresponding LRR regions. Most positively selected amino acid sites occur in the N- and C-terminal LRR units, and polymorphisms in the first seven and last four LRR units contribute to recognition specificity of L5 and L6 respectively. This further confirms that multiple, additive contact points occur between AvrL567 variants and either L5 or L6. However, we also observed that recognition of AvrL567 is affected by co-operative polymorphisms between both adjacent and distant domains of the R protein, including the TIR, ARC and LRR domains, implying that these residues are involved in intramolecular interactions to optimize detection of the pathogen and defense signal activation. We suggest a model where Avr ligand interaction directly competes with intramolecular interactions to cause activation of the R protein.
Formatted abstract
L locus resistance (R) proteins are nucleotide binding (NB-ARC) leucine-rich repeat (LRR) proteins from flax (Linum usitatissimum) that provide race-specific resistance to the causal agent of flax rust disease, Melampsora lini. L5 and L6 are two alleles of the L locus that directly recognize variants of the fungal effector AvrL567. In this study, we have investigated the molecular details of this recognition by site-directed mutagenesis of AvrL567 and construction of chimeric L proteins. Single, double and triple mutations of polymorphic residues in a variety of AvrL567 variants showed additive effects on recognition strength, suggesting that multiple contact points are involved in recognition. Domain-swap experiments between L5 and L6 show that specificity differences are determined by their corresponding LRR regions. Most positively selected amino acid sites occur in the N- and C-terminal LRR units, and polymorphisms in the first seven and last four LRR units contribute to recognition specificity of L5 and L6 respectively. This further confirms that multiple, additive contact points occur between AvrL567 variants and either L5 or L6. However, we also observed that recognition of AvrL567 is affected by co-operative polymorphisms between both adjacent and distant domains of the R protein, including the TIR, ARC and LRR domains, implying that these residues are involved in intramolecular interactions to optimize detection of the pathogen and defense signal activation. We suggest a model where Avr ligand interaction directly competes with intramolecular interactions to cause activation of the R protein.
Keyword Leucine-rich repeats
Rust avirulence proteins
Innate immune receptor
For-gene specificity
Q-Index Code C1
Q-Index Status Confirmed Code
Grant ID 5RO1 GM074265-01A2
DP0984827
Institutional Status UQ
Additional Notes Article # e1003004

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2013 Collection
School of Chemistry and Molecular Biosciences
Institute for Molecular Bioscience - Publications
 
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