scholarly journals Dissection of Cell Death Induction by Wheat Stem Rust Resistance Protein Sr35 and Its Matching Effector AvrSr35

2020 ◽  
Vol 33 (2) ◽  
pp. 308-319 ◽  
Author(s):  
Stephen Bolus ◽  
Eduard Akhunov ◽  
Gitta Coaker ◽  
Jorge Dubcovsky
Keyword(s):  
Cell Death ◽  
Transient Expression ◽  
Stem Rust ◽  
Fluorescent Protein ◽  
Coiled Coil ◽  
Nucleotide Binding ◽  
Leucine Rich Repeat ◽  
Wheat Stem Rust ◽  
Pathogen Effector ◽  
Lrr Domain

Nucleotide-binding leucine-rich repeat receptors (NLRs) are the most abundant type of immune receptors in plants and can trigger a rapid cell-death (hypersensitive) response upon sensing pathogens. We previously cloned the wheat NLR Sr35, which encodes a coiled-coil (CC) NLR that confers resistance to the virulent wheat stem rust race Ug99. Here, we investigated Sr35 signaling after Agrobacterium-mediated transient expression in Nicotiana benthamiana. Expression of Sr35 in N. benthamiana leaves triggered a mild cell-death response, which is enhanced in the autoactive mutant Sr35 D503V. The N-terminal tagging of Sr35 with green fluorescent protein (GFP) blocked the induction of cell death, whereas a C-terminal GFP tag did not. No domain truncations of Sr35 generated cell-death responses as strong as the wild type, but a truncation including the NB-ARC (nucleotide binding adaptor) shared by APAF-1, R proteins, and CED-4 domains in combination with the D503V autoactive mutation triggered cell death. In addition, coexpression of Sr35 with the matching pathogen effector protein AvrSr35 resulted in robust cell death and electrolyte leakage levels that were similar to autoactive Sr35 and significantly higher than Sr35 alone. Coexpression of Sr35-CC-NB-ARC and AvrSr35 did not induce cell death, confirming the importance of the leucine-rich repeat (LRR) domain for AvrSr35 recognition. These findings were confirmed through Agrobacterium-mediated transient expression in barley. Taken together, these results implicate the CC-NB-ARC domains of Sr35 in inducing cell death and the LRR domain in AvrSr35 recognition. [Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

scholarly journals TIR-only protein RBA1 recognizes a pathogen effector to regulate cell death inArabidopsis

2017 ◽  
Vol 114 (10) ◽  
pp. E2053-E2062 ◽  
Author(s):  
Marc T. Nishimura ◽  
Ryan G. Anderson ◽  
Karen A. Cherkis ◽  
Terry F. Law ◽  
Qingli L. Liu ◽  
...  
Keyword(s):  
Cell Death ◽  
Immune System ◽  
Pasteurella Multocida ◽  
Coiled Coil ◽  
Nucleotide Binding ◽  
Leucine Rich Repeat ◽  
Multidomain Structure ◽  
Pathogen Effector ◽  
Self Association ◽  
And Function

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.

scholarly journals The CC domain structure from the wheat stem rust resistance protein Sr33 challenges paradigms for dimerization in plant NLR proteins

2016 ◽  
Vol 113 (45) ◽  
pp. 12856-12861 ◽  
Author(s):  
Lachlan W. Casey ◽  
Peter Lavrencic ◽  
Adam R. Bentham ◽  
Stella Cesari ◽  
Daniel J. Ericsson ◽  
...  
Keyword(s):  
Cell Death ◽  
Stem Rust ◽  
Plant Pathogens ◽  
Molecular Mechanisms ◽  
Structural Basis ◽  
Wheat Stem Rust ◽  
Pathogen Effector ◽  
Resistance Protein ◽  
Cell Death Signaling ◽  
Self Association

Plants use intracellular immunity receptors, known as nucleotide-binding oligomerization domain-like receptors (NLRs), to recognize specific pathogen effector proteins and induce immune responses. These proteins provide resistance to many of the world’s most destructive plant pathogens, yet we have a limited understanding of the molecular mechanisms that lead to defense signaling. We examined the wheat NLR protein, Sr33, which is responsible for strain-specific resistance to the wheat stem rust pathogen, Puccinia graminis f. sp. tritici. We present the solution structure of a coiled-coil (CC) fragment from Sr33, which adopts a four-helix bundle conformation. Unexpectedly, this structure differs from the published dimeric crystal structure of the equivalent region from the orthologous barley powdery mildew resistance protein, MLA10, but is similar to the structure of the distantly related potato NLR protein, Rx. We demonstrate that these regions are, in fact, largely monomeric and adopt similar folds in solution in all three proteins, suggesting that the CC domains from plant NLRs adopt a conserved fold. However, larger C-terminal fragments of Sr33 and MLA10 can self-associate both in vitro and in planta, and this self-association correlates with their cell death signaling activity. The minimal region of the CC domain required for both cell death signaling and self-association extends to amino acid 142, thus including 22 residues absent from previous biochemical and structural protein studies. These data suggest that self-association of the minimal CC domain is necessary for signaling but is likely to involve a different structural basis than previously suggested by the MLA10 crystallographic dimer.

scholarly journals The Coiled-Coil and Leucine-Rich Repeat Domain of the Potyvirus Resistance Protein Pvr4 Has a Distinct Role in Signaling and Pathogen Recognition

2018 ◽  
Vol 31 (9) ◽  
pp. 906-913 ◽  
Author(s):  
Saet-Byul Kim ◽  
Hye-Young Lee ◽  
Eun-Hye Choi ◽  
Eunsook Park ◽  
Ji-Hyun Kim ◽  
...  
Keyword(s):  
Cell Death ◽  
Coiled Coil ◽  
Mitogen Activated Protein Kinase ◽  
Protein Signaling ◽  
Death Domain ◽  
Leucine Rich Repeat ◽  
Domain Swap ◽  
Mitogen Activated Protein ◽  
And Function ◽  
Lrr Domain

The pepper Pvr4 protein encoding coiled-coil (CC) nucleotide-binding (NB) leucine-rich repeat (LRR) (NLR) confer hypersensitive response (HR) to potyviruses, including Pepper mottle virus (PepMoV), by recognizing the viral avirulence protein NIb. To figure out the Pvr4-mediated HR mechanism, we analyzed signaling component genes and structure-function relationships of Pvr4, using chimeras and deletion mutants in Nicotiana benthamiana. Molecular chaperone components including HSP90, SGT1, and RAR1 were required, while plant hormones and mitogen-activated protein kinase signaling components had little effect on Pvr4-NIb-mediated HR cell death. Domain swap analyses indicated that the LRR domain of Pvr4 determines recognition of PepMoV-NIb. Our deletion analysis further revealed that the CC domain or CC-NBARC domain alone can trigger autoactive cell death in N. benthamiana. However, the fragments having only an LRR domain could suppress CC-NBARC domain-induced cell death in trans. Further, C-terminal truncation analysis of Pvr4 revealed that a minimum three of five LRR exons showing high similarity was essential for Pvr4 function. The LRR domain may maintain Pvr4 in an inactive state in the absence of NIb. These results provide further insight into the structure and function of NLR protein signaling in plants.

scholarly journals Phenotypes Conferred by Wheat Multiple Pathogen Resistance Locus, Sr2, Include Cell Death in Response to Biotic and Abiotic Stresses

2019 ◽  
Vol 109 (10) ◽  
pp. 1751-1759
Author(s):  
Linda Tabe ◽  
Sharon Samuel ◽  
Matthew Dunn ◽  
Rosemary White ◽  
Rohit Mago ◽  
...  
Keyword(s):  
Cell Death ◽  
Powdery Mildew ◽  
Stem Rust ◽  
Abiotic Stresses ◽  
Resistance Locus ◽  
Petroleum Jelly ◽  
Wheat Stem Rust ◽  
Mesophyll Cells ◽  
Rust Infection ◽  
Photosynthetic Cells

The wheat Sr2 locus confers partial resistance to four biotrophic pathogens: wheat stem rust (Puccinia graminis f. sp. tritici), leaf rust (P. triticina), stripe rust (P. striiformis f. sp. tritici), and powdery mildew (Blumeria graminis f. sp. tritici). In addition, Sr2 is linked with a brown coloration of ears and stems, termed pseudo-black chaff (PBC). PBC, initially believed to be elicited by stem rust infection, was subsequently recognized to occur in the absence of pathogen infection. The current study demonstrates that the resistance response to stem rust is associated with the death of photosynthetic cells around rust infection sites in the inoculated leaf sheath. Similarly, Sr2-dependent resistance to powdery mildew was associated with the death of leaf mesophyll cells around mildew infection sites. We demonstrate that PBC occurring in the absence of pathogen inoculation also corresponds with death and the collapse of photosynthetic cells in the affected parts of stems and ears. In addition, Sr2-dependent necrosis was inducible in leaves by application of petroleum jelly or by heat treatments. Thus, Sr2 was found to be associated with cell death, which could be triggered by either biotic or abiotic stresses. Our results suggest a role for the Sr2 locus in controlling cell death in response to stress.

scholarly journals Analysis of intraspecies diversity reveals a subset of highly variable plant immune receptors and predicts their binding sites

2021 ◽  
Author(s):  
Judith Van Dingenen
Keyword(s):  
Interleukin 1 ◽  
Nucleotide Binding ◽  
Coiled Coils ◽  
Leucine Rich Repeat ◽  
Signal Transducers ◽  
Receptor Oligomerization ◽  
Continuous Generation ◽  
Pathogen Recognition Receptors ◽  
Intraspecies Diversity ◽  
Lrr Domain

Abstract Plants have two kinds of pathogen recognition receptors: extracellular receptor like kinases and proteins (RLKs and RLPs) and intracellular Nucleotide-Binding Leucine Rich Repeat (NLR) receptors. NLRs comprise three main domains: a central Nucleotide Binding domain (NB-ARC) that mediates receptor oligomerization upon activation, a C-terminal Leucine Rich Repeat (LRR) domain that defines receptor specificity and an N-terminal domain that mediates immunity. Based on the latter domain, the NLRs are subdivided into three monophyletic groups: RNLs (Resistance to Powdery Mildew8), CNLs (Coiled-Coils) and TNLs (Toll/Interleukin-1 Receptor homology). NLRs can be sensors or signal transducers. As sensors, NLRs can recognize pathogens by directly binding the effectors, by recognizing the effector’s action on other proteins, or by recognition of modifications to a non-canonical NLR domain. Continuous generation of NLR diversity is required to keep up with a range of rapidly evolving pathogens.

scholarly journals RicePi5-Mediated Resistance toMagnaporthe oryzaeRequires the Presence of Two Coiled-Coil–Nucleotide-Binding–Leucine-Rich Repeat Genes

Genetics ◽  
2009 ◽  
Vol 181 (4) ◽  
pp. 1627-1638 ◽  
Author(s):  
Sang-Kyu Lee ◽  
Min-Young Song ◽  
Young-Su Seo ◽  
Hye-Kyung Kim ◽  
Seho Ko ◽  
...  
Keyword(s):  
Coiled Coil ◽  
Nucleotide Binding ◽  
Leucine Rich Repeat
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