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 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 Multiple functional self-association interfaces in plant TIR domains

2017 ◽  
Vol 114 (10) ◽  
pp. E2046-E2052 ◽  
Author(s):  
Xiaoxiao Zhang ◽  
Maud Bernoux ◽  
Adam R. Bentham ◽  
Toby E. Newman ◽  
Thomas Ve ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Cell Death ◽  
Interleukin 1 ◽  
Tir Domain ◽  
Disease Resistance Protein ◽  
Resistance Protein ◽  
Cell Death Signaling ◽  
Self Association ◽  
Tir Domains ◽  
Diverse Plant

The self-association of Toll/interleukin-1 receptor/resistance protein (TIR) domains has been implicated in signaling in plant and animal immunity receptors. Structure-based studies identified different TIR-domain dimerization interfaces required for signaling of the plant nucleotide-binding oligomerization domain-like receptors (NLRs) L6 from flax and disease resistance protein RPS4 fromArabidopsis. Here we show that the crystal structure of the TIR domain from theArabidopsisNLR suppressor of npr1-1, constitutive 1 (SNC1) contains both an L6-like interface involving helices αD and αE (DE interface) and an RPS4-like interface involving helices αA and αE (AE interface). Mutations in either the AE- or DE-interface region disrupt cell-death signaling activity of SNC1, L6, and RPS4 TIR domains and full-length L6 and RPS4. Self-association of L6 and RPS4 TIR domains is affected by mutations in either region, whereas only AE-interface mutations affect SNC1 TIR-domain self-association. We further show two similar interfaces in the crystal structure of the TIR domain from theArabidopsisNLR recognition ofPeronospora parasitica1 (RPP1). These data demonstrate that both the AE and DE self-association interfaces are simultaneously required for self-association and cell-death signaling in diverse plant NLRs.

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 Comprehensive Map of the Regulated Cell Death Signaling Network: A Powerful Analytical Tool for Studying Diseases

Cancers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 990
Author(s):  
Jean-Marie Ravel ◽  
L. Cristobal Monraz Gomez ◽  
Nicolas Sompairac ◽  
Laurence Calzone ◽  
Boris Zhivotovsky ◽  
...  
Keyword(s):  
Cell Death ◽  
Molecular Mechanisms ◽  
Signaling Network ◽  
Tumor Subtypes ◽  
Navigation Data ◽  
Manual Curation ◽  
Regulated Cell Death ◽  
Powerful Analytical Tool ◽  
Cell Death Signaling ◽  
The Difference

The processes leading to, or avoiding cell death are widely studied, because of their frequent perturbation in various diseases. Cell death occurs in three highly interconnected steps: Initiation, signaling and execution. We used a systems biology approach to gather information about all known modes of regulated cell death (RCD). Based on the experimental data retrieved from literature by manual curation, we graphically depicted the biological processes involved in RCD in the form of a seamless comprehensive signaling network map. The molecular mechanisms of each RCD mode are represented in detail. The RCD network map is divided into 26 functional modules that can be visualized contextually in the whole seamless network, as well as in individual diagrams. The resource is freely available and accessible via several web platforms for map navigation, data integration, and analysis. The RCD network map was employed for interpreting the functional differences in cell death regulation between Alzheimer’s disease and non-small cell lung cancer based on gene expression data that allowed emphasizing the molecular mechanisms underlying the inverse comorbidity between the two pathologies. In addition, the map was used for the analysis of genomic and transcriptomic data from ovarian cancer patients that provided RCD map-based signatures of four distinct tumor subtypes and highlighted the difference in regulations of cell death molecular mechanisms.

scholarly journals The mirid bug Apolygus lucorum deploys a glutathione peroxidase as a candidate effector to enhance plant susceptibility

2020 ◽  
Vol 71 (9) ◽  
pp. 2701-2712
Author(s):  
Yumei Dong ◽  
Maofeng Jing ◽  
Danyu Shen ◽  
Chenyang Wang ◽  
Meiqian Zhang ◽  
...  
Keyword(s):  
Cell Death ◽  
Salivary Gland ◽  
Glutathione Peroxidase ◽  
Large Scale ◽  
Plant Pathogens ◽  
Molecular Mechanisms ◽  
Mechanism Analysis ◽  
Apolygus Lucorum ◽  
Mirid Bug ◽  
Plant Susceptibility

Abstract The mirid bug Apolygus lucorum has become a major agricultural pest since the large-scale cultivation of Bt-cotton. It was assumed that A. lucorum, similarly to other phloem sap insects, could secrete saliva that contains effector proteins into plant interfaces to perturb host cellular processes during feeding. However, the secreted effectors of A. lucorum are still uncharacterized and unstudied. In this study, 1878 putative secreted proteins were identified from the transcriptome of A. lucorum, which either had homology with published aphid effectors or shared common features with plant pathogens and insect effectors. One hundred and seventy-two candidate effectors were used for cell death-inducing/suppressing assays, and a putative salivary gland effector, Apolygus lucorum cell death inhibitor 6 (Al6), was characterized. The mRNAs of Al6 were enriched at feeding stages (nymph and adult) and, in particular, in salivary glands. Moreover, we revealed that the secreted Al6 encoded an active glutathione peroxidase that reduced reactive oxygen species (ROS) accumulation induced by INF1 or Flg22. Expression of the Al6 gene in planta altered insect feeding behavior and promoted plant pathogen infections. Inhibition of cell death and enhanced plant susceptibility to insect and pathogens are dependent on glutathione peroxidase activity of Al6. Thus, this study shows that a candidate salivary gland effector, Al6, functions as a glutathione peroxidase and suppresses ROS induced by pathogen-associated molecular pattern to inhibit pattern-triggered immunity (PTI)-induced cell death. The identification and molecular mechanism analysis of the Al6 candidate effector in A. lucorum will provide new insight into the molecular mechanisms of insect–plant interactions.

scholarly journals NAD+ cleavage activity by animal and plant TIR domains in cell death pathways

Science ◽  
2019 ◽  
Vol 365 (6455) ◽  
pp. 793-799 ◽  
Author(s):  
Shane Horsefield ◽  
Hayden Burdett ◽  
Xiaoxiao Zhang ◽  
Mohammad K. Manik ◽  
Yun Shi ◽  
...  
Keyword(s):  
Cell Death ◽  
Nicotinamide Adenine Dinucleotide ◽  
Interleukin 1 ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Effector Proteins ◽  
Nicotinamide Adenine ◽  
Cleavage Activity ◽  
Pathogen Effector ◽  
Cell Death Signaling ◽  
Tir Domains

SARM1 (sterile alpha and TIR motif containing 1) is responsible for depletion of nicotinamide adenine dinucleotide in its oxidized form (NAD+) during Wallerian degeneration associated with neuropathies. Plant nucleotide-binding leucine-rich repeat (NLR) immune receptors recognize pathogen effector proteins and trigger localized cell death to restrict pathogen infection. Both processes depend on closely related Toll/interleukin-1 receptor (TIR) domains in these proteins, which, as we show, feature self-association–dependent NAD+ cleavage activity associated with cell death signaling. We further show that SARM1 SAM (sterile alpha motif) domains form an octamer essential for axon degeneration that contributes to TIR domain enzymatic activity. The crystal structures of ribose and NADP+ (the oxidized form of nicotinamide adenine dinucleotide phosphate) complexes of SARM1 and plant NLR RUN1 TIR domains, respectively, reveal a conserved substrate binding site. NAD+ cleavage by TIR domains is therefore a conserved feature of animal and plant cell death signaling pathways.

scholarly journals Molecular mechanisms of host cell manipulation by plant pathogens

2014 ◽  
Vol 70 (a1) ◽  
pp. C801-C801
Author(s):  
Richard Hughes ◽  
Stuart King ◽  
Abbas Maqbool ◽  
Hazel McLellan ◽  
Tolga Bozkurt ◽  
...  
Keyword(s):  
Cell Death ◽  
Crop Production ◽  
Plant Pathogens ◽  
Molecular Mechanisms ◽  
Complex Structure ◽  
Effector Proteins ◽  
Plant Diseases ◽  
Cell Manipulation ◽  
Cell Physiology ◽  
Structural Studies

An estimated 15% of global crop production is lost to pre-harvest disease every year. New ways to manage plant diseases are required. A mechanistic understanding of how plant pathogens re-program their hosts to enable colonisation may provide novel genetic or chemical opportunities to interfere with disease. One notorious plant parasite is the Irish potato famine pathogen Phytophthora infestans. This pathogen remains a considerable threat to potato/tomato crops today as the agent of late blight. Plant pathogens secrete effector proteins outside of and into plant cells to suppress host defences and manipulate cell physiology. Structural studies have provided insights into effector evolution and enabled experiments to probe function [1-3]. Crystal structures of 4 Phytophthora RXLR-type effectors, which are unrelated in primary sequence, revealed similarities in the fold of these proteins. This fold was proposed to act as a stable scaffold that supports diversification of effectors. Further, molecular modelling has enabled mapping of single-site variants responsible for specialisation of a Phytophthora Cystatin-like effector, revealing how effectors can adapt to new hosts after a "host jump". Structural studies describing how RXLR-effectors interact with host targets are lacking. We have used Y2H/co-IP studies to identify host proteins that interact with P. infestans effectors PexRD2 and PexRD54. PexRD2 interacts with MAPKKKe, a component of plant immune signalling pathways, and suppressed cell death activities of this protein. We used the structure of PexRD2 to design mutants that fail to interact with MAPKKKe, and no longer suppress cell-death activities. We found that PexRD54 interacts with potato homologues of the autophagy protein ATG8. We have obtained a crystal structure for PexRD54 in the presence of ATG8. We are now using X-ray scattering to verify the complex structure in solution prior to establishing the role of this interaction during infection.

The Structural Basis of Necroptotic Cell Death Signaling

2019 ◽  
Vol 44 (1) ◽  
pp. 53-63 ◽  
Author(s):  
Emma J. Petrie ◽  
Peter E. Czabotar ◽  
James M. Murphy
Keyword(s):  
Cell Death ◽  
Structural Basis ◽  
Cell Death Signaling

scholarly journals Cytosolic activation of cell death and stem rust resistance by cereal MLA-family CC–NLR proteins

2016 ◽  
Vol 113 (36) ◽  
pp. 10204-10209 ◽  
Author(s):  
Stella Cesari ◽  
John Moore ◽  
Chunhong Chen ◽  
Daryl Webb ◽  
Sambasivam Periyannan ◽  
...  
Keyword(s):  
Cell Death ◽  
Disease Resistance ◽  
Stem Rust ◽  
Nuclear Export ◽  
Rust Resistance ◽  
Stem Rust Resistance ◽  
Full Length ◽  
Induce Cell Death ◽  
Immune Receptors ◽  
Cell Death Signaling

Plants possess intracellular immune receptors designated “nucleotide-binding domain and leucine-rich repeat” (NLR) proteins that translate pathogen-specific recognition into disease-resistance signaling. The wheat immune receptors Sr33 and Sr50 belong to the class of coiled-coil (CC) NLRs. They confer resistance against a broad spectrum of field isolates of Puccinia graminis f. sp. tritici, including the Ug99 lineage, and are homologs of the barley powdery mildew-resistance protein MLA10. Here, we show that, similarly to MLA10, the Sr33 and Sr50 CC domains are sufficient to induce cell death in Nicotiana benthamiana. Autoactive CC domains and full-length Sr33 and Sr50 proteins self-associate in planta. In contrast, truncated CC domains equivalent in size to an MLA10 fragment for which a crystal structure was previously determined fail to induce cell death and do not self-associate. Mutations in the truncated region also abolish self-association and cell-death signaling. Analysis of Sr33 and Sr50 CC domains fused to YFP and either nuclear localization or nuclear export signals in N. benthamiana showed that cell-death induction occurs in the cytosol. In stable transgenic wheat plants, full-length Sr33 proteins targeted to the cytosol provided rust resistance, whereas nuclear-targeted Sr33 was not functional. These data are consistent with CC-mediated induction of both cell-death signaling and stem rust resistance in the cytosolic compartment, whereas previous research had suggested that MLA10-mediated cell-death and disease resistance signaling occur independently, in the cytosol and nucleus, respectively.

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