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Peter Moffett - One of the best experts on this subject based on the ideXlab platform.
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Mechanisms of recognition in dominant R gene mediated resistance.
Advances in Virus Research, 2020Co-Authors: Peter MoffettAbstract:One branch of plant innate immunity is mediated through what is traditionally known as race-specific or gene-for-gene resistance wherein the outcome of an attempted infection is determined by the genotypes of both the host and the pathogen. Dominant plant disease resistance (R) genes confer resistance to a variety of biotrophic pathogens, including viruses, encoding corresponding dominant avirulence (Avr) genes. R genes are among the most highly variable plant genes known, both within and between populations. Plant genomes encode hundreds of R genes that code for NB-LRR Proteins, so named because they posses nucleotide-binding (NB) and leucine-rich repeat (LRR) domains. Many matching pairs of NB-LRR and Avr Proteins have been identified as well as cellular Proteins that mediate R/Avr interactions, and the molecular analysis of these interactions have led to the formulation of models of how products of R genes recognize pathogens. Data from multiple NB-LRR systems indicate that the LRR domains of NB-LRR Proteins determine recognition specificity. However, recent evidence suggests that NB-LRR Proteins have co-opted cellular recognition co-factors that mediate interactions between Avr Proteins and the N-terminal domains of NB-LRR Proteins.
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Cell Death Mediated by the N-Terminal Domains of a Unique and Highly Conserved Class of NB-LRR Protein
Molecular Plant-microbe Interactions, 2011Co-Authors: Sarah M. Collier, Louis-philippe Hamel, Peter MoffettAbstract:Plant genomes encode large numbers of nucleotide-binding, leucine-rich repeat (NB-LRR) Proteins, many of which are active in pathogen detection and defense response induction. NB-LRR Proteins fall into two broad classes: those with a Toll and interleukin-1 receptor (TIR) domain at their N-terminus and those with a coiled-coil (CC) domain at the N-terminus. Within CC-NB-LRR-encoding genes, one basal clade is distinguished by having CC domains resembling the Arabidopsis thaliana RPW8 protein, which we refer to as CCR domains. Here, we show that CCR-NB-LRR-encoding genes are present in the genomes of all higher plants surveyed, and that they comprise two distinct subgroups: one typified by the Nicotiana benthamiana N-required gene 1 (NRG1) protein and the other typified by the Arabidopsis activated disease resistance gene 1 (ADR1) protein. We further report that, in contrast to CC-NB-LRR Proteins, the CCR domains of both NRG1- and ADR1-like Proteins are sufficient for the induction of defense responses, and ...
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The Cyst Nematode SPRYSEC Protein RBP-1 Elicits Gpa2- and RanGAP2-Dependent Plant Cell Death
PLOS Pathogens, 2009Co-Authors: Melanie A Sacco, K.b. Koropacka, Eric Grenier, Marianne J. Jaubert, Alexandra Blanchard, Aska Goverse, Geert Smant, Peter MoffettAbstract:Plant NB-LRR Proteins confer robust protection against microbes and metazoan parasites by recognizing pathogen-derived avirulence (Avr) Proteins that are delivered to the host cytoplasm. Microbial Avr Proteins usually function as virulence factors in compatible interactions; however, little is known about the types of metazoan Proteins recognized by NB-LRR Proteins and their relationship with virulence. In this report, we demonstrate that the secreted protein RBP-1 from the potato cyst nematode Globodera pallida elicits defense responses, including cell death typical of a hypersensitive response (HR), through the NB-LRR protein Gpa2. Gp-Rbp-1 variants from G. pallida populations both virulent and avirulent to Gpa2 demonstrated a high degree of polymorphism, with positive selection detected at numerous sites. All Gp-RBP-1 protein variants from an avirulent population were recognized by Gpa2, whereas virulent populations possessed Gp-RBP-1 protein variants both recognized and non-recognized by Gpa2. Recognition of Gp-RBP-1 by Gpa2 correlated to a single amino acid polymorphism at position 187 in the Gp-RBP-1 SPRY domain. Gp-RBP-1 expressed from Potato virus X elicited Gpa2-mediated defenses that required Ran GTPase-activating protein 2 (RanGAP2), a protein known to interact with the Gpa2 N terminus. Tethering RanGAP2 and Gp-RBP-1 variants via fusion Proteins resulted in an enhancement of Gpa2-mediated responses. However, activation of Gpa2 was still dependent on the recognition specificity conferred by amino acid 187 and the Gpa2 LRR domain. These results suggest a two-tiered process wherein RanGAP2 mediates an initial interaction with pathogen-delivered Gp-RBP-1 Proteins but where the Gpa2 LRR determines which of these interactions will be productive.
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virus resistance induced by nb LRR Proteins involves argonaute4 dependent translational control
Plant Journal, 2009Co-Authors: Saikat Bhattacharjee, Alejandro Zamora, Muhammad Azhar, Melanie A Sacco, Lester H Lambert, Peter MoffettAbstract:SUMMARYActive resistance to viruses is afforded by plant disease resistance (R) genes, which encode Proteins withnucleotide-binding (NB) and leucine-rich repeat (LRR) domains. Upon recognition of pathogen-derivedelicitors, these NB–LRR Proteins are thought to initiate a number of signaling pathways that lead to pathogenrestriction. However, little is known about the molecular mechanisms that ultimately curtail virus accumu-lation. Here, we show that the co-expression of a plant NB–LRR protein with its cognate elicitor results in anantiviral response that inhibits the translation of virus-encoded Proteins in Nicotiana benthamiana. Thisantiviral response is dependent on viral cis elements, and, upon activation of the NB–LRR protein, viraltranscripts accumulate but do not associate with ribosomes. The induced inhibition of viral transcripttranslation and NB–LRR-mediated virus resistance were compromised by the downregulation of Argonaute4-like genes. Argonaute Proteins have been implicated in small RNA-mediated RNA degradation, and indegradation-independent translational control. Our results suggest that the engagement of ArgonauteProteins in the specific translational control of viral transcripts is a key factor in virus resistance mediated byNB–LRR Proteins.Keywords: NBS–LRR, plant disease resistance, RNA silencing, Argonaute, translational control.INTRODUCTIONViruses establish infection by exploiting the cellular com-ponents of the host for replication and spread. As plant RNAviruses replicate in the cytoplasm,their open reading frames(ORFs) are not processed by the same machinery as cellularmessenger RNAs (mRNAs). As such, viruses have evolvedmultiple mechanisms to ensure the translation of theirgenetic material, often through direct interactions betweenvirus and host components (Thivierge et al., 2005; Dreherand Miller, 2006). Thus, translation represents a potential‘Achilles heel’ for viruses, and many recessive viralresistance genes encode variants of the host translationmachinery that no longer undergo a requisite interactionwith viral Proteins (Robaglia and Caranta, 2006).Plants have also evolved mechanisms to actively targetviruses. Viral RNAs can be targeted for degradation by theRNA silencing machinery of the plant. This involves theprocessing of viral double-stranded RNA (dsRNA) by Dicer-like enzymes, into small interfering RNAs (siRNAs), whichare subsequently incorporated into protein complexes thattarget viral RNAs for degradation, through the endonucleo-lytic activity of Argonaute (AGO) Proteins (Ding and Voinnet,2007; Omarov et al., 2007). However, RNA silencing isgenerally insufficient to rapidly limit infections by host-adaptedviruses,asmostvirusesencodeviralsuppressorsofRNA silencing (VSRs) (Ding and Voinnet, 2007; Diaz-Pendonand Ding, 2008). AGO Proteins also regulate endogeneexpression through RNA cleavage, as well as through othermechanisms (Vaucheret, 2008). For example, AGO1 andAGO10 have been reported to mediate the cleavage-inde-pendent control of translation (Brodersen et al., 2008), andAGO4 plays a key role in RNA-dependent DNA methylation(RdDM) (Zilberman et al., 2003, 2004).Arapidresistanceresponsetovirusesisaffordedbygene-for-gene resistance. Plant disease resistance (R) genesconfer immunity specifically to pathogens encoding match-ing avirulence (Avr) genes (Jones and Dangl, 2006). Thelargest class of R Proteins are predicted to be intracellular:encoding nucleotide-binding site (NB) and leucine-rich-repeat (LRR) domains (Kang et al., 2005). These NB–LRRProteins fall into two major groups, based on the domain
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The Coiled-Coil and Nucleotide Binding Domains of the Potato Rx Disease Resistance Protein Function in Pathogen Recognition and Signaling
The Plant Cell, 2008Co-Authors: Gregory J. Rairdan, Melanie A Sacco, Sarah M. Collier, Thomas T. Baldwin, Teresa Boettrich, Peter MoffettAbstract:Plant genomes encode large numbers of nucleotide binding and leucine-rich repeat (NB-LRR) Proteins, some of which mediate the recognition of pathogen-encoded Proteins. Following recognition, the initiation of a resistance response is thought to be mediated by the domains present at the N termini of NB-LRR Proteins, either a Toll and Interleukin-1 Receptor or a coiled-coil (CC) domain. In order to understand the role of the CC domain in NB-LRR function, we have undertaken a systematic structure–function analysis of the CC domain of the potato (Solanum tuberosum) CC-NB-LRR protein Rx, which confers resistance to Potato virus X. We show that the highly conserved EDVID motif of the CC domain mediates an intramolecular interaction that is dependent on several domains within the rest of the Rx protein, including the NB and LRR domains. Other conserved and nonconserved regions of the CC domain mediate the interaction with the Ran GTPase–activating protein, RanGAP2, a protein required for Rx function. Furthermore, we show that the Rx NB domain is sufficient for inducing cell death typical of hypersensitive plant resistance responses. We describe a model of CC-NB-LRR function wherein the LRR and CC domains coregulate the signaling activity of the NB domain in a recognition-specific manner.
Fumiaki Katagiri - One of the best experts on this subject based on the ideXlab platform.
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mutational analysis of the arabidopsis nucleotide binding site leucine rich repeat resistance gene rps2
The Plant Cell, 2000Co-Authors: Fenghua Yuan, Todd R Leister, Fumiaki Katagiri, Frederick M. AusubelAbstract:Disease resistance Proteins containing a nucleotide binding site (NBS) and a leucine-rich repeat (LRR) region compose the largest class of disease resistance Proteins. These so-called NBS-LRR Proteins confer resistance against a wide variety of phytopathogens. To help elucidate the mechanism by which NBS-LRR Proteins recognize and transmit pathogen-derived signals, we analyzed mutant versions of the Arabidopsis NBS-LRR protein RPS2. The RPS2 gene confers resistance against Pseudomonas syringae strains carrying the avirulence gene avrRpt2. The activity of RPS2 derivatives in response to AvrRpt2 was measured by using a functional transient expression assay or by expressing the mutant Proteins in transgenic plants. Directed mutagenesis revealed that the NBS and an N-terminal leucine zipper (LZ) motif were critical for RPS2 function. Mutations near the N terminus, including an LZ mutation, resulted in Proteins that exhibited a dominant negative effect on wild-type RPS2. Scanning the RPS2 molecule with a small in-frame internal deletion demonstrated that RPS2 does not have a large dispensable region. Overexpression of RPS2 in the transient assay in the absence of avrRpt2 also led to an apparent resistant response, presumably a consequence of a low basal activity of RPS2. The NBS and LZ were essential for this overdose effect, whereas the entire LRR was dispensable. RPS2 interaction with a 75-kD protein (p75) required an N-terminal portion of RPS2 that is smaller than the region required for the overdose effect. These findings illuminate the pathogen recognition mechanisms common among NBS-LRR Proteins.
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Mutational Analysis of the Arabidopsis Nucleotide Binding Site–Leucine-Rich Repeat Resistance Gene RPS2
The Plant Cell, 2000Co-Authors: Fenghua Yuan, Frederick M. Ausubel, R. Todd Leister, Fumiaki KatagiriAbstract:Disease resistance Proteins containing a nucleotide binding site (NBS) and a leucine-rich repeat (LRR) region compose the largest class of disease resistance Proteins. These so-called NBS-LRR Proteins confer resistance against a wide variety of phytopathogens. To help elucidate the mechanism by which NBS-LRR Proteins recognize and transmit pathogen-derived signals, we analyzed mutant versions of the Arabidopsis NBS-LRR protein RPS2. The RPS2 gene confers resistance against Pseudomonas syringae strains carrying the avirulence gene avrRpt2. The activity of RPS2 derivatives in response to AvrRpt2 was measured by using a functional transient expression assay or by expressing the mutant Proteins in transgenic plants. Directed mutagenesis revealed that the NBS and an N-terminal leucine zipper (LZ) motif were critical for RPS2 function. Mutations near the N terminus, including an LZ mutation, resulted in Proteins that exhibited a dominant negative effect on wild-type RPS2. Scanning the RPS2 molecule with a small in-frame internal deletion demonstrated that RPS2 does not have a large dispensable region. Overexpression of RPS2 in the transient assay in the absence of avrRpt2 also led to an apparent resistant response, presumably a consequence of a low basal activity of RPS2. The NBS and LZ were essential for this overdose effect, whereas the entire LRR was dispensable. RPS2 interaction with a 75-kD protein (p75) required an N-terminal portion of RPS2 that is smaller than the region required for the overdose effect. These findings illuminate the pathogen recognition mechanisms common among NBS-LRR Proteins.
Jeffery L Dangl - One of the best experts on this subject based on the ideXlab platform.
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plant intracellular innate immune receptor resistance to pseudomonas syringae pv maculicola 1 rpm1 is activated at and functions on the plasma membrane
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Eui Hwan Chung, Timothy K Eitas, Jeffery L DanglAbstract:Plants deploy intracellular innate immune receptors to recognize pathogens and initiate disease resistance. These nucleotide-binding, leucine-rich repeat (NB-LRR) Proteins are activated by pathogen effector Proteins that are delivered into the host cell to suppress host defense responses. Little is known about the sites and mechanisms of NB-LRR activation, but some NB-LRR Proteins can function inside the plant nucleus. We demonstrate that RPM1 is activated on the plasma membrane and does not relocalize to the nucleus. An autoactive RPM1(D505V) allele that recapitulates key features of normal RPM1 activation also resides on the plasma membrane. There is no detectable relocalization of activated RPM1 to the nucleus. Hindering potential nuclear entry of RPM1-Myc did not affect either its effector-triggered hypersensitive-response (HR) cell death or its disease resistance functions, further suggesting that nuclear translocation is not required for RPM1 function. RPM1 tethered onto the plasma membrane with a dual acylated N-terminal epitope tag retained the ability to mediate HR, consistent with this RPM1 function being activated on the plasma membrane. Plant NB-LRR Proteins can thus function at various locations in the cell.
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Expanded functions for a family of plant intracellular immune receptors beyond specific recognition of pathogen effectors
Proceedings of the National Academy of Sciences, 2011Co-Authors: V. Bonardi, A. Stallmann, K. Cherkis, S. Tang, M. Roberts, Jeffery L DanglAbstract:Plants and animals deploy intracellular immune receptors that perceive specific pathogen effector Proteins and microbial products delivered into the host cell. We demonstrate that the ADR1 family of Arabidopsis nucleotide-binding leucine-rich repeat (NB-LRR) receptors regulates accumulation of the defense hormone salicylic acid during three different types of immune response: (i) ADRs are required as "helper NB-LRRs" to transduce signals downstream of specific NB-LRR receptor activation during effector-triggered immunity; (ii) ADRs are required for basal defense against virulent pathogens; and (iii) ADRs regulate microbial-associated molecular pattern-dependent salicylic acid accumulation induced by infection with a disarmed pathogen. Remarkably, these functions do not require an intact P-loop motif for at least one ADR1 family member. Our results suggest that some NB-LRR Proteins can serve additional functions beyond canonical, P-loop-dependent activation by specific virulence effectors, extending analogies between intracellular innate immune receptor function from plants and animals.
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nb LRR Proteins pairs pieces perception partners and pathways
Current Opinion in Plant Biology, 2010Co-Authors: Timothy K Eitas, Jeffery L DanglAbstract:In plants, many of the innate immune receptors or disease resistance (R) Proteins contain a NB-LRR (Nucleotide-binding site, Leucine-rich repeat) structure. The recent findings regarding NB-LRR signaling are summarized in this article. An emerging theme is that two NB-LRRs can function together to mediate disease resistance against pathogen isolates. Also, recent results delineate the NB-LRR protein fragments that are sufficient to initiate defense signaling. Importantly, distinct fragments of different NB-LRRs are sufficient for function. Finally, we describe the new roles of accessory Proteins and downstream host genes in NB-LRR signaling.
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Arabidopsis TAO1 is a TIR-NB-LRR protein that contributes to disease resistance induced by the Pseudomonas syringae effector AvrB
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Timothy K Eitas, Zachary L. Nimchuk, Jeffery L DanglAbstract:The type III effector protein encoded by avirulence gene B (AvrB) is delivered into plant cells by pathogenic strains of Pseudomonas syringae. There, it localizes to the plasma membrane and triggers immunity mediated by the Arabidopsis coiled-coil (CC)-nucleotide binding (NB)-leucine-rich repeat (LRR) disease resistance protein RPM1. The sequence unrelated type III effector avirulence protein encoded by avirulence gene Rpm1 (AvrRpm1) also activates RPM1. AvrB contributes to virulence after delivery from P. syringae in leaves of susceptible soybean plants, and AvrRpm1 does the same in Arabidopsis rpm1 plants. Conditional overexpression of AvrB in rpm1 plants results in leaf chlorosis. In a genetic screen for mutants that lack AvrB-dependent chlorosis in an rpm1 background, we isolated TAO1 (target of AvrB operation), which encodes a Toll-IL-1 receptor (TIR)-NB-LRR disease resistance protein. In rpm1 plants, TAO1 function results in the expression of the pathogenesis-related protein 1 (PR-1) gene, suggestive of a defense response. In RPM1 plants, TAO1 contributes to disease resistance in response to Pto (P. syringae pathovars tomato) DC3000(avrB), but not against Pto DC3000(avrRpm1). The tao1–5 mutant allele, a stop mutation in the LRR domain of TAO1, posttranscriptionally suppresses RPM1 accumulation. These data provide evidence of genetically separable disease resistance responses to AvrB and AvrRpm1 in Arabidopsis. AvrB activates both RPM1, a CC-NB-LRR protein, and TAO1, a TIR-NB-LRR protein. These NB-LRR Proteins then act additively to generate a full disease resistance response to P. syringae expressing this type III effector.
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plant disease resistance protein signaling nbs LRR Proteins and their partners
Current Opinion in Plant Biology, 2004Co-Authors: Youssef Belkhadir, Rajagopal Subramaniam, Jeffery L DanglAbstract:Most plant disease resistance (R) Proteins contain a series of leucine-rich repeats (LRRs), a nucleotide-binding site (NBS), and a putative amino-terminal signaling domain. They are termed NBS-LRR Proteins. The LRRs of a wide variety of Proteins from many organisms serve as protein interaction platforms, and as regulatory modules of protein activation. Genetically, the LRRs of plant R Proteins are determinants of response specificity, and their action can lead to plant cell death in the form of the familiar hypersensitive response (HR). A total of 149 R genes are potentially expressed in the Arabidopsis genome, and plant cells must deal with the difficult task of assembling many of the Proteins encoded by these genes into functional signaling complexes. Eukaryotic cells utilize several strategies to deal with this problem. First, Proteins are spatially restricted to their sub-cellular site of function, thus improving the probability that they will interact with their proper partners. Second, these interactions are architecturally organized to avoid inappropriate signaling events and to maintain the fidelity and efficiency of the response when it is initiated. Recent results provide new insights into how the signaling potential of R Proteins might be created, managed and held in check until specific stimulation following infection. Nevertheless, the roles of the R protein partners in these regulatory events that have been defined to date are unclear.
Roger W Innes - One of the best experts on this subject based on the ideXlab platform.
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Activation of a plant nucleotide binding-leucine rich repeat disease resistance protein by a modified self protein
Cellular Microbiology, 2012Co-Authors: Brody J Deyoung, Dong Qi, Thomas P. Burke, Roger W InnesAbstract:Summary Nucleotide binding-leucine rich repeat (NB-LRR) Proteins function as intracellular receptors for the detection of pathogens in both plants and animals. Despite their central role in innate immunity, the molecular mechanisms that govern NB-LRR acti- vation are poorly understood. The Arabidopsis NB-LRR protein RPS5 detects the presence of the Pseudomonas syringae effector protein AvrPphB by monitoring the status of the Arabidopsis protein kinase PBS1. AvrPphB is a cysteine protease that targets PBS1 for cleavage at a single site within the activation loop of PBS1. Using a transient expres- sion system in the plant Nicotiana benthamiana and stable transgenic Arabidopsis plants we found that both PBS1 cleavage products are required to activate RPS5 and can do so in the absence of AvrPphB. We also found, however, that the require- ment for cleavage of PBS1 could be bypassed simply by inserting five amino acids at the PBS1 cleavage site, which is located at the apex of the activation loop of PBS1. Activation of RPS5 did not require PBS1 kinase function, and thus RPS5 appears to sense a subtle conformational change in PBS1, rather than cleavage. This finding suggests that NB-LRR Proteins may function as fine-tuned sensors of alterations in the structures of effector targets.
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indirect activation of a plant nucleotide binding site leucine rich repeat protein by a bacterial protease
Proceedings of the National Academy of Sciences of the United States of America, 2007Co-Authors: Brody J Deyoung, Catherine Golstein, Roger W InnesAbstract:Nucleotide binding site–leucine-rich repeat (NBS–LRR) Proteins mediate pathogen recognition in both mammals and plants. The molecular mechanisms by which pathogen molecules activate NBS–LRR Proteins are poorly understood. Here we show that RPS5, a NBS–LRR protein from Arabidopsis, is activated by AvrPphB, a bacterial protease, via an indirect mechanism. When transiently expressed in Nicotiana benthamiana leaves, full-length RPS5 protein triggered programmed cell death, but only when coexpressed with AvrPphB and a second Arabidopsis protein, PBS1, which is a specific substrate of AvrPphB. Using coimmunoprecipitation analysis, we found that PBS1 is in a complex with the N-terminal coiled coil (CC) domain of RPS5 before exposure to AvrPphB. Deletion of the RPS5 LRR domain caused RPS5 to constitutively activate programmed cell death, even in the absence of AvrPphB and PBS1, and this activation depended on both the CC and NBS domains. The LRR and CC domains both coimmunoprecipitate with the NBS domain but not with each other. Thus, the LRR domain appears to function in part to inhibit RPS5 signaling, and cleavage of PBS1 by AvrPphB appears to release RPS5 from this inhibition. An amino acid substitution in the NBS site of RPS5 that is known to inhibit ATP binding in other NBS–LRR Proteins blocked activation of RPS5, whereas a substitution thought to inhibit ATP hydrolysis constitutively activated RPS5. Combined, these data suggest that ATP versus ADP binding functions as a molecular switch that is flipped by cleavage of PBS1.
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plant nbs LRR Proteins in pathogen sensing and host defense
Nature Immunology, 2006Co-Authors: Brody J Deyoung, Roger W InnesAbstract:Plant Proteins belonging to the nucleotide-binding site–leucine-rich repeat (NBS-LRR) family are used for pathogen detection. Like the mammalian Nod-LRR protein 'sensors' that detect intracellular conserved pathogen-associated molecular patterns, plant NBS-LRR Proteins detect pathogen-associated Proteins, most often the effector molecules of pathogens responsible for virulence. Many virulence Proteins are detected indirectly by plant NBS-LRR Proteins from modifications the virulence Proteins inflict on host target Proteins. However, some NBS-LRR Proteins directly bind pathogen Proteins. Association with either a modified host protein or a pathogen protein leads to conformational changes in the amino-terminal and LRR domains of plant NBS-LRR Proteins. Such conformational alterations are thought to promote the exchange of ADP for ATP by the NBS domain, which activates 'downstream' signaling, by an unknown mechanism, leading to pathogen resistance.
Richard W. Michelmore - One of the best experts on this subject based on the ideXlab platform.
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Genetic diversity and genomic distribution of homologs encoding NBS-LRR disease resistance Proteins in sunflower
Molecular Genetics and Genomics, 2008Co-Authors: Osman Radwan, Sonali Gandhi, Adam Heesacker, Alex Plocik, Richard Kesseli, Chris Taylor, Brett Whitaker, Alexander Kozik, Richard W. Michelmore, Steven J. KnappAbstract:Three-fourths of the recognition-dependent disease resistance genes ( R -genes) identified in plants encode nucleotide binding site (NBS) leucine-rich repeat (LRR) Proteins. NBS-LRR homologs have only been isolated on a limited scale from sunflower ( Helianthus annuus L.), and most of the previously identified homologs are members of two large NBS-LRR clusters harboring downy mildew R -genes. We mined the sunflower EST database and used comparative genomics approaches to develop a deeper understanding of the diversity and distribution of NBS-LRR homologs in the sunflower genome. Collectively, 630 NBS-LRR homologs were identified, 88 by mining a database of 284,241 sunflower ESTs and 542 by sequencing 1,248 genomic DNA amplicons isolated from common and wild sunflower species. DNA markers were developed from 196 unique NBS-LRR sequences and facilitated genetic mapping of 167 NBS-LRR loci. The latter were distributed throughout the sunflower genome in 44 clusters or singletons. Wild species ESTs were a particularly rich source of novel NBS-LRR homologs, many of which were tightly linked to previously mapped downy mildew, rust, and broomrape R -genes. The DNA sequence and mapping resources described here should facilitate the discovery and isolation of recognition-dependent R -genes guarding sunflower from a broad spectrum of economically important diseases.
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Genetic diversity and genomic distribution of homologs encoding NBS-LRR disease resistance Proteins in sunflower
Molecular Genetics and Genomics, 2008Co-Authors: Osman Radwan, Sonali Gandhi, Adam Heesacker, Alex Plocik, Richard Kesseli, Chris Taylor, Brett Whitaker, Alexander Kozik, Richard W. Michelmore, Steven J. KnappAbstract:Three-fourths of the recognition-dependent disease resistance genes (R-genes) identified in plants encode nucleotide binding site (NBS) leucine-rich repeat (LRR) Proteins. NBS-LRR homologs have only been isolated on a limited scale from sunflower (Helianthus annuus L.), and most of the previously identified homologs are members of two large NBS-LRR clusters harboring downy mildew R-genes. We mined the sunflower EST database and used comparative genomics approaches to develop a deeper understanding of the diversity and distribution of NBS-LRR homologs in the sunflower genome. Collectively, 630 NBS-LRR homologs were identified, 88 by mining a database of 284,241 sunflower ESTs and 542 by sequencing 1,248 genomic DNA amplicons isolated from common and wild sunflower species. DNA markers were developed from 196 unique NBS-LRR sequences and facilitated genetic mapping of 167 NBS-LRR loci. The latter were distributed throughout the sunflower genome in 44 clusters or singletons. Wild species ESTs were a particularly rich source of novel NBS-LRR homologs, many of which were tightly linked to previously mapped downy mildew, rust, and broomrape R-genes. The DNA sequence and mapping resources described here should facilitate the discovery and isolation of recognition-dependent R-genes guarding sunflower from a broad spectrum of economically important diseases. Sunflower nucleotide and amino acid sequences have been deposited in DDBJ/EMBL/GenBank under accession numbers EF 560168-EF 559378 and ABQ 58077-ABQ 57529.
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plant nbs LRR Proteins adaptable guards
Genome Biology, 2006Co-Authors: Leah K Mchale, Patrice Koehl, Richard W. MichelmoreAbstract:The majority of disease resistance genes in plants encode nucleotide-binding site leucine-rich repeat (NBS-LRR) Proteins. This large family is encoded by hundreds of diverse genes per genome and can be subdivided into the functionally distinct TIR-domain-containing (TNL) and CC-domain-containing (CNL) subfamilies. Their precise role in recognition is unknown; however, they are thought to monitor the status of plant Proteins that are targeted by pathogen effectors.
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tir x and tir nbs Proteins two new families related to disease resistance tir nbs LRR Proteins encoded in arabidopsis and other plant genomes
Plant Journal, 2002Co-Authors: Blake C Meyers, Michele Morgante, Richard W. MichelmoreAbstract:Summary The Toll/interleukin-1 receptor (TIR) domain is found in one of the two large families of homologues of plant disease resistance Proteins (R Proteins) in Arabidopsis and other dicotyledonous plants. In addition to these TIR-NBS-LRR (TNL) R Proteins, we identified two families of TIR-containing Proteins encoded in the Arabidopsis Col-0 genome. The TIR-X (TX) family of Proteins lacks both the nucleotide-binding site (NBS) and the leucine rich repeats (LRRs) that are characteristic of the R Proteins, while the TIR-NBS (TN) Proteins contain much of the NBS, but lack the LRR. In Col-0, the TX family is encoded by 27 genes and three pseudogenes; the TN family is encoded by 20 genes and one pseudogene. Using massively parallel signa- ture sequencing (MPSS), expression was detected at low levels for approximately 85% of the TN-encoding genes. Expression was detected for only approximately 40% of the TX-encoding genes, again at low levels. Physical map data and phylogenetic analysis indicated that multiple genomic duplication events have increased the numbers of TX and TN genes in Arabidopsis. Genes encoding TX, TN and TNL Proteins were demonstrated in conifers; TX and TN genes are present in very low numbers in grass genomes. The expression, prevalence, and diversity of TX and TN genes suggests that these genes encode functional Proteins rather than resulting from degradation or deletions of TNL genes. These TX and TN Proteins could be plant analogues of small TIR-adapter Proteins that function in mammalian innate immune responses such as MyD88 and Mal.
