Molecular plant pathogensis
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Strigolactones in Plant Interactions with Beneficial and Detrimental Organisms: The Yin and Yang

Strigolactones in Plant Interactions with Beneficial and Detrimental Organisms: The Yin and Yang | Molecular plant pathogensis | Scoop.it
Strigolactones (SLs) are plant hormones that have important roles as modulators of
plant development. They were originally described as ex planta signaling molecules
in the rhizosphere that induce the germination of parasitic plants, a role that was
later linked to encouraging the beneficial symbiosis with arbuscular mycorrhizal (AM)
fungi. Recently, the focus has shifted to examining the role of SLs in plant–microbe
interactions, and has revealed roles for SLs in the association of legumes with nitrogen-fixing
rhizobacteria and in interactions with disease-causing pathogens.
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eLife: Plant immune and growth receptors share common signalling components but localise to distinct plasma membrane nanodomains (2017)

eLife: Plant immune and growth receptors share common signalling components but localise to distinct plasma membrane nanodomains (2017) | Molecular plant pathogensis | Scoop.it
Cell surface receptors govern a multitude of signalling pathways in multicellular organisms. In plants, prominent examples are the receptor kinases FLS2 and BRI1, which activate immunity and steroid-mediated growth, respectively. Intriguingly, despite inducing distinct signalling outputs, both receptors employ common downstream signalling components, which exist in plasma membrane (PM)-localised protein complexes. An important question is thus how these receptor complexes maintain signalling specificity. Live-cell imaging revealed that FLS2 and BRI1 form PM nanoclusters. Using single-particle tracking we could discriminate both cluster populations and we observed spatiotemporal separation between immune and growth signalling platforms. This finding was confirmed by visualising FLS2 and BRI1 within distinct PM nanodomains marked by specific remorin proteins and differential co-localisation with the cytoskeleton. Our results thus suggest that signalling specificity between these pathways may be explained by the spatial separation of FLS2 and BRI1 with their associated signalling components within dedicated PM nanodomains.

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The Sainsbury Lab's curator insight, March 6, 2017 11:55 AM
Cell surface receptors govern a multitude of signalling pathways in multicellular organisms. In plants, prominent examples are the receptor kinases FLS2 and BRI1, which activate immunity and steroid-mediated growth, respectively. Intriguingly, despite inducing distinct signalling outputs, both receptors employ common downstream signalling components, which exist in plasma membrane (PM)-localised protein complexes. An important question is thus how these receptor complexes maintain signalling specificity. Live-cell imaging revealed that FLS2 and BRI1 form PM nanoclusters. Using single-particle tracking we could discriminate both cluster populations and we observed spatiotemporal separation between immune and growth signalling platforms. This finding was confirmed by visualising FLS2 and BRI1 within distinct PM nanodomains marked by specific remorin proteins and differential co-localisation with the cytoskeleton. Our results thus suggest that signalling specificity between these pathways may be explained by the spatial separation of FLS2 and BRI1 with their associated signalling components within dedicated PM nanodomains.
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Changes in PUB22 Ubiquitination Modes Triggered by MITOGEN-ACTIVATED PROTEIN KINASE3 Dampen the Immune Response

Changes in PUB22 Ubiquitination Modes Triggered by MITOGEN-ACTIVATED PROTEIN KINASE3 Dampen the Immune Response | Molecular plant pathogensis | Scoop.it
Crosstalk between post-translational modifications such as ubiquitination and phosphorylation play key roles in controlling the duration and intensity of signalling events to ensure cellular homeostasis. However, the molecular mechanisms underlying the regulation of negative feedback loops remain poorly understood. Here we uncover a pathway in Arabidopsis thaliana by which a negative feedback loop involving the E3 ubiquitin ligase PUB22 that dampens the immune response is triggered by MITOGEN-ACTIVATED PROTEIN KINASE3 (MPK3), best known for its function in the activation of signalling. PUB22's stability is controlled by MPK3-mediated phosphorylation of residues localized in and adjacent to the E2 docking domain. We show that phosphorylation is critical for stabilization by inhibiting PUB22 oligomerization and thus autoubiquitination. The activity switch allows PUB22 to dampen the immune response. This regulatory mechanism also suggests that autoubiquitination, which is inherent to most single unit E3s in vitro, can function as a self-regulatory mechanism in vivo.

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The proteasome acts as a hub for plant immunity and is targeted by Pseudomonas type-III effectors

The proteasome acts as a hub for plant immunity and is targeted by Pseudomonas type-III effectors | Molecular plant pathogensis | Scoop.it
Recent evidence suggests that the ubiquitin-proteasome system (UPS) is involved in several aspects of plant immunity and a range of plant pathogens subvert the UPS to enhance their virulence. Here we show that proteasome activity is strongly induced during basal defense in Arabidopsis. Mutant lines of the proteasome subunits RPT2a and RPN12a support increased bacterial growth of virulent Pseudomonas syringae pv. tomato DC3000 (Pst) and Pseudomonas syringae pv. maculicola ES4326. Both proteasome subunits are required for Pathogen-associated molecular patterns (PAMP)-triggered immunity (PTI) responses. Analysis of bacterial growth after a secondary infection of systemic leaves revealed that the establishment of systemic-acquired resistance (SAR) is impaired in proteasome mutants, suggesting that the proteasome also plays an important role in defense priming and SAR. In addition, we show that Pst inhibits proteasome activity in a type-III secretion dependent manner. A screen for type-III effector proteins from Pst for their ability to interfere with proteasome activity revealed HopM1, HopAO1, HopA1 and HopG1 as putative proteasome inhibitors. Biochemical characterization of HopM1 by mass-spectrometry indicates that HopM1 interacts with several E3 ubiquitin ligases and proteasome subunits. This supports the hypothesis that HopM1 associates with the proteasome leading to its inhibition. Thus, the proteasome is an essential component of PTI and SAR, which is targeted by multiple bacterial effectors.

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Nat. Commun.: Altered expression of maize PLASTOCHRON1 enhances biomass and seed yield by extending cell division duration (2017)

Nat. Commun.: Altered expression of maize PLASTOCHRON1 enhances biomass and seed yield by extending cell division duration (2017) | Molecular plant pathogensis | Scoop.it
Maize is the highest yielding cereal crop grown worldwide. Here Sunet al. show that maize growth can be further enhanced by prolonging the duration of leaf elongation by targeted ectopic expression of the PLASTOCHRON1gene and show that this leads to increased yield in field trials.
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An E3 Ubiquitin Ligase-BAG Protein Module Controls Plant Innate Immunity and Broad-Spectrum Disease Resistance

An E3 Ubiquitin Ligase-BAG Protein Module Controls Plant Innate Immunity and Broad-Spectrum Disease Resistance | Molecular plant pathogensis | Scoop.it
Programmed cell death (PCD) and immunity in plants are tightly controlled to promote antimicrobial defense while preventing autoimmunity. However, the mechanisms contributing to this immune homeostasis are poorly understood. Here, we isolated a rice mutant ebr1 (enhanced blight and blast resistance 1) that shows enhanced broad-spectrum bacterial and fungal disease resistance, but displays spontaneous PCD, autoimmunity, and stunted growth. EBR1 encodes an E3 ubiquitin ligase that interacts with OsBAG4, which belongs to the BAG (Bcl-2-associated athanogene) family that functions in cell death, growth arrest, and immune responses in mammals. EBR1 directly targets OsBAG4 for ubiquitination-mediated degradation. Elevated levels of OsBAG4 in rice are necessary and sufficient to trigger PCD and enhanced disease resistance to pathogenic infection, most likely by activating pathogen-associated molecular patterns-triggered immunity (PTI). Together, our study suggests that an E3-BAG module orchestrates innate immune homeostasis and coordinates the trade-off between defense and growth in plants.

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Nature Biotech: A pigeonpea gene confers resistance to Asian soybean rust in soybean (2016)

Nature Biotech: A pigeonpea gene confers resistance to Asian soybean rust in soybean (2016) | Molecular plant pathogensis | Scoop.it

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The Sainsbury Lab's curator insight, April 26, 2016 4:45 AM
Asian soybean rust (ASR), caused by the fungus Phakopsora pachyrhizi, is one of the most economically important crop diseases, but is only treatable with fungicides, which are becoming less effective owing to the emergence of fungicide resistance. There are no commercial soybean cultivars with durable resistance to P. pachyrhizi, and although soybean resistance loci have been mapped, no resistance genes have been cloned. We report the cloning of a P. pachyrhizi resistance gene CcRpp1 (Cajanus cajan Resistance against Phakopsora pachyrhizi 1) from pigeonpea (Cajanus cajan) and show that CcRpp1 confers full resistance to P. pachyrhizi in soybean. Our findings show that legume species related to soybean such as pigeonpea, cowpea, common bean and others could provide a valuable and diverse pool of resistance traits for crop improvement.
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Plant Cell: The Arabidopsis Malectin-Like/LRR-RLK IOS1 is Critical for BAK1-Dependent and BAK1-Independent Pattern-Triggered Immunity (2016)

Plant Cell: The Arabidopsis Malectin-Like/LRR-RLK IOS1 is Critical for BAK1-Dependent and BAK1-Independent Pattern-Triggered Immunity (2016) | Molecular plant pathogensis | Scoop.it

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The Sainsbury Lab's curator insight, June 20, 2016 4:43 AM
Plasma membrane-localized pattern recognition receptors (PRRs) such as FLAGELLIN SENSING2 (FLS2), EF-TU RECEPTOR (EFR) and CHITIN ELICITOR RECEPTOR KINASE 1 (CERK1) recognize microbe-associated molecular patterns (MAMPs) to activate pattern-triggered immunity (PTI). A reverse genetics approach on genes responsive to the priming agent beta-aminobutyric acid (BABA) revealed IMPAIRED OOMYCETE SUSCEPTIBILITY1 (IOS1) as a critical PTI player. Arabidopsis thaliana ios1 mutants were hyper-susceptible to Pseudomonas syringae bacteria. Accordingly, ios1 mutants showed defective PTI responses, notably delayed up-regulation of the PTI-marker gene FLG22-INDUCED RECEPTOR-LIKE KINASE1 (FRK1), reduced callose deposition and mitogen-activated protein kinase activation upon MAMP treatment. Moreover, Arabidopsis lines over-expressing IOS1 were more resistant to bacteria and showed a primed PTI response. In vitro pull-down, bimolecular fluorescence complementation, co-immunoprecipitation, and mass spectrometry analyses supported the existence of complexes between the membrane-localized IOS1 and BRASSINOSTEROID INSENSITIVE1-ASSOCIATED KINASE1 (BAK1)-dependent PRRs FLS2 and EFR, as well as with the BAK1-independent PRR CERK1. IOS1 also associated with BAK1 in a ligand-independent manner, and positively regulated FLS2-BAK1 complex formation upon MAMP treatment. In addition, IOS1 was critical for chitin-mediated PTI. Finally, ios1 mutants were defective in BABA-induced resistance and priming. This work reveals IOS1 as a novel regulatory protein of FLS2-, EFR- and CERK1-mediated signaling pathways that primes PTI activation.
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Nat Rev Immun: Regulation of pattern recognition receptor signalling in plants (2016)

Nat Rev Immun: Regulation of pattern recognition receptor signalling in plants (2016) | Molecular plant pathogensis | Scoop.it

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The Sainsbury Lab's curator insight, August 1, 2016 7:34 AM
Recognition of pathogen-derived molecules by pattern recognition receptors (PRRs) is a common feature of both animal and plant innate immune systems. In plants, PRR signalling is initiated at the cell surface by kinase complexes, resulting in the activation of immune responses that ward off microorganisms. However, the activation and amplitude of innate immune responses must be tightly controlled. In this Review, we summarize our knowledge of the early signalling events that follow PRR activation and describe the mechanisms that fine-tune immune signalling to maintain immune homeostasis. We also illustrate the mechanisms used by pathogens to inhibit innate immune signalling and discuss how the innate ability of plant cells to monitor the integrity of key immune components can lead to autoimmune phenotypes following genetic or pathogen-induced perturbations of these components.
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New Phytologist: Nine things to know about elicitins (2016)

New Phytologist: Nine things to know about elicitins (2016) | Molecular plant pathogensis | Scoop.it

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The Sainsbury Lab's curator insight, September 2, 2016 9:22 AM
Elicitins are structurally conserved extracellular proteins in Phytophthora and Pythium oomycete pathogen species. They were first described in the late 1980s as abundant proteins in Phytophthora culture filtrates that have the capacity to elicit hypersensitive (HR) cell death and disease resistance in tobacco. Later, they became well-established as having features of microbe-associated molecular patterns (MAMPs) and to elicit defences in a variety of plant species. Research on elicitins culminated in the recent cloning of the elicitin response (ELR) cell surface receptor-like protein, from the wild potato Solanum microdontum, which mediates response to a broad range of elicitins. In this review, we provide an overview on elicitins and the plant responses they elicit. We summarize the state of the art by describing what we consider to be the nine most important features of elicitin biology.
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PLOS ONE: Directed Evolution of FLS2 towards Novel Flagellin Peptide Recognition (2016)

PLOS ONE: Directed Evolution of FLS2 towards Novel Flagellin Peptide Recognition (2016) | Molecular plant pathogensis | Scoop.it

Microbe-associated molecular patterns (MAMPs) are molecules, or domains within molecules, that are conserved across microbial taxa and can be recognized by a plant or animal immune system. Although MAMP receptors have evolved to recognize conserved epitopes, the MAMPs in some microbial species or strains have diverged sufficiently to render them unrecognizable by some host immune systems. In this study, we carried out in vitro evolution of the Arabidopsis thaliana flagellin receptor FLAGELLIN-SENSING 2 (FLS2) to isolate derivatives that recognize one or more flagellin peptides from bacteria for which the wild-type Arabidopsis FLS2 confers little or no response. A targeted approach generated amino acid variation at FLS2 residues in a region previously implicated in flagellin recognition. The primary screen tested for elevated response to the canonical flagellin peptide from Pseudomonas aeruginosa, flg22. From this pool, we then identified five alleles of FLS2 that confer modest (quantitatively partial) recognition of an Erwinia amylovora flagellin peptide. Use of this Erwinia-based flagellin peptide to stimulate Arabidopsis plants expressing the resulting FLS2 alleles did not lead to a detectable reduction of virulent P. syringae pv. tomato growth. However, combination of two identified mutations into a single allele further increased FLS2-mediated responses to the E. amylovora flagellin peptide. These studies demonstrate the potential to raise the sensitivity of MAMP receptors toward particular targets.


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PLOS Pathog: The E3 Ligase APIP10 Connects the Effector AvrPiz-t to the NLR Receptor Piz-t in Rice

PLOS Pathog: The E3 Ligase APIP10 Connects the Effector AvrPiz-t to the NLR Receptor Piz-t in Rice | Molecular plant pathogensis | Scoop.it
Although nucleotide-binding domain, leucine-rich repeat (NLR) proteins are the major immune receptors in plants, the mechanism that controls their activation and immune signaling remains elusive. Here, we report that the avirulence effector AvrPiz-t from Magnaporthe oryzae targets the rice E3 ligase APIP10 for degradation, but that APIP10, in return, ubiquitinates AvrPiz-t and thereby causes its degradation. Silencing of APIP10 in the non-Piz-t background compromises the basal defense against M. oryzae. Conversely, silencing of APIP10 in the Piz-t background causes cell death, significant accumulation of Piz-t, and enhanced resistance to M. oryzae, suggesting that APIP10 is a negative regulator of Piz-t. We show that APIP10 promotes degradation of Piz-t via the 26S proteasome system. Furthermore, we demonstrate that AvrPiz-t stabilizes Piz-t during M. oryzae infection. Together, our results show that APIP10 is a novel E3 ligase that functionally connects the fungal effector AvrPiz-t to its NLR receptor Piz-t in rice.

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Optimizing Crops for Biocontrol of Pests and Disease

Optimizing Crops for Biocontrol of Pests and Disease | Molecular plant pathogensis | Scoop.it

Research in Focus: Optimizing Crops for Biocontrol of Pests and Disease. This week we summarize an Opinion article from Trends in Plant Science on the potential applications of Volatile Organic Compounds and tritropic interactions for pest control. http://blog.aspb.org/…/optimizing-crops-for-biocontrol-of-…/ The article of the same name is published Open Access at Trends in Plant Science - check it out http://www.cell.com/…/pl…/abstract/S1360-1385%2815%2900208-3


Via Mary Williams, Daniel Wipf, Jean-Michel Ané
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Eric Vincill's curator insight, October 18, 2015 4:39 PM

I see this as a paradigm shift in how we think about trait enhancement and crop breeding to protecting our food crops.

 

Instead of focusing on finding 'beneficial' bacteria and fungi that confer disease and herbivory resistance to the current cultivars of agronomically important plant species, why not focus on the plant and find 'beneficial' plant traits that will attract or increase the spectrum of compatibility with beneficial bacteria and fungi to confer disease or herbivory resistance. 

 

 

 

 

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Mol. Plant Pathol.: The role of type III effectors from Xanthomonas axonopodis pv. manihotis in virulence and suppression of plant immunity (2017€

Xanthomonas axonopodis pv. manihotis (Xam) causes cassava bacterial blight, the most important bacterial disease of cassava. Xam, like other Xanthomonas species, requires type III effectors (T3Es
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Tweet from @PlantoPhagy: Three recent papers demonstrate antiviral role of autophagy in plants (2017)

Selective autophagy limits cauliflower mosaic virus infection by NBR1-mediated targeting of viral capsid protein and particles.
Hafrén A, Macia JL, Love AJ, Milner JJ, Drucker M, Hofius D.
http://www.pnas.org/content/early/2017/02/17/1610687114.abstract

 

A calmodulin-like protein suppresses RNA silencing and promotes geminivirus infection by degrading SGS3 via the autophagy pathway in Nicotiana benthamiana.
Li F, Zhao N, Li Z, Xu X, Wang Y, Yang X, Liu SS, Wang A, Zhou X.
http://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1006213#ppat-1006213-g003

 

Autophagy functions as an antiviral mechanism against geminiviruses in plants.
Haxim Y, Ismayil A, Jia Q, Wang Y, Zheng X, Chen T, Qian L, Liu N, Wang Y, Shaojie H, Cheng J, Yijun Q, Hong Y, Liu Y.
https://elifesciences.org/content/6/e23897


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A Phytophthora Effector Manipulates Host Histone Acetylation and Reprograms Defense Gene Expression to Promote Infection

A Phytophthora Effector Manipulates Host Histone Acetylation and Reprograms Defense Gene Expression to Promote Infection | Molecular plant pathogensis | Scoop.it
Immune response during pathogen infection requires extensive transcription reprogramming. A fundamental mechanism of transcriptional regulation is histone acetylation. However, how pathogens interfere with this process to promote disease remains largely unknown. Here we demonstrate that the cytoplasmic effector PsAvh23 produced by the soybean pathogen Phytophthora sojae acts as a modulator of histone acetyltransferase (HAT) in plants. PsAvh23 binds to the ADA2 subunit of the HAT complex SAGA and disrupts its assembly by interfering with the association of ADA2 with the catalytic subunit GCN5. As such, PsAvh23 suppresses H3K9 acetylation mediated by the ADA2/GCN5 module and increases plant susceptibility. Expression of PsAvh23 or silencing of GmADA2/GmGCN5 resulted in misregulation of defense-related genes, most likely due to decreased H3K9 acetylation levels at the corresponding loci. This study highlights an effective counter-defense mechanism by which a pathogen effector suppresses the activation of defense genes by interfering with the function of the HAT complex during infection.

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Conserved Atg8 recognition sites mediate Atg4 association with autophagosomal membranes and Atg8 deconjugation

Conserved Atg8 recognition sites mediate Atg4 association with autophagosomal membranes and Atg8 deconjugation | Molecular plant pathogensis | Scoop.it
Deconjugation of the Atg8/LC3 protein family members from phosphatidylethanolamine (PE) by Atg4 proteases is essential for autophagy progression, but how this event is regulated remains to be understood. Here, we show that yeast Atg4 is recruited onto autophagosomal membranes by direct binding to Atg8 via two evolutionarily conserved Atg8 recognition sites, a classical LC3‐interacting region (LIR) at the C‐terminus of the protein and a novel motif at the N‐terminus. Although both sites are important for Atg4–Atg8 interaction in vivo, only the new N‐terminal motif, close to the catalytic center, plays a key role in Atg4 recruitment to autophagosomal membranes and specific Atg8 deconjugation. We thus propose a model where Atg4 activity on autophagosomal membranes depends on the cooperative action of at least two sites within Atg4, in which one functions as a constitutive Atg8 binding module, while the other has a preference toward PE‐bound Atg8.

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Suayib Üstün's curator insight, March 27, 2017 9:25 AM
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Agrobacterium-delivered virulence protein VirE2 is trafficked inside host cells via a myosin XI-K–powered ER/actin network

Agrobacterium-delivered virulence protein VirE2 is trafficked inside host cells via a myosin XI-K–powered ER/actin network | Molecular plant pathogensis | Scoop.it
Agrobacterium tumefaciens causes crown gall tumors on various plants by delivering transferred DNA (T-DNA) and virulence proteins into host plant cells. Under laboratory conditions, the bacterium is widely used as a vector to genetically modify a wide range of organisms, including plants, yeasts, fungi, and algae. Various studies suggest that T-DNA is protected inside host cells by VirE2, one of the virulence proteins. However, it is not clear how Agrobacterium-delivered factors are trafficked through the cytoplasm. In this study, we monitored the movement of Agrobacterium-delivered VirE2 inside plant cells by using a split-GFP approach in real time. Agrobacterium-delivered VirE2 trafficked via the endoplasmic reticulum (ER) and F-actin network inside plant cells. During this process, VirE2 was aggregated as filamentous structures and was present on the cytosolic side of the ER. VirE2 movement was powered by myosin XI-K. Thus, exogenously produced and delivered VirE2 protein can use the endogenous host ER/actin network for movement inside host cells. The A. tumefaciens pathogen hijacks the conserved host infrastructure for virulence trafficking. Well-conserved infrastructure may be useful for Agrobacterium to target a wide range of recipient cells and achieve a high efficiency of transformation.
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Nature Biotech: News & Views - Plant immunity switched from bacteria to virus (2016)

Nature Biotech: News & Views - Plant immunity switched from bacteria to virus (2016) | Molecular plant pathogensis | Scoop.it
Each year, staple crops around the world suffer massive losses in yield owing to the destructive effects of pathogens. Improving the disease resistance of crops by boosting their immunity has been a key objective of agricultural biotech ever since the discovery of plant immune receptors in the 1990s. Nucleotide-binding leucine-rich repeat (NLR) proteins, a family of intracellular immune receptors that recognize pathogen molecules, are promising targets for enhancing pathogen resistance. In a recent paper in Science, Kim et al.1 describe a clever twist on this approach in which the host target protein for the pathogen effector is engineered rather than the NLR protein itself.

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Mol Plant Path: Bacterial pathogenesis of plants: Future challenges from a microbial perspective (2016)

Mol Plant Path: Bacterial pathogenesis of plants: Future challenges from a microbial perspective (2016) | Molecular plant pathogensis | Scoop.it

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The Sainsbury Lab's curator insight, May 16, 2016 4:03 AM
Plant infection is a complicated process. Upon encountering a plant, pathogenic microorganisms must first adapt to life on the epiphytic surface, and survive long enough to initiate an infection. Responsiveness to the environment is critical throughout infection, with intracellular and community-level signal transduction pathways integrating environmental signals and triggering appropriate responses in the bacterial population. Ultimately, phytopathogens must migrate from the epiphytic surface into the plant tissue using motility and chemotaxis pathways. This migration is coupled to overcoming the physical and chemical barriers to entry into the plant apoplast. Once inside the plant, bacteria use an array of secretion systems to release phytotoxins and protein effectors that fulfil diverse pathogenic functions (Fig. 1)(Phan Tran et al., 2011, Melotto & Kunkel, 2013).
The Pub Club's curator insight, May 17, 2016 8:23 AM
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Rakesh Yashroy's curator insight, May 18, 2016 9:54 PM
Host-pathogen interface is the real battle field of survival against odds both for animals and plant infections @ https://en.wikipedia.org/wiki/Host-pathogen_interface
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JBC: Structural basis of host Autophagy-related protein 8 (ATG8) binding by the Irish potato famine pathogen effector protein PexRD54 (2016)

JBC: Structural basis of host Autophagy-related protein 8 (ATG8) binding by the Irish potato famine pathogen effector protein PexRD54 (2016) | Molecular plant pathogensis | Scoop.it

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The Sainsbury Lab's curator insight, July 28, 2016 8:07 AM
Filamentous plant pathogens deliver effector proteins to host cells to promote infection. The Phytophthora infestans RXLR-type effector PexRD54 binds potato ATG8 via its ATG8-family interacting motif (AIM) and perturbs host selective autophagy. However, the structural basis of this interaction remains unknown. Here we define the crystal structure of PexRD54, which comprises a modular architecture including five tandem repeat domains, with the AIM sequence presented at the disordered C-terminus. To determine the interface between PexRD54 and ATG8, we solved the crystal structure of potato ATG8CL in complex with a peptide comprising the effectors AIM sequence, and established a model of the full-length PexRD54/ATG8CL complex using small angle X-ray scattering. Structure-informed deletion of the PexRD54 tandem domains reveals retention of ATG8CL binding in vitro and in planta. This study offers new insights into structure/function relationships of oomycete RXLR effectors and how these proteins engage with host cell targets to promote disease.
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BMC Genomics: LRR-RLK family from two Citrus species: genome-wide identification and evolutionary aspects (2016)

BMC Genomics: LRR-RLK family from two Citrus species: genome-wide identification and evolutionary aspects (2016) | Molecular plant pathogensis | Scoop.it
Leucine-rich repeat receptor-like kinases (LRR-RLKs) represent the largest subfamily of plant RLKs. The functions of most LRR-RLKs have remained undiscovered, and a few that have been experimentally characterized have been shown to have important roles in growth and development as well as in defense responses. Although RLK subfamilies have been previously studied in many plants, no comprehensive study has been performed on this gene family in Citrus species, which have high economic importance and are frequent targets for emerging pathogens. In this study, we performed in silico analysis to identify and classify LRR-RLK homologues in the predicted proteomes of Citrus clementina (clementine) and Citrus sinensis (sweet orange). In addition, we used large-scale phylogenetic approaches to elucidate the evolutionary relationships of the LRR-RLKs and further narrowed the analysis to the LRR-XII group, which contains several previously described cell surface immune receptors.

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PNAS: Clathrin-dependent endocytosis is required for immunity mediated by pattern recognition receptor kinases (2016)

PNAS: Clathrin-dependent endocytosis is required for immunity mediated by pattern recognition receptor kinases (2016) | Molecular plant pathogensis | Scoop.it
National Academy of Sciences

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The Sainsbury Lab's curator insight, September 26, 2016 5:46 AM
Plants detect conserved molecular patterns of pathogens via cell surface-localized receptors, such as the flagellin receptor kinase FLS2, that initiate effective plant immunity. Activated FLS2 is endocytosed, but the degree to which other receptor kinases exhibit similar spatiotemporal dynamics remains unclear. We show that internalization into a common endosomal pathway after ligand perception is a general phenomenon of the tested receptor kinases, including the danger peptide receptor PEPR1. FLS2 endocytosis is mediated by clathrin and is uncoupled from the regulation of acute pathogen-induced responses, but is involved in steady defenses and contributes to plant immunity against bacterial infection. We propose that clathrin-dependent internalization of ligand-activated receptor kinases into a common endosomal pathway facilitates the responses required for full plant immunity.
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A resistance locus in the American heirloom rice variety Carolina Gold Select is triggered by TAL
effectors with diverse predicted targets and is effective against African strains of Xanthomonas o...

A resistance locus in the American heirloom rice variety Carolina Gold Select is triggered by TAL <br/>effectors with diverse predicted targets and is effective against African strains of Xanthomonas o... | Molecular plant pathogensis | Scoop.it

(Via T. Lahaye, thx)

Triplett et al, 2016

The rice pathogens Xanthomonas oryzae pathovar (pv.) oryzae and pv. oryzicola produce numerous transcription activator-like (TAL) effectors that increase bacterial virulence by activating expression of host susceptibility genes. Rice resistance mechanisms against TAL effectors include polymorphisms that prevent effector binding to susceptibility gene promoters, or that allow effector activation of resistance genes. This study identifies, in the heirloom variety Carolina Gold Select, a third mechanism of rice resistance involving TAL effectors. This resistance manifests through strong suppression of disease development in response to diverse TAL effectors from both X. oryzae pathovars. The resistance can be triggered by an effector with only 3.5 central repeats, is independent of the composition of the repeat variable diresidues that determine TAL effector binding specificity, and is independent of the transcriptional activation domain. We determined that the resistance is conferred by a single dominant locus, designated Xo1, that maps to a 1.09 Mbp fragment on chromosome 4. The Xo1 interval also confers complete resistance to the strains in the African clade of X. oryzae pv. oryzicola, representing the first dominant resistance locus against bacterial leaf streak in rice. The strong phenotypic similarity between the TAL effector triggered resistance conferred by Xo1 and that conferred by the tomato resistance gene Bs4 suggests that monocots and dicots share an ancient or convergently evolved mechanism to recognize analogous TAL effector epitopes.


Via dromius
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dromius's curator insight, May 22, 2016 9:00 AM

This is cool! Evidence for a Bs4-type recognition in rice. Bs4 is a TIR-NB-LRR, unlikely to be present in monocot rice. Mechanism behind NB-LRR recognition of diverse TALs is still not solved. Can't wait to hear what gene in the 1 Mb target interval confers this resistance.

 

Rescooped by Zeng Xuan from Microbes, plant immunity, and crop science
Scoop.it!

Nature Plants: Immunity: One receptor, many pathogens (2015)

Nature Plants: Immunity: One receptor, many pathogens (2015) | Molecular plant pathogensis | Scoop.it

Most plant pattern recognition receptors induce immune responses by detecting molecular patterns typical to one group of microbes. A newly identified complex, on the other hand, monitors effector proteins widely distributed among bacteria, fungi and oomycetes, casting a new light on the evolution of pattern recognition in plants.

 

See also Albert et al. An RLP23–SOBIR1–BAK1 complex mediates NLP-triggered immunity. Nature Plants http://www.nature.com/articles/nplants2015140


Via Kamoun Lab @ TSL, Nicolas Denancé
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