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Nature: A Xanthomonas uridine 5′-monophosphate transferase inhibits plant immune kinases (2012)

Nature: A Xanthomonas uridine 5′-monophosphate transferase inhibits plant immune kinases (2012) | Plants and Microbes | Scoop.it

Plant innate immunity is activated on the detection of pathogen-associated molecular patterns (PAMPs) at the cell surface, or of pathogen effector proteins inside the plant cell1, 2, 3, 4. Together, PAMP-triggered immunity and effector-triggered immunity constitute powerful defences against various phytopathogens. Pathogenic bacteria inject a variety of effector proteins into the host cell to assist infection or propagation. A number of effector proteins have been shown to inhibit plant immunity5, but the biochemical basis remains unknown for the vast majority of these effectors. Here we show that the Xanthomonas campestris pathovar campestris type III effector AvrAC enhances virulence and inhibits plant immunity by specifically targeting Arabidopsis BIK1 and RIPK, two receptor-like cytoplasmic kinases known to mediate immune signalling6, 7, 8. AvrAC is a uridylyl transferase that adds uridine 5′-monophosphate to and conceals conserved phosphorylation sites in the activation loop of BIK1 and RIPK, reducing their kinase activity and consequently inhibiting downstream signalling.

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PLOS Pathogens: The Activation of Phytophthora Effector Avr3b by Plant Cyclophilin is Required for the Nudix Hydrolase Activity of Avr3b (2015)

PLOS Pathogens: The Activation of Phytophthora  Effector Avr3b by Plant Cyclophilin is Required for the Nudix Hydrolase Activity of Avr3b (2015) | Plants and Microbes | Scoop.it

Plant pathogens secrete an arsenal of effector proteins to impair host immunity. Some effectors possess enzymatic activities that can modify their host targets. Previously, we demonstrated that a Phytophthora sojae RXLR effector Avr3b acts as a Nudix hydrolase when expressed in planta; and this enzymatic activity is required for full virulence of Psojae strain P6497 in soybean (Glycine max). Interestingly, recombinant Avr3b produced by Ecoli does not have the hydrolase activity unless it was incubated with plant protein extracts. Here, we report the activation of Avr3b by a prolyl-peptidyl isomerase (PPIase), cyclophilin, in plant cells. Avr3b directly interacts with soybean cyclophilin GmCYP1, which activates the hydrolase activity of Avr3b in a PPIase activity-dependent manner. Avr3b contains a putative Glycine-Proline (GP) motif; which is known to confer cyclophilin-binding in other protein substrates. Substitution of the Proline (P132) in the putative GP motif impaired the interaction of Avr3b with GmCYP1; as a result, the mutant Avr3bP132A can no longer be activated by GmCYP1, and is also unable to promote Phytophthora infection. Avr3b elicits hypersensitive response (HR) in soybean cultivars producing the resistance protein Rps3b, but Avr3bP132A lost its ability to trigger HR. Furthermore, silencing of GmCYP1 rendered reduced cell death triggered by Avr3b, suggesting that GmCYP1-mediated Avr3b maturation is also required for Rps3b recognition. Finally, cyclophilins of Nicotiana benthamiana can also interact with Avr3b and activate its enzymatic activity. Overall, our results demonstrate that cyclophilin is a “helper” that activates the enzymatic activity of Avr3b after it is delivered into plant cells; as such, cyclophilin is required for the avirulence and virulence functions of Avr3b.

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BMC Genomics: Deciphering common and specific transcriptional immune responses in pea towards the oomycete pathogens Aphanomyces euteiches and Phytophthora pisi (2015)

BMC Genomics: Deciphering common and specific transcriptional immune responses in pea towards the oomycete pathogens Aphanomyces euteiches and Phytophthora pisi (2015) | Plants and Microbes | Scoop.it

Background - Root rot caused by Aphanomyces euteiches is one of the most destructive pea diseases while a distantly related species P. pisi has been recently described as the agent of pea and faba bean root rot. These two oomycete pathogens with different pathogenicity factor repertories have both evolved specific mechanisms to infect pea. However, little is known about the genes and mechanisms of defence against these pathogens in pea. In the present study, the transcriptomic response of pea to these two pathogens was investigated at two time points during early phase of infection using a Medicago truncatula microarray.


Results - Of the 37,976 genes analysed, 574 and 817 were differentially expressed in response to A. euteiches at 6 hpi and 20 hpi, respectively, while 544 and 611 genes were differentially regulated against P. pisi at 6 hpi and 20 hpi, respectively. Differentially expressed genes associated with plant immunity responses were involved in cell wall reinforcement, hormonal signalling and phenylpropanoid metabolism. Activation of cell wall modification, regulation of jasmonic acid biosynthesis and induction of ethylene signalling pathway were among the common transcriptional responses to both of these oomycetes. However, induction of chalcone synthesis and the auxin pathway were specific transcriptional changes against A. euteiches.


Conclusions - Our results demonstrate a global view of differentially expressed pea genes during compatible interactions with P. pisi and A. euteiches at an early phase of infection. The results suggest that distinct signalling pathways are triggered in pea by these two pathogens that lead to common and specific immune mechanisms in response to these two oomycetes. The generated knowledge may eventually be used in breeding pea varieties with resistance against root rot disease.

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Storify: Tweets from #evolpathkiel Evolutionary genomics of plant pathogens, Kiel, August 2015

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New Disease Reports: A bacterial leaf spot of aquilegia caused by Pseudomonas syringae (2014)

New Disease Reports: A bacterial leaf spot of aquilegia caused by Pseudomonas syringae (2014) | Plants and Microbes | Scoop.it

Aquilegia vulgaris (Ranunculaceae) (Columbine) is a flowering herbaceous perennial native to Europe and widely cultivated in UK gardens. It is an important crop for some commercial nurseries that produce large numbers of potted plants for retail sale in garden centres. In 2008, 100% crop loss due to a bacterial disease was reported by one grower. Subsequently, during a survey of bacterial diseases of herbaceous perennials on commercial nurseries carried out during 2010 (Roberts, 2011), symptoms consisting of black spots or larger lesions with a water-soaked margin were observed on the leaves and stems of plants at two nurseries in different regions of the UK.

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News: How plant sensors detect pathogens (2015)

News: How plant sensors detect pathogens (2015) | Plants and Microbes | Scoop.it

In the mid-20th century, an American scientist named Harold Henry Flor helped explain how certain varieties of plants can fight off some plant killers (pathogens), but not others, with a model called the “gene-for-gene” hypothesis. Seventy years later, an international team of scientists describes precisely how a plant senses a pathogen, bringing an unprecedented level of detail to Flor’s model.


“We know that plants have sensors to detect pathogens but we knew little about how they work,” says Professor Banfield from the John Innes Centre (UK).


In a study published in eLife, the team led by Professor Mark Banfield, in collaboration with the Iwate Biotechnology Research Centre (Japan) and The Sainsbury Laboratory (UK), investigated how one sensor protein from rice called Pik binds AVR-Pik, a protein from the rice blast pathogen. This fungus causes the most devastating disease of rice crops. Using X-ray crystallography facilities at Diamond Light Source in Oxfordshire, the team succeeded in imaging the contact points between the plant and pathogen proteins at the molecular level – the first time this has been done for a pair of plant and pathogen proteins that follow the gene-for-gene model.


Dr Abbas Maqbool from the JIC, first author of the study added, “Harold Flor predicted that plant sensors discriminate between different pathogen types, but at the time he had no knowledge of the molecules involved. It is remarkable that his ideas have now crystallized into detailed molecular models.”


Dr Maqbool, Professor Banfield and colleagues went on to discover that the strength at which the Pik sensor binds the pathogen AVR-Pik protein correlates with the strength of the plant’s response. This opens up new avenues for engineering better plant responses against pathogens by building sensors with increased strength of binding to pathogen proteins, and therefore conferring enhanced resistance to disease.


“Once we understand how these plant sensors detect invading pathogens, we can devise strategies to ‘boost’ the plant immune system and help protect rice and other important food crops from disease,” says Professor Banfield.


Maqbool et al. eLife http://elifesciences.org/content/4/e08709

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Current Biology: Functional Divergence of Two Secreted Immune Proteases of Tomato (2015)

Current Biology: Functional Divergence of Two Secreted Immune Proteases of Tomato (2015) | Plants and Microbes | Scoop.it

• Rcr3 and Pip1 are paralogous secreted tomato proteases that diverged >36 mya
• Rcr3 and Pip1 differ in expression levels and solvent-exposed residues
• Pip1 depletion increases susceptibility to unrelated apoplastic pathogens
• Without Cf-2, Rcr3 depletion increases susceptibility only to oomycete infection


Rcr3 and Pip1 are paralogous secreted papain-like proteases of tomato. Both proteases are inhibited by Avr2 from the fungal pathogen Cladosporium fulvum, but only Rcr3 acts as a co-receptor for Avr2 recognition by the tomato Cf-2 immune receptor [ 1–4 ]. Here, we show that Pip1-depleted tomato plants are hyper-susceptible to fungal, bacterial, and oomycete plant pathogens, demonstrating that Pip1 is an important broad-range immune protease. By contrast, in the absence of Cf-2, Rcr3 depletion does not affect fungal and bacterial infection levels but causes increased susceptibility only to the oomycete pathogen Phytophthora infestans. Rcr3 and Pip1 reside on a genetic locus that evolved over 36 million years ago. These proteins differ in surface-exposed residues outside the substrate-binding groove, and Pip1 is 5- to 10-fold more abundant than Rcr3. We propose a model in which Rcr3 and Pip1 diverged functionally upon gene duplication, possibly driven by an arms race with pathogen-derived inhibitors or by coevolution with the Cf-2 immune receptor detecting inhibitors of Rcr3, but not of Pip1.

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Davell Logan's curator insight, August 25, 2:55 AM

Reading about this topic is very educational I'm all aspects.

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bioRxiv: Efficient Disruption and Replacement of an Effector Gene in the Oomycete Phytophthora sojae using CRISPR/Cas9 (2015)

bioRxiv: Efficient Disruption and Replacement of an Effector Gene in the Oomycete Phytophthora sojae using CRISPR/Cas9 (2015) | Plants and Microbes | Scoop.it

Phytophthora sojae is a pathogenic oomycete that infects soybean seedlings as well as stems and roots of established plants, costing growers $1–2 billion per year. Due to its economic importance, P. sojae has become a model for the study of oomycete genetics, physiology and pathology. Despite the availability of several genome sequences, the lack of efficient techniques for targeted mutagenesis and gene replacement have long hampered genetic studies of pathogenicity in Phytophthora species. Here, we describe a CRISPR/Cas9 system enabling rapid and efficient genome editing in P. sojae. Using the RXLR effector gene Avr4/6 as target, we observed that in the absence of a homologous template, the repair of Cas9-induced double-strand breaks (DSBs) in P. sojae was mediated by non-homologous end joining (NHEJ), primarily resulting in short indels. Most mutants were homozygous, presumably due to gene conversion triggered by Cas9-mediated cleavage of non-mutant alleles. When donor DNA was present, homology directed repair (HDR) was observed, which resulted in the replacement of the target gene with the donor DNA. By testing the specific virulence of several NHEJ mutants and HDR -mediated gene replacements on soybeans, we have validated the contribution of Avr4/6 to recognition by soybean R gene loci, Rps4 and Rps6, but also uncovered additional contributions to resistance by these two loci. Our results establish a powerful tool for studying functional genomics in Phytophthora, which provides new avenues for better control of this pathogen.

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Annual Review of Phytopathology: A Moving View: Subcellular Trafficking Processes in Pattern Recognition Receptor–Triggered Plant Immunity (2015)

Annual Review of Phytopathology: A Moving View: Subcellular Trafficking Processes in Pattern Recognition Receptor–Triggered Plant Immunity (2015) | Plants and Microbes | Scoop.it

A significant challenge for plants is to induce localized defense responses at sites of pathogen attack. Therefore, host subcellular trafficking processes enable accumulation and exchange of defense compounds, which contributes to the plant on-site defenses in response to pathogen perception. This review summarizes our current understanding of the transport processes that facilitate immunity, the significance of which is highlighted by pathogens reprogramming membrane trafficking through host cell translocated effectors. Prominent immune-related cargos of plant trafficking pathways are the pattern recognition receptors (PRRs), which must be present at the plasma membrane to sense microbes in the apoplast. We focus on the dynamic localization of the FLS2 receptor and discuss the pathways that regulate receptor transport within the cell and their link to FLS2-mediated immunity. One emerging theme is that ligand-induced late endocytic trafficking is conserved across different PRR protein families as well as across different plant species.


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The Sainsbury Lab's curator insight, August 7, 4:36 AM

A significant challenge for plants is to induce localized defense responses at sites of pathogen attack. Therefore, host subcellular trafficking processes enable accumulation and exchange of defense compounds, which contributes to the plant on-site defenses in response to pathogen perception. This review summarizes our current understanding of the transport processes that facilitate immunity, the significance of which is highlighted by pathogens reprogramming membrane trafficking through host cell translocated effectors. Prominent immune-related cargos of plant trafficking pathways are the pattern recognition receptors (PRRs), which must be present at the plasma membrane to sense microbes in the apoplast. We focus on the dynamic localization of the FLS2 receptor and discuss the pathways that regulate receptor transport within the cell and their link to FLS2-mediated immunity. One emerging theme is that ligand-induced late endocytic trafficking is conserved across different PRR protein families as well as across different plant species.

Sridhar Ranganathan's curator insight, August 7, 11:41 PM

A significant challenge for plants is to induce localized defense responses at sites of pathogen attack. Therefore, host subcellular trafficking processes enable accumulation and exchange of defense compounds, which contributes to the plant on-site defenses in response to pathogen perception. This review summarizes our current understanding of the transport processes that facilitate immunity, the significance of which is highlighted by pathogens reprogramming membrane trafficking through host cell translocated effectors. Prominent immune-related cargos of plant trafficking pathways are the pattern recognition receptors (PRRs), which must be present at the plasma membrane to sense microbes in the apoplast. We focus on the dynamic localization of the FLS2 receptor and discuss the pathways that regulate receptor transport within the cell and their link to FLS2-mediated immunity. One emerging theme is that ligand-induced late endocytic trafficking is conserved across different PRR protein families as well as across different plant species.

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Frontiers in Plant Science: TAL effectors and the executor R genes (2015)

Frontiers in Plant Science: TAL effectors and the executor R genes (2015) | Plants and Microbes | Scoop.it

(via T. Lahaye, thx)

Zhang et al, 2015

Transcription activation-like (TAL) effectors are bacterial type III secretion proteins that function as transcription factors in plants during Xanthomonas/plant interactions, conditioning either host susceptibility and/or host resistance. Three types of TAL effector associated resistance (R) genes have been characterized - recessive, dominant non-transcriptional and dominant TAL effector-dependent transcriptional based resistance. Here, we discuss the last type of R genes, whose functions are dependent on direct TAL effector binding to discrete effector binding elements in the promoters. Only five of the so-called executor R genes have been cloned, and commonalities are not clear. We have placed the protein products in two groups for conceptual purposes. Group 1 consists solely of the protein from pepper, BS3, which is predicted to have catalytic function on the basis of homology to a large conserved protein family. Group 2 consists of BS4C-R, XA27, XA10, and XA23, all of which are relatively short proteins from pepper or rice with multiple potential transmembrane domains. Group 2 members have low sequence similarity to proteins of unknown function in closely related species. Firm predictions await further experimentation on these interesting new members to the R gene repertoire, which have potential broad application in new strategies for disease resistance.


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#PlantSciCurators: IPM Lab

#PlantSciCurators: IPM Lab | Plants and Microbes | Scoop.it

Plant Immunity And Microbial Effectors - Dedicated to the research done on the molecular dialogue between plants and pathogens (but also to any interesting report)


Natural Products for Plant Protection

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Rakesh Yashroy's curator insight, August 6, 9:40 PM

Plants and animals have to constantly fight against pathogen onslaught with virulence molecules packed as nanovesicles, targeted towards host cells, via a complex remote-control mechanism, by pathogens @ http://www.labome.org/research/Membrane-vesicle-trafficking-in-prokaryotes-molecular-biomechanics-of-biogenesis-of-outer-membrane-v.html

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#PlantSciCurators: Nicolas Denancé

#PlantSciCurators: Nicolas Denancé | Plants and Microbes | Scoop.it

PhD in Plant Biology and Phytopathology. I am interested in microbiology, pathogen effectors and plant immunity.


Effectors and Plant Immunity - Strategies of plant defense and microbe attacks


Published articles - Scientific works to which I have contributed

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Curr Opin Microbiol: How eukaryotic filamentous pathogens evade plant recognition (2015)

Curr Opin Microbiol: How eukaryotic filamentous pathogens evade plant recognition (2015) | Plants and Microbes | Scoop.it

• A broad spectrum of fungal and oomycete mechanisms facilitate disease development.

• Biotrophic interfaces contain complex sets of components to evade host plant defences.
• Pathogen effector secretion is a key feature for reprograming host metabolism.
• Highly specialized effectors suppress pathogen recognition by host plants.
• Pathogen cell wall remodeling supports the host invasion process.

Plant pathogenic fungi and oomycetes employ sophisticated mechanisms for evading host recognition. After host penetration, many fungi and oomycetes establish a biotrophic interaction. It is assumed that different strategies employed by these pathogens to avoid triggering host defence responses, including establishment of biotrophic interfacial layers between the pathogen and host, masking of invading hyphae and active suppression of host defence mechanisms, are essential for a biotrophic parasitic lifestyle. During the infection process, filamentous plant pathogens secrete various effectors, which are hypothesized to be involved in facilitating effective host infection. Live-cell imaging of fungi and oomycetes secreting fluorescently labeled effector proteins as well as functional characterization of the components of biotrophic interfaces have led to the recent progress in understanding how eukaryotic filamentous pathogens evade plant recognition.

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Olive Oil Times: European Commission Publishes Xylella Fastidiosa Factsheet (2015)

Olive Oil Times: European Commission Publishes Xylella Fastidiosa Factsheet (2015) | Plants and Microbes | Scoop.it

The European Commission recently published a question-and-answer factsheet on the bacterium Xylella fastidiosa on its Food Safety website.


The Xylella fastidiosa bacterium has been responsible for the destruction of olive groves in Italy’s Apulia region resulting in the adoption of urgent European Union (EU) measures to try to combat and contain the outbreak and prevent its spread to other member states of the EU.


The introduction to the factsheet points out that Xylella fastidiosa is one of the world’s deadliest plant bacteria which can have an enormous economic impact, and confirms that the outbreak affecting olive groves in Apulia is the only confirmed outbreak in the EU.


It explains that there are four different subspecies of Xylella fastidiosa and that the strain identified in Apulia is a new genetic variant which has so far only attacked olive and plum trees. The bacterium is spread by spittlebugs, cicadas and sharpshooters which feed on the infected plant tissue.


A study by the EU’s Food Safety Authority had warned that the risk of the deadly bacterium spreading to regions in other EU countries was very high. In the face of uncertainty and misinformation about the bacterium and in an effort to educate the general public, the European Commission has released the factsheet which answers six questions:


What measures have been taken by the Commission to prevent further spread into the Union territory?
How will the Commission prevent the further introduction of Xylella fastidiosa from non-EU countries?
Is there any financial support available for farmers affected by Xylella fastidiosa
Could there be other causes for the decline of olive trees since some scientific papers argue that it is caused by a combination of fungi which weaken the plants before being attacked by Xylella fastidiosa, and specific treatments seem to exist?
How can Xylella fastidiosa be controlled?
What can I do as citizen to prevent further spread of Xylella fastidiosa in the EU?

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New Phytologist: Comparative genomics of Fusarium oxysporum f. sp. melonis reveals the secreted protein recognized by the Fom-2 resistance gene in melon (2015)

New Phytologist: Comparative genomics of Fusarium oxysporum f. sp. melonis reveals the secreted protein recognized by the Fom-2 resistance gene in melon (2015) | Plants and Microbes | Scoop.it
  • Development of resistant crops is the most effective way to control plant diseases to safeguard food and feed production. Disease resistance is commonly based on resistance genes, which generally mediate the recognition of small proteins secreted by invading pathogens. These proteins secreted by pathogens are called ‘avirulence’ proteins. Their identification is important for being able to assess the usefulness and durability of resistance genes in agricultural settings.
  • We have used genome sequencing of a set of strains of the melon wilt fungus Fusarium oxysporum f. sp. melonis (Fom), bioinformatics-based genome comparison and genetic transformation of the fungus to identify AVRFOM2, the gene that encodes the avirulence protein recognized by the melon Fom-2 gene.
  • Both an unbiased and a candidate gene approach identified a single candidate for the AVRFOM2 gene. Genetic complementation of AVRFOM2 in three different race 2 isolates resulted in resistance of Fom-2-harbouring melon cultivars. AvrFom2 is a small, secreted protein with two cysteine residues and weak similarity to secreted proteins of other fungi.
  • The identification of AVRFOM2 will not only be helpful to select melon cultivars to avoid melon Fusarium wilt, but also to monitor how quickly a Fom population can adapt to deployment of Fom-2-containing cultivars in the field.
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Nature Biotechnology: Oxitec trials GM sterile moth to combat agricultural infestations (2015)

Nature Biotechnology: Oxitec trials GM sterile moth to combat agricultural infestations (2015) | Plants and Microbes | Scoop.it

The first US caged field studies of a genetically modified (GM) insect for use in agriculture began in July in upstate New York. The GM diamondback moth developed by Oxitec, a spin-out from Oxford University, headquartered in Milton Park, UK, is intended as a tool for crop growers to control infestations without chemical insecticides. Cornell entomologist Anthony Shelton has started testing the transgenic moths, which carry an autocidal gene that causes the insects' female progeny to die before reaching reproductive stage. The results of these trials, and of a handful of others in the works, will provide an indication whether the approach has commercial potential in agriculture and will provide a barometer of attitudes to the release of GM insects that lack a compelling trait for consumers.


Diamondback moths, Plutella xylostella, are an invasive species and a global nemesis of brassica vegetables such as broccoli, cabbage, kale, Brussels sprouts and the field crop canola. Diamondback moths cost the global economy an estimated $4–5 billion annually in damaged crops and pest control methods. “The damage the diamondback moth can do is incredible. I've seen whole fields wiped out,” says Shelton. The moth has also evolved resistance to over 90 insecticide ingredients, forcing farmers to increase pesticide use, further exacerbating resistance.


Oxitec's solution to this pest is the OX4319L moth. The genetically engineered insect contains a synthetic 'self-limiting' gene encoding tetracycline repressible transcription activator variant (tTAV). At high expression levels this protein ties up cells' transcriptional machinery, shutting down cell function and eventually killing the insect. The tTAV protein also binds and induces the tetracycline operator (tetO) sequences, which in turn increases expression of tTAV. The more tTAV binds to tetO, the more tTAV is produced—a positive feedback system. The moths also carry a fluorescent marker gene (DsRed2) that gives the insects color under a certain wavelength of green light, enabling them to be distinguished from wild pests.

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JBC: The Potato Nucleotide-Binding Leucine-Rich Repeat (NLR) Immune Receptor Rx1 is a Pathogen Dependent DNA-Deforming Protein (2015)

JBC: The Potato Nucleotide-Binding Leucine-Rich Repeat (NLR) Immune Receptor Rx1 is a Pathogen Dependent DNA-Deforming Protein (2015) | Plants and Microbes | Scoop.it

Background: Direct targets for plant NLR proteins in immune signalling are largely unknown.


Results: The Rx1 NLR protein of potato binds and distorts DNA following pathogen perception resulting in immune activation.


Conclusion: DNA is a direct signalling target for a plant NLR immune receptor.


Significance: Plant NLR receptors might regulate immune transcriptional responses by directly interacting with plant chromatin.


Plant NLR proteins enable cells to respond to pathogen attack. Several NLRs act in the nucleus, however, conserved nuclear targets that support their role in immunity are unknown. Previously we noted a structural homology between the NB domain of NLRs and DNA replication origin-binding Cdc6/Orc1 proteins. Here we show that the NB-ARC domain of the Rx1 NLR of potato binds nucleic acids. Rx1 induces ATP-dependent bending and melting of DNA in vitro dependent upon a functional P-loop. In situ full-length Rx1 binds nuclear DNA following activation by its cognate pathogen-derived effector protein, the coat protein of potato virus X. In line with its obligatory nucleocytoplasmic distribution, DNA-binding was only observed when Rx1 was allowed to freely translocate between both compartments and was activated in the cytoplasm. Immune activation induced by an unrelated NLR-effector pair did not trigger a Rx1-DNA interaction. DNA-binding is therefore not merely a consequence of immune activation. These data establish a role for DNA distortion in Rx1 immune signalling and defines DNA as a molecular target of an activated NLR.

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BMC Evolutionary Biology: Phylogeography and virulence structure of the powdery mildew population on its 'new' host triticale (2012)

BMC Evolutionary Biology: Phylogeography and virulence structure of the powdery mildew population on its 'new' host triticale (2012) | Plants and Microbes | Scoop.it

Background - Powdery mildew, caused by the obligate biotrophic fungus Blumeria graminis, is a major problem in cereal production as it can reduce quality and yield. B. graminis has evolved eight distinct formae speciales (f.sp.) which display strict host specialization. In the last decade, powdery mildew has emerged on triticale, the artificial intergeneric hybrid between wheat and rye. This emergence is probably triggered by a host range expansion of the wheat powdery mildew B. graminis f.sp. tritici. To gain more precise information about the evolutionary processes that led to this host range expansion, we pursued a combined pathological and genetic approach.


Results - B. graminis isolates were sampled from triticale, wheat and rye from different breeding regions in Europe. Pathogenicity tests showed that isolates collected from triticale are highly pathogenic on most of the tested triticale cultivars. Moreover, these isolates were also able to infect several wheat cultivars (their previous hosts), although a lower aggressiveness was observed compared to isolates collected from wheat. Phylogenetic analysis of nuclear gene regions identified two statistically significant clades, which to a certain extent correlated with pathogenicity. No differences in virulence profiles were found among the sampled regions, but the distribution of genetic variation demonstrated to be geography dependent. A multilocus haplotype network showed that haplotypes pathogenic on triticale are distributed at different sites in the network, but always clustered at or near the tips of the network.


Conclusions - This study reveals a genetic structure in B. graminis with population differentiation according to geography and host specificity. In addition, evidence is brought forward demonstrating that the host range expansion of wheat isolates to the new host triticale occurred recently and multiple times at different locations in Europe.

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eLife: Structural basis of pathogen recognition by an integrated HMA domain in a plant NLR immune receptor (2015)

eLife: Structural basis of pathogen recognition by an integrated HMA domain in a plant NLR immune receptor (2015) | Plants and Microbes | Scoop.it

Plants have evolved intracellular immune receptors to detect pathogen proteins known as effectors. How these immune receptors detect effectors remains poorly understood. Here we describe the structural basis for direct recognition of AVR-Pik, an effector from the rice blast pathogen, by the rice intracellular NLR immune receptor Pik. AVR-PikD binds a dimer of the Pikp-1 HMA integrated domain with nanomolar affinity. The crystal structure of the Pikp-HMA/AVR-PikD complex enabled design of mutations to alter protein interaction in yeast and in vitro, and perturb effector-mediated response both in a rice cultivar containing Pikp and upon expression of AVR-PikD and Pikp in the model plant Nicotiana benthamiana. These data reveal the molecular details of a recognition event, mediated by a novel integrated domain in an NLR, which initiates a plant immune response and resistance to rice blast disease. Such studies underpin novel opportunities for engineering disease resistance to plant pathogens in staple food crops.

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Nature: Structural basis of JAZ repression of MYC transcription factors in jasmonate signalling (2015)

Nature: Structural basis of JAZ repression of MYC transcription factors in jasmonate signalling (2015) | Plants and Microbes | Scoop.it
The plant hormone jasmonate plays crucial roles in regulating plant responses to herbivorous insects and microbial pathogens and is an important regulator of plant growth and development1, 2, 3, 4, 5, 6, 7. Key mediators of jasmonate signalling include MYC transcription factors, which are repressed by jasmonate ZIM-domain (JAZ) transcriptional repressors in the resting state. In the presence of active jasmonate, JAZ proteins function as jasmonate co-receptors by forming a hormone-dependent complex with COI1, the F-box subunit of an SCF-type ubiquitin E3 ligase8, 9, 10, 11. The hormone-dependent formation of the COI1–JAZ co-receptor complex leads to ubiquitination and proteasome-dependent degradation of JAZ repressors and release of MYC proteins from transcriptional repression3, 10, 12. The mechanism by which JAZ proteins repress MYC transcription factors and how JAZ proteins switch between the repressor function in the absence of hormone and the co-receptor function in the presence of hormone remain enigmatic. Here we show that Arabidopsis MYC3 undergoes pronounced conformational changes when bound to the conserved Jas motif of the JAZ9 repressor. The Jas motif, previously shown to bind to hormone as a partly unwound helix, forms a complete α-helix that displaces the amino (N)-terminal helix of MYC3 and becomes an integral part of the MYC N-terminal fold. In this position, the Jas helix competitively inhibits MYC3 interaction with the MED25 subunit of the transcriptional Mediator complex. Our structural and functional studies elucidate a dynamic molecular switch mechanism that governs the repression and activation of a major plant hormone pathway.

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Nature Chemical Biology: A fungal monooxygenase-derived jasmonate attenuates host innate immunity (2015)

Nature Chemical Biology: A fungal monooxygenase-derived jasmonate attenuates host innate immunity (2015) | Plants and Microbes | Scoop.it

Distinct modifications fine-tune the activity of jasmonic acid (JA) in regulating plant growth and immunity. Hydroxylated JA (12OH-JA) promotes flower and tuber development but prevents induction of JA signaling, plant defense or both. However, biosynthesis of 12OH-JA has remained elusive. We report here an antibiotic biosynthesis monooxygenase (Abm) that converts endogenous free JA into 12OH-JA in the model rice blast fungus Magnaporthe oryzae. Such fungal 12OH-JA is secreted during host penetration and helps evade the defense response. Loss of Abm in M. oryzae led to accumulation of methyl JA (MeJA), which induces host defense and blocks invasive growth. Exogenously added 12OH-JA markedly attenuated abmΔ-induced immunity in rice. Notably, Abm itself is secreted after invasion and most likely converts plant JA into 12OH-JA to facilitate host colonization. This study sheds light on the chemical arms race during plant-pathogen interaction, reveals Abm as an antifungal target and outlines a synthetic strategy for transformation of a versatile small-molecule phytohormone.

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Davell Logan's curator insight, August 12, 1:58 PM

Very interesting in what was discovered.

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PLOS Pathogens: Genome-Wide Analysis of Hypoxia-Responsive Genes in the Rice Blast Fungus, Magnaporthe oryzae (2015)

PLOS Pathogens: Genome-Wide Analysis of Hypoxia-Responsive Genes in the Rice Blast Fungus,  Magnaporthe oryzae (2015) | Plants and Microbes | Scoop.it
Rice blast fungus, Magnaporthe oryzae, is the most destructive pathogen in the rice-growing area. This fungus has a biotrophic phase early in infection and later switches to a necrotrophic lifestyle. During the biotrophic phase, the fungus competes with its host for nutrients and oxygen. Continuous uptake of oxygen is essential for successful establishment of blast disease of this pathogen. Here, we report transcriptional responses of the fungus to oxygen limitation. Transcriptome analysis using RNA-Seq identified that 1,047 genes were up-regulated in response to hypoxia. Those genes are involved in mycelial development, sterol biosynthesis, and metal ion transport based on hierarchical GO terms, and are well-conserved among three fungal species. In addition, null mutants of two hypoxia-responsive genes were generated and their roles in fungal development and pathogenicity tested. The mutant for the sterol regulatory element-binding protein gene, MoSRE1, exhibited increased sensitivity to a hypoxia-mimicking agent, increased conidiation, and delayed invasive growth within host cells, which is suggestive of important roles in fungal development. However, such defects did not cause any significant decrease in disease severity. The other null mutant, for the alcohol dehydrogenase gene MoADH1, showed no defect in the hypoxia-mimicking condition (using cobalt chloride) and fungal development. Taken together, this comprehensive transcriptional profiling in response to a hypoxic condition with experimental validations would provide new insights into fungal development and pathogenicity in plant pathogenic fungi.

Via Elsa Ballini
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Xylella Fastidiosa : Avis d'information aux voyageurs (2015)

Xylella Fastidiosa : Avis d'information aux voyageurs (2015) | Plants and Microbes | Scoop.it

La Préfecture de Haute-Corse informe les voyageurs de l'interdiction d'introduction des végétaux dans le cadre de la lutte contre la Xylella Fastidiosa.


The prefecture of Haute-Corse inform passengers of the prohibition of introduction of plants as part of the fight against Xylella fastidiosa.

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#PlantSciCurators: dromius

#PlantSciCurators: dromius | Plants and Microbes | Scoop.it

Sebastian Schornack. Co-discoverer of the TAL effector DNA binding code. Current research focus: plant processes leading to development of symbiosome structures between roots and microorganisms (schornacklab.net)


TAL effector science - infos on novel DNA-binding proteins of bacteria and their biotech use


Plant Cell Biology and Microscopy - Methods and Tools for Plant Cell Biology

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Royal Society: Tackling emerging fungal threats to animal health, food security and ecosystem resilience, March 7-8, 2016

Royal Society: Tackling emerging fungal threats to animal health, food security and ecosystem resilience, March 7-8, 2016 | Plants and Microbes | Scoop.it

An unprecedented number of new pathogenic fungi and variants of extant strains are emerging to cause disease in animals and plants, putting the resilience of wild and managed ecosystems in jeopardy. This meeting will unite researchers sharing a common aim – to exploit advances in biology to understand the drivers causing the emergence of fungi and to forge a research agenda to mitigate their impact.

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BBC: France acts against olive disease outbreak in Corsica (2015)

BBC: France acts against olive disease outbreak in Corsica (2015) | Plants and Microbes | Scoop.it

A bacterial infection ravaging olive trees in the far south of Italy has spread to Corsica, where emergency measures are being implemented.


Xylella fastidiosa, spread by insects, was found at Propriano in southern Corsica. The bacterium can also attack citrus trees and vineyards.


France has destroyed plants around the infected bush found in Propriano.


Xylella is one of the biggest disease threats to plants worldwide, the European Commission says.


There is no effective treatment for infected plants and new Commission regulations say the only solution is to destroy them and establish Xylella-free buffer zones around them.


Corsica - a Mediterranean island near Italy - has a small olive oil industry, with about 500 employees and more than 2,000ha (4,940 acres) of trees.


But the bacterium is a threat to about 300 plant species. It was first detected on the island last week.


On Wednesday France's Agriculture Minister Stephane Le Foll visited Propriano and pledged "a total commitment" to isolating the outbreak.


French authorities suspect that the bacterium arrived via a ferry from the nearby Italian island of Sardinia.


French health inspectors are checking ferry passengers arriving at the small Corsican port of Bonifacio, in an effort to prevent any further Xylella contamination.

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