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Cellular Microb. (2012): Consequences of flagellin export through the type III secretion system of Pseudomonas syringae reveal a major difference in the innate immune systems of mammals and the mod...

Cellular Microb. (2012): Consequences of flagellin export through the type III secretion system of Pseudomonas syringae reveal a major difference in the innate immune systems of mammals and the mod... | Effectors and Plant Immunity | Scoop.it

Bacterial flagellin is perceived as a microbe (or pathogen)-associated molecular pattern (MAMP or PAMP) by the extracellular pattern recognition receptors, FLS2 and TLR5, of plants and mammals, respectively. Flagellin accidently translocated into mammalian cells by pathogen type III secretion systems (T3SSs) is recognized by nucleotide-binding leucine-rich repeat receptor NLRC4 as a pattern of pathogenesis and induces a death-associated immune response. The nonpathogen Pseudomonas fluorescens Pf0-1, expressing a Pseudomonas syringae T3SS, and the plant pathogen P. syringae pv. tomato DC3000 were used to seek evidence of an analogous cytoplasmic recognition system for flagellin in the model plant Nicotiana benthamiana. Flagellin (FliC) was secreted in culture and translocated into plant cells by the T3SS expressed in Pf0-1 and DC3000 and in their ΔflgGHI flagellar pathway mutants. ΔfliC and ΔflgGHI mutants of Pf0-1 and DC3000 were strongly reduced in elicitation of reactive oxygen species production and in immunity induction as indicated by the ability of challenge bacteria inoculated 6 h later to translocate a type III effector-reporter and to elicit effector-triggered cell death. Agrobacterium-mediated transient expression in N. benthamiana of FliC with or without a eukaryotic export signal peptide, coupled with virus-induced gene silencing of FLS2, revealed no immune response that was not FLS2 dependent. Transiently expressed FliC from DC3000 and Pectobacterium carotovorum did not induce cell death in N. benthamiana, tobacco, or tomato leaves. Flagellin is the major Pseudomonas MAMP perceived by N. benthamiana, and although flagellin secretion through the plant cell wall by the T3SS may partially contribute to FLS2-dependent immunity, flagellin in the cytosol does not elicit immune-associated cell death. We postulate that a death response to translocated MAMPs would produce vulnerability to the many necrotrophic pathogens of plants, such as P. carotovorum, which differ from P. syringae and other (hemi)biotrophic pathogens in benefitting from death-associated immune responses.

 

Hai-Lei Wei, Suma Chakravarthy, Jay N. Worley, Alan Collmer

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3rd International Summer School “From genes to ecosystems” (12-18 July 2014). Labex TULIP, Toulouse

3rd International Summer School “From genes to ecosystems” (12-18 July 2014). Labex TULIP, Toulouse | Effectors and Plant Immunity | Scoop.it

This Summer School in Integrative Ecology and Biology in english is part of the TULIP Labex (Laboratory of Excellence) training program of the  and will take place in the French Pyrenees in a grandiose scenery at the foot of the well-known “Pic du Midi”, a 2800m-high mountain with one of the last functional astronomy observatories in Europe.

 

Some international researchers will participate to this event. Below the list of those who have already confirmed their participation:

Julio Salinas (Spain - Departamento de Biología Medioambiental)

Patricia Beldade (Portugal - Evolutionary Biology, Instituto Gulbenkian de Ciencia)

Uta Paszkowski (UK - Department of Plant Science)

Thierry Rigaud (France - Biogosciences Laboratory)

Mike Hochberg (France - Institute of Evolutionary Sciences, fellow in Berlin)

Janet Rankin (UK - Teaching & Learning Laboratory)

Eleanor Gilroy (UK, The James Hutton Institute)

 

 

Through plenary lectures and workshops, the program will cover many features of organism-organism interactions from both ecological and biological points of view. The programme will also include visit of unique place like the Experimental Ecology Center of CNRS in Moulis... At a glance :

Actively participate in elaborating research projects during workshops,Meet experts from Toulouse and other internationally renowned laboratories,Enjoy the inspiring Pyrenees location chosen for the Summer School.

 

Free accommodation is provided for all participants, limited in number to a total of 25 (undergraduate, graduate and post-docs)

 

 

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New Phytol.: Virtual issue on Phytopathogen effector proteins (2014)

Read also the introduction to this issue by Hannah Kuhn and Ralph Panstruga

http://onlinelibrary.wiley.com/doi/10.1111/nph.12804/pdf

 

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Frontiers Plant Science: The genome sequence and effector complement of the flax rust pathogen Melampsora lini (2014)

Frontiers Plant Science: The genome sequence and effector complement of the flax rust pathogen Melampsora lini (2014) | Effectors and Plant Immunity | Scoop.it

Rust fungi cause serious yield reductions on crops, including wheat, barley, soybean, coffee, and represent real threats to global food security. Of these fungi, the flax rust pathogen Melampsora lini has been developed extensively over the past 80 years as a model to understand the molecular mechanisms that underpin pathogenesis. During infection, M. lini secretes virulence effectors to promote disease. The number of these effectors, their function and their degree of conservation across rust fungal species is unknown. To assess this, we sequenced and assembled de novo the genome of M. lini isolate CH5 into 21,130 scaffolds spanning 189 Mbp (scaffold N50 of 31 kbp). Global analysis of the DNA sequence revealed that repetitive elements, primarily retrotransposons, make up at least 45% of the genome. Using ab initio predictions, transcriptome data and homology searches, we identified 16,271 putative protein-coding genes. An analysis pipeline was then implemented to predict the effector complement of M. lini and compare it to that of the poplar rust, wheat stem rust and wheat stripe rust pathogens to identify conserved and species-specific effector candidates. Previous knowledge of four cloned M. lini avirulence effector proteins and two basidiomycete effectors was used to optimise parameters of the effector prediction pipeline. Markov clustering based on sequence similarity was performed to group effector candidates from all four rust pathogens. Clusters containing at least one member from M. lini were further analysed and prioritized based on features including expression in isolated haustoria and infected leaf tissue and conservation across rust species. Herein, we describe 200 of 940 clusters that ranked highest on our priority list, representing 725 flax rust candidate effectors. Our findings on this important model rust species provide insight into how effectors of rust fungi are conserved across species and how they may act to promote infection on their hosts.


Via Francis Martin, Kamoun Lab @ TSL
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Francis Martin's curator insight, March 4, 11:30 AM

A long awaited genome! More rust genomes needed.

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HopZ4 from Pseudomonas syringae, a member of the HopZ type III effector family from the YopJ superfamily, inhibits the proteasome in plants

HopZ4 from Pseudomonas syringae, a member of the HopZ type III effector family from the YopJ superfamily, inhibits the proteasome in plants | Effectors and Plant Immunity | Scoop.it

The YopJ-family of type III effector (T3E) proteins is one of the largest and widely distributed families of effector proteins whose members are highly diversified in virulence functions. In the present study, HopZ4, a member of the YopJ-family of T3Es from the cucumber pathogen Pseudomonas syringae pv. lachrymans is described. HopZ4 shares high sequence similarity with the Xanthomonas T3E XopJ and a functional analysis suggests a conserved virulence function between these two T3Es. As has previously shown for XopJ, HopZ4 interacts with the proteasomal subunit RPT6 in yeast and in planta to inhibit proteasome activity during infection. The inhibitory effect on the proteasome is dependent on localization of HopZ4 to the plasma membrane as well as on an intact catalytic triad of the effector protein. Furthermore, HopZ4 is able to complement loss of XopJ in Xanthomonas as it prevents precocious host cell death during a compatible interaction of Xanthomonas with pepper. The data presented here suggest that different bacterial species employ inhibition of the proteasome as a virulence strategy by making use of conserved T3Es from the YopJ-family of bacterial effector proteins.


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From dead leaf, to new life: TAL effectors as tools for synthetic biology - Plant Journal

From dead leaf, to new life: TAL effectors as tools for synthetic biology - Plant Journal | Effectors and Plant Immunity | Scoop.it

de Lange et al, 2014

Whether rice, yeast, or fly there is barely a model organism not yet reached by transcription activator like effectors (TALEs) and their derivative fusion proteins. Insights into fundamental biology are now arriving on the back of work in the last years to develop these proteins as tools for molecular biology. This began with the publication of the simple cipher determining base-specific DNA recognition by TALEs in 2009 and now encompasses a huge variety of established fusion proteins mediating targeted modifications to transcriptome, genome, and recently, epigenome. Straightforward design and exquisite specificity, allowing unique sites to be targeted even within complex eukaryote genomes, are key to the popularity of this system. Synthetic biology is one field that is just beginning to make use of these properties with a number of recent publications demonstrating TALE-mediated regulation of synthetic genetic circuits. Intense interest has surrounded the CRISPR/Cas9 system within the last twelve months and it is already proving its mettle as a tool for targeted gene modifications and transcriptional regulation. However, questions over off-target activity and means for independent regulation of multiple Cas9-guide RNA pairs will have to be resolved before this method enters into the synthetic biology toolbox. TALEs are already showing promise as regulators of synthetic biological systems, a role that will likely be developed further in the coming years.


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dromius's curator insight, March 7, 3:28 AM

Cool review. I really like the figures!

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Identification of putative TAL effector targets of the citrus canker pathogens shows functional convergence underlying disease development and defense response - BMC Genomics

Identification of putative TAL effector targets of the citrus canker pathogens shows functional convergence underlying disease development and defense response - BMC Genomics | Effectors and Plant Immunity | Scoop.it

(via T. Lahaye & T. Schreiber, thx both)

Pereira et al, 2014

Based on, 1) the TAL effector-DNA binding code, 2) gene expression data of Xc and XaC-infiltrated sweet orange leaves, and 3) citrus hypocotyls transformed with PthA2, PthA4 or PthC1, we have identified a collection of Citrus sinensis genes potentially targeted by Xc and XaC TAL effectors. Our results suggest that similar with other strains of Xanthomonas TAL effectors, PthA2 and PthA4, and PthC1 to some extent, functionally converge. In particular, towards induction of genes involved in the auxin and gibberellin synthesis and response, cell division, and defense response. We also present evidence indicating that the TAL effectors act as transcriptional repressors and that the best scoring predicted DNA targets of PthA"s" and PthC"s" in citrus promoters predominantly overlap with or localize near to TATA boxes of core promoters, supporting the idea that TAL effectors interact with the host basal transcriptional machinery to recruit the RNA pol II and start transcription.


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PLoS Biol.: How Do Filamentous Pathogens Deliver Effector Proteins into Plant Cells? (2014)

PLoS Biol.: How Do Filamentous Pathogens Deliver Effector Proteins into Plant Cells? (2014) | Effectors and Plant Immunity | Scoop.it

Fungal and oomycete plant parasites are among the most devastating pathogens of food crops. These microbes secrete effector proteins inside plant cells to manipulate host processes and facilitate colonization. How these effectors reach the host cytoplasm remains an unclear and debated area of plant research. In this article, we examine recent conflicting findings that have generated discussion in the field. We also highlight promising approaches based on studies of both parasite and host during infection. Ultimately, this knowledge may inform future broad spectrum strategies for protecting crops from such pathogens.

 

 Benjamin Petre and Sophien Kamoun

 

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The Rice TAL Effector–Dependent Resistance Protein XA10 Triggers Cell Death and Calcium Depletion in the Endoplasmic Reticulum

The Rice TAL Effector–Dependent Resistance Protein XA10 Triggers Cell Death and Calcium Depletion in the Endoplasmic Reticulum | Effectors and Plant Immunity | Scoop.it

The recognition between disease resistance (R) genes in plants and their cognate avirulence (Avr) genes in pathogens can produce a hypersensitive response of localized programmed cell death. However, our knowledge of the early signaling events of the R gene–mediated hypersensitive response in plants remains limited. Here, we report the cloning and characterization of Xa10, a transcription activator–like (TAL) effector-dependent R gene for resistance to bacterial blight in rice (Oryza sativa). Xa10 contains a binding element for the TAL effector AvrXa10 (EBEAvrXa10) in its promoter, and AvrXa10 specifically induces Xa10 expression. Expression of Xa10 induces programmed cell death in rice, Nicotiana benthamiana, and mammalian HeLa cells. The Xa10 gene product XA10 localizes as hexamers in the endoplasmic reticulum (ER) and is associated with ER Ca2+ depletion in plant and HeLa cells. XA10 variants that abolish programmed cell death and ER Ca2+ depletion in N. benthamiana and HeLa cells also abolish disease resistance in rice. We propose that XA10 is an inducible, intrinsic terminator protein that triggers programmed cell death by a conserved mechanism involving disruption of the ER and cellular Ca2+ homeostasis.


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BMC Genomics (2013): A predicted functional gene network for the plant pathogen Phytophthora infestans as a framework for genomic biology

BMC Genomics (2013): A predicted functional gene network for the plant pathogen Phytophthora infestans as a framework for genomic biology | Effectors and Plant Immunity | Scoop.it

Associations between proteins are essential to understand cell biology. While this complex interplay between proteins has been studied in model organisms, it has not yet been described for the oomycete late blight pathogen Phytophthora infestans.

We present an integrative probabilistic functional gene network that provides associations for 37 percent of the predicted P. infestans proteome. Our method unifies available genomic, transcriptomic and comparative genomic data into a single comprehensive network using a Bayesian approach. Enrichment of proteins residing in the same or related subcellular localization validates the biological coherence of our predictions. The network serves as a framework to query existing genomic data using network-based methods, which thus far was not possible in Phytophthora. We used the network to study the set of interacting proteins that are encoded by genes co-expressed during sporulation. This identified potential novel roles for proteins in spore formation through their links to proteins known to be involved in this process such as the phosphatase Cdc14.

The functional association network represents a novel genome-wide data source for P. infestans that also acts as a framework to interrogate other system-wide data. In both capacities it will improve our understanding of the complex biology of P. infestans and related oomycete pathogens.

 


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Proposed Gypsy Moth Quarantine in Minnesota (US)

Proposed Gypsy Moth Quarantine in Minnesota (US) | Effectors and Plant Immunity | Scoop.it
The gypsy moth is one of America’s most destructive forests pests. The pests eat the leaves of many trees and shrubs, favoring oak, poplar, birch and willow.

Via Anne-Sophie Roy
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Anne-Sophie Roy's curator insight, January 24, 12:56 AM

The State of Minnesota (US) is envisaging to take quarantine measures to prevent the spead of gypsy moth (Lymantria dispar) which will affect travellers and citizens.

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COST FA1208 Workshop: cellular dynamics of effector action and recognition, Toulouse, France from 9-11 April 2014

COST FA1208 Workshop: cellular dynamics of effector action and recognition, Toulouse, France from 9-11 April 2014 | Effectors and Plant Immunity | Scoop.it

The first workshop of the action, focussing on cellular dynamics of effector action and recognition is scheduled to take place in Toulouse, France from 9-11 April 2014.  The workshop will be hosted by the Laboratory of Plant-Microbe Interactions and is expected to welcome 30 participants.

 

Recent years have shown that the localization of effectors, their target proteins and their immune receptors hold important information for the understanding of their function. Effectors can act in many different cellular compartments to promote disease or act, in certain cases, only on particular cell types. NB-LRR proteins acting as receptors of the plant immune system can undergo complex relocalizations which proved in certain cases crucial for their function. Since this is a fast moving research field, it appeared important to adress cellular dynamics of effector action and recognition by a workshops. The following topics will be adressed:

 

1. Which host cells and tissues are subject to effector action?

2. How do effectors enter the host cell (compartments)?

3. Where do effectors localize and act in the host cell?

4. How do effectors affect the localization and cellular dynamics of their host targets? This includes mechanisms related to complex formation/dissociation, (de)stabilizing host targets, post-translational modifications effecting the distribution in the cell

5. Where do immune receptors/R proteins localize and act in the cell and how do effectors manipulate this?

 

Confirmed speakers are:

 

Richard O’Connell, INRA Versailles-Grignon FR

Bruno Favery, INRA Sophia, FR

Nemo Peeters, INRA Toulouse, FR

Sebastian Schornack CUSL, Cambridge, UK

Petra Boevink, JHI, Dundee, UK

Edgar Huitema, Dundee university UK

Ralh Hueckelhoven, Technical University Munich DE

Laurent deslandes, CNRS, Toulouse, FR

Hans Thordal-Christensen, Copenhagen University DK

Silke Robatzek, TSL, Norwich,UK

Aska Goverse, Wageningen university, NL

Thomas Kroj, INRA Montpellier, FR


Via Kamoun Lab @ TSL
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François Lafont's curator insight, January 18, 4:49 AM

A great conference in Toulouse :-)

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BMC Genomics: Repertoire, unified nomenclature and evolution of the Type III effector gene set in the Ralstonia solanacearum species complex (2013)

BMC Genomics: Repertoire, unified nomenclature and evolution of the Type III effector gene set in the Ralstonia solanacearum species complex (2013) | Effectors and Plant Immunity | Scoop.it

Ralstonia solanacearum is a soil-borne beta-proteobacterium that causes bacterial wilt disease in many food crops and is a major problem for agriculture in intertropical regions. R. solanacearum is a heterogeneous species, both phenotypically and genetically, and is considered as a species complex. Pathogenicity of R. solanacearum relies on the Type III secretion system that injects Type III effector (T3E) proteins into plant cells. T3E collectively perturb host cell processes and modulate plant immunity to enable bacterial infection. We provide the catalogue of T3E in the R. solanacearum species complex, as well as candidates in newly sequenced strains. 95 T3E orthologous groups were defined on phylogenetic bases and ordered using a uniform nomenclature. This curated T3E catalog is available on a public website and a bioinformatic pipeline has been designed to rapidly predict T3E genes in newly sequenced strains. Systematical analyses were performed to detect lateral T3E gene transfer events and identify T3E genes under positive selection. Our analyses also pinpoint the RipF translocon proteins as major discriminating determinants among the phylogenetic lineages. Establishment of T3E repertoires in strains representatives of the R. solanacearum biodiversity allowed determining a set of 22 T3E present in all the strains but provided no clues on host specificity determinants. The definition of a standardized nomenclature and the optimization of predictive tools will pave the way to understanding how variation of these repertoires is correlated to the diversification of this species complex and how they contribute to the different strain pathotypes. 

 

Nemo Peeters, Sébastien Carrère, Maria Anisimova, Laure Plener, Anne-Claire Cazalé and Stephane Genin

 

Database interface: https://iant.toulouse.inra.fr/bacteria/annotation/cgi/ralso_effectome/ralso_effectome.cgi

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COST Action SUSTAIN - TALEN & CRISPR Training School / March 2014 Halle

COST Action SUSTAIN - TALEN & CRISPR Training School / March 2014 Halle | Effectors and Plant Immunity | Scoop.it

The first training school of the action - TALEN & CRISPR Training School - is scheduled to take place on 24 - 28 March 2014 in Halle, Germany. The training school will be hosted by Dr. Jens Boch at the Martin Luther University in Halle.

For more information about the training school, please refer to the presentation.


Via dromius
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dromius's curator insight, November 28, 2013 1:23 PM

My first scientific home...ah...memories :)

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PLANT SCIENCE SUMMER SCHOOL ANGERS 1st Edition - 30th June – 12th July 2014 Faculty of sciences, University of Angers

PLANT SCIENCE SUMMER SCHOOL ANGERS 1st Edition -  30th June – 12th July 2014 Faculty of sciences, University of Angers | Effectors and Plant Immunity | Scoop.it

 

This program will provide the students with some insights into
new developments in plant science research. The purpose is to
give students the opportunity to be exposed to multidisciplinary
approaches in the field of sustainable management of plant
health and quality.

 

Workshops:
Visits of international research institutes
– GEVES lab (the French Group for the Study and Inspection of Varieties and Seeds)
– LSV-ANSES (Plant Health Laboratory)
– CIRM-CFBP (French Collection of Bacteria associated to Plants)
– ANAN (Nucleic acid analysis) Platform
– ITEPMAI (Institute for medicinal and aromatic plants)
– Visits of a botanical garden, a rose garden, and an organic vineyard

 

The program relies on interactive classes and hands-on ativities. Several workshops are organized, among them

"Experiments in chemical ecology and pest management"
"In Silico design of plant pathogen identification tests"
"Field observations of Black spot disease on rose genotypes"
"Extraction-identification and biological activity testing of plant polyphenols"
"Macroscopic and microscopic observations of medicinal plants"
"Rose phenotyping and genotyping"
"Analytical methods for assessing fruit quality"

 

Sessions:
Plenary conference by Prof Jean Weissenbach
Session 1: Chemical ecology and Pest management
Session 2: Genomic and Bacterial diagnostic
Session 3: Fungal foliar disease on ornamentals
Session 4: Weed control in intercropping systems
Session 5: Metabolomics and medicinal plants
Session 6: Ornamentals Interaction genotype X environment
Session 7: Fruit production, Fruit development and self-thinning
Session 8: Fruit production and quality

 

Invited speakers:
– J. Weissenbach
– P. Anderson, Alnarp, Sweden
– M M. López, Valencia, Spain
– T. Debener, Hannover, Germany
– JL. Wolfender, Genève, Switzerland
– MC. van Labeke, Gent, Belgium
– Al. Botton, Padova, Italy

 

Criteria:
The program is open to undergraduate students in the fields of agriculture, plant science and biological science who may be interested in pursuing Ph.D. programs and envision a career in plant science/agriculture.

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The Pepper SGT1 Interacts with the Receptor-Like Cytoplasmic Kinase 1 and AvrBsT and Promotes Hypersensitive Cell Death Response in a Phosphorylation-Dependent Manner

The Pepper SGT1 Interacts with the Receptor-Like Cytoplasmic Kinase 1 and AvrBsT and Promotes Hypersensitive Cell Death Response in a Phosphorylation-Dependent Manner | Effectors and Plant Immunity | Scoop.it

Xanthomonas campestris pv. vesicatoria type III effector protein, AvrBsT, triggers hypersensitive cell death in pepper (Capsicum annuum). Here, we have identified the pepper SGT1 (suppressor of the G2 allele of skp1) as a host interactor of AvrBsT and also the pepper PIK1 (receptor-like cytoplasmic kinase 1). PIK1 specifically phosphorylates SGT1 and AvrBsT in vitro. AvrBsT specifically binds to the CS domain of SGT1, resulting in the inhibition of PIK1-mediated SGT1 phosphorylation and subsequent nuclear transport of the SGT1-PIK1 complex. Liquid chromatography-tandom mass spectrometry (LC/MS/MS) of the proteolytic peptides of SGT1 identified the residues Serine 98 and Serine 279 of SGT1 as the major PIK1-mediated phosphorylation sites. Site directed mutagenesis of SGT1 revealed that the identified SGT1 phosphorylation sites are responsible for the activation of AvrBsT-triggered cell death in planta. SGT1 forms a heterotrimeric complex with both AvrBsT and PIK1 exclusively in the cytoplasm. Agrobacterium-mediated co-expression of SGT1 and PIK1 with avrBsT promotes avrBsT-triggered cell death in Nicotiana benthamiana, dependent on PIK1. Virus-induced silencing of SGT1 and/or PIK1 compromises avrBsT-triggered cell death, H2O2 production, defense gene induction and salicylic acid accumulation, leading to the enhanced bacterial pathogen growth in pepper. Together, these results suggest that SGT1 interacts with PIK1 and bacterial effector protein AvrBsT and promotes hypersensitive cell death associated with PIK1-mediated phosphorylation in plants.


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Science: A Bacterial Tyrosine Phosphatase Inhibits Plant Pattern Recognition Receptor Activation (2014)

Science: A Bacterial Tyrosine Phosphatase Inhibits Plant Pattern Recognition Receptor Activation (2014) | Effectors and Plant Immunity | Scoop.it

Innate immunity relies on the perception of pathogen-associated molecular patterns (PAMPs) by pattern-recognition receptors (PRRs) located on the host cell’s surface. Many plant PRRs are kinases. Here, we report that the Arabidopsis receptor kinase EF-TU RECEPTOR EFR, which perceives the elf18 peptide derived from bacterial elongation factor Tu, is activated upon ligand binding by phosphorylation on its tyrosine residues. Phosphorylation of a single tyrosine residue, Y836, is required for activation of EFR and downstream immunity to the phytopathogenic bacterium Pseudomonas syringae. A tyrosine phosphatase, HopAO1, secreted by P. syringae, reduces EFR phosphorylation and derails subsequent immune responses. Thus host and pathogen battle to take control of PRR tyrosine phosphorylation used to initiate anti-bacterial immunity.

 

Alberto P. Macho, Benjamin Schwessinger, Vardis Ntoukakis, Alexandre Brutus, Cécile Segonzac, Sonali Roy, Yasuhiro Kadota, Man-Ho Oh, Jan Sklenar, Paul Derbyshire, Rosa Lozano-Durán, Frederikke Gro Malinovsky, Jacqueline Monaghan, Frank L. Menke, Steven C. Huber, Sheng Yang He, Cyril Zipfel

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Plant–microbe interactions as drivers of ecosystem functions relevant for the biodegradation of organic contaminants

Plant–microbe interactions as drivers of ecosystem functions relevant for the biodegradation of organic contaminants | Effectors and Plant Immunity | Scoop.it

Highlights• Biotransformation is an ecosystem property.• Microbes are the main drivers in biotransformation.• Dispersal of chemicals and bacteria drives degradation effectiveness.• Ecosystem stability is increased by plant–microbe interactions


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Code-Assisted Discovery of TAL Effector Targets in Bacterial Leaf Streak of Rice Reveals Contrast with Bacterial Blight and a Novel Susceptibility Gene - PLOS Pathogens

Code-Assisted Discovery of TAL Effector Targets in Bacterial Leaf Streak of Rice Reveals Contrast with Bacterial Blight and a Novel Susceptibility Gene  - PLOS Pathogens | Effectors and Plant Immunity | Scoop.it

(via T. Lahaye, thx)

Cernadas et al, 2014

Bacterial leaf streak of rice, caused by Xanthomonas oryzae pv. oryzicola (Xoc) is an increasingly important yield constraint in this staple crop. A mesophyll colonizer, Xoc differs from X. oryzae pv. oryzae (Xoo), which invades xylem to cause bacterial blight of rice. Both produce multiple distinct TAL effectors, type III-delivered proteins that transactivate effector-specific host genes. A TAL effector finds its target(s) via a partially degenerate code whereby the modular effector amino acid sequence identifies nucleotide sequences to which the protein binds. Virulence contributions of some Xoo TAL effectors have been shown, and their relevant targets, susceptibility (S) genes, identified, but the role of TAL effectors in leaf streak is uncharacterized. We used host transcript profiling to compare leaf streak to blight and to probe functions of Xoc TAL effectors. We found that Xoc and Xoo induce almost completely different host transcriptional changes. Roughly one in three genes upregulated by the pathogens is preceded by a candidate TAL effector binding element. Experimental analysis of the 44 such genes predicted to be Xoc TAL effector targets verified nearly half, and identified most others as false predictions. None of the Xoc targets is a known bacterial blight S gene. Mutational analysis revealed that Tal2g, which activates two genes, contributes to lesion expansion and bacterial exudation. Use of designer TAL effectors discriminated a sulfate transporter gene as the S gene. Across all targets, basal expression tended to be higher than genome-average, and induction moderate. Finally, machine learning applied to real vs. falsely predicted targets yielded a classifier that recalled 92% of the real targets with 88% precision, providing a tool for better target prediction in the future. Our study expands the number of known TAL effector targets, identifies a new class of S gene, and improves our ability to predict functional targeting.


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PLoS ONE: A Modular Plasmid Assembly Kit for Multigene Expression, Gene Silencing and Silencing Rescue in Plants (2014)

PLoS ONE: A Modular Plasmid Assembly Kit for Multigene Expression, Gene Silencing and Silencing Rescue in Plants (2014) | Effectors and Plant Immunity | Scoop.it

The Golden Gate (GG) modular assembly approach offers a standardized, inexpensive and reliable way to ligate multiple DNA fragments in a pre-defined order in a single-tube reaction. We developed a GG based toolkit for the flexible construction of binary plasmids for transgene expression in plants. Starting from a common set of modules, such as promoters, protein tags and transcribed regions of interest, synthetic genes are assembled, which can be further combined to multigene constructs. As an example, we created T-DNA constructs encoding multiple fluorescent proteins targeted to distinct cellular compartments (nucleus, cytosol, plastids) and demonstrated simultaneous expression of all genes in Nicotiana benthamiana, Lotus japonicus and Arabidopsis thaliana. We assembled an RNA interference (RNAi) module for the construction of intron-spliced hairpin RNA constructs and demonstrated silencing of GFP in N. benthamiana. By combination of the silencing construct together with a codon adapted rescue construct into one vector, our system facilitates genetic complementation and thus confirmation of the causative gene responsible for a given RNAi phenotype. As proof of principle, we silenced a destabilized GFP gene (dGFP) and restored GFP fluorescence by expression of a recoded version of dGFP, which was not targeted by the silencing construct.

 

Andreas Binder, Jayne Lambert, Robert Morbitzer, Claudia Popp, Thomas Ott, Thomas Lahaye, Martin Parniske


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J. Exp. Bot: A trade off between mlo resistance to powdery mildew and increased susceptibility of barley to a newly important disease, Ramularia leaf spot (2014)

J. Exp. Bot: A trade off between mlo resistance to powdery mildew and increased susceptibility of barley to a newly important disease, Ramularia leaf spot (2014) | Effectors and Plant Immunity | Scoop.it

Ramularia leaf spot (RLS), caused by the fungus Ramularia collo-cygni, is a serious, recently emerged disease of barley in Europe and other temperate regions. This study investigated the trade off between strong resistance to powdery mildew conferred by mlo mutant alleles and increased susceptibility to RLS. In field trials and seedling tests, the presence of mlo alleles increased severity of RLS. Genetic analysis of a doubled-haploid population identified one quantitative trait locus for susceptibility to RLS, colocalizing with the mlo-11 allele for mildew resistance. The effect of mlo-11 on RLS severity was environmentally sensitive. Analysis of near-isogenic lines of different mlo mutations in various genetic backgrounds confirmed that mlo alleles increased RLS severity in seedlings and adult plants. For mlo resistance to mildew to be fully effective, the genes ROR1 and ROR2 are required. RLS symptoms were significantly reduced on mlo-5 ror double mutants but fungal DNA levels remained as high as in mlo-5 single mutants, implying that ror alleles modify the transition of the fungus from endophytism to necrotrophy. These results indicate that the widespread use of mlo resistance to control mildew may have inadvertently stimulated the emergence of RLS as a major disease of barley.

 

Graham R. D. McGrann, Anna Stavrinides, Joanne Russell, Margaret M. Corbitt, Allan Booth, Laetitia Chartrain, William T. B. Thomas and James K. M. Brown

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Mycorrhizae 101

See how Mycorrhizae Premier Tech works on the plant's root system to enhance growth and resistance to plants.

Via Jean-Michel Ané
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Rescooped by Nicolas Denancé from MycorWeb Plant-Microbe Interactions
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A secreted Ustilago maydis effector promotes virulence by targeting anthocyanin biosynthesis in maize

A secreted Ustilago maydis effector promotes virulence by targeting anthocyanin biosynthesis in maize | Effectors and Plant Immunity | Scoop.it

The biotrophic fungus Ustilago maydis causes smut disease in maize with characteristic tumor formation and anthocyanin induction. Here, we show that anthocyanin biosynthesis is induced by the virulence promoting secreted effector protein Tin2. Tin2 protein functions inside plant cells where it interacts with maize protein kinase ZmTTK1. Tin2 masks a ubiquitin–proteasome degradation motif in ZmTTK1, thus stabilizing the active kinase. Active ZmTTK1 controls activation of genes in the anthocyanin biosynthesis pathway. Without Tin2, enhanced lignin biosynthesis is observed in infected tissue and vascular bundles show strong lignification. This is presumably limiting access of fungal hyphae to nutrients needed for massive proliferation. Consistent with this assertion, we observe that maize brown midrib mutants affected in lignin biosynthesis are hypersensitive to U. maydis infection. We speculate that Tin2 rewires metabolites into the anthocyanin pathway to lower their availability for other defense responses. - See more at: http://elife.elifesciences.org/content/3/e01355#sthash.wpafBL8j.dpuf


Via Francis Martin
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Genetic Diversity of Transcriptional Activator-like Effectors genes in Chinese Isolates of Xanthomonas oryzae pv. oryzicola - Phytopathology

Genetic Diversity of Transcriptional Activator-like Effectors genes in Chinese Isolates of Xanthomonas oryzae pv. oryzicola - Phytopathology | Effectors and Plant Immunity | Scoop.it

(via T. Lahaye, thx)

Zakria et al, 2014

Xanthomonas oryzae pv. oryzicola (Xoc) causes bacterial leaf streak (BLS), a devastating disease of rice in Asia countries. Xoc utilizes repertoires of transcriptional activator-like effectors (TALEs) to manipulate host resistance or susceptibility; thus TALEs can determine the outcome of BLS. In this report, we studied genetic diversity in putative tale genes of 65 Xoc strains that originated from nine provinces of southern China. Genomic DNAs from the 65 strains were digested with BamHI and hybridized with an internal fragment of avrXa3, a tale gene originating from the related pathogen, X. oryzae pv. oryzae (Xoo) that causes bacterial leaf blight (BLB). Southern blot analysis indicated that the strains contained a variable number (9 to 22) of avrXa3-hybridizing fragments (e.g. putative tale genes). Based on the number and size of hybridizing bands, strains were classified into 14 genotypes (designated 1 to 14), and genotypes 3 and 10 represented 29.23% and 24.64% of the total, respectively. A high molecular weight BamHI fragment (HMWB; ~6.0 kb) was present in 12 of the 14 genotypes, and sequence analysis of the HMWB revealed the presence of a C-terminally-truncated tale, an insertion element related to IS1403, and genes encoding phosphoglycerate mutase (pgm) and endonuclease V (enaV). Primers were developed from the 6.0-kb HMWB fragment and showed potential in genotyping Xoc strains by PCR. Virulence of Xoc strains was assessed on 23 rice cultivars containing different R genes for BLB. The Xoc strains could be grouped into 14 pathotypes (I to XIV), and the grouping of strains was almost identical to the categories determined by genotypic analysis. In general, strains containing higher numbers of putative tale genes were more virulent on rice than strains containing fewer tales. The results also indicate that there are no gene-for-gene relationships between the tested rice lines and Xoc strains. To our knowledge, this is the first description of genetic diversity of Xoc strains based on tale gene analysis.


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The ISME Journal: Host immune responses accelerate pathogen evolution (2013)

The ISME Journal: Host immune responses accelerate pathogen evolution (2013) | Effectors and Plant Immunity | Scoop.it

Pathogens face a hostile and often novel environment when infecting a new host, and adaptation is likely to be an important determinant of the success in colonization and establishment. We hypothesized that resistant hosts will impose stronger selection on pathogens than susceptible hosts, which should accelerate pathogen evolution through selection biased toward effector genes. To test this hypothesis, we conducted an experimental evolution study on Xanthomonas citri subsp. citri (Xcc) in a susceptible plant species and a resistant plant species. We performed 55 rounds of repeated reinoculation of Xcc through susceptible host grapefruit (isolates G1, G2, G3) and resistant host kumquat (isolates K1, K2, K3). Consequently, only K1 and K3 isolates lost their ability to elicit a hypersensitive response (HR) in kumquat. Illumina sequencing of the parental and descendant strains P, G1, G2, G3, K1, K2 and K3 revealed that fixed mutations were biased toward type three secretion system effectors in isolates K1 and K3. Parallel evolution was observed in the K1 and K3 strains, suggesting that the mutations result from selection rather than by random drift. Our results support our hypothesis and suggest that repeated infection of resistant hosts by pathogens should be prevented to avoid selecting for adaptive pathogens.

 

Pankaj Trivedi and Nian Wang


Via Pierre-Marc Delaux
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Steve Marek's curator insight, December 10, 2013 7:56 PM

Comparative genomics elucidates the evolution of virulence in bacterial plant pathogen, Xanthomonas citri. 

This experiment needs to be done with fungal pathogens.

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PLoS ONE: Genomic Survey of Pathogenicity Determinants and VNTR Markers in the Cassava Bacterial Pathogen Xanthomonas axonopodis pv. Manihotis Strain CIO151 (2013)

PLoS ONE: Genomic Survey of Pathogenicity Determinants and VNTR Markers in the Cassava Bacterial Pathogen Xanthomonas axonopodis pv. Manihotis Strain CIO151 (2013) | Effectors and Plant Immunity | Scoop.it

Xanthomonas axonopodis pv. manihotis (Xam) is the causal agent of bacterial blight of cassava, which is among the main components of human diet in Africa and South America. Current information about the molecular pathogenicity factors involved in the infection process of this organism is limited. Previous studies in other bacteria in this genus suggest that advanced draft genome sequences are valuable resources for molecular studies on their interaction with plants and could provide valuable tools for diagnostics and detection. Here we have generated the first manually annotated high-quality draft genome sequence of Xam strain CIO151. Its genomic structure is similar to that of other xanthomonads, especially Xanthomonas euvesicatoria and Xanthomonas citri pv. citri species. Several putative pathogenicity factors were identified, including type III effectors, cell wall-degrading enzymes and clusters encoding protein secretion systems. Specific characteristics in this genome include changes in the xanthomonadin cluster that could explain the lack of typical yellow color in all strains of this pathovar and the presence of 50 regions in the genome with atypical nucleotide composition. The genome sequence was used to predict and evaluate 22 variable number of tandem repeat (VNTR) loci that were subsequently demonstrated as polymorphic in representative Xam strains. Our results demonstrate that Xanthomonas axonopodis pv. manihotis strain CIO151 possesses ten clusters of pathogenicity factors conserved within the genus Xanthomonas. We report 126 genes that are potentially unique to Xam, as well as potential horizontal transfer events in the history of the genome. The relation of these regions with virulence and pathogenicity could explain several aspects of the biology of this pathogen, including its ability to colonize both vascular and non-vascular tissues of cassava plants. A set of 16 robust, polymorphic VNTR loci will be useful to develop a multi-locus VNTR analysis scheme for epidemiological surveillance of this disease.

 

Mario L. Arrieta-Ortiz,  Luis M. Rodríguez-R,  Álvaro L. Pérez-Quintero,  Lucie Poulin,  Ana C. Díaz,  Nathalia Arias Rojas,  Cesar Trujillo,  Mariana Restrepo Benavides,  Rebecca Bart,  Jens Boch,  Tristan Boureau,  Armelle Darrasse,  Perrine David,  Thomas Dugé de Bernonville,  Paula Fontanilla,  Lionel Gagnevin,  Fabien Guérin,  Marie-Agnès Jacques,  Emmanuelle Lauber,  Pierre Lefeuvre,  Cesar Medina,  Edgar Medina,  Nathaly Montenegro,  Alejandra Muñoz Bodnar,  Laurent D. Noël,  Juan F. Ortiz Quiñones,  Daniela Osorio,  Carolina Pardo,  Prabhu B. Patil,  Stéphane Poussier,  Olivier Pruvost,  Isabelle Robène-Soustrade,  Robert P. Ryan,  Javier Tabima,  Oscar G. Urrego Morales,  Christian Vernière,  Sébastien Carrere,  Valérie Verdier,  Boris Szurek,  Silvia Restrepo,  Camilo López,  Ralf Koebnik and Adriana Bernal

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