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Frontiers in Plant Science: A gene for plant protection: expression of a bean polygalacturonase inhibitor in tobacco confers a strong resistance against Rhizoctonia solani and two oomycetes (2012)

Frontiers in Plant Science: A gene for plant protection: expression of a bean polygalacturonase inhibitor in tobacco confers a strong resistance against Rhizoctonia solani and two oomycetes (2012) | Effectors and Plant Immunity | Scoop.it

We have tested whether a gene encoding a polygalacturonase-inhibiting protein (PGIP) protects tobacco against a fungal pathogen (Rhizoctonia solani) and two oomycetes (Phytophthora parasitica var. nicotianae and Peronospora hyoscyami f. sp. tabacina). The trials were performed in greenhouse conditions for R. solani and P. parasitica and in the field for P. hyoscyami. Our results show that expression of PGIP is a powerful way of engineering a broad-spectrum disease resistance.

 

Orlando Borras-Hidalgo, Claudio Caprari, Ingrid Hernandez-Estevez, Giulia De Lorenzo and Felice Cervone

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Front. Plant Sci./Front. Microbiol.: Genomics and Effectomics of the crop killer Xanthomonas

Front. Plant Sci./Front. Microbiol.: Genomics and Effectomics of the crop killer Xanthomonas | Effectors and Plant Immunity | Scoop.it

Published articles:

 

8. Methods by Pérez-Quintero et al.:  QueTAL: a suite of tools to classify and compare TAL effectors functionally and phylogenetically. Front. Plant Sci. (2015)

 

7. Hypothesis and theory by Wilkins et al.: TAL effectors and activation of predicted host targets distinguish Asian from African strains of the rice pathogen Xanthomonas oryzae pv. oryzicola while strict conservation suggests universal importance of five TAL effectors. Front. Plant Sci. (2015)

 

6. Review by Hutin et al.: MorTAL Kombat: the story of defense against TAL effectors through loss-of-susceptibility. Front. Plant Sci. (2015)

 

5. Research article by Jacobs et al.: Comparative genomics of a cannabis pathogen reveals insight into the evolution of pathogenicity in Xanthomonas. Front. Plant Sci. (2015)

 

4. Research article by Schwartz et al.: Phylogenomics of Xanthomonas field strains infecting pepper and tomato reveals diversity in effector repertoires and identifies determinants of host specificity. Front. Microbiol. (2015)

 

3. Perspective by Dossa et al.: Decision tools for bacterial blight resistance gene deployment in rice-based agricultural ecosystems. Front. Plant Sci. (2015)

 

2. Mini-review by Pieretti et al.: What makes Xanthomonas albilineans unique amongst xanthomonads? Front. Plant Sci. (2015)

 

1. Mini-review by S. Üstün and F. Börnke: Interactions of Xanthomonas type-III effector proteins with the plant ubiquitin and ubiquitin-like pathways. Front. Plant Sci. (2014)

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Suayib Üstün's curator insight, July 29, 2014 2:57 PM

Great topic-excited!

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Front. Plant Sci.: TAL effectors and activation of predicted host targets distinguish Asian from African strains of the rice pathogen Xanthomonas oryzae pv. oryzicola while strict conservation sugg...

Front. Plant Sci.: TAL effectors and activation of predicted host targets distinguish Asian from African strains of the rice pathogen Xanthomonas oryzae pv. oryzicola while strict conservation sugg... | Effectors and Plant Immunity | Scoop.it

Xanthomonas oryzae pv. oryzicola (Xoc) causes the increasingly important disease bacterial leaf streak of rice (BLS) in part by type III delivery of repeat-rich transcription activator-like (TAL) effectors to upregulate host susceptibility genes. By pathogen whole genome, single molecule, real-time sequencing and host RNA sequencing, we compared TAL effector content and rice transcriptional responses across 10 geographically diverse Xoc strains. TAL effector content is surprisingly conserved overall, yet distinguishes Asian from African isolates. Five TAL effectors are conserved across all strains. In a prior laboratory assay in rice cv. Nipponbare, only two contributed to virulence in strain BLS256 but the strict conservation indicates all five may be important, in different rice genotypes or in the field. Concatenated and aligned, TAL effector content across strains largely reflects relationships based on housekeeping genes, suggesting predominantly vertical transmission. Rice transcriptional responses did not reflect these relationships, and on average, only 28% of genes upregulated and 22% of genes downregulated by a strain are up- and downregulated (respectively) by all strains. However, when only known TAL effector targets were considered, the relationships resembled those of the TAL effectors. Toward identifying new targets, we used the TAL effector-DNA recognition code to predict effector binding elements in promoters of genes upregulated by each strain, but found that for every strain, all upregulated genes had at least one. Filtering with a classifier we developed previously decreases the number of predicted binding elements across the genome, suggesting that it may reduce false positives among upregulated genes. Applying this filter and eliminating genes for which upregulation did not strictly correlate with presence of the corresponding TAL effector, we generated testable numbers of candidate targets for four of the five strictly conserved TAL effectors.

 

Wilkins KE, Booher NJ, Wang L and Bogdanove AJ

 

 

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5th Xanthomonas Genomics Conference 2015 - July 8 - 11, 2015. Bogotá, Colombia

5th Xanthomonas Genomics Conference 2015 - July 8 - 11, 2015. Bogotá, Colombia | Effectors and Plant Immunity | Scoop.it

The final program of the XGC 2015... sounds really promising!

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Front. Plant Sci.: Comparative genomics of a cannabis pathogen reveals insight into the evolution of pathogenicity in Xanthomonas (2015)

Front. Plant Sci.: Comparative genomics of a cannabis pathogen reveals insight into the evolution of pathogenicity in Xanthomonas (2015) | Effectors and Plant Immunity | Scoop.it

Pathogenic bacteria in the genus Xanthomonas cause diseases on over 350 plant species, including cannabis (Cannabis sativa L.). Because of regulatory limitations, the biology of the Xanthomonas-cannabis pathosystem remains largely unexplored. To gain insight into the evolution of Xanthomonas strains pathogenic to cannabis, we sequenced the genomes of two geographically distinct Xanthomonas strains, NCPPB 3753 and NCPPB 2877, which were previously isolated from symptomatic plant tissue in Japan and Romania. Comparative multilocus sequence analysis of housekeeping genes revealed that they belong to Group 2, which comprises most of the described species of Xanthomonas. Interestingly, both strains lack the Hrp Type III secretion system and do not contain any of the known Type III effectors. Yet their genomes notably encode two key Hrp pathogenicity regulators HrpG and HrpX, and hrpG and hrpX are in the same genetic organization as in the other Group 2 xanthomonads. Promoter prediction of HrpX-regulated genes suggests the induction of an aminopeptidase, a lipase and two polygalacturonases upon plant colonization, similar to other plant-pathogenic xanthomonads. Genome analysis of the distantly related Xanthomonas maliensis strain 97M, which was isolated from a rice leaf in Mali, similarly demonstrated the presence of HrpG, HrpX and a HrpX-regulated polygalacturonase, and the absence of the Hrp Type III secretion system and known Type III effectors. Given the observation that some Xanthomonas strains across distinct taxa do not contain hrpG and hrpX, we speculate a stepwise evolution of pathogenicity, which involves (i) acquisition of key regulatory genes and cell wall-degrading enzymes, followed by (ii) acquisition of the Hrp type III secretion system, which is ultimately accompanied by (iii) successive acquisition of type III effectors.

 

Jacobs JM, Pesce C, Lefeuvre P and Koebnik R

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Cell: A Plant Immune Receptor Detects Pathogen Effectors that Target WRKY Transcription Factors (2015)

Cell: A Plant Immune Receptor Detects Pathogen Effectors that Target WRKY Transcription Factors (2015) | Effectors and Plant Immunity | Scoop.it

Defense against pathogens in multicellular eukaryotes depends on intracellular immune receptors, yet surveillance by these receptors is poorly understood. Several plant nucleotide-binding, leucine-rich repeat (NB-LRR) immune receptors carry fusions with other protein domains. The Arabidopsis RRS1-R NB-LRR protein carries a C-terminal WRKY DNA binding domain and forms a receptor complex with RPS4, another NB-LRR protein. This complex detects the bacterial effectors AvrRps4 or PopP2 and then activates defense. Both bacterial proteins interact with the RRS1 WRKY domain, and PopP2 acetylates lysines to block DNA binding. PopP2 and AvrRps4 interact with other WRKY domain-containing proteins, suggesting these effectors interfere with WRKY transcription factor-dependent defense, and RPS4/RRS1 has integrated a “decoy” domain that enables detection of effectors that target WRKY proteins. We propose that NB-LRR receptor pairs, one member of which carries an additional protein domain, enable perception of pathogen effectors whose function is to target that domain.

 

Panagiotis F. Sarris, Zane Duxbury, Sung Un Huh, Yan Ma, Cécile Segonzac, Jan Sklenar, Paul Derbyshire, Volkan Cevik, Ghanasyam Rallapalli, Simon B. Saucet, Lennart Wirthmueller, Frank L.H. Menke, Kee Hoon Sohn, Jonathan D.G. Jones

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Transport of defense compounds from source to sink: lessons learned from glucosinolates: Trends in Plant Science

Transport of defense compounds from source to sink: lessons learned from glucosinolates: Trends in Plant Science | Effectors and Plant Immunity | Scoop.it
Plants synthesize a plethora of defense compounds crucial for their survival in a challenging and changing environment. Transport processes are important for shaping the distribution pattern of defense compounds, albeit focus hitherto has been mostly on their biosynthetic pathways. A recent identification of two glucosinolate transporters represents a breakthrough in our understanding of glucosinolate transport in Arabidopsis and has advanced knowledge in transport of defense compounds. In this review, we discuss the role of the glucosinolate transporters in establishing dynamic glucosinolate distribution patterns and source–sink relations. We focus on lessons learned from glucosinolate transport that may apply to transport of other defense compounds and discuss future avenues in the emerging field of defense compound transport.

Via Christophe Jacquet
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Gene targeting by the TAL effector PthXo2 reveals cryptic resistance gene for bacterial blight of rice - Plant J.

Gene targeting by the TAL effector PthXo2 reveals cryptic resistance gene for bacterial blight of rice - Plant J. | Effectors and Plant Immunity | Scoop.it

(via T. Schreiber, thx)

Bacterial blight of rice is caused by the γ-proteobacterium Xanthomonas oryzae pv. oryzae, which utilizes a group of type III TAL (transcription activator-like) effectors to induce host gene expression and condition host susceptibility. Five SWEET genes are functionally redundant to support bacterial disease, but only two were experimentally proven targets of natural TAL effectors. Here, we report the identification of the sucrose transporter gene OsSWEET13 as the disease susceptibility gene for PthXo2 and the existence of cryptic recessive resistance to PthXo2-dependent X. oryzae pv. oryzae due to promoter variations of OsSWEET13 in japonica rice. PthXo2-containing strains induce OsSWEET13 in indica rice IR24 due to the presence of an unpredicted and undescribed effector binding site not present in the alleles in japonica rice Nipponbare and Kitaake. The specificity of effector-associated gene induction and disease susceptibility is attributable to a single nucleotide polymorphism (SNP), which is also found in a polymorphic allele of OsSWEET13 known as the recessive resistance gene xa25 from the rice cultivar Minghui 63. The mutation of OsSWEET13 with CRISPR/Cas9 technology further corroborates the requirement of OsSWEET13 expression for the state of PthXo2-dependent disease susceptibility to X. oryzae pv. oryzae. Gene profiling of a collection of 104 strains revealed OsSWEET13 induction by 42 isolates of X. oryzae pv. oryzae. Heterologous expression of OsSWEET13 in Nicotiana benthamiana leaf cells elevates sucrose concentrations in the apoplasm. The results corroborate a model whereby X. oryzae pv. oryzae enhances the release of sucrose from host cells in order to exploit the host resources.

 


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J. Exp. Bot.: Identification of a molecular dialogue between developing seeds of Medicago truncatula and seedborne xanthomonads (2015)

J. Exp. Bot.: Identification of a molecular dialogue between developing seeds of Medicago truncatula and seedborne xanthomonads (2015) | Effectors and Plant Immunity | Scoop.it

Plant pathogenic bacteria disseminate and survive mainly in association with seeds. This study addresses whether seeds are passive carriers or engage a molecular dialogue with pathogens during their development. We developed two pathosystems using Medicago truncatula with Xanthomonas alfalfae subsp. alfalfae (Xaa), the natural Medicago sp. pathogen and Xanthomonas campestris pv. campestris (Xcc), a Brassicaceae pathogen. Three days after flower inoculation, the transcriptome of Xcc-infected pods showed activation of an innate immune response that was strongly limited in Xcc mutated in the type three secretion system, demonstrating an incompatible interaction of Xcc with the reproductive structures. In contrast, the presence of Xaa did not result in an activation of defence genes. Transcriptome profiling during development of infected seeds exhibited time-dependent and differential responses to Xcc and Xaa. Gene network analysis revealed that the transcriptome of Xcc-infected seeds was mainly affected during seed filling whereas that of Xaa-infected seeds responded during late maturation. The Xcc-infected seed transcriptome exhibited an activation of defence response and a repression of targeted seed maturation pathways. Fifty-one percent of putative ABSCISIC ACID INSENSITIVE3 targets were deregulated by Xcc, including oleosin, cupin, legumin and chlorophyll degradation genes. At maturity, these seeds displayed decreased weight and increased chlorophyll content. In contrast, these traits were not affected by Xaa infection. These findings demonstrate the existence of a complex molecular dialogue between xanthomonads and developing seeds and provides insights into a previously unexplored trade-off between seed development and pathogen defence.

 

Emmanuel Terrasson, Armelle Darrasse, Karima Righetti, Julia Buitink, David Lalanne, Benoit Ly Vu, Sandra Pelletier, William Bolingue, Marie-Agnès Jacques, and Olivier Leprince

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Secondary metabolites in plant innate immunity

Secondary metabolites in plant innate immunity | Effectors and Plant Immunity | Scoop.it
Plant secondary metabolites carry out numerous functions in interactions between plants and a broad range of other organisms. Experimental evidence strongly supports the indispensable contribution of many constitutive and pathogen-inducible phytochemicals to plant innate immunity. Extensive studies on model plant species, particularly Arabidopsis thaliana, have brought significant advances in our understanding of the molecular mechanisms underpinning pathogen-triggered biosynthesis and activation of defensive secondary metabolites. However, despite the proven significance of secondary metabolites in plant response to pathogenic microorganisms, little is known about the precise mechanisms underlying their contribution to plant immunity. This insufficiency concerns information on the dynamics of cellular and subcellular localization of defensive phytochemicals during the encounters with microbial pathogens and precise knowledge on their mode of action. As many secondary metabolites are characterized by their in vitro antimicrobial activity, these compounds were commonly considered to function in plant defense as in planta antibiotics. Strikingly, recent experimental evidence suggests that at least some of these compounds alternatively may be involved in controlling several immune responses that are evolutionarily conserved in the plant kingdom, including callose deposition and programmed cell death.

Via Christophe Jacquet
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Perception of pathogenic or beneficial bacteria and their evasion of host immunity: pattern recognition receptors in the frontline

Perception of pathogenic or beneficial bacteria and their evasion of host immunity: pattern recognition receptors in the frontline | Effectors and Plant Immunity | Scoop.it
Plants are continuously monitoring the presence of microorganisms to establish an adapted response. Plants commonly use pattern recognition receptors (PRRs) to perceive microbe- or pathogen-associated molecular patterns (MAMPs/PAMPs) which are microorganism molecular signatures. Located at the plant plasma membrane, the PRRs are generally receptor-like kinases (RLKs) or receptor-like proteins (RLPs). MAMP detection will lead to the establishment of a plant defense program called MAMP-triggered immunity (MTI). In this review, we overview the RLKs and RLPs that assure early recognition and control of pathogenic or beneficial bacteria. We also highlight the crucial function of PRRs during plant-microbe interactions, with a special emphasis on the receptors of the bacterial flagellin and peptidoglycan. In addition, we discuss the multiple strategies used by bacteria to evade PRR-mediated recognition.

Via Jean-Michel Ané
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Jean-Michel Ané's curator insight, April 14, 12:53 PM

Another nice review

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Refined Requirements for Protein Regions Important for Activity of the TALE AvrBs3 - PLOS One

Refined Requirements for Protein Regions Important for Activity of the TALE AvrBs3 - PLOS One | Effectors and Plant Immunity | Scoop.it

Schreiber et al, 2015

AvrBs3, the archetype of the family of transcription activator-like (TAL) effectors from phytopathogenic Xanthomonas bacteria, is translocated by the type III secretion system into the plant cell. AvrBs3 localizes to the plant cell nucleus and activates the transcription of target genes. Crucial for this is the central AvrBs3 region of 17.5 34-amino acid repeats that functions as a DNA-binding domain mediating recognition in a “one-repeat-to-one base pair” manner. Although AvrBs3 forms homodi


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NLR Biology in Plants and Animals - Interactions, Bavaria, Germany from May 3–6, 2015

NLR Biology in Plants and Animals - Interactions, Bavaria, Germany from May 3–6, 2015 | Effectors and Plant Immunity | Scoop.it

This workshop aims to draw together researchers in plant and animal NLR biology to discuss recent conceptual advances and future directions for the field. The workshop will take place at Schloss Ringberg in Bavaria, Germany from May 3–6, 2015. View the workshop poster for more information on how to register and submit an abstract.


Via Kamoun Lab @ TSL
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Nat. Commun.: Bacterial killing via a type IV secretion system (2015)

Nat. Commun.: Bacterial killing via a type IV secretion system (2015) | Effectors and Plant Immunity | Scoop.it

http://www.nature.com/ncomms/2015/150306/ncomms7453/full/ncomms7453.html?WT.ec_id=NCOMMS-20150311

 

Type IV secretion systems (T4SSs) are multiprotein complexes that transport effector proteins and protein–DNA complexes through bacterial membranes to the extracellular milieu or directly into the cytoplasm of other cells. Many bacteria of the family Xanthomonadaceae, which occupy diverse environmental niches, carry a T4SS with unknown function but with several characteristics that distinguishes it from other T4SSs. Here we show that the Xanthomonas citri T4SS provides these cells the capacity to kill other Gram-negative bacterial species in a contact-dependent manner. The secretion of one type IV bacterial effector protein is shown to require a conserved C-terminal domain and its bacteriolytic activity is neutralized by a cognate immunity protein whose 3D structure is similar to peptidoglycan hydrolase inhibitors. This is the first demonstration of the involvement of a T4SS in bacterial killing and points to this special class of T4SS as a mediator of both antagonistic and cooperative interbacterial interactions.

 

Diorge P. Souza, Gabriel U. Oka, Cristina E. Alvarez-Martinez, Alexandre W. Bisson-Filho, German Dunger, Lise Hobeika, Nayara S. Cavalcante, Marcos C. Alegria, Leandro R.S. Barbosa, Roberto K. Salinas, Cristiane R. Guzzo & Chuck S. Farah

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Front. Plant Sci.: QueTAL: a suite of tools to classify and compare TAL effectors functionally and phylogenetically (2015)

Front. Plant Sci.: QueTAL: a suite of tools to classify and compare TAL effectors functionally and phylogenetically (2015) | Effectors and Plant Immunity | Scoop.it
Transcription Activator-Like (TAL) effectors from Xanthomonas plant pathogenic bacteria can bind to the promoter region of plant genes and induce their expression. DNA-binding specificity is governed by a central domain made of nearly identical repeats, each determining the recognition of one base pair via two amino acid residues (a.k.a. Repeat Variable Di-residue, or RVD). Knowing how TAL effectors differ from each other within and between strains would be useful to infer functional and evolutionary relations, but their repetitive nature precludes reliable use of traditional alignment methods. The suite QueTAL was therefore developed to offer tailored tools for comparison of TAL effector genes. The program DisTAL considers each repeat as a unit, transforms a TAL effector sequence into a sequence of coded repeats and makes pair-wise alignments between these coded sequences to construct trees. The program FuncTAL is aimed at finding TAL effectors with similar DNA-binding capabilities. It calculates correlations between position weight matrices obtained from the RVD sequence, and builds trees based on these correlations. The programs accurately represented phylogenetic and functional relations between TAL effectors using either simulated or literature-curated data. When using the programs on a large set of TAL effector sequences, the DisTAL tree largely reflected the expected species phylogeny. In contrast, FuncTAL showed that TAL effectors with similar binding capabilities can be found between phylogenetically distant taxa. This suite will help users to rapidly analyse any TAL effector genes of interest and compare them to other available TAL genes and should improve our understanding of TAL effectors evolution. It is available at http://bioinfo-web.mpl.ird.fr/cgi-bin2/quetal/quetal.cgi.
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Front. Plant Sci.: MorTAL Kombat: the story of defense against TAL effectors through loss-of-susceptibility (2015)

Front. Plant Sci.: MorTAL Kombat: the story of defense against TAL effectors through loss-of-susceptibility (2015) | Effectors and Plant Immunity | Scoop.it

Many plant-pathogenic xanthomonads rely on Transcription Activator-Like (TAL) effectors to colonize their host. This particular family of type III effectors functions as specific plant transcription factors via a novel programmable DNA-binding domain. Upon binding to the promoters of plant disease susceptibility genes in a sequence-specific manner, the expression of these host genes is induced. However, plants have evolved specific strategies to counter the action of TAL effectors and confer resistance. One mechanism is to avoid the binding of TAL effectors by mutations of their DNA binding sites, resulting in resistance by loss-of-susceptibility. This article reviews our current knowledge of the susceptibility hubs targeted by Xanthomonas TAL effectors, possible evolutionary scenarios for plants to combat the pathogen with loss-of-function alleles, and how this knowledge can be used overall to develop new pathogen-informed breeding strategies and improve crop resistance.

 

Hutin M, Pérez-Quintero AL, Lopez C and Szurek B

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Cell Host Microb.: Pseudomonas syringae pv. tomato DC3000 Type III Secretion Effector Polymutants Reveal an Interplay between HopAD1 and AvrPtoB (2015)

Cell Host Microb.: Pseudomonas syringae pv. tomato DC3000 Type III Secretion Effector Polymutants Reveal an Interplay between HopAD1 and AvrPtoB (2015) | Effectors and Plant Immunity | Scoop.it

The bacterial pathogen Pseudomonas syringae pv. tomato DC3000 suppresses the two-tiered plant innate immune system by injecting a complex repertoire of type III secretion effector (T3E) proteins. Beyond redundancy and interplay, individual T3Es may interact with multiple immunity-associated proteins, rendering their analysis challenging. We constructed a Pst DC3000 polymutant lacking all 36 T3Es and restored individual T3Es or their mutants to explore the interplay among T3Es. The weakly expressed T3E HopAD1 was sufficient to elicit immunity-associated cell death in Nicotiana benthamiana. HopAD1-induced cell death was suppressed partially by native AvrPtoB and completely by AvrPtoBM3, which has mutations disrupting its E3 ubiquitin ligase domain and two known domains for interacting with immunity-associated kinases. AvrPtoBM3 also gained the ability to interact with the immunity-kinase MKK2, which is required for HopAD1-dependent cell death. Thus, AvrPtoB has alternative, competing mechanisms for suppressing effector-triggered plant immunity. This approach allows the deconvolution of individual T3E activities.

 

Hai-Lei Wei, Suma Chakravarthy, Johannes Mathieu, Tyler C. Helmann, Paul Stodghill, Bryan Swingle, Gregory B. Martin, Alan Collmer

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Cell: A Receptor Pair with an Integrated Decoy Converts Pathogen Disabling of Transcription Factors to Immunity (2015)

Cell: A Receptor Pair with an Integrated Decoy Converts Pathogen Disabling of Transcription Factors to Immunity (2015) | Effectors and Plant Immunity | Scoop.it

Microbial pathogens infect host cells by delivering virulence factors (effectors) that interfere with defenses. In plants, intracellular nucleotide-binding/leucine-rich repeat receptors (NLRs) detect specific effector interference and trigger immunity by an unknown mechanism. The Arabidopsis-interacting NLR pair, RRS1-R with RPS4, confers resistance to different pathogens, including Ralstonia solanacearum bacteria expressing the acetyltransferase effector PopP2. We show that PopP2 directly acetylates a key lysine within an additional C-terminal WRKY transcription factor domain of RRS1-R that binds DNA. This disrupts RRS1-R DNA association and activates RPS4-dependent immunity. PopP2 uses the same lysine acetylation strategy to target multiple defense-promoting WRKY transcription factors, causing loss of WRKY-DNA binding and transactivating functions needed for defense gene expression and disease resistance. Thus, RRS1-R integrates an effector target with an NLR complex at the DNA to switch a potent bacterial virulence activity into defense gene activation.

 

Clémentine Le Roux, Gaëlle Huet, Alain Jauneau, Laurent Camborde, Dominique Trémousaygue, Alexandra Kraut, Binbin Zhou, Marie Levaillant, Hiroaki Adachi, Hirofumi Yoshioka, Sylvain Raffaele, Richard Berthomé, Yohann Couté, Jane E. Parker, Laurent Deslandes

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The transmitters: a new blog for people interested in plant-pathogen-vector interactions

The transmitters: a new blog for people interested in plant-pathogen-vector interactions | Effectors and Plant Immunity | Scoop.it

The goal of this blog is to discuss topics relevant to scientists and other parties interested in the vector transmission of plant pathogens, as well as the diseases caused by these pathogens.  This specific field of science is, by definition, multidisciplinary and interdisciplinary; consequently, it is fragmented and very challenging to follow. Here we attempt to bring together colleagues that work on proteomics and ecological modeling, for example, hoping to foment new concepts and ideas, as well as bringing scientists with shared interests closer together.

We are a group of scientists curious about how vectors transmit plant pathogens. We work on the biology, ecology, and evolution of vector-pathogen-plant interactions.  We bring many disciplines, from molecular biology to mathematical modeling, to bear on fundamental and applied questions about the organisms involved in these interactions, as well as on the diseases caused by this group of pathogens.  We also include diverse, international perspectives, and by no means agree on everything, let alone controversial topics in the field. Yet, we still enjoy meeting each other and talking science while sharing a beer, glass of wine, or pastis.

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Front. Microbiol.: Phylogenomics of Xanthomonas field strains infecting pepper and tomato reveals diversity in effector repertoires and identifies determinants of host specificity (2015)

Front. Microbiol.: Phylogenomics of Xanthomonas field strains infecting pepper and tomato reveals diversity in effector repertoires and identifies determinants of host specificity (2015) | Effectors and Plant Immunity | Scoop.it

Bacterial spot disease of pepper and tomato is caused by four distinct Xanthomonas species and is a severely limiting factor on fruit yield in these crops. The genetic diversity and the type III effector repertoires of a large sampling of field strains for this disease have yet to be explored on a genomic scale, limiting our understanding of pathogen evolution in an agricultural setting. Genomes of sixty-seven Xanthomonas euvesicatoria (Xe), Xanthomonas perforans (Xp), and Xanthomonas gardneri (Xg) strains isolated from diseased pepper and tomato fields in the southeastern and midwestern United States were sequenced in order to determine the genetic diversity in field strains. Type III effector repertoires were computationally predicted for each strain, and multiple methods of constructing phylogenies were employed to understand better the genetic relationship of strains in the collection. A division in the Xp population was detected based on core genome phylogeny, supporting a model whereby the host-range expansion of Xp field strains on pepper is due, in part, to a loss of the effector AvrBsT. Xp-host compatibility was further studied with the observation that a double deletion mutant of AvrBsT and XopQ in Xp experiences a host gain for Nicotiana benthamiana. Extensive sampling of field strains and an improved understanding of effector content will aid in efforts to design disease resistance strategies targeted against highly conserved core effectors.

 

Schwartz AR, Potnis N, Timilsina S, Wilson M, Patane J, Martins J, Minsavage GV, Dahlbeck D, Akhunova A, Almeida N, Vallad GE, Barak JD, White FF, Miller SA, Ritchie D, Goss E, Bart RS, Setubal JC, Jones JB and Staskawicz BJ

 

 

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#NLR2015 Twitter Archive: NLR BIOLOGY IN PLANTS AND ANIMALS; WORKSHOP AT SCHLOSS RINGBERG; May 2015 DAYS 1/2


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Front. Plant Sci.: Decision tools for bacterial blight resistance gene deployment in rice-based agricultural ecosystems (2015)

Front. Plant Sci.: Decision tools for bacterial blight resistance gene deployment in rice-based agricultural ecosystems (2015) | Effectors and Plant Immunity | Scoop.it

Attempting to achieve long-lasting and stable resistance using uniformly deployed rice varieties is not a sustainable approach. The real situation appears to be much more complex and dynamic, one in which pathogens quickly adapt to resistant varieties. To prevent disease epidemics, deployment should be customized and this decision will require interdisciplinary actions. This perspective article aims to highlight the current progress on disease resistance deployment to control bacterial blight in rice. Although the model system rice−Xanthomonas oryzae pv. oryzae has distinctive features that underpin the need for a case-by-case analysis, strategies to integrate those elements into a unique decision tool could be easily extended to other crops.

 

Gerbert Sylvestre Dossa, Adam H. Sparks, Casiana Vera Cruz and Ricardo Oliva

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Molecular Genetics and Genomics: Full-genome identification and characterization of NBS-encoding disease resistance genes in wheat (2014)

Molecular Genetics and Genomics: Full-genome identification and characterization of NBS-encoding disease resistance genes in wheat (2014) | Effectors and Plant Immunity | Scoop.it

Host resistance is the most economical, effective and ecologically sustainable method of controlling diseases in crop plants. In bread wheat, despite the high number of resistance loci that have been cataloged to date, only few have been cloned, underlying the need for genomics-guided investigations capable of providing a prompt and acute knowledge on the identity of effective resistance genes that can be used in breeding programs. Proteins with a nucleotide-binding site (NBS) encoded by the major plant disease resistance (R) genes play an important role in the responses of plants to various pathogens. In this study, a comprehensive analysis of NBS-encoding genes within the whole wheat genome was performed, and the genome scale characterization of this gene family was established. From the recently published wheat genome sequence, we used a data mining and automatic prediction pipeline to identify 580 complete ORF candidate NBS-encoding genes and 1,099 partial-ORF ones. Among complete gene models, 464 were longer than 200 aa, among them 436 had less than 70 % of sequence identity to each other. This gene models set was deeply characterized. (1) First, we have analyzed domain architecture and identified, in addition to typical domain combinations, the presence of particular domains like signal peptides, zinc fingers, kinases, heavy-metal-associated and WRKY DNA-binding domains. (2) Functional and expression annotation via homology searches in protein and transcript databases, based on sufficient criteria, enabled identifying similar proteins for 60 % of the studied gene models and expression evidence for 13 % of them. (3) Shared orthologous groups were defined using NBS-domain proteins of rice and Brachypodium distachyon. (4) Finally, alignment of the 436 NBS-containing gene models to the full set of scaffolds from the IWGSC’s wheat chromosome survey sequence enabled high-stringence anchoring to chromosome arms. The distribution of the R genes was found balanced on the three wheat sub-genomes. In contrast, at chromosome scale, 50 % of members of this gene family were localized on 6 of the 21 wheat chromosomes and ~22 % of them were localized on homeologous group 7. The results of this study provide a detailed analysis of the largest family of plant disease resistance genes in allohexaploid wheat. Some structural traits reported had not been previously identified and the genome-derived data were confronted with those stored in databases outlining the functional specialization of members of this family. The large reservoir of NBS-type genes presented and discussed will, firstly, form an important framework for marker-assisted improvement of resistance in wheat, and, secondly, open up new perspectives for a better understanding of the evolution dynamics of this gene family in grass species and in polyploid systems.


Via Christophe Jacquet, Kamoun Lab @ TSL
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Front. Plant Sci.: What makes Xanthomonas albilineans unique amongst xanthomonads? (2015)

Front. Plant Sci.: What makes Xanthomonas albilineans unique amongst xanthomonads? (2015) | Effectors and Plant Immunity | Scoop.it

Xanthomonas albilineans causes leaf scald, a lethal disease of sugarcane. Compared to other species of Xanthomonas, X. albilineans exhibits distinctive pathogenic mechanisms, ecology and taxonomy. Its genome, which has experienced significant erosion, has unique genomic features. It lacks two loci required for pathogenicity in other plant pathogenic species of Xanthomonas: the xanthan gum biosynthesis and the Hrp-T3SS (hypersensitive response and pathogenicity-type three secretion system) gene clusters. Instead, X. albilineans harbours in its genome an SPI-1 (Salmonella pathogenicity island-1) T3SS gene cluster usually found in animal pathogens. X. albilineans produces a potent DNA gyrase inhibitor called albicidin, which blocks chloroplast differentiation, resulting in the characteristic white foliar stripe symptoms. The antibacterial activity of albicidin also confers on X. albilineans a competitive advantage against rival bacteria during sugarcane colonization. Recent chemical studies have uncovered the unique structure of albicidin and allowed us to partially elucidate its fascinating biosynthesis apparatus, which involves an enigmatic hybrid PKS/NRPS (polyketide synthase/non-ribosomal peptide synthetase) machinery.

 

Isabelle Pieretti, Alexander Pesic, Daniel Petras, Monique Royer, Roderich D. Süssmuth and Stéphane Cociancich

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Genome Announc.: Draft Genome Sequence of the Xylella fastidiosa CoDiRO Strain (2015)

We determined the draft genome sequence of the Xylella fastidiosa CoDiRO strain, which has been isolated from olive plants in southern Italy (Apulia). It is associated with olive quick decline syndrome (OQDS) and characterized by extensive scorching and desiccation of leaves and twigs.

 

Giampetruzzi A, Chiumenti M, Saponari M, Donvito G, Italiano A, Loconsole G, Boscia D, Cariddi C, Martelli GP, Saldarelli P.

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New Phytologist: Arabidopsis EF-Tu receptor enhances bacterial disease resistance in transgenic wheat (2015)

New Phytologist: Arabidopsis EF-Tu receptor enhances bacterial disease resistance in transgenic wheat (2015) | Effectors and Plant Immunity | Scoop.it

Perception of pathogen (or microbe)-associated molecular patterns (PAMPs/MAMPs) by pattern recognition receptors (PRRs) is a key component of plant innate immunity. The Arabidopsis PRR EF-Tu receptor (EFR) recognizes the bacterial PAMP elongation factor Tu (EF-Tu) and its derived peptide elf18. Previous work revealed that transgenic expression of AtEFR in Solanaceae confers elf18 responsiveness and broad-spectrum bacterial disease resistance.In this study, we developed a set of bioassays to study the activation of PAMP-triggered immunity (PTI) in wheat. We generated transgenic wheat (Triticum aestivum) plants expressing AtEFR driven by the constitutive rice actin promoter and tested their response to elf18.We show that transgenic expression of AtEFR in wheat confers recognition of elf18, as measured by the induction of immune marker genes and callose deposition. When challenged with the cereal bacterial pathogen Pseudomonas syringae pv. oryzae, transgenic EFR wheat lines had reduced lesion size and bacterial multiplication.These results demonstrate that AtEFR can be transferred successfully from dicot to monocot species, further revealing that immune signalling pathways are conserved across these distant phyla. As novel PRRs are identified, their transfer between plant families represents a useful strategy for enhancing resistance to pathogens in crops.


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The Sainsbury Lab's curator insight, March 12, 5:48 AM
Perception of pathogen (or microbe)-associated molecular patterns (PAMPs/MAMPs) by pattern recognition receptors (PRRs) is a key component of plant innate immunity. The Arabidopsis PRR EF-Tu receptor (EFR) recognizes the bacterial PAMP elongation factor Tu (EF-Tu) and its derived peptide elf18. Previous work revealed that transgenic expression of AtEFR in Solanaceae confers elf18 responsiveness and broad-spectrum bacterial disease resistance.In this study, we developed a set of bioassays to study the activation of PAMP-triggered immunity (PTI) in wheat. We generated transgenic wheat (Triticum aestivum) plants expressing AtEFR driven by the constitutive rice actin promoter and tested their response to elf18.We show that transgenic expression of AtEFR in wheat confers recognition of elf18, as measured by the induction of immune marker genes and callose deposition. When challenged with the cereal bacterial pathogen Pseudomonas syringae pv. oryzae, transgenic EFR wheat lines had reduced lesion size and bacterial multiplication.These results demonstrate that AtEFR can be transferred successfully from dicot to monocot species, further revealing that immune signalling pathways are conserved across these distant phyla. As novel PRRs are identified, their transfer between plant families represents a useful strategy for enhancing resistance to pathogens in crops.
Rescooped by Nicolas Denancé from TAL effector science
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TAL effectors - December 2014 Molecule of the Month by David Goodsell

TAL effectors - December 2014 Molecule of the Month by David Goodsell | Effectors and Plant Immunity | Scoop.it

doi: 10.2210/rcsb_pdb/mom_2014_12 (ePub Version  )


Via dromius
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