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Plasma membrane calcium ATPases are important components of receptor-mediated signalling in plant immune responses and development

Plasma membrane calcium ATPases are important components of receptor-mediated signalling in plant immune responses and development | Effectors and Plant Immunity | Scoop.it

Plasma membrane-resident receptor kinases (RKs) initiate signalling pathways important for plant immunity and development. In Arabidopsis thaliana, the receptor for the elicitor-active peptide epitope of bacterial flagellin, flg22, is encoded by FLS2, which promotes plant immunity. Despite its relevance, the molecular components regulating the FLS2-mediated signalling remain largely unknown. We show that the plasma membrane calcium (Ca2+) ATPase ACA8 forms a complex with FLS2 in planta. ACA8 and its closest homologue ACA10 are required for limiting the growth of virulent bacteria. One of the earliest flg22 responses is the transient increase of cytosolic Ca2+ ions, which is crucial for many of the well-described downstream responses, e.g. generation of reactive oxygen species (ROS) and the transcriptional activation of defence-associated genes. Mutant aca8 aca10 plants show decreased flg22-induced Ca2+ and ROS bursts, and exhibit altered transcriptional reprogramming. In particular, mitogen-activated protein kinase (MAPK)-dependent flg22-induced gene expression is elevated, while calcium-dependent protein kinase (CDPK)-dependent flg22-induced gene expression is reduced. These results demonstrate that the fine regulation of Ca2+ fluxes across the plasma membrane is critical for the coordination of the downstream MAMP responses and suggest a mechanistic link between the FLS2 receptor complex and signalling kinases via the secondary messenger Ca2+. ACA8 also interacts with other RKs such as BRI1 and CLV1 known to regulate plant development, and both aca8 and aca10 mutants show morphological phenotypes, suggesting additional roles for ACA8 and ACA10 in developmental processes. Thus, Ca2+ ATPases appear to represent general regulatory components of RK-mediated signalling pathways.

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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

Phytopathogenic bacteria of the Xanthomonas genus cause severe diseases on hundreds host plants, including economically important crops, such as rice, wheat, cassava, banana, mango, tomato, citrus, cabbage, pepper, bean and cotton. Diseases occurring in nature comprise black rot, leaf/fruit spot, canker, wilt, leaf blight and streak. These bacteria are present worldwide where some phytopathogenic strains are emergent or re-emergent and, consequently, dramatically impact agriculture, economy and food safety.

Xanthomonas bacteria provide excellent models for genomic studies and hundreds of Xanthomonas genome sequences have been obtained since 2002 and many other are underway (www.xanthomonas.org/genomes.html). Comparative genomics between and/or within bacterial species and/or pathovars will be of a great help to decipher commonalities and particularities that underly host range definition.

Most of the Xanthomonas possesses a type III secretion system (T3SS) that is required for injection of various effectors inside plant cells, thus contributing to pathogenicity. Transcription Activator-Like (tal) genes, encode bacterial transcription factors which are injected through the T3SS by many Xanthomonas to promote pathogenicity. Some Ralstonia, Bulkholderia and marine bacteria also express TAL-like proteins which function and mode of action is starting to be deciphered. TALs are addressed to the plant nucleus where they activate plant gene expression by direct binding to the corresponding promoter sequences. Targeted genes essentially act as susceptibility genes. A few years after the cracking of the code allowing the TAL/Host promoter sequence recognition, combined to the ever-growing availability of plant genomes, many efforts have been done to identify TAL targets. These data collected for many Xanthomonas/host pathosystems will assuredly help breeders to breed resistance resistant in important crops.

In this Research Topic we aim to collect manuscripts covering the current knowledge of Xanthomonas genomics and effectomics. Specifically, we encourage the submission of manuscripts (Original Research, Hypothesis & Theory, Methods, Reviews, Mini Reviews, Perspective and Opinion) covering the following topics:
1. Manuscripts reporting genome sequencing of Xanthomonas strains.
2. Manuscripts describing functional and comparative genomics in Xanthomonas species/pathovars.
3. Manuscripts describing functional studies on Xanthomonas type III effectors.
3. Manuscripts describing discovery, evolution, bio-informatics and functional genomics of TAL effectors and their targets in plant genomes.
4. Manuscripts describing applications of TAL effector research for resistance breeding in crops.

We anticipate that this Research Topic will be of importance for plant pathologists and breeders.

 

Nicolas Denancé
Guest Associate Editor, Plant-Microbe Interaction
www.frontiersin.org

Nicolas Denancé's insight:

Published articles:

 

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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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.
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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  )


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Nature Comms: Two linked pairs of Arabidopsis TNL resistance genes independently confer recognition of bacterial effector ​AvrRps4 (2015)

Nature Comms: Two linked pairs of Arabidopsis TNL resistance genes independently confer recognition of bacterial effector ​AvrRps4 (2015) | Effectors and Plant Immunity | Scoop.it

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The Sainsbury Lab's curator insight, March 6, 3:09 PM

Plant immunity requires recognition of pathogen effectors by intracellular NB-LRR immune receptors encoded by Resistance (R) genes. Most R proteins recognize a specific effector, but some function in pairs that recognize multiple effectors. Arabidopsis thaliana TIR-NB-LRR proteins RRS1-R and RPS4together recognize two bacterial effectors, AvrRps4 from Pseudomonas syringae and PopP2 from Ralstonia solanacearum. However, AvrRps4, but not PopP2, is recognized in rrs1/rps4 mutants. We reveal an R gene pair that resembles and is linked to RRS1/RPS4, designated as RRS1B/RPS4B, which confers recognition of AvrRps4 but not PopP2. Like RRS1/RPS4, RRS1B/RPS4B proteins associate and activate defence genes upon AvrRps4 recognition. Inappropriate combinations (RRS1/RPS4B or RRS1B/RPS4) are non-functional and this specificity is not TIR domain dependent. Distinct putative orthologues of both pairs are maintained in the genomes of Arabidopsis thalianarelatives and are likely derived from a common ancestor pair. Our results provide novel insights into paired R gene function and evolution.

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Plant Science Summer School - University of Angers, Fr.

Plant Science Summer School - University of Angers, Fr. | Effectors and Plant Immunity | Scoop.it

You will find the summer programs of the University of Angers in the field of health sciences and plant science, which will be held from June 29th to July 10th 2015. Our summer schools offer an unique opportunity for students from all over the world to enjoy Science in a beautiful environment. Each program entirely conducted in English includes conferences by international researchers, hands-on activities, visits of research facilities and biotech companies and an attractive social program. Come and meet in Angers international students who share your passion for Science!

 

Plenary conference by Prof. Gareth Williams, renowned professor.

Session 1 : Plant defense stimulation, plant protection and plant memory

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 : Physiology and Nutritional Quality of seeds             

Session 7: Fruit production, Fruit development and self-thinning

Session 8: Post-harvest fruit quality management

 

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MBPP2015 | 2015 Molecular Biology of Plant Pathogens Conference at the University of the West of England, Bristol on 8-9 April 2015

MBPP2015 | 2015 Molecular Biology of Plant Pathogens Conference at the University of the West of England, Bristol on 8-9 April 2015 | Effectors and Plant Immunity | Scoop.it

The 2015 Molecular Biology of Plant Pathogens (MBPP) conference will be held at the University of the West of England (UWE), Bristol on the 8th-9th April 2015. This will be the 23rd MBPP conference!

 

UWE is the largest university in the South West of England with over 30,000 students and approximately 3,500 staff. UWE has a long and interesting history starting life as a Merchant Venturer’s Navigation College in 1595 and undergoing many changes before gaining University status in 1992. Today UWE attracts students from all over the UK as well as a significant number of international students from 140 countries worldwide.

 

UWE has an active research community which makes a significant contribution to advances in industry, commerce, health and technology both nationally and internationally. The organisers of this years’ MBPP conference, Professor Dawn Arnold, Dr Carrie Brady and Dr Helen Neale work within the Centre for Research in Bioscience (CRIB) which leads world-class research in areas of strategic importance including plant science, agri-food, bio-sensing and biomedicine.

 

MBPP provides an excellent forum for networking between junior and senior scientists. The primary focus is on providing PhD students and post-doctoral scientists the opportunity to give oral presentations in front of a wide range of national and international researchers.

 

There will also be three keynote talks by internationally renowned scientists Professor Pietro Spanu (Imperial College), Dr Chris Ridout (John Innes Centre) and Professor Teresa Coutinho (Forestry and Agricultural Biotechnology Institute, University of Pretoria, South Africa). Please see our biographies tab for more information on these speakers.


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Front. Microbiol.: Agroforestry leads to shifts within the gammaproteobacterial microbiome of banana plants cultivated in Central America (2015)

Front. Microbiol.: Agroforestry leads to shifts within the gammaproteobacterial microbiome of banana plants cultivated in Central America (2015) | Effectors and Plant Immunity | Scoop.it

Bananas (Musa spp.) belong to the most important global food commodities, and their cultivation represents the world's largest monoculture. Although the plant-associated microbiome has substantial influence on plant growth and health, there is a lack of knowledge of the banana microbiome and its influencing factors. We studied the impact of (i) biogeography, and (ii) agroforestry on the banana-associated gammaproteobacterial microbiome analyzing plants grown in smallholder farms in Nicaragua and Costa Rica. Profiles of 16S rRNA genes revealed high abundances of Pseudomonadales, Enterobacteriales, Xanthomonadales, and Legionellales. An extraordinary high diversity of the gammaproteobacterial microbiota was observed within the endophytic microenvironments (endorhiza and pseudostem), which was similar in both countries. Enterobacteria were identified as dominant group of above-ground plant parts (pseudostem and leaves). Neither biogeography nor agroforestry showed a statistically significant impact on the gammaproteobacterial banana microbiome in general. However, indicator species for each microenvironment and country, as well as for plants grown in Coffea intercropping systems with and without agri-silvicultural production of different Fabaceae trees (Inga spp. in Nicaragua and Erythrina poeppigiana in Costa Rica) could be identified. For example, banana plants grown in agroforestry systems were characterized by an increase of potential plant-beneficial bacteria, like Pseudomonas and Stenotrophomonas, and on the other side by a decrease of Erwinia. Hence, this study could show that as a result of legume-based agroforestry the indigenous banana-associated gammaproteobacterial community noticeably shifted.

 

Martina Köberl, Miguel Dita, Alfonso Martinuz, Charles Staver, and Gabriele Berg

 

 

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Colloque SFP, 2-5 Juin 2015 - Colmar, Fr

Colloque SFP, 2-5 Juin 2015 - Colmar, Fr | Effectors and Plant Immunity | Scoop.it

En agriculture, les agents phytopathogènes (champignons, virus, bactéries) sont responsables de pertes considérables de rendements et de qualité. Ces pathologies combinées avec la croissance démographique mondiale et les changements climatiques constituent un risque majeur pour la sécurité alimentaire.  Pour mettre en place des actions appropriées il est indispensable de détecter, d'identifier  et de mieux connaitre ces organismes. Après le congres de Paris en 2012, la SFP continue son compagnonnage et, cette année, le colloque se tiendra en Alsace à Colmar du 2 au 5 juin 2015 au CREF (centre de rencontres, d'échanges et de formation) au 5 Rue des jardins.

Ce colloque, est ouvert aux phytopathologistes français et étrangers. C'est une opportunité d’aborder tous les domaines de la santé des végétaux et de faciliter le dialogue entre chercheurs à thématiques différentes. Pour présenter vos travaux, vous informer des recherches récentes dans ce domaine en France et au-delà, faire des rencontres et des échanges entre collègues, venez au 9éme colloque de la SFP, qui propose un programme passionnant, tant scientifique que touristique. C'est aussi l'occasion de découvrir la gastronomie alsacienne et les richesses touristiques de Colmar.

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Summer School "PLANT MICROBE INTERACTIONS" @ The Sainsbury Laboratory, 17-28 August 2015, Norwich, UK

Summer School "PLANT MICROBE INTERACTIONS" @ The Sainsbury Laboratory, 17-28 August 2015, Norwich, UK | Effectors and Plant Immunity | Scoop.it
The last 20 years have provided a sophisticated understanding of how plants recognise relatively conserved microbial patterns to activate defence. In recent years DNA sequencing allowed genomes and transcriptomes of eukaryotic rusts and mildew pathogens to be studied and high-throughput imaging permit the study and visualisation of intracellular interactions during pathogenesis and defence.

 

We will present many aspects of plant- microbe interactions including:

- gene discovery
- genome analysis
- intra-cellular interactions with high-throughput imaging technology
- mechanistic understanding of cellular and molecular processes to translational activities

 

The focus on the dynamic and interactive practical sessions will naturally promote strong interactions between lecturers and participants.


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Bharat Employment's curator insight, February 25, 1:58 AM

http://www.bharatemployment.com

Jean-Michel Ané's curator insight, February 25, 11:53 AM

That seems an awesome Summer School.

BTW... I want the same chair as Dan MacLean :-)

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A TALE of Transposition: Tn3-Like Transposons Play a Major Role in the Spread of Pathogenicity Determinants of Xanthomonas citri and Other Xanthomonads - mBio

A TALE of Transposition: Tn3-Like Transposons Play a Major Role in the Spread of Pathogenicity Determinants of Xanthomonas citri and Other Xanthomonads - mBio | Effectors and Plant Immunity | Scoop.it

(via T. Lahaye, thx)

Marini Ferreira et al, 2015

Members of the genus Xanthomonas are among the most important phytopathogens. A key feature of Xanthomonas pathogenesis is the translocation of type III secretion system (T3SS) effector proteins (T3SEs) into the plant target cells via a T3SS. Several T3SEs and a murein lytic transglycosylase gene (mlt, required for citrus canker symptoms) are found associated with three transposition-related genes in Xanthomonas citri plasmid pXAC64. These are flanked by short inverted repeats (IRs). The region was identified as a transposon, TnXax1, with typical Tn3 family features, including a transposase and two recombination genes. Two 14-bp palindromic sequences within a 193-bp potential resolution site occur between the recombination genes. Additional derivatives carrying different T3SEs and other passenger genes occur in different Xanthomonas species. The T3SEs include transcription activator-like effectors (TALEs). Certain TALEs are flanked by the same IRs as found in TnXax1 to form mobile insertion cassettes (MICs), suggesting that they may be transmitted horizontally. A significant number of MICs carrying other passenger genes (including a number of TALE genes) were also identified, flanked by the same TnXax1 IRs and delimited by 5-bp target site duplications. We conclude that a large fraction of T3SEs, including individual TALEs and potential pathogenicity determinants, have spread by transposition and that TnXax1, which exhibits all of the essential characteristics of a functional transposon, may be involved in driving MIC transposition. We also propose that TALE genes may diversify by fork slippage during the replicative Tn3 family transposition. These mechanisms may play a crucial role in the emergence of Xanthomonas pathogenicity.


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MPMI: The Plant Microbiome at Work (20015)

MPMI: The Plant Microbiome at Work (20015) | Effectors and Plant Immunity | Scoop.it

Plants host distinct microbial communities on and inside their tissues designated the plant microbiota. Microbial community profiling enabled the description of the phylogenetic structure of the plant microbiota to an unprecedented depth, whereas functional insights are largely derived from experiments using individual microorganisms. The binary interplay between isolated members of the plant microbiota and host plants ranges from mutualistic to commensalistic and pathogenic relationships. However, how entire microbial communities capable of executing both growth-promoting and growth-compromising activities interfere with plant fitness remains largely unknown. Ultimately, unravelling the net result of microbial activities encoded in the extended plant genome—the plant microbiome—will be key to understanding and exploiting the full yield potential of a crop plant. In this perspective, we summarize first achievements of plant-microbiome research, we discuss future research directions, and we provide ideas for the translation of basic science to application to capitalize on the plant microbiome at work.

 

KlausSchlaeppi and DavideBulgarelli

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Draft Genome Sequences of Two Xanthomonas euvesicatoria Strains from the Balkan Peninsula - Genome announcements

Vanceva et al, 2015

We report the draft genome sequences of two Xanthomonas euvesicatoria strains from the Balkan Peninsula, which were isolated from symptomatic pepper plants. The availability of these genome sequences will facilitate the development of modern genotyping assays for X. euvesicatoria strains and to define targets for resistance breeding.

Comparison with the completely sequenced strain 85-10, which was isolated in Florida in 1985, revealed some unique effectors that are present or absent in one or the other strain (e.g., AvrBs1, AvrBs3, XopE3, XopG, XopH, XopAF, and XopAQ).


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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.


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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. Microbiol.: rpoN1, but not rpoN2, is required for twitching motility, natural competence, growth on nitrate and virulence of Ralstonia solanacearum (2015)

Front. Microbiol.: rpoN1, but not rpoN2, is required for twitching motility, natural competence, growth on nitrate and virulence of Ralstonia solanacearum (2015) | Effectors and Plant Immunity | Scoop.it
The plant pathogen Ralstonia solanacearum has two genes encoding for the sigma factor 54: rpoN1, located in the chromosome and rpoN2, located in a distinct ‘megaplasmid’ replicon. In this study, individual mutants as well as a double mutant of rpoN were created in R. solanacearum strain GMI1000 in order to determine the extent of functional overlap between these two genes. By virulence assay we observed that rpoN1 is required for virulence whereas rpoN2 is not. In addition rpoN1 controls other important functions such twitching motility, natural transformation and growth on nitrate, unlike rpoN2. The rpoN1 and rpoN2 genes have different expression pattern, the expression of rpoN1 being constitutive whereas rpoN2 expression is induced in minimal medium and in the presence of plant cells. Moreover, the expression of rpoN2 is dependent upon rpoN1. Our work therefore reveals that the two rpoN genes are not functionally redundant in R.solanacearum. A list of potential sigma 54 targets was identified in the R. solanacearum genome and suggests that multiple traits are under the control of these regulators. Based on these findings, we provide a model describing the functional connection between RpoN1and the PehR pathogenicity regulator and their dual role in the control of several R. solanacearum virulence determinants.

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Trends Plant Sci.: Rhizobium–legume symbioses: the crucial role of plant immunity (2015)

Trends Plant Sci.: Rhizobium–legume symbioses: the crucial role of plant immunity (2015) | Effectors and Plant Immunity | Scoop.it

New research results have significantly revised our understanding of the rhizobium–legume infection process. For example, Nod factors (NFs), previously thought to be absolutely essential for this symbiosis, were shown to be dispensable under particular conditions. Similarly, an NF receptor, previously considered to be solely involved in symbiosis, was shown to function during plant pathogen infections. Indeed, there is a growing realization that plant innate immunity is a crucial component in the establishment and maintenance of symbiosis. We review here the factors involved in the suppression of plant immunity during rhizobium–legume symbiosis, and we attempt to place this information into context with the most recent and sometimes surprising research results.

 

Benjamin Gourion, Fathi Berrabah, Pascal Ratet, Gary Stacey

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Nature Immunology: A lectin S-domain receptor kinase mediates lipopolysaccharide sensing in Arabidopsis thaliana

Nature Immunology: A lectin S-domain receptor kinase mediates lipopolysaccharide sensing in Arabidopsis thaliana | Effectors and Plant Immunity | Scoop.it

The sensing of microbe-associated molecular patterns (MAMPs) triggers innate immunity in animals and plants. Lipopolysaccharide (LPS) from Gram-negative bacteria is a potent MAMP for mammals, with the lipid A moiety activating proinflammatory responses via Toll-like receptor 4 (TLR4). Here we found that the plant Arabidopsis thaliana specifically sensed LPS of Pseudomonas and Xanthomonas. We isolated LPS-insensitive mutants defective in the bulb-type lectin S-domain-1 receptor–like kinase LORE (SD1-29), which were hypersusceptible to infection with Pseudomonas syringae. Targeted chemical degradation of LPS from Pseudomonas species suggested that LORE detected mainly the lipid A moiety of LPS. LORE conferred sensitivity to LPS onto tobacco after transient expression, which demonstrated a key function in LPS sensing and indicated the possibility of engineering resistance to bacteria in crop species.


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J. Exp. Bot.: Greasy tactics in the plant–pathogen molecular arms race (2015)

J. Exp. Bot.: Greasy tactics in the plant–pathogen molecular arms race (2015) | Effectors and Plant Immunity | Scoop.it

The modification of proteins by the attachment of fatty acids is a targeting tactic involved in mechanisms of both plant immunity and bacterial pathogenesis. The plant plasma membrane (PM) is a key battleground in the war against disease-causing microbes. This membrane is armed with an array of sensor proteins that function as a surveillance system to detect invading pathogens. Several of these sensor proteins are directed to the plasma membrane through the covalent addition of fatty acids, a process termed fatty acylation. Phytopathogens secrete effector proteins into the plant cell to subvert these surveillance mechanisms, rendering the host susceptible to infection. The targeting of effectors to specific locales within plant cells, particularly the internal face of the host PM, is critical for their virulence function. Several bacterial effectors hijack the host fatty acylation machinery to be modified and directed to this contested locale. To find and fight these fatty acylated effectors the plant leverages lipid-modified intracellular sensors. This review provides examples featuring how fatty acylation is a battle tactic used by both combatants in the molecular arms race between plants and pathogens. Also highlighted is the exploitation of a specific form of host-mediated fatty acid modification, which appears to be exclusively employed by phytopathogenic effector proteins.

 

 

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Plants and Pathogens teaching tool updated and revised

Plants and Pathogens teaching tool updated and revised | Effectors and Plant Immunity | Scoop.it

We've updated and revised TTPB22, "Plants and Pathogens". http://www.plantcell.org/site/teachingtools/TTPB22.xhtml
Lots and lots of new references, a few new case studies and some new slides too. What a fascinating and wonderful topic to have a chance to revisit!


Via Mary Williams
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FEMS Microbiol. Rev.: The battle for chitin recognition in plant-microbe interactions (2015)

FEMS Microbiol. Rev.: The battle for chitin recognition in plant-microbe interactions (2015) | Effectors and Plant Immunity | Scoop.it

Fungal cell walls play dynamic functions in interaction of fungi with their surroundings. In pathogenic fungi, the cell wall is the first structure to make physical contact with host cells. An important structural component of fungal cell walls is chitin, a well-known elicitor of immune responses in plants. Research into chitin perception has sparked since the chitin receptor from rice was cloned nearly a decade ago. Considering the widespread nature of chitin perception in plants, pathogens evidently evolved strategies to overcome detection, including alterations in the composition of cell walls, modification of their carbohydrate chains and secretion of effectors to provide cell wall protection or target host immune responses. Also non-pathogenic fungi contain chitin in their cell walls and are recipients of immune responses. Intriguingly, various mutualists employ chitin-derived signaling molecules to prepare their hosts for the mutualistic relationship. Research on the various types of interactions has revealed different molecular components that play crucial roles and, moreover, that various chitin-binding proteins contain dissimilar chitin-binding domains across species that differ in affinity and specificity. Considering the various strategies from microbes and hosts focused on chitin recognition, it is evident that this carbohydrate plays a central role in plant–fungus interactions.

 

Andrea Sánchez-Vallet , Jeroen R. Mesters , Bart P.H.J. Thomma

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Annu. Rev. PLant Biol.: Effector-Triggered Immunity: From Pathogen Perception to Robust Defense (2015)

Annu. Rev. PLant Biol.: Effector-Triggered Immunity: From Pathogen Perception to Robust Defense (2015) | Effectors and Plant Immunity | Scoop.it

In plant innate immunity, individual cells have the capacity to sense and respond to pathogen attack. Intracellular recognition mechanisms have evolved to intercept perturbations by pathogen virulence factors (effectors) early in host infection and convert it to rapid defense. One key to resistance success is a polymorphic family of intracellular nucleotide-binding/leucine-richrepeat (NLR) receptors that detect effector interference in different parts of the cell. Effector-activated NLRs connect, in various ways, to a conserved basal resistance network in order to transcriptionally boost defense programs. Effector-triggered immunity displays remarkable robustness against pathogen disturbance, in part by employing compensatory mechanisms within the defense network. Also, the mobility of some NLRs and coordination of resistance pathways across cell compartments provides flexibility to fine-tune immune outputs. Furthermore, a number of NLRs function close to the nuclear chromatin by balancing actions of defense-repressing and defense-activating transcription factors to program cells dynamically for effective disease resistance.

 

Haitao Cui, Kenichi Tsuda, Jane E. Parker
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5th Xanthomonas Genomics Conference, July 8 - 11, 2015, Bogotá, Colombia

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

Via Kamoun Lab @ TSL
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Trends Plant Sci.: Phytopathogen emergence in the genomics era (2015)

Trends Plant Sci.: Phytopathogen emergence in the genomics era (2015) | Effectors and Plant Immunity | Scoop.it

Phytopathogens are a global threat to plant agriculture and biodiversity. The genomics era has lead to an exponential rise in comparative gene and genome studies of both economically significant and insignificant microorganisms. In this review we highlight some recent comparisons and discuss how they identify shared genes or genomic regions associated with host virulence. The two major mechanisms of rapid genome adaptation – horizontal gene transfer and hybridisation – are reviewed and we consider how intra-specific pan-genome sequences encode alternative host specificity. We also discuss the power that access to expansive gene databases provides in aiding the study of phytopathogen emergence. These databases can rapidly enable the identification of an unknown pathogen and its origin, as well as genomic adaptations required for emergence.

 

 Elisha Thynne, Megan C. McDonald, Peter S. Solomon

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Transcriptional networks in plant immunity - Tsuda - 2015 - New Phytologist - Wiley Online Library

Transcriptional networks in plant immunity - Tsuda - 2015 - New Phytologist - Wiley Online Library | Effectors and Plant Immunity | Scoop.it
Next to numerous abiotic stresses, plants are constantly exposed to a variety of pathogens within their environment. Thus, their ability to survive and prosper during the course of evolution was strongly dependent on adapting efficient strategies to perceive and to respond to such potential threats. It is therefore not surprising that modern plants have a highly sophisticated immune repertoire consisting of diverse signal perception and intracellular signaling pathways. This signaling network is intricate and deeply interconnected, probably reflecting the diverse lifestyles and infection strategies used by the multitude of invading phytopathogens. Moreover it allows signal communication between developmental and defense programs thereby ensuring that plant growth and fitness are not significantly retarded. How plants integrate and prioritize the incoming signals and how this information is transduced to enable appropriate immune responses is currently a major research area. An important finding has been that pathogen-triggered cellular responses involve massive transcriptional reprogramming within the host. Additional key observations emerging from such studies are that transcription factors (TFs) are often sites of signal convergence and that signal-regulated TFs act in concert with other context-specific TFs and transcriptional co-regulators to establish sensory transcription regulatory networks required for plant immunity.

Via Suayib Üstün, Jim Alfano
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