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


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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

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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.

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New Phytologist: Meetings - A snapshot of molecular plant–microbe interaction research (2014)

New Phytologist: Meetings - A snapshot of molecular plant–microbe interaction research (2014) | Effectors and Plant Immunity | Scoop.it

Plants and microbes are in a continuous arms race to maintain their predominance within their particular niche. Understanding the complexity of these plant–microbe interactions is of utmost importance as it can provide new insights into the mechanisms mediating disease processes and in turn inspire new plant breeding strategies. The International Society for Molecular Plant–Microbe Interactions (IS-MPMI) invited scientists from around the world to share their findings during the XVI International Congress on Molecular Plant–Microbe Interactions, which was held on the beautiful island of Rhodes in Greece. The congress was organized by the Agricultural University of Athens, the Hellenic Phytopathology Society, and the Hellenic Society of Phytiatry and provided over 1100 participants from 55 countries with the opportunity to present and discuss their current and future research. A great number of talks and posters were presented, however our aim within this report is to provide a snapshot of the discipline by focusing on just some of the exciting research and discussions which took place. The key topics discussed were virulence factors, epigenetic regulation, hormones, symbiosis factors, toxins, signaling pathways, microbe recognition, immunity, and pathogen diagnostics. Effector biology was also a recurrent theme in many plenary and concurrent sessions, indicating the importance of a topic that was also highlighted recently by a Virtual Special Issue in New Phytologist (see Kuhn & Panstruga, 2014). In addition to this, throughout the meeting next generation sequencing (NGS) techniques were described and shown to be shedding new light on long-standing issues in microbial ecology.


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Bibhya Sharma's curator insight, January 22, 2:53 AM

Interesting read.

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Regulatory uncertainty over genome editing - Nature Plants

Regulatory uncertainty over genome editing - Nature Plants | Effectors and Plant Immunity | Scoop.it

Jones 2015

Genome editing opens up opportunities for the precise and rapid alteration of crops to boost yields, protect against pests and diseases and enhance nutrient content. The extent to which applied plant research and crop breeding benefit will depend on how the EU decides to regulate this fledgling technology.

 


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Video: Fifi The Oomycete (2014)

Happy holidays from the @KamounLab!

 

FiFi (Phytophthora) The Oomycete


(adapted from Frosty The Snowman)

 

Fifi the oomycete is a scary parasite,
With flagellated spores and hyphal threads
She kills crops and triggers blight.

 

Fifi the oomycete is a heterokont, they say,
She’s fungus-like but the scientists
Know how she had plastids one day.

 

There must have been some magic in those
Transposons they found.
For when they mapped ‘em on the genome
They began to jump around.

 

Fifi the oomycete has a big genome, they say,
Full of repeats but don’t call it junk
‘cause can be handy one day.

 

O, Fifi the oomycete
Was as virulent as she’s been;
and scientists say she secretes her way
Inside potatoes and bean.

 

Fifi the oomycete found
A resistant plant that day,
So she said, "Let's run and
There’ll be no fun
Until I mutate away."

 

There must have been some magic in those
Transposons they found.
For when they mapped ‘em on the genome
They began to jump around.

 

For Fifi the oomycete
Keeps evolving in her way,
But don’t wave her goodbye,
Don't you even try,
She’ll be back again some day.

 


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Mary Williams's curator insight, December 10, 2014 12:46 PM

She's adorable (or maybe not...). Nice song though!

Easwaramurthy Rgr's curator insight, December 19, 2014 2:37 PM

Happy holidays from the @KamounLab!

 

FiFi (Phytophthora) The Oomycete


(adapted from Frosty The Snowman),scopped by Jean Michel

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36th New Phytologist Symposium: Cell biology at the plant–microbe interface, Munich, Germany 29 Nov – 1 Dec 2015

36th New Phytologist Symposium: Cell biology at the plant–microbe interface, Munich, Germany 29 Nov – 1 Dec 2015 | Effectors and Plant Immunity | Scoop.it

Symposium aim - We aim to organize a cutting edge meeting focused on the application of cell biology approaches to understand the mechanisms that diverse microbes use to manipulate plant cells to benefit their life styles. The meeting will bring together researchers working on a broad spectrum of microbes across different taxa (bacteria, fungi, oomycetes) that form a variety of different interactions (pathogenic, symbiotic) with plant organs/tissues (leaves, roots). With the explosion in microbial/host genome sequences and the identification of genes/proteins involved in these interactions, the focus of the field is moving rapidly towards using cell and molecular biology techniques and new imaging technologies to understand the molecular dialogue between plants and their microbial pathogens/symbionts. The need for a conference on this topic, the first of its type, is evidenced by the growing prominence of cell biology in the literature. Students and scientists in this field face many challenges in the application and interpretation of cell biology data and would greatly benefit from a specialized conference on this topic. The symposium will bring together a broad representation of researchers focussing on different cell biology aspects and will allow researchers across the different disciplines to present and exchange their recent advances in this important topic of plant biology.

Symposium rationale and scope - Plant organs are subject to colonisation and manipulation by microbes, and this requires reprogramming of host cell biology to accommodate microbial structures within tissues/cells and to mediate responses for proper immunity or for symbiosis. Host cell biology changes during microbial invasion were first reported more than 100 years ago based on microscopy studies revealing that many microbes project structures (haustoria, arbuscules) into plant cells that are enveloped with a specialized plant-­derived membrane and evidence now suggests an intimate molecular exchange takes place across these membrane interfaces. However, recent identification of some of the molecular players in these interactions is only now providing appropriate tools to analyse these events. The symposium will focus on advances in understanding the molecular interactions that occur between a microbe and its host at a cellular and subcellular level, such as:

how root and leaf cells accommodate microbial structures through biogenesis of specialized plant derived membranes, microbial invasion and spreading strategies (via stomata, roots, vasculature, plasmodesmata), the dynamic localization of cell surface and cytosolic receptors recognizing microbial signals the reprogramming of host membrane trafficking (focal accumulation, secretion), the delivery of microbial molecules from fungal and oomycete species into plant cells.

With recent advances in high resolution/throughput bioimaging we are gaining new insights into the cell biology mechanisms and pathways of plant cell interactions with diverse microbes. Therefore the symposium provides a timely and important opportunity to overview the application of these technologies to plant–microbe interactions, and to discuss recent discoveries emerging from diverse host–microbe interactions illustrating common underlying principles and differences of strategies used by the microbes to gain access to plant tissues/cells. The symposium will certainly trigger a wealth of discussions, exchange of findings and methodologies, and will promote new lines of research and ideas in this rapidly expanding field.


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Front. Plant Sci. : Interactions of Xanthomonas type-III effector proteins with the plant ubiquitin and ubiquitin-like pathways (2014)

Front. Plant Sci. : Interactions of Xanthomonas type-III effector proteins with the plant ubiquitin and ubiquitin-like pathways (2014) | Effectors and Plant Immunity | Scoop.it

In eukaryotes, regulated protein turnover is required during many cellular processes, including defense against pathogens. Ubiquitination and degradation of ubiquitinated proteins via the ubiquitin – proteasome system (UPS) is the main pathway for the turnover of intracellular proteins in eukaryotes. The extensive utilization of the UPS in host cells makes it an ideal pivot for the manipulation of cellular processes by pathogens. Like many other Gram-negative bacteria, Xanthomonas species secrete a suite of type-III effector proteins (T3Es) into their host cells to promote virulence. Some of these T3Es exploit the plant UPS to interfere with immunity. This review summarizes T3E examples from the genus Xanthomonas with a proven or suggested interaction with the host UPS or UPS-like systems and also discusses the apparent paradox that arises from the presence of T3Es that inhibit the UPS in general while others rely on its activity for their function.

 

S. Üstün and F. Börnke

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Mini-review published in the Research topic on Genomics and Effectomics of the crop killer Xanthomonas.

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EMBO: GRIM REAPER peptide binds to receptor kinase PRK5 to trigger cell death in Arabidopsis

EMBO: GRIM REAPER peptide binds to receptor kinase PRK5 to trigger cell death in Arabidopsis | Effectors and Plant Immunity | Scoop.it
Recognition of extracellular peptides by plasma membrane‐localized receptor proteins is commonly used in signal transduction. In plants, very little is known about how extracellular peptides are processed and activated in order to allow recognition by receptors. Here, we show that induction of cell death in planta by a secreted plant protein GRIM REAPER (GRI) is dependent on the activity of the type II metacaspase METACASPASE‐9. GRI is cleaved by METACASPASE‐9 in vitro resulting in the release of an 11 amino acid peptide. This peptide bound in vivo to the extracellular domain of the plasma membrane‐localized, atypical leucine‐rich repeat receptor‐like kinase POLLEN‐SPECIFIC RECEPTOR‐LIKE KINASE 5 (PRK5) and was sufficient to induce oxidative stress/ROS‐dependent cell death. This shows a signaling pathway in plants from processing and activation of an extracellular protein to recognition by its receptor.

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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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PLos Patho.: The Phylogenetically-Pattern Recognition Receptors EFR and XA21 Recruit Similar Immune Signaling Components in Monocots and Dicots (2015)

PLos Patho.: The Phylogenetically-Pattern Recognition Receptors EFR and XA21 Recruit Similar Immune Signaling Components in Monocots and Dicots (2015) | Effectors and Plant Immunity | Scoop.it

During plant immunity, surface-localized pattern recognition receptors (PRRs) recognize pathogen-associated molecular patterns (PAMPs). The transfer of PRRs between plant species is a promising strategy for engineering broad-spectrum disease resistance. Thus, there is a great interest in understanding the mechanisms of PRR-mediated resistance across different plant species. Two well-characterized plant PRRs are the leucine-rich repeat receptor kinases (LRR-RKs) EFR and XA21 from Arabidopsis thaliana (Arabidopsis) and rice, respectively. Interestingly, despite being evolutionary distant, EFR and XA21 are phylogenetically closely related and are both members of the sub-family XII of LRR-RKs that contains numerous potential PRRs. Here, we compared the ability of these related PRRs to engage immune signaling across the monocots-dicots taxonomic divide. Using chimera between Arabidopsis EFR and rice XA21, we show that the kinase domain of the rice XA21 is functional in triggering elf18-induced signaling and quantitative immunity to the bacteria Pseudomonas syringae pv. tomato (Pto) DC3000 and Agrobacterium tumefaciens in Arabidopsis. Furthermore, the EFR:XA21 chimera associates dynamically in a ligand-dependent manner with known components of the EFR complex. Conversely, EFR associates with Arabidopsis orthologues of rice XA21-interacting proteins, which appear to be involved in EFR-mediated signaling and immunity in Arabidopsis. Our work indicates the overall functional conservation of immune components acting downstream of distinct LRR-RK-type PRRs between monocots and dicots.

 

Nicholas Holton, Vladimir Nekrasov, Pamela C. Ronald, Cyril Zipfel

 

 

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News: Xylella Disease 'major threat' to EU olives (2015)

News: Xylella Disease 'major threat' to EU olives (2015) | Effectors and Plant Immunity | Scoop.it

A virulent pathogen that starves olive trees poses a serious threat to EU olive production, experts have warned.

 

"Major consequences", such as reduced yields and costly control measures, would be the outcome if it spreads to other olive producing regions.

 

It is already affecting a vast area in southern Italy and, as it has numerous hosts and vectors, the bacterium is expected to spread further.

 

The dire warning was made in a report by the European Food Safety Authority http://www.efsa.europa.eu/en/efsajournal/pub/3989.htm


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Insights into the origin and evolution of plant hormone signaling machinery

Insights into the origin and evolution of plant hormone signaling machinery | Effectors and Plant Immunity | Scoop.it

"Our multi-species genome-wide analysis reveals: i) AUX, CK and SL signaling pathways originated in charophyte lineages; ii) ABA, JA, and SA signaling pathways arose in the last common ancestor of land plants; iii) the GA signaling evolved after the divergence of bryophytes from land plants; iv) the canonical BR signaling originated before the emergence of angiosperms but likely after the split of gymnosperms and angiosperms; v) the origin of the canonical ETH signaling pathway postdates shortly the emergence of angiosperms. Our findings might have important implications in understanding the molecular mechanisms underlying the emergence of land plants"


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Mary Williams's curator insight, January 8, 5:36 AM

This is a pretty fabulous paper - I'm sure it'll find many uses, not the least being the one-page figure that summarizes all of the hormone signaling pathways. The figure shown here examines the presence or absence of signaling gene homologs in green algal species.

Jorge Lozano-Juste's curator insight, January 8, 7:15 PM

Nice!

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A multicolor panel of TALE-KRAB based transcriptional repressor vectors enabling knockdown of multiple gene targets - Sci. Reports

A multicolor panel of TALE-KRAB based transcriptional repressor vectors enabling knockdown of multiple gene targets - Sci. Reports | Effectors and Plant Immunity | Scoop.it

(via T. Schreiber, thx)

Zhang et al, 2014

Stable and efficient knockdown of multiple gene targets is highly desirable for dissection of molecular pathways. Because it allows sequence-specific DNA binding, transcription activator-like effector (TALE) offers a new genetic perturbation technique that allows for gene-specific repression. Here, we constructed a multicolor lentiviral TALE-Kruppel-associated box (KRAB) expression vector platform that enables knockdown of multiple gene targets. This platform is fully compatible with the Golden Gate TALEN and TAL Effector Kit 2.0, a widely used and efficient method for TALE assembly. We showed that this multicolor TALE-KRAB vector system when combined together with bone marrow transplantation could quickly knock down c-kit and PU.1 genes in hematopoietic stem and progenitor cells of recipient mice. Furthermore, our data demonstrated that this platform simultaneously knocked down both c-Kit and PU.1 genes in the same primary cell populations. Together, our results suggest that this multicolor TALE-KRAB vector platform is a promising and versatile tool for knockdown of multiple gene targets and could greatly facilitate dissection of molecular pathways.


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SRB's curator insight, December 12, 2014 4:27 PM

PMID: 25475013 

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New Phytologist: Medicago truncatula symbiosis mutants affected in the interaction with a biotrophic root pathogen (2014)

New Phytologist: Medicago truncatula symbiosis mutants affected in the interaction with a biotrophic root pathogen (2014) | Effectors and Plant Immunity | Scoop.it

Understanding how plants balance between enabling microbial symbionts and fending off pathogens has direct implications both for basic plant biology and optimal use of crop plants in agriculture. The degree to which the processes associated with these two types of interactions overlap is poorly known. Recent studies revealed that symbiotic and pathogenic filamentous microbes require common plant genetic elements to establish colonization (Wang et al., 2012; Rey et al., 2013), supporting the long-held view that plants have evolved the ability to accommodate microbes (Parniske, 2000) and that pathogens have exploited these pathways. However, the extent to which plant genes implicated in fungal or bacterial symbioses are involved in interactions with biotrophic pathogens is unknown and research has been hampered by the lack of suitable common host experimental systems.


In this study, we took advantage of a newly established quantitative Phytophthora palmivora–Medicago truncatula system to assess the extent to which mutants perturbed in colonization by arbuscular mycorrhiza fungi (AM fungi) and/or bacterial root nodule symbiosis are affected in the early/biotrophic stages of oomycete pathogenesis (Supporting Information Table S1). We devised and implemented a high throughput seedling infection assay and applied it to 19 M. truncatula lines mutated in 14 genes (for details see Methods S1; for explanation of gene abbreviations see Table S1). We measured both the overall root length and disease development, then plotted them as a ratio (Figs 1a,c, S1; Table S2). Of the 14 genes tested, seven (nine alleles) showed an altered response to P. palmivora inoculation compared with the wild-type Jemalong A17. Mutants in RAM2 and NIP/LATD showed enhanced resistance whereas mutants in five genes, NFP, LYK3, ERN, EFD, and LIN, all of which are impaired in the interaction with nitrogen fixing rhizobia displayed enhanced susceptibility. Expression levels of two defence response genes in M. truncatula mutants with altered disease symptoms were not overall significantly different from levels observed during infection of wild-type A17 seedlings (Fig. S2). This suggests that observed differences in disease extent are not attributable to altered defence responses in these mutants. These findings reveal a significant overlap between processes that define symbiosis and disease in M. truncatula roots. However, the remaining M. truncatula mutants unaltered in P. palmivora disease development include the common symbiotic signalling pathway (CSSP) mutants dmi1, dmi2 and dmi3, suggesting that the CSSP is not a major modulator of susceptibility to P. palmivora in M. truncatula.


Via Kamoun Lab @ TSL
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Rescooped by Nicolas Denancé from MycorWeb Plant-Microbe Interactions
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The inter-kingdom volatile signal indole promotes root development by interfering with auxin signalling

The inter-kingdom volatile signal indole promotes root development by interfering with auxin signalling | Effectors and Plant Immunity | Scoop.it
Recently, emission of volatile organic compounds (VOCs) has emerged as a mode of communication between bacteria and plants. Although some bacterial VOCs that promote plant growth have been identified, their underlying mechanism of action is unknown. Here we demonstrate that indole, which was identified using a screen for Arabidopsis growth promotion by VOCs from soil-borne bacteria, is a potent plant-growth modulator. Its prominent role in increasing the plant secondary root network is mediated by interfering with the auxin-signalling machinery. Using auxin reporter lines and classic auxin physiological and transport assays we show that the indole signal invades the plant body, reaches zones of auxin activity and acts in a polar auxin transport-dependent bimodal mechanism to trigger differential cellular auxin responses. Our results suggest that indole, beyond its importance as a bacterial signal molecule, can serve as a remote messenger to manipulate plant growth and development.

Via Francis Martin
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