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Current Opinion in Plant Biology: Fungal endophytes of grasses (2012)

Current Opinion in Plant Biology: Fungal endophytes of grasses (2012) | Plants and Microbes | Scoop.it

Epichloae endophytes form mutualistic symbiotic associations with temperate grasses and confer on the host a number of bioprotective benefits through production of fungal secondary metabolites and changed host metabolism. Maintenance of this mutualistic interaction requires that growth of the endophyte within the host is restricted. Recent work has shown that epichloae endophytes grow in the leaves by intercalary division and extension rather than tip growth. This novel pattern of growth enables the fungus to synchronise its growth with that of the host. Reactive oxygen species signalling is required to maintain this pattern of growth. Disruption of components of the NADPH oxidase complex or a MAP kinase, result in a switch from restricted to proliferative growth and a breakdown in the symbiosis. RNAseq analysis of mutant and wild-type associations identifies key fungal and plant genes that define the symbiotic state. Endophyte genes for secondary metabolite biosynthesis are only expressed in the plant and under conditions of restricted growth.

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Cell Host & Microbe: The Calcium-Dependent Protein Kinase CPK28 Buffers Plant Immunity and Regulates BIK1 Turnover (2014)

Cell Host & Microbe: The Calcium-Dependent Protein Kinase CPK28 Buffers Plant Immunity and Regulates BIK1 Turnover (2014) | Plants and Microbes | Scoop.it

• A forward-genetic screen identifies loci regulating Arabidopsis immune signaling
• MOB1/CPK28 negatively regulates immune signaling triggered by infection and PAMPs
• CPK28 interacts with and phosphorylates the central immune regulator BIK1
• CPK28 buffers immune responses and contributes to BIK1 turnover


Plant perception of pathogen-associated molecular patterns (PAMPs) triggers a phosphorylation relay leading to PAMP-triggered immunity (PTI). Despite increasing knowledge of PTI signaling, how immune homeostasis is maintained remains largely unknown. Here we describe a forward-genetic screen to identify loci involved in PTI and characterize the Arabidopsis calcium-dependent protein kinase CPK28 as a negative regulator of immune signaling. Genetic analyses demonstrate that CPK28 attenuates PAMP-triggered immune responses and antibacterial immunity. CPK28 interacts with and phosphorylates the plasma-membrane-associated cytoplasmic kinase BIK1, an important convergent substrate of multiple pattern recognition receptor (PRR) complexes. We find that BIK1 is rate limiting in PTI signaling and that it is continuously turned over to maintain cellular homeostasis. We further show that CPK28 contributes to BIK1 turnover. Our results suggest a negative regulatory mechanism that continually buffers immune signaling by controlling the turnover of this key signaling kinase.

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Cell: Species-wide Genetic Incompatibility Analysis Identifies Immune Genes as Hot Spots of Deleterious Epistasis (2014)

Cell: Species-wide Genetic Incompatibility Analysis Identifies Immune Genes as Hot Spots of Deleterious Epistasis (2014) | Plants and Microbes | Scoop.it

• A species-wide genetic analysis identifies incompatibility hot spots in the genome


• Antagonistic epistasis involving plant NLR immune receptors is a common cause


• Polymorphic NLR tandem arrays can generate multiple incompatibility alleles


• Deleterious epistasis limits the accessible space of immune receptor combinations


Intraspecific genetic incompatibilities prevent the assembly of specific alleles into single genotypes and influence genome- and species-wide patterns of sequence variation. A common incompatibility in plants is hybrid necrosis, characterized by autoimmune responses due to epistatic interactions between natural genetic variants. By systematically testing thousands of F1 hybrids of Arabidopsis thaliana strains, we identified a small number of incompatibility hot spots in the genome, often in regions densely populated by nucleotide-binding domain and leucine-rich repeat (NLR) immune receptor genes. In several cases, these immune receptor loci interact with each other, suggestive of conflict within the immune system. A particularly dangerous locus is a highly variable cluster of NLR genes, DM2, which causes multiple independent incompatibilities with genes that encode a range of biochemical functions, including NLRs. Our findings suggest that deleterious interactions of immune receptors limit the combinations of favorable disease resistance alleles accessible to plant genomes.

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PhD Thesis: On the involvement of host proteins in Cowpea mosaic virus intercellular spread (Paulus den Hollander, Wageningen University, 2014)

PhD Thesis: On the involvement of host proteins in Cowpea mosaic virus intercellular spread (Paulus den Hollander, Wageningen University, 2014) | Plants and Microbes | Scoop.it
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Gregor Mendel Institute - Youssef Belkhadir (2014)

Gregor Mendel Institute - Youssef Belkhadir (2014) | Plants and Microbes | Scoop.it

A key question in biology is how organisms “adapt”, or acquire environment-dependent fitness advantages. Plants must grow fast enough to compete with their neighbours, while maintaining appropriate defences to survive in the presence of pathogens. Understanding how plants make the "decision" to keep safe from harm while growing is crucial to our quest for an abundant food supply and cheap, dependable sources of energy. In my laboratory we utilize of a complex array of technologies to understand how light and growth hormones signals allow plants to optimize the fluctuating investments they are making towards growth and defences in specific cells and organs but also at the population level. The laboratory aims at training a new breed of scientists who will not only be able to integrate plant developmental processes in the face of plant defences but will also understand plant defence responses in the context of environmental (light) and endogenous cues (hormones).

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Gregor Mendel Institute - Armin Djamei (2014)

Gregor Mendel Institute - Armin Djamei (2014) | Plants and Microbes | Scoop.it

Biotrophic fungi colonize living host tissue and are therefore masters in manipulating the immune defense responses, metabolism and development of their host plants. The focus of our research is to elucidate the underlying molecular mechanisms of biotrophy in the model pathosystems Ustilago maydis/Maize and Ustilago bromivora/Brachypodium. In an integrative approach we functionally explore the effectome (pathogen derived secreted manipulative molecules) to gain insights into the targeted host metabolic processes and to understand the critical needs of the pathogens.

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PLOS One: Functional Analysis of Hyaloperonospora arabidopsidis RXLR Effectors (2014)

PLOS One: Functional Analysis of Hyaloperonospora arabidopsidis RXLR Effectors (2014) | Plants and Microbes | Scoop.it

The biotrophic plant pathogen Hyaloperonospora arabidopsidis produces a set of putative effector proteins that contain the conserved RXLR motif. For most of these RXLR proteins the role during infection is unknown. Thirteen RXLR proteins from H. arabidopsidis strain Waco9 were analyzed for sequence similarities and tested for a role in virulence. The thirteen RXLR proteins displayed conserved N-termini and this N-terminal conservation was also found in the 134 predicted RXLR genes from the genome of H. arabidopsidis strain Emoy2. To investigate the effects of single RXLR effector proteins on plant defense responses, thirteen H. arabidopsidis Waco9 RXLR genes were expressed in Arabidopsis thaliana. Subsequently, these plants were screened for altered susceptibility to the oomycetes H. arabidopsidis and Phytophthora capsici, and the bacterial pathogen Pseudomonas syringae. Additionally, the effect of the RXLR proteins on flg22-triggered basal immune responses was assessed. Multifactorial analysis of results collated from all experiments revealed that, except for RXLR20, all RXLR effector proteins tested affected plant immunity. For RXLR9 this was confirmed using a P. syringae ΔCEL-mediated effector delivery system. Together, the results show that many H. arabidopsidis RXLR effectors have small effects on the plant immune response, suggesting that suppression of host immunity by this biotrophic pathogen is likely to be caused by the combined actions of effectors.

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PLOS Pathogens: A Conserved Peptide Pattern from a Widespread Microbial Virulence Factor Triggers Pattern-Induced Immunity in Arabidopsis (2014)

PLOS Pathogens: A Conserved Peptide Pattern from a Widespread Microbial Virulence Factor Triggers Pattern-Induced Immunity in Arabidopsis (2014) | Plants and Microbes | Scoop.it

Microbe- or host damage-derived patterns mediate activation of pattern-triggered immunity (PTI) in plants. Microbial virulence factor (effector)-triggered immunity (ETI) constitutes a second layer of plant protection against microbial attack. Various necrosis and ethylene-inducing peptide 1 (Nep1)-like proteins (NLPs) produced by bacterial, oomycete and fungal microbes are phytotoxic virulence factors that exert immunogenic activities through phytotoxin-induced host cell damage. We here show that multiple cytotoxic NLPs also carry a pattern of 20 amino acid residues (nlp20) that triggers immunity-associated plant defenses and immunity to microbial infection in Arabidopsis thaliana and related plant species with similar characteristics as the prototype pattern, bacterial flagellin. Characteristic differences in flagellin and nlp20 plant responses exist however, as nlp20s fail to trigger extracellular alkalinization in Arabidopsis cell suspensions and seedling growth inhibition. Immunogenic nlp20 peptide motifs are frequently found in bacterial, oomycete and fungal NLPs. Such an unusually broad taxonomic distribution within three phylogenetic kingdoms is unprecedented among microbe-derived triggers of immune responses in either metazoans or plants. Our findings suggest that cytotoxic NLPs carrying immunogenic nlp20 motifs trigger PTI in two ways as typical patterns and by inflicting host cell damage. We further propose that conserved structures within a microbial virulence factor might have driven the emergence of a plant pattern recognition system mediating PTI. As this is reminiscent of the evolution of immune receptors mediating ETI, our findings support the idea that there is a continuum between PTI and ETI.


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Frontiers: Epigenetic control of effectors in plant pathogens (2014)

Frontiers: Epigenetic control of effectors in plant pathogens (2014) | Plants and Microbes | Scoop.it

Plant pathogens display impressive versatility in adapting to host immune systems. Pathogen effector proteins facilitate disease but can become avirulence (Avr) factors when the host acquires discrete recognition capabilities that trigger immunity. The mechanisms that lead to changes to pathogen Avr factors that enable escape from host immunity are diverse, and include epigenetic switches that allow for reuse or recycling of effectors. This perspective outlines possibilities of how epigenetic control of Avr effector gene expression may have arisen and persisted in plant pathogens, and how it presents special problems for diagnosis and detection of specific pathogen strains or pathotypes.

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PNAS: Herbivore exploits orally secreted bacteria to suppress plant defenses (2013)

PNAS: Herbivore exploits orally secreted bacteria to suppress plant defenses (2013) | Plants and Microbes | Scoop.it

The role of herbivore-associated microbes in modifying plant defenses has received scant attention. The Colorado potato beetle secretes symbiotic bacteria to wounds to manipulate plant defenses. The bacteria elicit salicylic acid (SA)-regulated defenses, and because SA signaling often negatively cross-talks with jasmonate signaling, plants are unable to fully activate their jasmonate-mediated resistance against the herbivore. From the plants’ perspective, they recognize herbivores not as such, but as microbial threats. We identified the specific bacteria from the beetle secretions and also characterized one of the bacterial effectors responsible for defense suppression. This clever, deceptive strategy for suppressing defenses has not been previously documented. Our results add a significant, unique concept to plant–insect interactions and how herbivores hijack plant defense signaling.

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Frontiers: The past, present and future of breeding rust resistant wheat (2014)

Frontiers: The past, present and future of breeding rust resistant wheat (2014) | Plants and Microbes | Scoop.it

Two classes of genes are used for breeding rust resistant wheat. The first class, called R (for resistance) genes, are pathogen race-specific in their action, effective at all plant growth stages and probably mostly encode immune receptors of the nucleotide binding leucine rich repeat (NB-LRR) class. The second class called Adult Plant Resistance genes (APR) because resistance is usually functional only in adult plants, and, in contrast to most R genes, the levels of resistance conferred by single APR genes are only partial and allow considerable disease development. Some but not all APR genes provide resistance to all isolates of a rust pathogen species and a subclass of these provides resistance to several fungal pathogen species. Initial indications are that APR genes encode a more heterogeneous range of proteins than R proteins. Two APR genes, Lr34 and Yr36, have been cloned from wheat and their products are an ABC transporter and a protein kinase, respectively. Lr34 and Sr2 have provided long lasting and widely used (durable) partial resistance and are mainly used in conjunction with other R and APR genes to obtain adequate rust resistance. We caution that some APR genes indeed include race-specific, weak R genes which may be of the NB-LRR class. A research priority to better inform rust resistance breeding is to characterize further APR genes in wheat and to understand how they function and how they interact when multiple APR and R genes are stacked in a single genotype by conventional and GM breeding. An important message is do not be complacent about the general durability of all APR genes.

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Nature Reviews Genetics: Microbial genome-enabled insights into plant-microorganism interactions (2014)

Nature Reviews Genetics: Microbial genome-enabled insights into plant-microorganism interactions (2014) | Plants and Microbes | Scoop.it

Advances in genome-based studies on plant-associated microorganisms have transformed our understanding of many plant pathogens and are beginning to greatly widen our knowledge of plant interactions with mutualistic and commensal microorganisms. Pathogenomics has revealed how pathogenic microorganisms adapt to particular hosts, subvert innate immune responses and change host range, as well as how new pathogen species emerge. Similarly, culture-independent community profiling methods, coupled with metagenomic and metatranscriptomic studies, have provided the first insights into the emerging field of research on plant-associated microbial communities. Together, these approaches have the potential to bridge the gap between plant microbial ecology and plant pathology, which have traditionally been two distinct research fields.

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PLOS Genetics: The Nuclear Immune Receptor RPS4 Is Required for RRS1SLH1-Dependent Constitutive Defense Activation in Arabidopsis thaliana (2014)

PLOS Genetics: The Nuclear Immune Receptor RPS4 Is Required for RRS1SLH1-Dependent Constitutive Defense Activation in Arabidopsis thaliana (2014) | Plants and Microbes | Scoop.it

Plant nucleotide-binding leucine-rich repeat (NB-LRR) disease resistance (R) proteins recognize specific “avirulent” pathogen effectors and activate immune responses. NB-LRR proteins structurally and functionally resemble mammalian Nod-like receptors (NLRs). How NB-LRR and NLR proteins activate defense is poorly understood. The divergently transcribed Arabidopsis R genes, RPS4 (resistance to Pseudomonas syringae 4) and RRS1 (resistance to Ralstonia solanacearum 1), function together to confer recognition of PseudomonasAvrRps4 and Ralstonia PopP2. RRS1 is the only known recessive NB-LRR R gene and encodes a WRKY DNA binding domain, prompting suggestions that it acts downstream of RPS4 for transcriptional activation of defense genes. We define here the early RRS1-dependent transcriptional changes upon delivery of PopP2 via Pseudomonas type III secretion. The Arabidopsis slh1 (sensitive to low humidity 1) mutant encodes an RRS1 allele (RRS1SLH1) with a single amino acid (leucine) insertion in the WRKY DNA-binding domain. Its poor growth due to constitutive defense activation is rescued at higher temperature. Transcription profiling data indicate that RRS1SLH1-mediated defense activation overlaps substantially with AvrRps4- and PopP2-regulated responses. To better understand the genetic basis of RPS4/RRS1-dependent immunity, we performed a genetic screen to identify suppressor of slhimmunity (sushi) mutants. We show that many sushi mutants carry mutations in RPS4, suggesting that RPS4 acts downstream or in a complex with RRS1. Interestingly, several mutations were identified in a domain C-terminal to the RPS4 LRR domain. Using an Agrobacterium-mediated transient assay system, we demonstrate that the P-loop motif of RPS4 but not of RRS1SLH1 is required for RRS1SLH1 function. We also recapitulate the dominant suppression of RRS1SLH1 defense activation by wild type RRS1 and show this suppression requires an intact RRS1 P-loop. These analyses of RRS1SLH1shed new light on mechanisms by which NB-LRR protein pairs activate defense signaling, or are held inactive in the absence of a pathogen effector.

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PLOS One: Seed Transmission of Pseudoperonospora cubensis (2014)

PLOS One: Seed Transmission of Pseudoperonospora cubensis (2014) | Plants and Microbes | Scoop.it

Pseudoperonospora cubensis, an obligate biotrophic oomycete causing devastating foliar disease in species of the Cucurbitaceae family, was never reported in seeds or transmitted by seeds. We now show that P. cubensis occurs in fruits and seeds of downy mildew-infected plants but not in fruits or seeds of healthy plants. About 6.7% of the fruits collected during 2012–2014 have developed downy mildew when homogenized and inoculated onto detached leaves and 0.9% of the seeds collected developed downy mildew when grown to the seedling stage. This is the first report showing that P. cubensis has become seed-transmitted in cucurbits. Species-specific PCR assays showed that P. cubensis occurs in ovaries, fruit seed cavity and seed embryos of cucurbits. We propose that international trade of fruits or seeds of cucurbits might be associated with the recent global change in the population structure of P. cubensis.

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The Australian: Disease hits $400m Tasmanian poppy crop (2014)

The Australian: Disease hits $400m Tasmanian poppy crop (2014) | Plants and Microbes | Scoop.it

THERE  are concerns for the ­future of Tasmania’s poppy industry — source for half the world’s morphine and related pharmaceutical opiates — as a so-far unstoppable disease threatens the $400 million crop.


In the six weeks since a virulent strain of downy mildew began to be noticed in the state’s poppy crops, up to 10 per cent has been hit by the disease.


There have been some promising trials of new chemical treatments but existing fungicides have so far failed to abate the fungus, whose spores can travel hundreds of kilometres on the wind.


An urgent research effort was launched this week by growers, government and industry to try to identify and tackle the mildew, which stunts plant growth and can decimate entire paddocks. While growers and experts insist the industry will survive, The Weekend Australian has learned of fears that because of the ­increased cost of more frequent fungicide treatments, farmers may dump poppies.


Poppy Growers Tasmania president Glynn Williams said such an increased burden, at a time of a decline in prices paid to poppy growers, could force some to walk away from the crop.


“I’m now spraying my crops on a weekly basis and that’s time and diesel and a lot of money spent on chemicals,” Mr Williams said.

“Prices (paid to farmers for poppies) haven’t risen for two years … and we’ve had a 12.5 per cent decrease from one company.


“And if you then see a significant increase in the cost of growing the crop, that could be something you have to look at pretty hard. If they don’t start raising prices, farmers will stop growing poppies.”


The crop is the state’s third most valuable agricultural product and is worth about $90 million at the farm gate and $400m to Tasmania’s gross state product.


While downy mildew has been present in Tasmanian poppy crops for more than a decade, damaging leaves of the plant, the new strain stunts entire plant growth, preventing flowering.


One of two lead researchers trying to identify and tackle the disease, Jason Scott, told The Weekend Australian an early task was to use DNA testing to discover if the new strain evolved from the existing one or had been recently introduced.


Dr Scott said if it was the existing strain involved, the research would have to work out why it had developed resistance to existing chemical treatments.


A $320,000 research fund will pay for a visit from Austrian ­expert Hermann Voglmayr, who has mapped gene sequences of poppy mildew species.

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Journal of Experimental Botany: Persistence and transgenerational effect of plant-mediated RNAi in aphids (2014)

Journal of Experimental Botany: Persistence and transgenerational effect of plant-mediated RNAi in aphids (2014) | Plants and Microbes | Scoop.it

Plant-mediated RNA interference (RNAi) has been successfully used as a tool to study gene function in aphids. The persistence and transgenerational effects of plant-mediated RNAi in the green peach aphid (GPA) Myzus persicae were investigated, with a focus on three genes with different functions in the aphid. Rack1 is a key component of various cellular processes inside aphids, while candidate effector genes MpC002and MpPIntO2 (Mp2) modulate aphid–plant interactions. The gene sequences and functions did not affect RNAi-mediated down-regulation and persistence levels in the aphids. Maximal reduction of gene expression was ~70% and this was achieved at between 4 d and 8 d of exposure of the aphids to double-stranded RNA (dsRNA)-producing transgenic Arabidopsis thaliana. Moreover, gene expression levels returned to wild-type levels within ~6 d after removal of the aphids from the transgenic plants, indicating that a continuous supply of dsRNA is required to maintain the RNAi effect. Target genes were also down-regulated in nymphs born from mothers exposed to dsRNA-producing transgenic plants, and the RNAi effect lasted twice as long (12–14 d) in these nymphs. Investigations of the impact of RNAi over three generations of aphids revealed that aphids reared on dsMpC002 transgenic plants experienced a 60% decline in aphid reproduction levels compared with a 40% decline of aphids reared on dsRack1 and dsMpPIntO2 plants. In a field setting, a reduction of the aphid reproduction by 40–60% would dramatically decrease aphid population growth, contributing to a substantial reduction in agricultural losses.

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PLOS Pathogens: The Plasmodesmal Protein PDLP1 Localises to Haustoria-Associated Membranes during Downy Mildew Infection and Regulates Callose Deposition (2014)

PLOS Pathogens: The Plasmodesmal Protein PDLP1 Localises to Haustoria-Associated Membranes during Downy Mildew Infection and Regulates Callose Deposition (2014) | Plants and Microbes | Scoop.it

The downy mildew pathogen Hyaloperonospora arabidopsidis (Hpa) is a filamentous oomycete that invades plant cells via sophisticated but poorly understood structures called haustoria. Haustoria are separated from the host cell cytoplasm and surrounded by an extrahaustorial membrane (EHM) of unknown origin. In some interactions, including Hpa-Arabidopsis, haustoria are progressively encased by host-derived, callose-rich materials but the molecular mechanisms by which callose accumulates around haustoria remain unclear. Here, we report that PLASMODESMATA-LOCATED PROTEIN 1 (PDLP1) is expressed at high levels in Hpainfected cells. Unlike other plasma membrane proteins, which are often excluded from the EHM, PDLP1 is located at the EHM in Hpa-infected cells prior to encasement. The transmembrane domain and cytoplasmic tail of PDLP1 are sufficient to convey this localization. PDLP1 also associates with the developing encasement but this association is lost when encasements are fully mature. We found that the pdlp1,2,3 triple mutant is more susceptible to Hpa while overexpression of PDLP1 enhances plant resistance, suggesting that PDLPs enhance basal immunity against Hpa. Haustorial encasements are depleted in callose in pdlp1,2,3 mutant plants whereas PDLP1 over-expression elevates callose deposition around haustoria and across the cell surface. These data indicate that PDLPs contribute to callose encasement of Hpa haustoria and suggests that the deposition of callose at haustoria may involve similar mechanisms to callose deposition at plasmodesmata.

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Curr Opin Microbiology: Targeting of plant pattern recognition receptor-triggered immunity by bacterial type-III secretion system effectors (2014)

Curr Opin Microbiology: Targeting of plant pattern recognition receptor-triggered immunity by bacterial type-III secretion system effectors (2014) | Plants and Microbes | Scoop.it

• Type-III effectors (T3Es) suppress plant immunity using multiple strategies.
• PRR-triggered immunity is redundantly targeted by multiple T3Es from a single bacterial strain.
• A single T3E can have multiple plant targets.
• A given immune component can be targeted by multiple T3Es.
• The study of T3Es reveals important immune components and unique biochemical processes.


During infection, microbes are detected by surface-localized pattern recognition receptors (PRRs), leading to an innate immune response that prevents microbial ingress. Therefore, successful pathogens must evade or inhibit PRR-triggered immunity to cause disease. In the past decade, a number of type-III secretion system effector (T3Es) proteins from plant pathogenic bacteria have been shown to suppress this layer of innate immunity. More recently, the detailed mechanisms of action have been defined for several of these effectors. Interestingly, effectors display a wide array of virulence targets, being able to prevent activation of immune receptors and to hijack immune signaling pathways. Besides being a fascinating example of pathogen-host co-evolution, effectors have also emerged as valuable tools to dissect important biological processes in host cells.

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Molecular Plant: XA23 is an executor R protein and confers broad-spectrum disease resistance in rice (2014)

Molecular Plant: XA23 is an executor R protein and confers broad-spectrum disease resistance in rice (2014) | Plants and Microbes | Scoop.it

The majority of plant disease resistance (R) genes encode proteins that share common structural features. However, the transcription activator-like effector (TALE) associated executor type R genes show no considerable sequence homology to any known R genes. We adopted a map-based cloning approach and TALE-based technology to isolate and characterize Xa23, a new executor R gene derived from the wild rice (Oryza rufipogon) that confers an extremely broad spectrum of resistance to bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo). Xa23 encodes a 113-amino acid protein that shares 50% identity to the known executor R protein XA10. The predicted transmembrane helices in XA23 also overlap with those of XA10. Unlike Xa10, however, Xa23 transcription is specifically activated by AvrXa23, a TALE present in all examined Xoo field isolates. Moreover, the susceptible xa23 allele has an identical open reading frame of Xa23, but differs in promoter region by lacking the TALE binding-element (EBE) for AvrXa23. XA23 can trigger strong hypersensitive response in rice, tobacco and tomato. Our results provide the first evidence that plant genomes have an executor R gene family in which members execute their function and spectrum of disease resistance by recognizing the cognate TALEs in pathogen.


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Frontiers in Plant-Microbe Interaction | Research Topics: Plant Immunity: From model systems to crops species (2014)

Frontiers in Plant-Microbe Interaction | Research Topics: Plant Immunity: From model systems to crops species (2014) | Plants and Microbes | Scoop.it

Plants posses an intricate innate immune system that enables them to fight off most invading pathogens. Around the world, agriculture relies on robust disease resistance to ensure adequate food and feed production. Researchers and breeders are constantly generating new resistant crop varieties mostly employing the lengthy process of conventional breeding. Nonetheless, crop losses due to plant pathogens are estimated to be over 15% every year - the main cause of such losses is rapid evolution of new virulent races. In order to keep up with emerging pathogens, we need to gain a deeper and more systematic understanding of the immune system of our crops. During the past two decades, molecular understanding of plant innate immune signaling has been greatly expanded using dicotyledonous model systems such as Arabidopsis thaliana. Now, it is time to connect this volume of knowledge with the immune system of the crop species.


In this Research Topic we aim to collect manuscripts covering the current knowledge of the immune systems of major crop species. Specifically, we encourage the submission of manuscripts (Original Research, Hypothesis & Theory, Methods, Reviews, Mini Reviews, Perspective and Opinion) covering the following topics:


a. Manuscripts describing our current understanding of the plant immune system with a focus on crop species or comparative analyses between model systems and crops.

b. Manuscripts exploring how to best exploit our insight into genomes of plant pathogens and molecular understanding of effector function.
c. Manuscripts debating (novel) strategies of how to generate more resistant crop varieties. These might include biotechnological, social and economical aspects of crop improvement.


We anticipate that this Research Topic will become an important resource for plant immunologists especially those interested in comparative studies of plant innate immune systems of model systems and crop species.


Topic Editors


Benjamin Schwessinger
UC Davis
Davis, USA


Rebecca Bart
Donald Danforth Plant Science Center
St. Louis, USA


Gitta Coaker
University of California, Davis
Davis, USA


Ksenia V Krasileva
University of California Davis
Davis, USA

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BMC Plant Biology: Loss and retention of resistance genes in five species of the Brassicaceae family (2014)

BMC Plant Biology: Loss and retention of resistance genes in five species of the Brassicaceae family (2014) | Plants and Microbes | Scoop.it

Plants have evolved disease resistance (R) genes encoding for nucleotide-binding site (NB) and leucine-rich repeat (LRR) proteins with N-terminals represented by either Toll/Interleukin-1 receptor (TIR) or coiled-coil (CC) domains. Here, a genome-wide study of presence and diversification of CC-NB-LRR and TIR-NB-LRR encoding genes, and shorter domain combinations in 19 Arabidopsis thaliana accessions and Arabidopsis lyrata, Capsella rubella, Brassica rapa and Eutrema salsugineum are presented.ResultsOut of 528 R genes analyzed, 12 CC-NB-LRR and 17 TIR-NB-LRR genes were conserved among the 19 A. thaliana genotypes, while only two CC-NB-LRRs, including ZAR1, and three TIR-NB-LRRs were conserved when comparing the five species. The RESISTANCE TO LEPTOSPHAERIA MACULANS 1 (RLM1) locus confers resistance to the Brassica pathogen L. maculans the causal agent of blackleg disease and has undergone conservation and diversification events particularly in B. rapa. On the contrary, the RLM3 locus important in the immune response towards Botrytis cinerea and Alternaria spp. has recently evolved in the Arabidopsis genus.ConclusionOur genome-wide analysis of the R gene repertoire revealed a large sequence variation in the 23 cruciferous genomes. The data provides further insights into evolutionary processes impacting this important gene family.


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YouTube: The Infected Pumpkin (2014)

Halloween Themed Time Lapse and Stop Motion Video. The Happy pumpkin is infected by Phytophthora capsici and doesn't like it.

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PRISM - The Philippine Rice Information System (2014)

PRISM - The Philippine Rice Information System (2014) | Plants and Microbes | Scoop.it

The Philippine Rice Information System (PRISM) is an operational system for monitoring rice. It supports decision making and activity planning for increased rice production in the Philippines, and has nationwide coverage to help improve food security. It also serves as a platform to develop consistent and regular assessments of rice crop production, crop health, and crop losses due to natural calamities such as floods, droughts, and outbreaks of pests and diseases.

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Frontiers: A novel conserved mechanism for plant NLR protein pairs: the ‘integrated decoy’ hypothesis (2014)

Frontiers: A novel conserved mechanism for plant NLR protein pairs: the ‘integrated decoy’ hypothesis (2014) | Plants and Microbes | Scoop.it

Plant immunity is often triggered by the specific recognition of pathogen effectors by intracellular nucleotide-binding, leucine-rich repeat (NLR) receptors. Plant NLRs contain an N-terminal signaling domain that is mostly represented by either a Toll-interleukin1 receptor (TIR) domain or a coiled coil (CC) domain. In many cases, single NLR proteins are sufficient for both effector recognition and signaling activation. However, many paired NLRs have now been identified where both proteins are required to confer resistance to pathogens. Recent detailed studies on the Arabidopsis thaliana TIR-NLR pair RRS1 and RPS4 and on the rice CC-NLR pair RGA4 and RGA5 have revealed for the first time how such protein pairs function together. In both cases, the paired partners interact physically to form a hetero-complex receptor in which each partner plays distinct roles in effector recognition or signaling activation, highlighting a conserved mode of action of NLR pairs across both monocotyledonous and dicotyledonous plants. We also discuss a new ‘integrated decoy’ effector recognition model to describe these receptor complexes that may be common to many other plant NLR pairs.

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Elsa Ballini's curator insight, October 29, 4:21 AM

In Rice/Magnaporthe an example is RGA4-RGA5

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PlantVillage: Rice blast disease: hopes for control (2014)

PlantVillage: Rice blast disease: hopes for control (2014) | Plants and Microbes | Scoop.it

Readers of PlantVillage (www.plantvillage.com) will be well aware of the devastation that plant diseases can cause, whether they are affecting garden produce or agricultural fields, the symptoms of plant diseases are very obvious from blights and rusts, to moulds and mildews.


The devastation reeked by plant pathogens also makes a huge impact on the ability of the world to feed itself. It has recently been estimated that losses due to plant pathogens are one of the most significant constraints on worldwide food production. Indeed, it has been estimated that if normal, low-level plant diseases could be effectively controlled, this would allow food production sufficient to feed 8.5% of the current human population (almost 600 million people). Therefore to ensure global food security, we will require more durable means of controlling plant diseases, and we have to do that in a more sustainable way that is less heavily dependent on fossil fuels, and does not adversely affect the environment, including human health. This is a big challenge and will take considerably greater understanding of plant diseases and the pathogens that cause them.


Continue reading at http://medium.com/@plantvillage/rice-blast-disease-hopes-for-control-910655049d10

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eLife: The kinase LYK5 is a major chitin receptor in Arabidopsis and forms a chitin-induced complex with related kinase CERK1 (2014)

eLife: The kinase LYK5 is a major chitin receptor in Arabidopsis and forms a chitin-induced complex with related kinase CERK1 (2014) | Plants and Microbes | Scoop.it

Chitin is a fungal microbe-associated molecular pattern (MAMP) that is recognized in Arabidopsis by a lysin motif receptor kinase (LYK), AtCERK1. Previous research suggested that AtCERK1 is the major chitin receptor in plants and mediates chitin-induced signaling through homodimerization and phosphorylation. However, the reported chitin binding affinity of AtCERK1 is quite low, suggesting another receptor with high chitin binding affinity might be present. Here, we propose that AtLYK5 is the primary chitin receptor in Arabidopsis. Mutations in AtLYK5 resulted in a significant reduction in the plant chitin response. However, AtLYK5 shares overlapping function with AtLYK4 and, therefore, only AtLYK4/AtLYK5-2 double mutants show a complete loss of chitin response. AtLYK5 interacts with AtCERK1 in a chitin-dependent manner. Chitin binding to AtLYK5 is indispensable for chitin-induced AtCERK1 phosphorylation. AtLYK5 binds chitin at a higher affinity than AtCERK1. The data suggest that AtLYK5 is the primary receptor for chitin to induce plant immunity.

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Jean-Michel Ané's curator insight, October 24, 12:06 PM

A must read if you are interested in Nod and Myc factor receptors too...