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PLOS Pathogens: A Pathogen Type III Effector with a Novel E3 Ubiquitin Ligase Architecture (2013)

PLOS Pathogens: A Pathogen Type III Effector with a Novel E3 Ubiquitin Ligase Architecture (2013) | Plants and Microbes | Scoop.it

Type III effectors are virulence factors of Gram-negative bacterial pathogens delivered directly into host cells by the type III secretion nanomachine where they manipulate host cell processes such as the innate immunity and gene expression. Here, we show that the novel type III effector XopL from the model plant pathogen Xanthomonas campestris pv. vesicatoriaexhibits E3 ubiquitin ligase activity in vitro and in planta, induces plant cell death and subverts plant immunity. E3 ligase activity is associated with the C-terminal region of XopL, which specifically interacts with plant E2 ubiquitin conjugating enzymes and mediates formation of predominantly K11-linked polyubiquitin chains. The crystal structure of the XopL C-terminal domain revealed a single domain with a novel fold, termed XL-box, not present in any previously characterized E3 ligase. Mutation of amino acids in the central cavity of the XL-box disrupts E3 ligase activity and prevents XopL-induced plant cell death. The lack of cysteine residues in the XL-box suggests the absence of thioester-linked ubiquitin-E3 ligase intermediates and a non-catalytic mechanism for XopL-mediated ubiquitination. The crystal structure of the N-terminal region of XopL confirmed the presence of a leucine-rich repeat (LRR) domain, which may serve as a protein-protein interaction module for ubiquitination target recognition. While the E3 ligase activity is required to provoke plant cell death, suppression of PAMP responses solely depends on the N-terminal LRR domain. Taken together, the unique structural fold of the E3 ubiquitin ligase domain within the Xanthomonas XopL is unprecedented and highlights the variation in bacterial pathogen effectors mimicking this eukaryote-specific activity.

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Frontiers: A perspective on CRN proteins in the genomics age: Evolution, Classification, Delivery and Function revisited (2017)

Frontiers: A perspective on CRN proteins in the genomics age: Evolution, Classification, Delivery and Function revisited (2017) | Plants and Microbes | Scoop.it

Plant associated microbes rely on secreted virulence factors (effectors) to modulate host immunity and ensure progressive infection. Amongst the secreted protein repertoires defined and studied in pathogens to date, the CRNs (for CRinkling and Necrosis) have emerged as one of only a few highly conserved protein families, spread across several kingdoms. CRN proteins were first identified in plant pathogenic oomycetes where they were found to be modular factors that are secreted and translocated inside host cells by means of a conserved N-terminal domain. Subsequent localization and functional studies have led to the view that CRN C-termini execute their presumed effector function in the host nucleus, targeting processes required for immunity. These findings have led to great interest in this large protein family and driven the identification of additional CRN-like proteins in other organisms. The identification of CRN proteins and subsequent functional studies have markedly increased the number of candidate CRN protein sequences, expanded the range of phenotypes tentatively associated with function and revealed some of their molecular functions towards virulence. The increased number of characterised CRNs also has presented a set of challenges that may impede significant progress in the future. Here, we summarise our current understanding of the CRNs and re-assess some basic assumptions regarding this protein family. We will discuss the latest findings on CRN biology and highlight exciting new hypotheses that have emanated from the field. Finally, we will discuss new approaches to study CRN functions that would lead to a better understanding of CRN effector biology as well as the processes that lead to host susceptibility and immunity.


Via Christophe Jacquet
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International Molecular Mycorrhiza Meeting 2017, 26th – 28th July 2017, Toulouse, France

International Molecular Mycorrhiza Meeting 2017, 26th – 28th July 2017, Toulouse, France | Plants and Microbes | Scoop.it
iMMM2017 Research into the molecular basis of symbiosis between plant roots and fungi has achieved major breakthroughs in recent years. The international Molecular Mycorrhiza Meeting (iMMM) is a response to the perceived need for a specialized meeting series covering the molecular mechanistic aspects of mycorrhizal symbioses including yet non-categorised endophytic root fungus interactions. After the success of the two first editions in Munich (2012) and Cambridge (2015), the 3rd international Molecular Mycorrhiza Meeting will be held in Toulouse in 2017. To keep the meeting highly interactive, the participant number will be limited to 150 people.

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Genome Biology: Rapid transcriptional plasticity of duplicated gene clusters enables a clonally reproducing aphid to colonise diverse plant species (2017)

Genome Biology: Rapid transcriptional plasticity of duplicated gene clusters enables a clonally reproducing aphid to colonise diverse plant species (2017) | Plants and Microbes | Scoop.it

Background. The prevailing paradigm of host-parasite evolution is that arms races lead to increasing specialisation via genetic adaptation. Insect herbivores are no exception and the majority have evolved to colonise a small number of closely related host species. Remarkably, the green peach aphid, Myzus persicae, colonises plant species across 40 families and single M. persicae clonal lineages can colonise distantly related plants. This remarkable ability makes M. persicae a highly destructive pest of many important crop species.


Results. To investigate the exceptional phenotypic plasticity of M. persicae, we sequenced the M. persicae genome and assessed how one clonal lineage responds to host plant species of different families. We show that genetically identical individuals are able to colonise distantly related host species through the differential regulation of genes belonging to aphid-expanded gene families. Multigene clusters collectively upregulate in single aphids within two days upon host switch. Furthermore, we demonstrate the functional significance of this rapid transcriptional change using RNA interference (RNAi)-mediated knock-down of genes belonging to the cathepsin B gene family. Knock-down of cathepsin B genes reduced aphid fitness, but only on the host that induced upregulation of these genes.


Conclusions. Previous research has focused on the role of genetic adaptation of parasites to their hosts. Here we show that the generalist aphid pest M. persicae is able to colonise diverse host plant species in the absence of genetic specialisation. This is achieved through rapid transcriptional plasticity of genes that have duplicated during aphid evolution.

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PNAS: TIR-only protein RBA1 recognizes a pathogen effector to regulate cell death in Arabidopsis (2017)

PNAS: TIR-only protein RBA1 recognizes a pathogen effector to regulate cell death in Arabidopsis (2017) | Plants and Microbes | Scoop.it

Detection of pathogens by plants is mediated by intracellular nucleotide-binding site leucine-rich repeat (NLR) receptor proteins. NLR proteins are defined by their stereotypical multidomain structure: an N-terminal Toll–interleukin receptor (TIR) or coiled-coil (CC) domain, a central nucleotide-binding (NB) domain, and a C-terminal leucine-rich repeat (LRR). The plant innate immune system contains a limited NLR repertoire that functions to recognize all potential pathogens. We isolated Response to the bacterial type III effector protein HopBA1 (RBA1), a gene that encodes a TIR-only protein lacking all other canonical NLR domains. RBA1 is sufficient to trigger cell death in response to HopBA1. We generated a crystal structure for HopBA1 and found that it has similarity to a class of proteins that includes esterases, the heme-binding protein ChaN, and an uncharacterized domain of Pasteurella multocida toxin. Self-association, coimmunoprecipitation with HopBA1, and function of RBA1 require two previously identified TIR–TIR dimerization interfaces. Although previously described as distinct in other TIR proteins, in RBA1 neither of these interfaces is sufficient when the other is disrupted. These data suggest that oligomerization of RBA1 is required for function. Our identification of RBA1 demonstrates that “truncated” NLRs can function as pathogen sensors, expanding our understanding of both receptor architecture and the mechanism of activation in the plant immune system.

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16th International Conference on Pseudomonas, Liverpool, UK, 5-9 September 2017

16th International Conference on Pseudomonas, Liverpool, UK, 5-9 September 2017 | Plants and Microbes | Scoop.it

The 16th International Conference on Pseudomonas will take place at St George's Hall in Liverpool, UK.

 

The Pseudomonas International Conference is a biennial event that brings together researchers from all over the world who are working on the genus Pseudomonas, including not only the important human pathogen Pseudomonas aeruginosa, but also a range of other important species with relevance to plant pathogenicity, bioremediation and environmental microbiology. It is also a group of organisms used widely for the study of host–pathogen interactions; cell–cell communication systems; evolutionary biology; gene regulation and metabolic networks; secretion systems; antibiotics (and resistance); bioremediation; biofilms; bacterial genomics; and other topics of broader relevance to microbiology and molecular biology generally.

 

The meeting is aimed primarily at scientists (from postgraduate students to PIs) with an interest in Pseudomonas, but because of the widespread use of this genus as a model to study multiple systems, it will be of general interest to other researchers active in areas such as evolutionary biology, communication systems, genomics and biofilm research. In addition, because P. aeruginosa is a key pathogen associated with both acute and chronic infections, and particularly important in the context of cystic fibrosis and antimicrobial resistance, the meeting will be of interest to clinicians and clinical researchers.

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bioRxiv: Host autophagosomes are diverted to a plant-pathogen interface (2017)

bioRxiv: Host autophagosomes are diverted to a plant-pathogen interface (2017) | Plants and Microbes | Scoop.it

Filamentous plant pathogens and symbionts invade their host cells but remain enveloped by host-derived membranes. The mechanisms underlying the biogenesis and functions of these host-microbe interfaces are poorly understood. Recently, we showed that PexRD54, an effector from the Irish potato famine pathogen Phytophthora infestans, binds host protein ATG8CL to stimulate autophagosome formation and deplete the selective autophagy receptor Joka2 from ATG8CL complexes. Here, we show that during P. infestans infection, ATG8CL autophagosomes are diverted to the pathogen interface. Our findings are consistent with the view that the pathogen coopts host selective autophagy for its own benefit.

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Plant Cell: OsCUL3a Negatively Regulates Cell Death and Immunity by Degrading OsNPR1 in Rice (2017)

Plant Cell: OsCUL3a Negatively Regulates Cell Death and Immunity by Degrading OsNPR1 in Rice (2017) | Plants and Microbes | Scoop.it

Cullin3-based RING E3 ubiquitin ligases (CRL3), composed of Cullin3 (CUL3), RBX1, and BTB proteins, are involved in plant immunity but the function of CUL3 in the process is largely unknown. Here, we show that rice OsCUL3a is important for the regulation of cell death and immunity. The rice lesion mimic mutant oscul3a displays a significant increase in the accumulation of flg22- and chitin-induced reactive oxygen species, and in pathogenesis-related gene expression as well as resistance to Magnaporthe oryzae and Xanthomonas oryzae pv. oryzae. We cloned the OsCUL3a gene via a map-based strategy and found that the lesion mimic phenotype of oscul3a is associated with the early termination of OsCUL3a protein. Interaction assays showed that OsCUL3a interacts with both OsRBX1a and OsRBX1b to form a multi-subunit CRL in rice. Strikingly, OsCUL3a interacts with and degrades OsNPR1, which acts as a positive regulator of cell death in rice. Accumulation of OsNPR1 protein is greater in the oscul3a mutant than in the wild type. Furthermore, the oscul3a osnpr1 double mutant does not exhibit the lesion mimic phenotype of the oscul3a mutant. Our data demonstrate that OsCUL3a negatively regulates cell death and immunity by degrading OsNPR1 in rice.

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MPMI: Can plant microbiome studies lead to effective biocontrol of plant diseases? (2017)

MPMI: Can plant microbiome studies lead to effective biocontrol of plant diseases? (2017) | Plants and Microbes | Scoop.it

In this commentary I question the wisdom and efficacy of studies seeking disease attenuating microbes and microbiomes only in healthy plant communities and posit the alternative view that success in biocontrol of crop diseases may come also come from studies of microbiota, or at least individual species isolates, associated with diseased plants. In support of this view I summarise the current extensive knowledge of the biology behind what is probably the most successful biocontrol of a plant disease, namely the biocontrol of crown gall of stone fruit using non-pathogenic Rhizobium rhizogenes strain K84 (New and Kerr, 1972; Kerr, 2016) where the biocontrol agent itself came from a diseased plant.

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Science: The receptor kinase FER is a RALF-regulated scaffold controlling plant immune signaling (2017)

Science: The receptor kinase FER is a RALF-regulated scaffold controlling plant immune signaling (2017) | Plants and Microbes | Scoop.it
In plants, perception of invading pathogens involves cell-surface immune receptor kinases. Here, we report that the Arabidopsis SITE-1 PROTEASE (S1P) cleaves endogenous RAPID ALKALINIZATION FACTOR (RALF) propeptides to inhibit plant immunity. This inhibition is mediated by the malectin-like receptor kinase FERONIA (FER), which otherwise facilitates the ligand-induced complex formation of the immune receptor kinases EF-TU RECEPTOR (EFR) and FLAGELLIN-SENSING 2 (FLS2) with their co-receptor BRASSINOSTEROID INSENSITIVE 1–ASSOCIATED KINASE 1 (BAK1) to initiate immune signaling. We show that FER acts as a RALF-regulated scaffold that modulates receptor kinase complex assembly. A similar scaffolding mechanism may underlie FER function in other signaling pathways.Empty description

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The Sainsbury Lab's curator insight, January 20, 4:00 AM
Small peptides allow rapid responses RALFs (rapid alkalinization factors), a family of small peptides in plants, are produced in response to rapidly changing conditions. Stegmann et al. studied the agility and diversity built into this signaling network. Some RALFs, such as RALF23 and its relative RALF33, are activated by proteolytic cleavage. Others, such as RALF32, are not. RALF23 and RALF33 are called into play after a pathogen triggers immune responses. RALF32, on the other hand, regulates seedling growth. All three of these RALFs use the same receptor kinase, which can interact with other signaling components. Thus, plant responses can be fine-tuned by rapid release of peptides.

In plants, perception of invading pathogens involves cell-surface immune receptor kinases. Here, we report that the Arabidopsis SITE-1 PROTEASE (S1P) cleaves endogenous RAPID ALKALINIZATION FACTOR (RALF) propeptides to inhibit plant immunity. This inhibition is mediated by the malectin-like receptor kinase FERONIA (FER), which otherwise facilitates the ligand-induced complex formation of the immune receptor kinases EF-TU RECEPTOR (EFR) and FLAGELLIN-SENSING 2 (FLS2) with their co-receptor BRASSINOSTEROID INSENSITIVE 1–ASSOCIATED KINASE 1 (BAK1) to initiate immune signaling. We show that FER acts as a RALF-regulated scaffold that modulates receptor kinase complex assembly. A similar scaffolding mechanism may underlie FER function in other signaling pathways.
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Phytochemistry: The bitter side of the nightshades: Genomics drives discovery in Solanaceae steroidal alkaloid metabolism (2015)

Phytochemistry: The bitter side of the nightshades: Genomics drives discovery in Solanaceae steroidal alkaloid metabolism (2015) | Plants and Microbes | Scoop.it

Steroidal alkaloids (SAs) and their glycosylated forms (SGAs) are toxic compounds largely produced by members of the Solanaceae and Liliaceae plant families. This class of specialized metabolites serves as a chemical barrier against a broad range of pest and pathogens. In humans and animals, SAs are considered anti-nutritional factors because they affect the digestion and absorption of nutrients from food and might even cause poisoning. In spite of the first report on SAs nearly 200 years ago, much of the molecular basis of their biosynthesis and regulation remains unknown. Aspects concerning chemical structures and biological activities of SAs have been reviewed extensively elsewhere; therefore, in this review the latest insights to the elucidation of the SAs biosynthetic pathway are highlighted. Recently, co-expression analysis combined with metabolic profiling revealed metabolic gene clusters in tomato and potato that contain core genes required for production of the prominent SGAs in these two species. Elaborating the knowledge regarding the SAs biosynthetic pathway, the subcellular transport of these molecules, as well as the identification of regulatory and signaling factors associated with SA metabolism will likely advance understanding of chemical defense mechanisms in Solanaceae and Liliaceae plants. It will also provide the means to develop, through classical breeding or genetic engineering, crops with modified levels of anti-nutritional SAs.

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Science: A paralogous decoy protects Phytophthora sojae apoplastic effector PsXEG1 from a host inhibitor (2017)

Science: A paralogous decoy protects Phytophthora sojae apoplastic effector PsXEG1 from a host inhibitor (2017) | Plants and Microbes | Scoop.it

The extracellular space (apoplast) of plant tissue represents a critical battleground between plants and attacking microbes. Here we show that a pathogen-secreted apoplastic Xyloglucan-specific EndoGlucanase PsXEG1 is a focus of this struggle in the Phytophthora sojae-soybean interaction. We show that soybean produces an apoplastic Glucanase Inhibitor Protein, (GmGIP1), that binds to PsXEG1 to block its contribution to virulence. P. sojae however, secretes a paralogous PsXEG1-Like Protein (PsXLP1) that has lost enzyme activity but binds to GmGIP1 more tightly than does PsXEG1, thus freeing PsXEG1 to support P. sojae infection. The PsXEG1 and PsXLP1gene pair is conserved in many Phytophthora species, and the P. parasitica orthologs PpXEG1 and PpXLP1 have similar functions. Thus this apoplastic decoy strategy maybe widely employed in Phytophthora pathosystems.

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MPMI: Current Understandings on Plant Nonhost Resistance (2016)

MPMI: Current Understandings on Plant Nonhost Resistance (2016) | Plants and Microbes | Scoop.it

Nonhost resistance, a resistance of plant species against all non-adapted pathogens, is considered the most durable and efficient immune system of plants but yet remains elusive. The underlying mechanism of nonhost resistance has been investigated at multiple levels of plant defense for several decades. In this review, we have comprehensively surveyed the latest literature on nonhost resistance in terms of pre-invasion, metabolic defense, pattern-triggered immunity, effector-triggered immunity, defense signaling, and possible application in crop protection. Overall, we summarize the current understanding of nonhost resistance mechanisms. Pre- and post-invasion is not much deviated from the knowledge on host resistance except for a few specific cases. Further insights on the roles of the pattern recognition receptor gene family, multiple interactions between effectors from non-adapted pathogen and plant factors, and plant secondary metabolites in host range determination could expand our knowledge on nonhost resistance and provide efficient tools for the future crop protection using combinational biotechnology approaches.


Via Christophe Jacquet, Jim Alfano
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Scienmag: Genome sequence reveals why the whitefly is such a formidable threat to food security (2016)

Scienmag: Genome sequence reveals why the whitefly is such a formidable threat to food security (2016) | Plants and Microbes | Scoop.it

ITHACA, NY–Researchers have sequenced the genome of the whitefly (Bemisia tabici), an invasive insect responsible for spreading plant viruses worldwide, causing billions of dollars in crop losses each year.

 

The genome study, led by Associate Professor Zhangjun Fei of the Boyce Thompson Institute (BTI), offers many clues to the insect's remarkable ability to resist pesticides, transmit more than 300 plant viruses, and to feed on at least 1,000 different plant species. Published today in the journal BMC Biology, the study will serve as a foundation for future work to combat this global pest.

"Whitefly is an economically important pest for agriculture crops. It causes direct damage and also is a major vector for viruses, like Tomato yellow leaf curl virus, Cassava mosaic virus and Cassava brown streak virus, so it creates huge crop losses and poses serious threats to food security, especially in Africa and other parts of the developing world," said Fei.

 

In collaboration with a group of international colleagues, BTI researchers created a high-quality draft genome sequence of the whitefly and identified genes that code for proteins. The genome sequence can be accessed at the whitefly genome database developed by the Fei lab.

 

An analysis showed that, compared to related species, the whitefly has expanded families of detoxification genes. It also has extra genes that code for proteins related to virus acquisition and transmission, as well as insecticide resistance.

 

In an impressive example of horizontal gene transfer, the whitefly has acquired 142 genes from bacteria or fungi, including some coding for enzymes that break down foreign chemicals. These genes likely allow the whitefly to feed on diverse types of plants and to rapidly evolve resistance to insecticides.

 

Because pesticides are ineffective at keeping whitefly populations in check, collaborators at USDA plan to use the genome sequence to develop a control strategy using RNA interference (RNAi). Once scientists pinpoint the genes necessary for virus transmission and survival in the whitefly genome, they can develop new varieties of crops that will produce RNA molecules that block the expression of those necessary genes, killing the whitefly or preventing it from spreading the virus .

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Nature Plants: Resistance: Double gain with one gene (2017)

Nature Plants: Resistance: Double gain with one gene (2017) | Plants and Microbes | Scoop.it

The rice gene Xa4 encodes a wall-associated kinase and controls disease resistance and mechanical strength, possibly through a common mechanism.


Crop plants experience a wide range of stresses that negatively affect their performance. Rice, one of the most important global crops, is the main calorie source for more than half of the global population. Two of the major constraints in rice cultivation are bacterial diseases and lodging (Fig. 1). In this issue of Nature Plants, Hu and colleagues unravel the identity and molecular function of the Xa4 gene1. This important diseaseresistance gene codes for a wall-associated kinase (WAK). The presence of Xa4 confers resistance to bacterial blight and was found to strengthen the cell wall, which is a primary entry point for pathogens. Interestingly, cell wall reinforcement also led to reduced height of Xa4-expressing plants, thereby increasing lodging resistance. Hence, this gene has a beneficial effect on multiple agronomic traits, which can explain its importance and widespread use in rice breeding.

 

Original paper by Hu et al. is here http://www.nature.com/articles/nplants20179

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TSL Summer School PLANT MICROBE INTERACTIONS, 31st July - 11th August 2017,  Norwich, UK

TSL Summer School PLANT MICROBE INTERACTIONS, 31st July - 11th August 2017,  Norwich, UK | Plants and Microbes | 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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PNAS: Multiple functional self-association interfaces in plant TIR domains (2017)

PNAS: Multiple functional self-association interfaces in plant TIR domains (2017) | Plants and Microbes | Scoop.it

The self-association of Toll/interleukin-1 receptor/resistance protein (TIR) domains has been implicated in signaling in plant and animal immunity receptors. Structure-based studies identified different TIR-domain dimerization interfaces required for signaling of the plant nucleotide-binding oligomerization domain-like receptors (NLRs) L6 from flax and disease resistance protein RPS4 from Arabidopsis. Here we show that the crystal structure of the TIR domain from the Arabidopsis NLR suppressor of npr1-1, constitutive 1 (SNC1) contains both an L6-like interface involving helices αD and αE (DE interface) and an RPS4-like interface involving helices αA and αE (AE interface). Mutations in either the AE- or DE-interface region disrupt cell-death signaling activity of SNC1, L6, and RPS4 TIR domains and full-length L6 and RPS4. Self-association of L6 and RPS4 TIR domains is affected by mutations in either region, whereas only AE-interface mutations affect SNC1 TIR-domain self-association. We further show two similar interfaces in the crystal structure of the TIR domain from the Arabidopsis NLR recognition of Peronospora parasitica 1 (RPP1). These data demonstrate that both the AE and DE self-association interfaces are simultaneously required for self-association and cell-death signaling in diverse plant NLRs.

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PLOS ONE: Floral Scent Mimicry and Vector-Pathogen Associations in a Pseudoflower-Inducing Plant Pathogen System (2016)

PLOS ONE: Floral Scent Mimicry and Vector-Pathogen Associations in a Pseudoflower-Inducing Plant Pathogen System (2016) | Plants and Microbes | Scoop.it

Several fungal plant pathogens induce ‘pseudoflowers’ on their hosts to facilitate insect-mediated transmission of gametes and spores. When spores must be transmitted to host flowers to complete the fungal life cycle, we predict that pseudoflowers should evolve traits that mimic flowers and attract the most effective vectors in the flower-visiting community. We quantified insect visitation to flowers, healthy leaves and leaves infected with Monilinia vaccinii-corymbosi(Mvc), the causative agent of mummy berry disease of blueberry. We developed a nested PCR assay for detecting Mvc spores on bees, flies and other potential insect vectors. We also collected volatiles from blueberry flowers, healthy leaves and leaves infected with Mvc, and experimentally manipulated specific pathogen-induced volatiles to assess attractiveness to potential vectors. Bees and flies accounted for the majority of contacts with flowers, leaves infected with Mvc and healthy leaves. Flowers were contacted most often, while there was no difference between bee or fly contacts with healthy and infected leaves. While bees contacted flowers more often than flies, flies contacted infected leaves more often than bees. Bees were more likely to have Mvc spores on their bodies than flies, suggesting that bees may be more effective vectors than flies for transmitting Mvc spores to flowers. Leaves infected with Mvc had volatile profiles distinct from healthy leaves but similar to flowers. Two volatiles produced by flowers and infected leaves, cinnamyl alcohol and cinnamic aldehyde, were attractive to bees, while no volatiles manipulated were attractive to flies or any other insects. These results suggest that Mvc infection of leaves induces mimicry of floral volatiles, and that transmission occurs primarily via bees, which had the highest likelihood of carrying Mvc spores and visited flowers most frequently.

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Those darn fungi!
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PLOS Pathogens: The Rice Dynamin-Related Protein OsDRP1E Negatively Regulates Programmed Cell Death by Controlling the Release of Cytochrome c from Mitochondria (2017)

PLOS Pathogens: The Rice Dynamin-Related Protein OsDRP1E Negatively Regulates Programmed Cell Death by Controlling the Release of Cytochrome c from Mitochondria (2017) | Plants and Microbes | Scoop.it

Programmed cell death (PCD) mediated by mitochondrial processes has emerged as an important mechanism for plant development and responses to abiotic and biotic stress. However, the role of translocation of cytochrome c from the mitochondria to the cytosol during PCD remains unclear. Here, we demonstrate that the rice dynamin-related protein 1E (OsDRP1E) negatively regulates PCD by controlling mitochondrial structure and cytochrome c release. We used a map-based cloning strategy to isolate OsDRP1E from the lesion mimic mutant dj-lm and confirmed that the E409V mutation in OsDRP1E causes spontaneous cell death in rice. Pathogen inoculation showed that dj-lm significantly enhances resistance to fungal and bacterial pathogens. Functional analysis of the E409V mutation showed that the mutant protein impairs OsDRP1E self-association and formation of a higher-order complex; this in turn reduces the GTPase activity of OsDRP1E. Furthermore, confocal microscopy showed that the E409V mutation impairs localization of OsDRP1E to the mitochondria. The E409V mutation significantly affects the morphogenesis of cristae in the mitochondria and causes the abnormal release of cytochrome c from the mitochondria into the cytoplasm. Taken together, our results demonstrate that the mitochondria-localized protein OsDRP1E functions as a negative regulator of cytochrome c release and PCD in plants.

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5th International Conference on Biotic Plant Interactions (5th ICBPI) in Xiamen, China on August 17-21, 2017

5th International Conference on Biotic Plant Interactions (5th ICBPI) in Xiamen, China on August 17-21, 2017 | Plants and Microbes | Scoop.it

On behalf of the Organizing Committee, we sincerely invite colleagues to attend the 5th International Conference on Biotic Plant Interactions (5th ICBPI) in Xiamen, China on August 17-21, 2017. The theme of this five-day conference is Biotic-Plant Interactions and Sustainable Control of Pests on Crops. As a continuing effort after the 1st conference (Brisbane, Australia in 2008), the 2nd conference (Kunming, China in 2011), the 3rd conference (Yanglin, China in 2013), and the 4th conference (Nanjing, China in 2015), this conference will be organized by the State Key Laboratory of Ecological Pest Control of Fujian and Taiwan Crops, Fujian Agriculture and Forestry University and Institute of Plant Physiology and Ecology at Chinese Academy of Science, Chinese Society for Plant Biology and Chinese Society for Plant Pathology. It will bring together 800-1000 scientists all over the world and cover nine sessions: plant-fungus interactions, plant-oomycete interactions, plant-bacteria interactions, plant-virus interactions, plant-insect interactions, parasitic plants/nematodes, plant symbiosis, epigenetics in biotic plant interactions, and molecular design in crop resistance.

 

We are looking forward to welcoming you in Xiamen, China.

 

Sincerely Yours!

 

Zonghua Wang,  Zuhua He, Regine Kahmann

Chairs of the Organizing Committee

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bioRxiv: Immune receptors with exogenous domain fusions form evolutionary hotspots in grass genomes (2017)

bioRxiv: Immune receptors with exogenous domain fusions form evolutionary hotspots in grass genomes (2017) | Plants and Microbes | Scoop.it

Understanding evolution of plant immunity is necessary to inform rational approaches for genetic control of plant diseases. The plant immune system is innate, encoded in the germline, yet plants are capable of recognizing diverse rapidly evolving pathogens. Plant immune receptors (NLRs) can gain pathogen recognition through point mutation, recombination of recognition domains with other receptors, and through acquisition of novel integrated protein domains. The exact molecular pathways that shape immune repertoire including new domain integration remain unknown. Here, we describe a non-uniform distribution of integrated domains among NLR subfamilies in grasses and identify genomic hotspots that demonstrate rapid expansion of NLR gene fusions. We show that just one clade in the Poaceae is responsible for the majority of unique integration events. Based on these observations we propose a model for the expansion of integrated domain repertoires that involves a flexible NLR acceptor that is capable of fusion to diverse domains derived across the genome. The identification of a subclass of NLRs that is naturally adapted to new domain integration can inform biotechnological approaches for generating synthetic receptors with novel pathogen traps.

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New Phytologist: Life, death and rebirth of avirulence effectors in a fungal pathogen of Brassica crops, Leptosphaeria maculans (2017)

New Phytologist: Life, death and rebirth of avirulence effectors in a fungal pathogen of Brassica crops, Leptosphaeria maculans (2017) | Plants and Microbes | Scoop.it

In agricultural systems, major (R) genes for resistance in plants exert strong selection pressure on cognate/corresponding avirulence effector genes of phytopathogens. However, a complex interplay often exists between trade-offs linked to effector function and the need to escape R gene recognition. Here, using the Leptosphaeria maculans–oilseed rape pathosystem we review evolution of effectors submitted to multiple resistance gene selection. Characteristics of this pathosystem include a crop in which resistance genes have been deployed intensively resulting in ‘boom and bust’ cycles; a fungal pathogen with a high adaptive potential in which seven avirulence genes are cloned and for which population surveys have been coupled with molecular analysis of events responsible for virulence. The mode of evolution of avirulence genes, all located in dispensable parts of the ‘two-speed’ genome, is a highly dynamic gene-specific process. In some instances, avirulence genes are readily deleted under selection. However, others, even when located in the most plastic genome regions, undergo only limited point mutations or their avirulence phenotype is ‘camouflaged’ by another avirulence gene. Thus, while hundreds of effector genes are present, some effectors are likely to have an important and nonredundant function, suggesting functional redundancy and dispensability of effectors might not be the rule.


Via Francis Martin
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Plant Cell: Recognition of the Magnaporthe oryzae effector AVR-Pia by the decoy domain of the rice NLR immune receptor RGA5 (2017)

Plant Cell: Recognition of the Magnaporthe oryzae effector AVR-Pia by the decoy domain of the rice NLR immune receptor RGA5 (2017) | Plants and Microbes | Scoop.it

Nucleotide-binding domain and leucine-rich repeat proteins (NLRs) are important receptors in plant immunity that allow recognition of pathogen effectors. The rice NLR RGA5 recognizes the Magnaporthe oryzae effector AVR-Pia through direct interaction. Here, we gained detailed insights into the molecular and structural bases of AVR-Pia-RGA5 interaction and the role of the RATX1 decoy domain of RGA5. NMR titration combined with in vitro and in vivo protein-protein interaction analyses identified the AVR-Pia interaction surface that binds to the RATX1 domain. Structure-informed AVR-Pia mutants showed that, although AVR-Pia associates with additional sites in RGA5, binding to the RATX1 domain is necessary for pathogen recognition, but can be of moderate affinity. Therefore, RGA5-mediated resistance is highly resilient to mutations in the effector. We propose a model that explains such robust effector recognition as a consequence, and an advantage, of the combination of integrated decoy domains with additional independent effector-NLR interactions.

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Population Genomics of Fungal and Oomycete Diseases of Animals and Plants, Ascona, Switzerland, 7-11 May 2017

Population Genomics of Fungal and Oomycete Diseases of Animals and Plants, Ascona, Switzerland, 7-11 May 2017 | Plants and Microbes | Scoop.it

The population genomics of emerging fungal and oomycete pathogens is a dynamic and rapidly growing area of research. New datasets, new sequencing methodologies and new analytical methods are enabling a deeper understanding of the evolutionary processes driving the emergence of fungal and oomycete pathogens. This conference aims to enrich our understanding of the processes driving the evolution of plant, animal and human pathogens, with an over-riding goal of identifying the genomic changes responsible for adaptation to novel hosts and environments. A secondary goal will be to determine how the relevant genes (and their underlying functions) vary along ecological/agronomic gradients associated with host specialization, including quantitative adaptation to host resistance. Another important goal is to facilitate networking of key scientists working on fungal and oomycete diseases of plants, animals and humans. The conference will be oriented around genome-based approaches, including; 1) using population genomics to understand pathogen emergence and host specialization, 2) using genome-wide association studies to identify key genes and genomic regions associated with pathogen local adaptation, 3) using population genomics to understand pathogen divergence/speciation, 4) developing new analytical methods for population genomic analyses.

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15th Congress of the Mediterranean Phytopathological Union, Córdoba, Spain, June 20-23 2017

15th Congress of the Mediterranean Phytopathological Union, Córdoba, Spain, June 20-23 2017 | Plants and Microbes | Scoop.it

The upcoming Congress of the Mediterranean Phytopathological Union entitled Plant health sustaining Mediterranean Ecosystems” will be held in Córdoba, Spain, from June 20-23, 2017. The meeting promotes dissemination of the latest scientific advances and encourages dialogue and collaboration between researchers interested in all aspects of Phytopathology. The conference language is English.

 

A detailed scientific program will be available in January 2017. Plenary, concurrent and poster sessions will be held on key topics such as Genome Analysis; Invasive Emerging Pathogens; Integrated Disease Management; Food Safety, New Tools In Diagnostics And Management; Molecular Pathogen-Host Interactions; Impact Of Climate Change; Biocontrol, Natural Compounds And Plant Stimulants; Epidemiology And Modelling; and Microbiomes In Plant Health. The meeting proceedings will be published in the international journal Phytopathologia Mediterranea.

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