Plants and Microbes
Follow
Find
181.9K views | +88 today
 
Scooped by Kamoun Lab @ TSL
onto Plants and Microbes
Scoop.it!

XVI International Botrytis Symposium Bari, Italy, June 23-28, 2013

XVI International Botrytis Symposium Bari, Italy, June 23-28, 2013 | Plants and Microbes | Scoop.it

The XVI International Botrytis Symposium will be organized by the Section of Plant Pathology of the Department of Soil, Plant and Food Sciences of the University of Bari (Italy) (DISSPA) in cooperation with the Research, Experimentation and Educational Centre in Agriculture "Basile Caramia" (CRSFA). The Symposium will be held from 23 to 28 June 2013 in Locorotondo (Bari, Italy), a small and old town looking out over the Itria Valley (Valle d'Itria), one of the most beautiful landscapes and touristic attractive areas all over the Puglia region (Southern Italy). Like in the past meetings, the Symposium will bring together scientists representing a broad spectrum of countries, topics, research approaches, crops, and agricultural practices all over the world. Skilled and young researchers with different backgrounds and interests, all focused on Botrytis and related fungi, will share knowledge, expertise, and ideas. The XVI International Botrytis Symposium will be based on invited key lectures, oral presentations and posters concerning all the most relevant aspects of Botrytis and related fungi: identification, management, ecology and epidemiology, biology, genetics, chemical and biological control, post-harvest management, -omics, post-genomics and host-pathogen interactions. The Scientific Committee and the Organizing Committee of the Symposium are doing all their best to combine an exciting scientific programme with the pleasant and friendly hospitality, excellent foods and wines, beautiful landscapes, and historical traditions characterizing the Itria Valley and the Puglia region.

more...
No comment yet.
Plants and Microbes
Everything related to the science of plant-microbe interactions
Your new post is loading...
Your new post is loading...
Scooped by Kamoun Lab @ TSL
Scoop.it!

bioRxiv: Phytophthora infestans RXLR-WY effector AVR3a associates with a Dynamin-Related Protein involved in endocytosis of a plant pattern recognition receptor (2014)

bioRxiv: Phytophthora infestans RXLR-WY effector AVR3a associates with a Dynamin-Related Protein involved in endocytosis of a plant pattern recognition receptor (2014) | Plants and Microbes | Scoop.it

Perception of pathogen associated molecular patterns (PAMPs) by cell surface localized pattern recognition receptors (PPRs), activates plant basal defense responses in a process known as PAMP/PRR–triggered immunity (PTI). In turn, pathogens deploy effector proteins that interfere with different steps in PTI signaling. However, our knowledge of PTI suppression by filamentous plant pathogens, i.e. fungi and oomycetes, remains fragmentary. Previous work revealed that BAK1/SERK3, a regulatory receptor of several PRRs, contributes to basal immunity against the Irish potato famine pathogen Phytophthora infestans. Moreover BAK1/SERK3 is required for the cell death induced by P. infestans elicitin INF1, a protein with characteristics of PAMPs. The P. infestans host-translocated RXLR-WY effector AVR3a is known to supress INF1-mediated defense by binding the E3 ligase CMPG1. In contrast, AVR3aKI-Y147del, a deletion mutant of the C-terminal tyrosine of AVR3a, fails to bind CMPG1 and suppress INF1 cell death. Here we studied the extent to which AVR3a and its variants perturb additional BAK1/SERK3 dependent PTI responses using the plant PRR FLAGELLIN SENSING 2 (FLS2). We found that all tested variants of AVR3a, including AVR3aKI-Y147del, suppress early defense responses triggered by the bacterial flagellin-derived peptide flg22 and reduce internalization of activated FLS2 from the plasma membrane without disturbing its nonactivated localization. Consistent with this effect of AVR3a on FLS2 endocytosis, we discovered that AVR3a associates with the Dynamin-Related Protein DRP2, a plant GTPase implicated in receptor-mediated endocytosis. Interestingly, DRP2 is required for ligand-induced FLS2 internalization but does not affect internalization of the growth receptor BRASSINOSTEROID INSENSITIVE 1 (BRI1). Furthermore, overexpression of DRP2 suppressed accumulation of reactive oxygen species triggered by PAMP treatment. We conclude that AVR3a associates with a key cellular trafficking and membrane-remodeling complex involved in immune receptor-mediated endocytosis and signaling. AVR3a is a multifunctional effector that can suppress BAK1/SERK3 mediated immunity through at least two different pathways.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

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

New Phytologist: Meetings - A snapshot of molecular plant–microbe interaction research (2014) | Plants and Microbes | 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.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

Plant Cell: Virulence Factors of Geminivirus Interact with MYC2 to Subvert Plant Resistance and Promote Vector Performance (2014)

Plant Cell: Virulence Factors of Geminivirus Interact with MYC2 to Subvert Plant Resistance and Promote Vector Performance (2014) | Plants and Microbes | Scoop.it

A pathogen may cause infected plants to promote the performance of its transmitting vector, which accelerates the spread of the pathogen. This positive effect of a pathogen on its vector via their shared host plant is termed indirect mutualism. For example, terpene biosynthesis is suppressed in begomovirus-infected plants, leading to reduced plant resistance and enhanced performance of the whiteflies (Bemisia tabaci) that transmit these viruses. Although begomovirus-whitefly mutualism has been known, the underlying mechanism is still elusive. Here, we identified βC1 of Tomato yellow leaf curl China virus, a monopartite begomovirus, as the viral genetic factor that suppresses plant terpene biosynthesis. βC1 directly interacts with the basic helix-loop-helix transcription factor MYC2 to compromise the activation of MYC2-regulated terpene synthase genes, thereby reducing whitefly resistance. MYC2 associates with the bipartite begomoviral protein BV1, suggesting that MYC2 is an evolutionarily conserved target of begomoviruses for the suppression of terpene-based resistance and the promotion of vector performance. Our findings describe how this viral pathogen regulates host plant metabolism to establish mutualism with its insect vector.

more...
Ed Rybicki's curator insight, December 18, 6:31 AM

Cunning trick, for a small virus!

Scooped by Kamoun Lab @ TSL
Scoop.it!

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 | Plants and Microbes | 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.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

BMC Plant Biology: Mutations in the Arabidopsis homoserine kinase gene DMR1 confer enhanced resistance to Fusarium culmorum and F. graminearum (2014)

BMC Plant Biology: Mutations in the Arabidopsis homoserine kinase gene DMR1 confer enhanced resistance to Fusarium culmorum and F. graminearum (2014) | Plants and Microbes | Scoop.it

Background - Mutation of Arabidopsis DMR1, encoding homoserine kinase, leads to elevation in homoserine and foliar resistance to the biotrophic pathogens Hyaloperonospora arabidopsidis and Oidium neolycopersici through activation of an unidentified defence mechanism. This study investigates the effect of mutation of dmr1 on resistance to the ascomycete pathogens Fusarium graminearum and F. culmorum, which cause Fusarium Ear Blight (FEB) disease on small grain cereals.


Results - We initially found that the dmr1-2 mutant allele confers increased resistance to F. culmorum and F. graminearum silique infection, and decreased colonisation of rosette leaves. Meanwhile the dmr1-1 allele supports less rosette leaf colonisation but has wild type silique resistance. Three additional dmr1 alleles were subsequently examined for altered F. culmorum susceptibility and all showed increased silique resistance, while leaf colonisation was reduced in two (dmr1-3 and dmr1-4). Amino acid analysis of dmr1 siliques revealed homoserine accumulation, which is undetectable in wild type plants. Exogenous application of L-homoserine reduced bud infection in both dmr1 and wild type plants, whilst D-homoserine application did not. Delayed leaf senescence was also observed in dmr1 plants compared to wild type and correlated with reduced Fusarium leaf colonisation.


Conclusions - These findings suggest that common Arabidopsis DMR1 mediated susceptibility mechanisms occur during infection by both obligate biotrophic oomycete and hemi-biotrophic fungal pathogens, not only in vegetative but also in reproductive plant tissues. This has the potential to aid the development of cereal crops with enhanced resistance to FEB.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

News: Millions of Ash Trees Are Dying, Creating Huge Headaches for Cities (2014)

News: Millions of Ash Trees Are Dying, Creating Huge Headaches for Cities (2014) | Plants and Microbes | Scoop.it

KANSAS CITY, Missouri—Forester Kevin Lapointe remembers clearly the day he and his colleagues at the Kansas City Parks and Recreation Department did their first autopsy on a dead ash tree. Under its peeling bark, they found S-shaped burrows running across every inch of the outer layer of wood. Looking closer, they discovered the killer: a slender green beetle smaller than a penny.


The emerald ash borer, or EAB, a native of East Asia, has already devastated entire ash populations in northern cities such as Detroit, where it first appeared in 2002. Since then, the insect has swept into 22 states across the country. In the summer of 2012 it reached the Kansas City metropolitan area.


There are seven billion ash trees in North America, and within the next few decades, the beetle could kill most of them—a die-off ten times bigger than the one caused by Dutch elm disease.


In big cities, where ash species account for up to a quarter of trees in public spaces, planners must consider the environmental consequences of the massive die-off—liability hazards, an increase in stormwater runoff, and the simple problem of disposing of millions of dead trees. And officials don't have time to waste.


Eight years after the initial discovery of the beetles in an area, about 50 percent of the ash population will die—all at once. The rest die within another two to three years. In the Kansas City metropolitan area, where Lapointe works, 6.4 million ashes are on track to die as early as 2015—unless they receive insecticide treatment.


Chad Tinkel, who inherited an EAB problem when he became the city arborist of Fort Wayne, Indiana, didn't have the luxury of early identification or a big city budget for prevention. Of the 18,000 ash trees that once shaded Fort Wayne's sidewalks and parking lots, only about 1,300 remain alive. Tinkel now speaks about EAB to municipalities across the country.


"If you know that it's coming, be proactive," he says. "Get your plan in place. Get your budget set. Too few decision-makers realize that trees are infrastructure—just like a city bench, just like a streetlight—and they pay back more than they cost to put in."

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

Norwich Rust Group (2014)

Norwich Rust Group (2014) | Plants and Microbes | Scoop.it

The John Innes CentreThe Sainsbury Laboratory and The Genome Analysis Centre are working collaboratively to tackle rust fungi.

 

There are more than 7,000 species of rust fungi, including some of agriculture’s most devastating plant diseases such as Wheat Stem Rust, Wheat Stripe Rust and Asian Soybean Rust which all cause significant yield and financial losses. Rust fungi pose a significant challenge for growers and a serious threat to food security.

 

The Norwich Rust Group (NRG) brings together seven scientific teams from these leading institutes that all study rust fungi. The close proximity of the three collaborating institutes on the Norwich Research Park allows the seven teams to work as a single force, with rapid access to each others complementary expertise and technologies, and allows for joint appointments across institutes. Together, the Norwich Rust Group works with 52 collaborators in 23 countries around the world in order to develop new technologies and approaches to combat rust fungi in an efficient and durable way.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

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.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

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.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

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
more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

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).

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

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.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

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.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

PLOS Pathogens: Loss of Arabidopsis thaliana Dynamin-Related Protein 2B Reveals Separation of Innate Immune Signaling Pathways (2014)

PLOS Pathogens: Loss of Arabidopsis thaliana Dynamin-Related Protein 2B Reveals Separation of Innate Immune Signaling Pathways (2014) | Plants and Microbes | Scoop.it

Vesicular trafficking has emerged as an important means by which eukaryotes modulate responses to microbial pathogens, likely by contributing to the correct localization and levels of host components necessary for effective immunity. However, considering the complexity of membrane trafficking in plants, relatively few vesicular trafficking components with functions in plant immunity are known. Here we demonstrate that Arabidopsis thaliana Dynamin-Related Protein 2B (DRP2B), which has been previously implicated in constitutive clathrin-mediated endocytosis (CME), functions in responses to flg22 (the active peptide derivative of bacterial flagellin) and immunity against flagellated bacteria Pseudomonas syringae pv. tomato (Pto) DC3000. Consistent with a role of DRP2B in Pattern-Triggered Immunity (PTI), drp2b null mutant plants also showed increased susceptibility to Pto DC3000 hrcC, which lacks a functional Type 3 Secretion System, thus is unable to deliver effectors into host cells to suppress PTI. Importantly, analysis of drp2b mutant plants revealed three distinct branches of the flg22-signaling network that differed in their requirement for RESPIRATORY BURST OXIDASE HOMOLOGUE D (RBOHD), the NADPH oxidase responsible for flg22-induced apoplastic reactive oxygen species production. Furthermore, in drp2b, normal MAPK signaling and increased immune responses via the RbohD/Ca2+-branch were not sufficient for promoting robust PR1 mRNA expression nor immunity against Pto DC3000 and PtoDC3000 hrcC. Based on live-cell imaging studies, flg22-elicited internalization of the plant flagellin-receptor, FLAGELLIN SENSING 2 (FLS2), was found to be partially dependent on DRP2B, but not the closely related protein DRP2A, thus providing genetic evidence for a component, implicated in CME, in ligand-induced endocytosis of FLS2. Reduced trafficking of FLS2 in response to flg22 may contribute in part to the non-canonical combination of immune signaling defects observed in drp2b. In conclusion, this study adds DRP2B to the relatively short list of known vesicular trafficking proteins with roles in flg22-signaling and PTI in plants.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

PLOS Pathogens: Apoplastic Venom Allergen-like Proteins of Cyst Nematodes Modulate the Activation of Basal Plant Innate Immunity by Cell Surface Receptors (2014)

PLOS Pathogens: Apoplastic Venom Allergen-like Proteins of Cyst Nematodes Modulate the Activation of Basal Plant Innate Immunity by Cell Surface Receptors (2014) | Plants and Microbes | Scoop.it

Despite causing considerable damage to host tissue during the onset of parasitism, nematodes establish remarkably persistent infections in both animals and plants. It is thought that an elaborate repertoire of effector proteins in nematode secretions suppresses damage-triggered immune responses of the host. However, the nature and mode of action of most immunomodulatory compounds in nematode secretions are not well understood. Here, we show that venom allergen-like proteins of plant-parasitic nematodes selectively suppress host immunity mediated by surface-localized immune receptors. Venom allergen-like proteins are uniquely conserved in secretions of all animal- and plant-parasitic nematodes studied to date, but their role during the onset of parasitism has thus far remained elusive. Knocking-down the expression of the venom allergen-like protein Gr-VAP1 severely hampered the infectivity of the potato cyst nematode Globodera rostochiensis. By contrast, heterologous expression of Gr-VAP1 and two other venom allergen-like proteins from the beet cyst nematode Heterodera schachtii in plants resulted in the loss of basal immunity to multiple unrelated pathogens. The modulation of basal immunity by ectopic venom allergen-like proteins in Arabidopsis thaliana involved extracellular protease-based host defenses and non-photochemical quenching in chloroplasts. Non-photochemical quenching regulates the initiation of the defense-related programmed cell death, the onset of which was commonly suppressed by venom allergen-like proteins from G. rostochiensisH. schachtii, and the root-knot nematode Meloidogyne incognita. Surprisingly, these venom allergen-like proteins only affected the programmed cell death mediated by surface-localized immune receptors. Furthermore, the delivery of venom allergen-like proteins into host tissue coincides with the enzymatic breakdown of plant cell walls by migratory nematodes. We, therefore, conclude that parasitic nematodes most likely utilize venom allergen-like proteins to suppress the activation of defenses by immunogenic breakdown products in damaged host tissue.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

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) | Plants and Microbes | 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.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

PNAS: Nep1-like proteins from three kingdoms of life act as a microbe-associated molecular pattern in Arabidopsis (2014)

PNAS: Nep1-like proteins from three kingdoms of life act as a microbe-associated molecular pattern in Arabidopsis (2014) | Plants and Microbes | Scoop.it

Necrosis and ethylene-inducing peptide 1 (Nep1)-like proteins (NLPs) are secreted by a wide range of plant-associated microorganisms. They are best known for their cytotoxicity in dicot plants that leads to the induction of rapid tissue necrosis and plant immune responses. The biotrophic downy mildew pathogen Hyaloperonospora arabidopsidis encodes 10 different noncytotoxic NLPs (HaNLPs) that do not cause necrosis. We discovered that these noncytotoxic NLPs, however, act as potent activators of the plant immune system in Arabidopsis thaliana. Ectopic expression of HaNLP3 in Arabidopsis triggered resistance to H. arabidopsidis, activated the expression of a large set of defense-related genes, and caused a reduction of plant growth that is typically associated with strongly enhanced immunity. N- and C-terminal deletions of HaNLP3, as well as amino acid substitutions, pinpointed to a small central region of the protein that is required to trigger immunity, indicating the protein acts as a microbe-associated molecular pattern (MAMP). This was confirmed in experiments with a synthetic peptide of 24 aa, derived from the central part of HaNLP3 and corresponding to a conserved region in type 1 NLPs that induces ethylene production, a well-known MAMP response. Strikingly, corresponding 24-aa peptides of fungal and bacterial type 1 NLPs were also able to trigger immunity in Arabidopsis. The widespread phylogenetic distribution of type 1 NLPs makes this protein family (to our knowledge) the first proteinaceous MAMP identified in three different kingdoms of life.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

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.


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

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

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

Happy holidays from the @KamounLab!

 

FiFi (Phytophthora) The Oomycete


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

Scooped by Kamoun Lab @ TSL
Scoop.it!

Frontiers: Oligogalacturonides: plant damage-associated molecular patterns and regulators of growth and development (2013)

Frontiers: Oligogalacturonides: plant damage-associated molecular patterns and regulators of growth and development (2013) | Plants and Microbes | Scoop.it

Oligogalacturonides (OGs) are oligomers of alpha-1,4-linked galacturonosyl residues released from plant cell walls upon partial degradation of homogalacturonan. OGs are able to elicit defense responses, including accumulation of reactive oxygen species and pathogenesis-related proteins, and protect plants against pathogen infections. Recent studies demonstrated that OGs are perceived by wall-associated kinases and share signaling components with microbe-associated molecular patterns. For this reason OGs are now considered true damage-associated molecular patterns that activate the plant innate immunity and may also be involved in the activation of responses to mechanical wounding. Furthermore, OGs appear to modulate developmental processes, likely through their ability to antagonize auxin responses. Here we review our current knowledge on the role and mode of action of this class of oligosaccharides in plant defense and development.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

Traffic: Rerouting of plant late endocytic trafficking towards a pathogen interface (2014)

Traffic: Rerouting of plant late endocytic trafficking towards a pathogen interface (2014) | Plants and Microbes | Scoop.it

The biogenesis and functions of the extrahaustorial membrane (EHM), an intimate interface between plants and filamentous pathogens, are poorly understood. One long-standing puzzle is why several membrane proteins, such as some cell surface receptors, are missing from the EHM. We gained a significant insight into how the EHM is formed and made an important step in understanding why certain membrane proteins are missing from the EHM. We discovered that late endosomes targeted to the vacuoles are rerouted to the EHM. This process is dynamic because, upon activation, a cell surface immune receptor traffics to this compartment. We propose a model in which some cell surface receptors that undergo ligand induced endocytosis and traffic to late endosomes get sorted to the host pathogen interface, instead of taking the default route to the vacuole as in uninfected cells.


--- A number of plant pathogenic and symbiotic microbes produce specialized cellular structures that invade host cells where they remain enveloped by host-derived membranes. The mechanisms underlying the biogenesis and functions of host-microbe interfaces are poorly understood. Here, we show that plant late endocytic trafficking is diverted towards the extrahaustorial membrane; a host-pathogen interface that develops in plant cells invaded by Irish potato famine pathogen Phytophthora infestans. A late endosome and tonoplast marker protein Rab7 GTPase RabG3c, but not a tonoplast-localized sucrose transporter, is recruited to the extrahaustorial membrane suggesting specific rerouting of vacuole targeted late endosomes to a host pathogen interface. We revealed the dynamic nature of this process by showing that, upon activation, a cell surface immune receptor traffics towards the haustorial interface. Our work provides insight into the biogenesis of the extrahaustorial membrane and reveals dynamic processes that recruit membrane compartments and immune receptors to this host-pathogen interface.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

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.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

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.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

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.

more...
No comment yet.
Scooped by Kamoun Lab @ TSL
Scoop.it!

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.

more...
Rescooped by Kamoun Lab @ TSL from TAL effector science
Scoop.it!

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.


Via dromius
more...
No comment yet.