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Rescooped by Xiaoli Zhang from Host Cell & Pathogen Interactions
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Host ESCRT Proteins Are Required for Bromovirus RNA Replication Compartment Assembly and Function

Host ESCRT Proteins Are Required for Bromovirus RNA Replication Compartment Assembly and Function | Plant pathogen | Scoop.it
Author Summary Positive-strand RNA {(+)RNA} viruses cause numerous human, animal, and plant diseases. (+)RNA viruses reorganize host intracellular membranes to assemble their RNA replication compartments, which are mini-organelles featuring the close association of both viral and host components. To further understand the role of host components in forming such RNA replication compartments, we used brome mosaic virus (BMV), a well characterized model virus, to study some common features of (+)RNA virus RNA replication. We show that knocking out several components of the cellular Endosomal Complex Required for Transport (ESCRT) machinery resulted in parallel defects in BMV RNA replication and replication compartment formation, whereas other ESCRT components affected RNA replication independently of replication compartment formation. Deleting a subset of ESCRT proteins altered the frequency of replication compartment formation but had no effect on the size of these compartments, whereas a second subset affected RNA replication independently of replication compartment formation. Moreover, BMV’s interaction with the ESCRT machinery appears to be distinct from that reported for other viruses and from the ESCRT requirements for forming vesicles in cellular multivesicular bodies. These findings further illuminate the remarkable abilities of positive-strand RNA viruses to integrate viral and host protein functions to remodel membranes, and suggest potentially potent new ways to control such viruses.

Via Kenzibit
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Rescooped by Xiaoli Zhang from Plant pathogenic fungi
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Knocking Out Bcsas1 in Botrytis cinerea Impacts Growth, Development, and Secretion of Extracellular Proteins, Which Decreases Virulence

Knocking Out Bcsas1 in Botrytis cinerea Impacts Growth, Development, and Secretion of Extracellular Proteins, Which Decreases Virulence | Plant pathogen | Scoop.it

“Pathogenic fungi usually secrete a series of virulence factors to the extracellular environment to facilitate infection. Rab GTPases play a central role in the secretory pathway. To explore the function of Rab/GTPase in filamentous fungi, we knocked out a Rab/GTPase family gene, Bcsas1, in Botrytis cinerea, an aggressive fungal pathogen that infects more than 200 plant species. A detailed analysis was conducted on the virulence and the secretory capability of the mutants. The results indicated that knockout of Bcsas1 inhibited hyphal development and reduced sporulation of B. cinerea on potato dextrose agar plates resulting in reduced virulence on various fruit hosts. Knocking out the Bcsas1 gene led to an accumulation of transport vesicles at the hyphal tip, significantly reduced extracellular protein content, and lowered the activity of polygalacturonase and xylanase in the extracellular medium. However, mutation of Bcsas1 did not affect the expression of genes encoding polygalacturonase and xylanase, suggesting the secretion of these two family enzymes was suppressed in the mutant. Moreover, a comparative analysis of the secretome provided further evidence that the disruption of Bcsas1 in mutant strains significantly depressed the secretion of polysaccharide hydrolases and proteases. The results indicate that Bcsas1, the Rab8/SEC4-like gene, plays a crucial role in development, protein secretion, and virulence of B. cinerea.”


Via IPM Lab, Steve Marek
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Rescooped by Xiaoli Zhang from Plant immunity and legume symbiosis
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Epigenetic responses to stress: triple defense?

Epigenetic responses to stress: triple defense? | Plant pathogen | Scoop.it

Stressful conditions for plants can originate from numerous physical, chemical and biological factors, and plants have developed a plethora of survival strategies including developmental and morphological adaptations, specific signaling and defense pathways as well as innate and acquired immunity. While it has become clear in recent years that many stress responses involve epigenetic components, we are far from understanding the mechanisms and molecular interactions. Extending our knowledge is fundamental, not least for plant breeding and conservation biology. This review will highlight recent insights into epigenetic stress responses at the level of signaling, chromatin modification, and potentially heritable consequences.


Via Christophe Jacquet
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Rescooped by Xiaoli Zhang from Plant Immunity And Microbial Effectors
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A Histone H3 Lysine-27 Methyltransferase Complex Represses Lateral Root Formation in Arabidopsis thaliana

Lateral root founder cell establishment is essential for primary root branching.

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Plant-Pathogen Interactions: Methods and Protocols

Plant-Pathogen Interactions: Methods and Protocols | Plant pathogen | Scoop.it
Available in: Hardcover. Plant-Pathogen Interactions: Methods and Protocols, Second Edition expands upon the first edition with current, detailed protocols for the study of plant pathogen genome sequences.
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Rescooped by Xiaoli Zhang from Plant pathogenic fungi
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DNA methylation as a system of plant genomic immunity

DNA methylation as a system of plant genomic immunity | Plant pathogen | Scoop.it

Establishment of DNA methylation is guided by the RNA interference pathway.

DNA methylation is maintained by three interconnected pathways.

Several pathways protect genes from the deleterious effects of DNA methylation.

DNA demethylation and RNA-directed DNA methylation regulate gene expression.


Via Steve Marek
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Rescooped by Xiaoli Zhang from Plants and Microbes
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Nature Reviews Microbiology: On the front line: structural insights into plant-pathogen interactions (2013)

Nature Reviews Microbiology: On the front line: structural insights into plant-pathogen interactions (2013) | Plant pathogen | Scoop.it

Over the past decade, considerable advances have been made in understanding the molecular mechanisms that underpin the arms race between plant pathogens and their hosts. Alongside genomic, bioinformatic, proteomic, biochemical and cell biological analyses of plant–pathogen interactions, three-dimensional structural studies of virulence proteins deployed by pathogens to promote infection, in some cases complexed with their plant cell targets, have uncovered key insights into the functions of these molecules. Structural information on plant immune receptors, which regulate the response to pathogen attack, is also starting to emerge. Structural studies of bacterial plant pathogen–host systems have been leading the way, but studies of filamentous plant pathogens are gathering pace. In this Review, we summarize the key developments in the structural biology of plant pathogen–host interactions.


Via Kamoun Lab @ TSL
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Rescooped by Xiaoli Zhang from Arabidopsis
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RNA Polymerase V targets transcriptional silencing components to promoters of protein-coding genes - Zheng - The Plant Journal - Wiley Online Library

RNA Polymerase V targets transcriptional silencing components to promoters of protein-coding genes - Zheng - The Plant Journal - Wiley Online Library | Plant pathogen | Scoop.it

Summary

Transcriptional gene silencing controls transposons and other repetitive elements through RNA-directed DNA methylation (RdDM) and heterochromatin formation. A key component of the Arabidopsis RdDM pathway is ARGONAUTE4 (AGO4), which associates with siRNAs to mediate DNA methylation. Here, we show that AGO4 preferentially targets transposable elements embedded within promoters of protein-coding genes. We find that this pattern of AGO4 binding cannot be simply explained by the sequences of AGO4-bound siRNAs, but instead AGO4 binding to specific gene promoters is also mediated by long non-coding RNAs (lncRNAs) produced by RNA Polymerase V. lncRNA-mediated AGO4 binding to gene promoters directs asymmetric DNA methylation to these genomic regions and is involved in regulating the expression of targeted genes. Finally, AGO4-binding overlaps sites of DNA methylation affected by biotic stress response. Based on these findings, we propose that targets of AGO4-directed RdDM are regulatory units responsible for controlling gene expression under specific environmental conditions.

 

© 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd


Via GMI Vienna
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hedgeshandy's comment, October 17, 2013 6:31 AM
Its interesting
Rescooped by Xiaoli Zhang from Amazing Science
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Scientists have found that memories may be passed down through generations in our DNA

Scientists have found that memories may be passed down through generations in our DNA | Plant pathogen | Scoop.it

New research from Emory University School of Medicine, in Atlanta, has shown that it is possible for some information to be inherited biologically through chemical changes that occur in DNA. During the tests they learned that that mice can pass on learned information about traumatic or stressful experiences – in this case a fear of the smell of cherry blossom – to subsequent generations.


Using olfactory molecular specificity, the researchers examined the inheritance of parental traumatic exposure, a phenomenon that has been frequently observed, but is not fully understood. The scientists subjected F0 mice to odor fear conditioning before conception and found that subsequently conceived F1 and F2 generations had an increased behavioral sensitivity to the F0-conditioned odor, but not to other odors. When an odor (acetophenone) that activates a known odorant receptor (Olfr151) was used to condition F0 mice, the behavioral sensitivity of the F1 and F2 generations to acetophenone was complemented by an enhanced neuroanatomical representation of the Olfr151 pathway.


Bisulfite sequencing of sperm DNA from conditioned F0 males and F1 naive offspring revealed CpG hypomethylation in the Olfr151 gene. In addition, in vitro fertilization, F2 inheritance and cross-fostering revealed that these transgenerational effects are inherited via parental gametes.


These findings provide a framework for addressing how environmental information may be inherited transgenerationally at behavioral, neuroanatomical and epigenetic levels.


Professor Marcus Pembrey, a paediatric geneticist at University College London, said the work provided “compelling evidence” for the biological transmission of memory. He added: “It addresses constitutional fearfulness that is highly relevant to phobias, anxiety and post-traumatic stress disorders, plus the controversial subject of transmission of the ‘memory’ of ancestral experience down the generations.



Via Dr. Stefan Gruenwald
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Rescooped by Xiaoli Zhang from Plant-Microbe Interaction
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A Novel Botrytis Species Is Associated with a Newly Emergent Foliar Disease in Cultivated Hemerocallis

A Novel Botrytis Species Is Associated with a Newly Emergent Foliar Disease in Cultivated Hemerocallis | Plant pathogen | Scoop.it
Foliar tissue samples of cultivated daylilies (Hemerocallis hybrids) showing the symptoms of a newly emergent foliar disease known as ‘spring sickness’ were investigated for associated fungi. The cause(s) of this disease remain obscure. We isolated repeatedly a fungal species which proved to be member of the genus Botrytis, based on immunological tests. DNA sequence analysis of these isolates, using several different phyogenetically informative genes, indicated that they represent a new Botrytis species, most closely related to B. elliptica (lily blight, fire blight) which is a major pathogen of cultivated Lilium. The distinction of the isolates was confirmed by morphological analysis of asexual sporulating cultures. Pathogenicity tests on Hemerocallis tissues in vitro demonstrated that this new species was able to induce lesions and rapid tissue necrosis. Based on this data, we infer that this new species, described here as B. deweyae, is likely to be an important contributor to the development of ‘spring sickness’ symptoms. Pathogenesis may be promoted by developmental and environmental factors that favour assault by this necrotrophic pathogen. The emergence of this disease is suggested to have been triggered by breeding-related changes in cultivated hybrids, particularly the erosion of genetic diversity. Our investigation confirms that emergent plant diseases are important and deserve close monitoring, especially in intensively in-bred plants.

Via Guogen Yang
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Rescooped by Xiaoli Zhang from Plant pathogenic fungi
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Knocking Out Bcsas1 in Botrytis cinerea Impacts Growth, Development, and Secretion of Extracellular Proteins, Which Decreases Virulence

Knocking Out Bcsas1 in Botrytis cinerea Impacts Growth, Development, and Secretion of Extracellular Proteins, Which Decreases Virulence | Plant pathogen | Scoop.it

“Pathogenic fungi usually secrete a series of virulence factors to the extracellular environment to facilitate infection. Rab GTPases play a central role in the secretory pathway. To explore the function of Rab/GTPase in filamentous fungi, we knocked out a Rab/GTPase family gene, Bcsas1, in Botrytis cinerea, an aggressive fungal pathogen that infects more than 200 plant species. A detailed analysis was conducted on the virulence and the secretory capability of the mutants. The results indicated that knockout of Bcsas1 inhibited hyphal development and reduced sporulation of B. cinerea on potato dextrose agar plates resulting in reduced virulence on various fruit hosts. Knocking out the Bcsas1 gene led to an accumulation of transport vesicles at the hyphal tip, significantly reduced extracellular protein content, and lowered the activity of polygalacturonase and xylanase in the extracellular medium. However, mutation of Bcsas1 did not affect the expression of genes encoding polygalacturonase and xylanase, suggesting the secretion of these two family enzymes was suppressed in the mutant. Moreover, a comparative analysis of the secretome provided further evidence that the disruption of Bcsas1 in mutant strains significantly depressed the secretion of polysaccharide hydrolases and proteases. The results indicate that Bcsas1, the Rab8/SEC4-like gene, plays a crucial role in development, protein secretion, and virulence of B. cinerea.”


Via IPM Lab, Steve Marek
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Rescooped by Xiaoli Zhang from Plants and Microbes
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Mol Cell: Plant PRRs and the Activation of Innate Immune Signaling (2014)

Mol Cell: Plant PRRs and the Activation of Innate Immune Signaling (2014) | Plant pathogen | Scoop.it

Despite being sessile organisms constantly exposed to potential pathogens and pests, plants are surprisingly resilient to infections. Plants can detect invaders via the recognition of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs). Plant PRRs are surface-localized receptor-like kinases, which comprise a ligand-binding ectodomain and an intracellular kinase domain, or receptor-like proteins, which do not exhibit any known intracellular signaling domain. In this review, we summarize recent discoveries that shed light on the molecular mechanisms underlying ligand perception and subsequent activation of plant PRRs. Notably, plant PRRs appear as central components of multiprotein complexes at the plasma membrane that contain additional transmembrane and cytosolic kinases required for the initiation and specificity of immune signaling. PRR complexes are under tight control by protein phosphatases, E3 ligases, and other regulatory proteins, illustrating the exquisite and complex regulation of these molecular machines whose proper activation underlines a crucial layer of plant immunity.


Via Kamoun Lab @ TSL
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Rescooped by Xiaoli Zhang from Plant immunity and legume symbiosis
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The Arabidopsis PEPR pathway couples local and systemic plant immunity

The Arabidopsis PEPR pathway couples local and systemic plant immunity | Plant pathogen | Scoop.it

Recognition of microbial challenges leads to enhanced immunity at both the local and systemic levels. In Arabidopsis, EFR and PEPR1/PEPR2 act as the receptor for the bacterial elongation factor EF‐Tu (elf18 epitope) and for the endogenous PROPEP‐derived Pep epitopes, respectively. The PEPR pathway has been described to mediate defence signalling following microbial recognition. Here we show that PROPEP2/PROPEP3 induction upon pathogen challenges is robust against jasmonate, salicylate, or ethylene dysfunction. Comparative transcriptome profiling between Pep2‐ and elf18‐treated plants points to co‐activation of otherwise antagonistic jasmonate‐ and salicylate‐mediated immune branches as a key output of PEPR signalling. Accordingly, as well as basal defences against hemibiotrophic pathogens, systemic immunity is reduced in pepr1 pepr2 plants. Remarkably, PROPEP2/PROPEP3 induction is essentially restricted to the pathogen challenge sites during pathogen‐induced systemic immunity. Localized Pep application activates genetically separable jasmonate and salicylate branches in systemic leaves without significant PROPEP2/PROPEP3 induction. Our results suggest that local PEPR activation provides a critical step in connecting local to systemic immunity by reinforcing separate defence signalling pathways.


Via Christophe Jacquet
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Rescooped by Xiaoli Zhang from Plants and Microbes
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Nature Reviews Microbiology: Filamentous plant pathogen effectors in action (2013)

Nature Reviews Microbiology: Filamentous plant pathogen effectors in action (2013) | Plant pathogen | Scoop.it

Live-cell imaging assisted by fluorescent markers has been fundamental to understanding the focused secretory 'warfare' that occurs between plants and biotrophic pathogens that feed on living plant cells. Pathogens succeed through the spatiotemporal deployment of a remarkably diverse range of effector proteins to control plant defences and cellular processes. Some effectors can be secreted by appressoria even before host penetration, many enter living plant cells where they target diverse subcellular compartments and others move into neighbouring cells to prepare them before invasion. This Review summarizes the latest advances in our understanding of the cell biology of biotrophic interactions between plants and their eukaryotic filamentous pathogens based on in planta analyses of effectors.


Via Kamoun Lab @ TSL
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Rescooped by Xiaoli Zhang from Plant pathogens and pests
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Assessing the Effects of Light on Differentiation and Virulence of the Plant Pathogen Botrytis cinerea: Characterization of the White Collar Complex

Assessing the Effects of Light on Differentiation and Virulence of the Plant Pathogen Botrytis cinerea: Characterization of the White Collar Complex | Plant pathogen | Scoop.it

Organisms are exposed to a tough environment, where acute daily challenges, like light, can strongly affect several aspects of an individual's physiology, including pathogenesis. While several fungal models have been widely employed to understand the physiological and molecular events associated with light perception, various other agricultural-relevant fungi still remain, in terms of their responsiveness to light, in the dark. The fungus Botrytis cinerea is an aggressive pathogen able to cause disease on a wide range of plant species. Natural B. cinerea isolates exhibit a high degree of diversity in their predominant mode of reproduction. Thus, the majority of naturally occurring strains are known to reproduce asexually via conidia and sclerotia, and sexually via apothecia. Studies from the 1970′s reported on specific developmental responses to treatments with near-UV, blue, red and far-red light. To unravel the signaling machinery triggering development – and possibly also connected with virulence – we initiated the functional characterization of the transcription factor/photoreceptor BcWCL1 and its partner BcWCL2, that form the White Collar Complex (WCC) in B. cinerea. Using mutants either abolished in or exhibiting enhanced WCC signaling (overexpression of both bcwcl1 and bcwcl2), we demonstrate that the WCC is an integral part of the mentioned machinery by mediating transcriptional responses to white light and the inhibition of conidiation in response to this stimulus. Furthermore, the WCC is required for coping with excessive light, oxidative stress and also to achieve full virulence. Although several transcriptional responses are abolished in the absence of bcwcl1, the expression of some genes is still light induced and a distinct conidiation pattern in response to daily light oscillations is enhanced, revealing a complex underlying photobiology. Though overlaps with well-studied fungal systems exist, the light-associated machinery of B. cinerea appears more complex than those of Neurospora crassa and Aspergillus nidulans.

 

 


Via Christophe Jacquet
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Rescooped by Xiaoli Zhang from Plants and Microbes
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Plant Cell: Plant Immune Responses Against Viruses: How Does a Virus Cause Disease? (2013)

Plant Cell: Plant Immune Responses Against Viruses: How Does a Virus Cause Disease? (2013) | Plant pathogen | Scoop.it

Plants respond to pathogens using elaborate networks of genetic interactions. Recently, significant progress has been made in understanding RNA silencing and how viruses counter this apparently ubiquitous antiviral defense. In addition, plants also induce hypersensitive and systemic acquired resistance responses, which together limit the virus to infected cells and impart resistance to the noninfected tissues. Molecular processes such as the ubiquitin proteasome system and DNA methylation are also critical to antiviral defenses. Here, we provide a summary and update of advances in plant antiviral immune responses, beyond RNA silencing mechanisms—advances that went relatively unnoticed in the realm of RNA silencing and nonviral immune responses. We also document the rise of Brachypodium and Setaria species as model grasses to study antiviral responses in Poaceae, aspects that have been relatively understudied, despite grasses being the primary source of our calories, as well as animal feed, forage, recreation, and biofuel needs in the 21st century. Finally, we outline critical gaps, future prospects, and considerations central to studying plant antiviral immunity. To promote an integrated model of plant immunity, we discuss analogous viral and nonviral immune concepts and propose working definitions of viral effectors, effector-triggered immunity, and viral pathogen-triggered immunity.


Via Mary Williams, Kamoun Lab @ TSL
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Andres Zurita's curator insight, May 29, 2013 8:28 AM

Open Access pdf

María Serrano's curator insight, June 24, 2014 12:30 PM
Respuesta inmune de las plantas frente a los virus.