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NPR3 and NPR4 are receptors for the immune signal salicylic acid in plants

NPR3 and NPR4 are receptors for the immune signal salicylic acid in plants | autophagy | Scoop.it

Salicylic acid (SA) is a plant immune signal produced after pathogen challenge to induce systemic acquired resistance. It is the only major plant hormone for which the receptor has not been firmly identified. Systemic acquired resistance in Arabidopsis requires the transcription cofactor nonexpresser of PR genes 1 (NPR1), the degradation of which acts as a molecular switch. Here we show that the NPR1 paralogues NPR3 and NPR4 are SA receptors that bind SA with different affinities. NPR3 and NPR4 function as adaptors of the Cullin 3 ubiquitin E3 ligase to mediate NPR1 degradation in an SA-regulated manner. Accordingly, the Arabidopsis npr3 npr4double mutant accumulates higher levels of NPR1, and is insensitive to induction of systemic acquired resistance. Moreover, this mutant is defective in pathogen effector-triggered programmed cell death and immunity. Our study reveals the mechanism of SA perception in determining cell death and survival in response to pathogen challenge.


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Rescooped by Rameshvetukuri from Plant Pathogenomics
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PLOS Pathogens: Diverse Lifestyles and Strategies of Plant Pathogenesis Encoded in the Genomes of Eighteen Dothideomycetes Fungi (2012)

PLOS Pathogens: Diverse Lifestyles and Strategies of Plant Pathogenesis Encoded in the Genomes of Eighteen Dothideomycetes Fungi (2012) | autophagy | Scoop.it

The class Dothideomycetes is one of the largest groups of fungi with a high level of ecological diversity including many plant pathogens infecting a broad range of hosts. Here, we compare genome features of 18 members of this class, including 6 necrotrophs, 9 (hemi)biotrophs and 3 saprotrophs, to analyze genome structure, evolution, and the diverse strategies of pathogenesis. The Dothideomycetes most likely evolved from a common ancestor more than 280 million years ago. The 18 genome sequences differ dramatically in size due to variation in repetitive content, but show much less variation in number of (core) genes. Gene order appears to have been rearranged mostly within chromosomal boundaries by multiple inversions, in extant genomes frequently demarcated by adjacent simple repeats. Several Dothideomycetes contain one or more gene-poor, transposable element (TE)-rich putatively dispensable chromosomes of unknown function. The 18 Dothideomycetes offer an extensive catalogue of genes involved in cellulose degradation, proteolysis, secondary metabolism, and cysteine-rich small secreted proteins. Ancestors of the two major orders of plant pathogens in the Dothideomycetes, the Capnodiales and Pleosporales, may have had different modes of pathogenesis, with the former having fewer of these genes than the latter. Many of these genes are enriched in proximity to transposable elements, suggesting faster evolution because of the effects of repeat induced point (RIP) mutations. A syntenic block of genes, including oxidoreductases, is conserved in most Dothideomycetes and upregulated during infection in L. maculans, suggesting a possible function in response to oxidative stress.


Via Kamoun Lab @ TSL
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Rescooped by Rameshvetukuri from Plants and Microbes
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Scientific Reports: Plant viruses alter insect behavior to enhance their spread (2012)

Scientific Reports: Plant viruses alter insect behavior to enhance their spread (2012) | autophagy | Scoop.it

Pathogens and parasites can induce changes in host or vector behavior that enhance their transmission. In plant systems, such effects are largely restricted to vectors, because they are mobile and may exhibit preferences dependent upon plant host infection status. Here we report the first evidence that acquisition of a plant virus directly alters host selection behavior by its insect vector. We show that the aphid Rhopalosiphum padi, after acquiring Barley yellow dwarf virus (BYDV) during in vitro feeding, prefers noninfected wheat plants, while noninfective aphids also fed in vitro prefer BYDV-infected plants. This behavioral change should promote pathogen spread since noninfective vector preference for infected plants will promote acquisition, while infective vector preference for noninfected hosts will promote transmission. We propose the “Vector Manipulation Hypothesis” to explain the evolution of strategies in plant pathogens to enhance their spread to new hosts. Our findings have implications for disease and vector management.


Via Kamoun Lab @ TSL
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Rescooped by Rameshvetukuri from Plant-Microbe Interaction
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Trends in Plant Science - Autophagy: a multifaceted intracellular system for bulk and selective recycling

Trends in Plant Science - Autophagy: a multifaceted intracellular system for bulk and selective recycling | autophagy | Scoop.it

Plants have evolved sophisticated mechanisms to recycle intracellular constituents. One gaining in appreciation is autophagy, which involves specialized vesicles engulfing and delivering unwanted cytoplasmic material to the vacuole for breakdown. Central to this process is the ubiquitin-fold protein autophagy (ATG)-8, which becomes tethered to the developing autophagic membranes by lipidation. Here, we review data showing that the ATG8 moiety provides a docking site not only for proteins that help shape the enclosing vesicles and promote their fusion with the tonoplast, but also for a host of receptors that recruit appropriate autophagic cargo. The identity of these receptors has dramatically altered the view of autophagy as being a relatively nonspecific mechanism to one that may selectively sequester aggregated proteins, protein complexes, organelles, and even invading pathogens.


Via Guogen Yang
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Rescooped by Rameshvetukuri from Plant-microbe interaction
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NPR3 and NPR4 are receptors for the immune signal salicylic acid in plants

NPR3 and NPR4 are receptors for the immune signal salicylic acid in plants | autophagy | Scoop.it

Salicylic acid (SA) is a plant immune signal produced after pathogen challenge to induce systemic acquired resistance. It is the only major plant hormone for which the receptor has not been firmly identified. Systemic acquired resistance in Arabidopsis requires the transcription cofactor nonexpresser of PR genes 1 (NPR1), the degradation of which acts as a molecular switch. Here we show that the NPR1 paralogues NPR3 and NPR4 are SA receptors that bind SA with different affinities. NPR3 and NPR4 function as adaptors of the Cullin 3 ubiquitin E3 ligase to mediate NPR1 degradation in an SA-regulated manner. Accordingly, the Arabidopsis npr3 npr4double mutant accumulates higher levels of NPR1, and is insensitive to induction of systemic acquired resistance. Moreover, this mutant is defective in pathogen effector-triggered programmed cell death and immunity. Our study reveals the mechanism of SA perception in determining cell death and survival in response to pathogen challenge.


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Rescooped by Rameshvetukuri from Plant Biology Teaching Resources (Higher Education)
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How to Collaborate - Science Careers -

How to Collaborate - Science Careers - | autophagy | Scoop.it
Scientist seeks honest, reliable partner for meaningful research discussions and maybe more, ideally for a long-term relationship .

Via Mary Williams
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Rescooped by Rameshvetukuri from Plant Biology Teaching Resources (Higher Education)
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Interspecific RNA Interference of SHOOT MERISTEMLESS-Like Disrupts Cuscuta pentagona Plant Parasitism

Interspecific RNA Interference of SHOOT MERISTEMLESS-Like Disrupts Cuscuta pentagona Plant Parasitism | autophagy | Scoop.it

This gets my vote for "best paper to give undergraduates". It's straightforward and easy to read, but covers topics ranging from homeobox genes, RNA silencing, development, and the very exciting potential application of protecting crops from parastic plants, which is a major problem in some areas. This is one of those rare papers that has something for everybody, and is quite accessible in its approaches. Put it on your reading list!


Via Mary Williams
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Selective autophagy degrades DICER and AGO2 an... [Nat Cell Biol. 2012] - PubMed - NCBI

Selective autophagy degrades DICER and AGO2 and regulates miRNA activity

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Rescooped by Rameshvetukuri from autophagy
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CML9, an Arabidopsis calmodulin-like protein, contributes to plant innate immunity through a flagellin-dependent signalling pathway - Leba - 2012 - The Plant Journal - Wiley Online Library

CML9, an Arabidopsis calmodulin-like protein, contributes to plant innate immunity through a flagellin-dependent signalling pathway - Leba - 2012 - The Plant Journal - Wiley Online Library | autophagy | Scoop.it

Many stimuli such as hormones and elicitors induce changes in intracellular calcium levels to integrate information and activate appropriate responses. The Ca2+ signals are perceived by various Ca2+ sensors, and calmodulin (CaM) is one of the best characterized in eukaryotes. Calmodulin-like (CML) proteins extend the Ca2+ toolkit in plants; they share sequence similarity with the ubiquitous and highly conserved CaM but their roles at physiological and molecular levels are largely unknown. Knowledge of the contribution of Ca2+ decoding proteins to plant immunity is emerging, and we report here data on Arabidopsis thaliana CML9, whose expression is rapidly induced by phytopathogenic bacteria, flagellin and salicylic acid. Using a reverse genetic approach, we present evidence that CML9 is involved in plant defence by modulating responses to bacterial strains of Pseudomonas syringae. Compared to wild-type plants, the later responses normally observed upon flagellin application are altered in knockout mutants and over-expressing transgenic lines. Collectively, using PAMP treatment and P. syringae strains, we have established that CML9 participates in plant innate immunity.


Via Suayib Üstün, Rameshvetukuri
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Rescooped by Rameshvetukuri from Plant-microbe interaction
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CML9, an Arabidopsis calmodulin-like protein, contributes to plant innate immunity through a flagellin-dependent signalling pathway - Leba - 2012 - The Plant Journal - Wiley Online Library

CML9, an Arabidopsis calmodulin-like protein, contributes to plant innate immunity through a flagellin-dependent signalling pathway - Leba - 2012 - The Plant Journal - Wiley Online Library | autophagy | Scoop.it

Many stimuli such as hormones and elicitors induce changes in intracellular calcium levels to integrate information and activate appropriate responses. The Ca2+ signals are perceived by various Ca2+ sensors, and calmodulin (CaM) is one of the best characterized in eukaryotes. Calmodulin-like (CML) proteins extend the Ca2+ toolkit in plants; they share sequence similarity with the ubiquitous and highly conserved CaM but their roles at physiological and molecular levels are largely unknown. Knowledge of the contribution of Ca2+ decoding proteins to plant immunity is emerging, and we report here data on Arabidopsis thaliana CML9, whose expression is rapidly induced by phytopathogenic bacteria, flagellin and salicylic acid. Using a reverse genetic approach, we present evidence that CML9 is involved in plant defence by modulating responses to bacterial strains of Pseudomonas syringae. Compared to wild-type plants, the later responses normally observed upon flagellin application are altered in knockout mutants and over-expressing transgenic lines. Collectively, using PAMP treatment and P. syringae strains, we have established that CML9 participates in plant innate immunity.


Via Suayib Üstün
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Rescooped by Rameshvetukuri from Plant Pathogenomics
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Eukaryotic Cell: Dynamics and innovations within oomycete genomes: insights into biology, pathology, and evolution (2012)

Eukaryotic Cell: Dynamics and innovations within oomycete genomes: insights into biology, pathology, and evolution (2012) | autophagy | Scoop.it

The eukaryotic microbes known as oomycetes are common inhabitants of terrestrial and aquatic environments, and include saprophytes and pathogens. Lifestyles of the pathogens extend from biotrophy to necrotrophy, obligate to facultative pathogenesis, and narrow to broad host ranges on plants or animals. Sequencing of several pathogens has revealed striking variation in genome size and content, a plastic set of genes related to pathogenesis, and adaptations associated with obligate biotrophy. Features of genome evolution include repeat-driven expansions, deletions, gene fusions, and horizontal gene transfer, in a landscape organized into gene-dense and gene-sparse sectors and influenced by transposable elements. Gene expression profiles are also highly dynamic throughout oomycete life cycles, with transcriptional polymorphisms as well as differences in protein sequence contributing to variation. The genome projects have set the foundation for functional studies and should spur the sequencing of additional species, including more diverse pathogens and nonpathogens.


Via IPM Lab, Kamoun Lab @ TSL
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Rescooped by Rameshvetukuri from Fungal|Oomycete Biology
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Mobile Genetic Elements: Can silencing of transposons contribute to variation in effector gene expression in Phytophthora infestans? (2012)

Mobile Genetic Elements: Can silencing of transposons contribute to variation in effector gene expression in Phytophthora infestans? (2012) | autophagy | Scoop.it

Transposable elements are ubiquitous residents in eukaryotic genomes. Often considered to be genomic parasites, they can lead to dramatic changes in genome organization, gene expression, and gene evolution. The oomycete plant pathogen Phytophthora infestans has evolved a genome organization where core biology genes are predominantly located in genome regions that have relatively few resident transposons. In contrast, disease effector-encoding genes are most frequently located in rapidly evolving genomic regions that are rich in transposons. P. infestans, as a eukaryote, likely uses RNA silencing to minimize the activity of transposons. We have shown that fusion of a short interspersed element (SINE) to an effector gene in P. infestans leads to the silencing of both the introduced fusion and endogenous homologous sequences. This is also likely to occur naturally in the genome of P. infestans, as transcriptional inactivation of effectors is known to occur, and over half of the translocated “RXLR class” of effectors are located within 2 kb of transposon sequences in the P. infestans genome. In this commentary, we review the diverse transposon inventory of P. infestans, its control by RNA silencing, and consequences for expression modulation of nearby effector genes in this economically important plant pathogen.


Via Kamoun Lab @ TSL, Alejandro Rojas
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