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Rescooped by WeiGao from Plant immunity and legume symbiosis
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Expression profiling of marker genes responsive to the defence-associated phytohormones salicylic acid, jasmonic acid and ethylene in Brachypodium distachyon

Expression profiling of marker genes responsive to the defence-associated phytohormones salicylic acid, jasmonic acid and ethylene in Brachypodium distachyon | plant-microbe interactions | Scoop.it
“ Background Brachypodium distachyon is a promising model plants for grasses. Infections of Brachypodium by various pathogens that severely impair crop production have been reported, and the species accordingly provides an alternative platform for investigating molecular mechanisms of pathogen virulence and plant disease resistance. To date, we have a broad picture of plant immunity only in Arabidopsis and rice; therefore, Brachypodium may constitute a counterpart that displays the commonality and uniqueness of defence systems among plant species. Phytohormones play key roles in plant biotic stress responses, and hormone-responsive genes are used to qualitatively and quantitatively evaluate disease resistance responses during pathogen infection. For these purposes, defence-related phytohormone marker genes expressed at time points suitable for defence-response monitoring are needed. Information about their expression profiles over time as well as their response specificity is also helpful. However, useful marker genes are still rare in Brachypodium. Results We selected 34 candidates for Brachypodium marker genes on the basis of protein-sequence similarity to known marker genes used in Arabidopsis and rice. Brachypodium plants were treated with the defence-related phytohormones salicylic acid, jasmonic acid and ethylene, and their transcription levels were measured 24 and 48 h after treatment. Two genes for salicylic acid, 7 for jasmonic acid and 2 for ethylene were significantly induced at either or both time points. We then focused on 11 genes encoding pathogenesis-related (PR) 1 protein and compared their expression patterns with those of Arabidopsis and rice. Phylogenetic analysis suggested that Brachypodium contains several PR1-family genes similar to rice genes. Our expression profiling revealed that regulation patterns of some PR1 genes as well as of markers identified for defence-related phytohormones are closely related to those in rice. Conclusion We propose that the Brachypodium immune hormone marker genes identified in this study will be useful to plant pathologists who use Brachypodium as a model pathosystem, because the timing of their transcriptional activation matches that of the disease resistance response. Our results using Brachypodium also suggest that monocots share a characteristic immune system, defined as the common defence system, that is different from that of dicots.”
Via Christophe Jacquet
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Identification of Multiple Phytotoxins Produced by Fusarium virguliforme Including a Phytotoxic Effector (FvNIS1) Associated With Sudden Death Syndrome Foliar Symptoms — Molecular Plant-Microbe Int...

Identification of Multiple Phytotoxins Produced by Fusarium virguliforme Including a Phytotoxic Effector (FvNIS1) Associated With Sudden Death Syndrome Foliar Symptoms — Molecular Plant-Microbe Int... | plant-microbe interactions | Scoop.it
“ Sudden death syndrome (SDS) of soybean is caused by a soilborne pathogen, Fusarium virguliforme. Phytotoxins produced by F. virguliforme are translocated from infected roots to leaves, in which they cause SDS foliar symptoms. In this study, additional putative phytotoxins of F. virguliforme were identified, including three secondary metabolites and 11 effectors. While citrinin, fusaric acid, and radicicol induced foliar chlorosis and wilting, Soybean mosaic virus (SMV)-mediated overexpression of F. virguliforme necrosis-inducing secreted protein 1 (FvNIS1) induced SDS foliar symptoms that mimicked the development of foliar symptoms in the field. The expression level of fvnis1 remained steady over time, although foliar symptoms were delayed compared with the expression levels. SMV::FvNIS1 also displayed genotype-specific toxicity to which 75 of 80 soybean cultivars were susceptible. Genome-wide association mapping further identified three single nucleotide polymorphisms at two loci, where three leucine-rich repeat receptor-like protein kinase (LRR-RLK) genes were found. Culture filtrates of fvnis1 knockout mutants displayed a mild reduction in phytotoxicity, indicating that FvNIS1 is one of the phytotoxins responsible for SDS foliar symptoms and may contribute to the quantitative susceptibility of soybean by interacting with the LRR-RLK genes.”
Via Christophe Jacquet
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The cotton MYB108 forms a positive feedback regulation loop with CML11 and participates in the defense response against Verticillium dahliae infection

The cotton MYB108 forms a positive feedback regulation loop with CML11 and participates in the defense response against Verticillium dahliae infection | plant-microbe interactions | Scoop.it
“ Accumulating evidence indicates that plant MYB transcription factors participate in defense against pathogen attack, but their regulatory targets and related signaling processes remain largely unknown. Here, we identified a defense-related MYB gene (GhMYB108) from upland cotton (Gossypium hirsutum) and characterized its functional mechanism. Expression of GhMYB108 in cotton plants was induced by Verticillium dahliae infection and responded to the application of defense signaling molecules, including salicylic acid, jasmonic acid, and ethylene. Knockdown of GhMYB108 expression led to increased susceptibility of cotton plants to V. dahliae, while ecotopic overexpression of GhMYB108 in Arabidopsis thaliana conferred enhanced tolerance to the pathogen. Further analysis demonstrated that GhMYB108 interacted with the calmodulin-like protein GhCML11, and the two proteins form a positive feedback loop to enhance the transcription of GhCML11 in a calcium-dependent manner. Verticillium dahliae infection stimulated Ca2+ influx into the cytosol in cotton root cells, but this response was disrupted in both GhCML11-silenced plants and GhMYB108-silenced plants in which expression of several calcium signaling-related genes was down-regulated. Taken together, these results indicate that GhMYB108 acts as a positive regulator in defense against V. dahliae infection by interacting with GhCML11. Furthermore, the data also revealed the important roles and synergetic regulation of MYB transcription factor, Ca2+, and calmodulin in plant immune responses.”
Via Christophe Jacquet
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Live-cell fluorescence imaging to investigate the dynamics of plant cell death during infection by the rice blast fungus Magnaporthe oryzae

Live-cell fluorescence imaging to investigate the dynamics of plant cell death during infection by the rice blast fungus Magnaporthe oryzae | plant-microbe interactions | Scoop.it
“ Background Plant cell death plays important roles during plant-pathogen interactions. To study pathogen-induced cell death, there is a need for cytological tools that allow determining not only host cell viability, but also cellular events leading to cell death with visualization of pathogen development. Here we describe a live cell imaging method to provide insights into the dynamics of cell death in rice (Oryza sativa). This method uses live-cell confocal microscopy of rice sheath cells mechanically damaged or invaded by fluorescently-tagged Magnaporthe oryzae together with fluorescent dyes fluorescein diacetate (FDA) and propidium iodide (PI). FDA stains the cytoplasm of live cells exclusively, thus also visualizing the vacuole, whereas PI stains nuclei of dead cells. Results We first demonstrated that confocal microscopy of rice leaf sheaths stained with FDA and PI discriminated between live cells and mechanically-killed cells. FDA-derived fluorescein was confined to the cytoplasm of live cells, indicating the intact vacuolar and plasma membranes. We also observed previously unreported fluorescein patterns in mechanically damaged cells. These patterns include: (1) homogeneous distribution of fluorescein in the increased area of the cytoplasm due to the shrunken vacuole; (2) the increase of the fluorescein intensity; and (3) containment of the brighter fluorescein signal only in affected cells likely due to closure of plasmodesmata. We refer to these as novel fluorescein patterns in this study. Simultaneous imaging of fluorescently-tagged M. oryzae (red) and FDA staining (green) in rice cells revealed characteristic features of the hemibiotrophic interaction. That is, newly invaded cells are alive but subsequently become dead when the fungus spreads into neighbor cells, and biotrophic interfacial complexes are associated with the host cytoplasm. This also revealed novel fluorescein patterns in invaded cells. Time-lapse imaging suggested that the FDA staining pattern in the infected host cell progressed from typical cytoplasmic localization (live cell with the intact vacuole), to novel patterns (dying cell with closed plasmodesmata with the shrunken or ruptured vacuole), to lack of fluorescence (dead cell). Conclusion We have developed a method to visualize cellular events leading to host cell death during rice blast disease. This method can be used to compare and contrast host cell death associated with disease resistance and susceptibility in rice-M. oryzae and other host-pathogen interactions. ”

Via Christophe Jacquet
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Overexpression of potato miR482e enhanced plant sensitivity to Verticillium dahliae infection - Yang - 2015 - Journal of Integrative Plant Biology - Wiley Online Library

Overexpression of potato miR482e enhanced plant sensitivity to Verticillium dahliae infection - Yang - 2015 - Journal of Integrative Plant Biology - Wiley Online Library | plant-microbe interactions | Scoop.it

Verticillium wilt of potato is caused by the fungus pathogen Verticillium dahliae. Present sRNA sequencing data revealed that miR482 was in response to V. dahliaeinfection, but the function in potato is elusive. Here, we characterized potato miR482 family and its putative role resistance to Verticillium wilt. Members of the potato miR482 superfamily are variable in sequence, but all variants target a class of disease-resistance proteins with nucleotide binding site (NBS) and leucine-rich repeat (LRR) motifs. When potato plantlets were infected with V. dahliae, the expression level of miR482e was downregulated, and that of several NBS-LRR targets of miR482e were upregulated. Transgenic potato plantlets overexpressing miR482e showed hypersensitivity to V. dahliae infection. Using sRNA and degradome datasets, we validated that miR482e targets mRNAs of NBS-LRR disease-resistance proteins and triggers the production of trans-acting (ta)-siRNAs, most of which target mRNAs of defense-related proteins. Thus, the hypersensitivity of transgenic potato could be explained by enhanced miR482e and miR482e-derived ta-siRNA-mediated silencing on NBS-LRR-disease-resistance proteins. It is speculated that a miR482-mediated silencing cascade mechanism is involved in regulating potato resistance against V. dahliae infection and could be a counter defense action of plant in response to pathogen infection.

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Genome Biology | Full text | CRISPR/Cas9-mediated viral interference in plants

Genome Biology | Full text | CRISPR/Cas9-mediated viral interference in plants | plant-microbe interactions | Scoop.it
“ Background The CRISPR/Cas9 system provides bacteria and archaea with molecular immunity against invading phages and conjugative plasmids. Recently, CRISPR/Cas9 has been used for targeted genome editing in diverse eukaryotic species. Results In this study, we investigate whether the CRISPR/Cas9 system could be used in plants to confer molecular immunity against DNA viruses. We deliver sgRNAs specific for coding and non-coding sequences of tomato yellow leaf curl virus (TYLCV) into Nicotiana benthamiana plants stably overexpressing the Cas9 endonuclease, and subsequently challenge these plants with TYLCV. Our data demonstrate that the CRISPR/Cas9 system targeted TYLCV for degradation and introduced mutations at the target sequences. All tested sgRNAs exhibit interference activity, but those targeting the stem-loop sequence within the TYLCV origin of replication in the intergenic region (IR) are the most effective. N. benthamiana plants expressing CRISPR/Cas9 exhibit delayed or reduced accumulation of viral DNA, abolishing or significantly attenuating symptoms of infection. Moreover, this system could simultaneously target multiple DNA viruses. Conclusions These data establish the efficacy of the CRISPR/Cas9 system for viral interference in plants, thereby extending the utility of this technology and opening the possibility of producing plants resistant to multiple viral infections.”
Via Christophe Jacquet
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Artificial transcription factor-mediated regulation of gene expression

Artificial transcription factor-mediated regulation of gene expression | plant-microbe interactions | Scoop.it

Tol & van der Zaal, 2014

The transcriptional regulation of endogenous genes with artificial transcription factors (TFs) can offer new tools for plant biotechnology. Three systems are available for mediating site-specific DNA recognition of artificial TFs: those based on zinc fingers, TALEs, and on the CRISPR/Cas9 technology. Artificial TFs require an effector domain that controls the frequency of transcription initiation at endogenous target genes. These effector domains can be transcriptional activators or repressors, but can also have enzymatic activities involved in chromatin remodeling or epigenetic regulation. Artificial TFs are able to regulate gene expression in trans, thus allowing them to evoke dominant mutant phenotypes. Large scale changes in transcriptional activity are induced when the DNA binding domain is deliberately designed to have lower binding specificity. This technique, known as genome interrogation, is a powerful tool for generating novel mutant phenotypes. Genome interrogation has clear mechanistic and practical advantages over activation tagging, which is the technique most closely resembling it. Most notably, genome interrogation can lead to the discovery of mutant phenotypes that are unlikely to be found when using more conventional single gene-based approaches.


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EMBO J: The NB-LRR proteins RGA4 and RGA5 interact functionally and physically to confer disease resistance (2014)

EMBO J: The NB-LRR proteins RGA4 and RGA5 interact functionally and physically to confer disease resistance (2014) | plant-microbe interactions | Scoop.it

Plant resistance proteins of the class of nucleotide-binding and leucine-rich repeat domain proteins (NB-LRRs) are immune sensors which recognize pathogen-derived molecules termed avirulence (AVR) proteins. We show that RGA4 and RGA5, two NB-LRRs from rice, interact functionally and physically to mediate resistance to the fungal pathogen Magnaporthe oryzae and accomplish different functions in AVR recognition. RGA4 triggers an AVR-independent cell death that is repressed in the presence of RGA5 in both rice protoplasts and Nicotiana benthamiana. Upon recognition of the pathogen effector AVR-Pia by direct binding to RGA5, repression is relieved and cell death occurs. RGA4 and RGA5 form homo- and hetero-complexes and interact through their coiled-coil domains. Localization studies in rice protoplast suggest that RGA4 and RGA5 localize to the cytosol. Upon recognition of AVR-Pia, neither RGA4 nor RGA5 is re-localized to the nucleus. These results establish a model for the interaction of hetero-pairs of NB-LRRs in plants: RGA4 mediates cell death activation, while RGA5 acts as a repressor of RGA4 and as an AVR receptor.


Via Kamoun Lab @ TSL, Jennifer Mach
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Plant Immune Responses Against Viruses: How Does a Virus Cause Disease?

Plant Immune Responses Against Viruses: How Does a Virus Cause Disease? | plant-microbe interactions | Scoop.it

New review article in Plant Cell.

"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."


Via Mary Williams, R K Upadhyay
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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.
Rescooped by WeiGao from Plants and Microbes
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MPMI: Comparative and functional analysis of the widely occurring family of Nep1-like proteins (2014)

MPMI: Comparative and functional analysis of the widely occurring family of Nep1-like proteins (2014) | plant-microbe interactions | Scoop.it

Nep-1 Like Proteins (NLPs) are best known for their cytotoxic activity in dicot plants. NLPs are taxonomically widespread among microbes with very different lifestyles. To learn more about this enigmatic protein family we analyzed more than 500 available NLP protein sequences from fungi, oomycetes, and bacteria. Phylogenetic clustering showed that, besides the previously documented two types, an additional more divergent third NLP type could be distinguished. By closely examining the three NLP types, we identified a non-cytotoxic subgroup of type 1 NLPs (designated type 1a), which have substitutions in amino acids making up a cation-binding pocket that is required for cytotoxicity. Type 2 NLPs were found to contain a putative calcium-binding motif, which was shown to be required for cytotoxicity. Members of both type 1 and type 2 NLPs were found to possess additional cysteine residues that, based on their predicted proximity, make up potential disulfide bridges that could provide additional stability to these secreted proteins. Type 1 and type 2 NLPs, although both cytotoxic to plant cells, differ in their ability to induce necrosis when artificially targeted to different cellular compartments in planta, suggesting they have different mechanisms of cytotoxicity.


Via Kamoun Lab @ TSL
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MPMI: Pseudomonas syringae evades host immunity by degrading flagellin monomers with alkaline protease AprA (2014)

MPMI: Pseudomonas syringae evades host immunity by degrading flagellin monomers with alkaline protease AprA (2014) | plant-microbe interactions | Scoop.it

Bacterial flagellin molecules are strong inducers of innate immune responses in both mammals and plants. The opportunistic pathogenPseudomonas aeruginosa secretes an alkaline protease called AprA that degrades flagellin monomers. Here, we show that AprA is widespread among a wide variety of bacterial species. In addition we investigated the role of AprA in virulence of the bacterial plant pathogen Pseudomonas syringae pv. tomato DC3000 (Pst). The AprA-deficient Pst ∆aprA knockout mutant was significantly less virulent on both tomato and A. thaliana. Moreover, infiltration of A. thaliana Col-0 leaves with Pst ∆aprA evoked a significantly higher level of expression of the defense-related genes FRK1 and PR-1 than did wild-type Pst. In the flagellin receptor mutant fls2, pathogen virulence and defense-related gene activation did not differ between Pst and Pst ∆aprA. Together, these results suggest that AprA of Pst is important for evasion of recognition by the FLS2 receptor, allowing wild-type Pst to be more virulent on its host plant than AprA-deficient Pst ∆aprA. To provide further evidence for the role of Pst AprA in host immune evasion, we overexpressed the AprA inhibitory peptide AprI of Pst in A. thaliana to counteract the immune evasive capacity of Pst AprA. Ectopic expression of aprI in A. thaliana resulted in an enhanced level of resistance against wild-type Pst, while the already elevated level of resistance against Pst ∆aprA remained unchanged. Together, these results indicate that evasion of host immunity by the alkaline protease AprA is important for full virulence of Pst and likely acts by preventing flagellin monomers from being recognized by its cognate immune receptor.


Via Kamoun Lab @ TSL
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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-microbe interactions | 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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Curr Opin Plant Biol: Inside plant: biotrophic strategies to modulate host immunity and metabolism (2014)

Curr Opin Plant Biol: Inside plant: biotrophic strategies to modulate host immunity and metabolism (2014) | plant-microbe interactions | Scoop.it
Filamentous plant pathogens that establish biotrophic interactions need to avoid plant immune responses. Recent findings from different pathosystems suggest that sufficient suppression of host immunity is based on the modulation of a rather limited number of host targets. Microbial strategies to target host physiology dependent on the duration of biotrophy, the style of host tissue colonization and the degree of interference with plant development. In this article, we present current concepts in biotrophic virulence strategies and discuss mechanisms of pathogen adaptation and effector specialization.
Via Kamoun Lab @ TSL
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Potato NPH3/RPT2-like protein StNRL1, targeted by a Phytophthora infestans RXLR effector, is a susceptibility factor

Potato NPH3/RPT2-like protein StNRL1, targeted by a Phytophthora infestans RXLR effector, is a susceptibility factor | plant-microbe interactions | Scoop.it
“ Plant pathogens deliver effectors to manipulate host processes. We know little about how fungal and oomycete effectors target host proteins to promote susceptibility, yet such knowledge is vital to understand crop disease. We show that either transient expression in Nicotiana benthamiana, or stable transgenic expression in potato (Solanum tuberosum), of Phytophthora infestans RXLR effector Pi02860 enhances leaf colonization by the pathogen. Expression of Pi02860 also attenuates cell death triggered by the P. infestans MAMP INF1, indicating that the effector suppresses pattern-triggered immunity (PTI). However, the effector does not attenuate cell death triggered by Cf4/Avr4 co-expression, showing that it does not suppress all cell death activated by cell surface receptors. Pi02860 interacts in yeast-2-hybrid assays with potato NPH3/RPT2-like 1 (NRL1). Interaction of Pi02860 in planta was confirmed by co-immunoprecipitation and bimolecular fluorescence complementation assays. Virus-induced gene silencing (VIGS) of NRL1 in N. benthamiana resulted in reduced P. infestans colonization and accelerated INF1-mediated cell death, indicating that this host protein acts as a negative regulator of immunity. Moreover, whereas NRL1 VIGS had no effect on the ability of P. infestans effector AVR3a to suppress INF1-mediated cell death, such suppression by Pi02860 was significantly attenuated, indicating that this activity of Pi02860 is mediated by NRL1. Transient overexpression of NRL1 resulted in suppression of INF1-mediated cell death and enhanced P. infestans leaf colonization, demonstrating that NRL1 acts as a susceptibility factor to promote late blight disease.”
Via Christophe Jacquet, Suayib Üstün
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The cotton MYB108 forms a positive feedback regulation loop with CML11 and participates in the defense response against Verticillium dahliae infection

The cotton MYB108 forms a positive feedback regulation loop with CML11 and participates in the defense response against Verticillium dahliae infection | plant-microbe interactions | Scoop.it
“ Accumulating evidence indicates that plant MYB transcription factors participate in defense against pathogen attack, but their regulatory targets and related signaling processes remain largely unknown. Here, we identified a defense-related MYB gene (GhMYB108) from upland cotton (Gossypium hirsutum) and characterized its functional mechanism. Expression of GhMYB108 in cotton plants was induced by Verticillium dahliae infection and responded to the application of defense signaling molecules, including salicylic acid, jasmonic acid, and ethylene. Knockdown of GhMYB108 expression led to increased susceptibility of cotton plants to V. dahliae, while ecotopic overexpression of GhMYB108 in Arabidopsis thaliana conferred enhanced tolerance to the pathogen. Further analysis demonstrated that GhMYB108 interacted with the calmodulin-like protein GhCML11, and the two proteins form a positive feedback loop to enhance the transcription of GhCML11 in a calcium-dependent manner. Verticillium dahliae infection stimulated Ca2+ influx into the cytosol in cotton root cells, but this response was disrupted in both GhCML11-silenced plants and GhMYB108-silenced plants in which expression of several calcium signaling-related genes was down-regulated. Taken together, these results indicate that GhMYB108 acts as a positive regulator in defense against V. dahliae infection by interacting with GhCML11. Furthermore, the data also revealed the important roles and synergetic regulation of MYB transcription factor, Ca2+, and calmodulin in plant immune responses.”
Via Christophe Jacquet
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SERK co-receptor kinases

SERK co-receptor kinases | plant-microbe interactions | Scoop.it
“ What are they? Somatic embryogenesis receptor-like kinases (SERKs) are small membrane-embedded signaling proteins. They are part of a plant-specific family of leucine-rich repeat (LRR) receptor kinases (RKs). LRR-RKs are membrane receptors that sense a diverse set of extracellular ligands, and that relay these signals into the cytosol to trigger specific cellular responses (Figure 1). The genome of Arabidopsis thaliana encodes at least 220 LRR-RKs, five of which are SERKs. SERK proteins consist of a small extracellular LRR-domain with 5 repeats, a single membrane-spanning helix and a cytoplasmic kinase domain, which can auto- and trans-phosphorylate on Ser/Thr and Tyr residues (dual-specificity kinase). ”

Via Christophe Jacquet
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Molecular Plant Pathology: Plant hormones: A fungal point of view (2016)

Molecular Plant Pathology: Plant hormones: A fungal point of view (2016) | plant-microbe interactions | Scoop.it

Most classical plant hormones are also produced by pathogenic and symbiotic fungi. The way these molecules favor the invasion of plant tissues and the development of fungi inside plant tissues is still largely unknown. In this review, we examine the different roles of such hormone production by pathogenic fungi. Converging evidence suggest that these fungal-derived molecules have potentially two modes of action: (i) they may perturb plant processes, either positively or negatively, to favor invasion and nutrient uptake and (ii) they may also act as signals for the fungi themselves to engage appropriate developmental and physiological processes adapted to their environment. Indirect evidences suggest that abscisic acid, gibberellic acid and ethylene produced by fungi participate to pathogenicity. There is now evidence that auxin and cytokinins could be positive regulators required for virulence. Further research should establish whether or not fungal-derived hormones act like other fungal effectors. This article is protected by copyright. All rights reserved.


Via Kamoun Lab @ TSL, Christophe Jacquet
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Maize Homologs of Hydroxycinnamoyltransferase, a Key Enzyme in Lignin Biosynthesis, Bind the Nucleotide Binding Leucine-Rich Repeat Rp1 Proteins to Modulate the Defense Response

Maize Homologs of Hydroxycinnamoyltransferase, a Key Enzyme in Lignin Biosynthesis, Bind the Nucleotide Binding Leucine-Rich Repeat Rp1 Proteins to Modulate the Defense Response | plant-microbe interactions | Scoop.it
“ In plants, most disease resistance genes encode nucleotide binding Leu-rich repeat (NLR) proteins that trigger a rapid localized cell death called a hypersensitive response (HR) upon pathogen recognition. The maize (Zea mays) NLR protein Rp1-D21 derives from an intragenic recombination between two NLRs, Rp1-D and Rp1-dp2, and confers an autoactive HR in the absence of pathogen infection. From a previous quantitative trait loci and genome-wide association study, we identified a single-nucleotide polymorphism locus highly associated with variation in the severity of Rp1-D21-induced HR. Two maize genes encoding hydroxycinnamoyltransferase (HCT; a key enzyme involved in lignin biosynthesis) homologs, termed HCT1806 and HCT4918, were adjacent to this single-nucleotide polymorphism. Here, we show that both HCT1806 and HCT4918 physically interact with and suppress the HR conferred by Rp1-D21 but not other autoactive NLRs when transiently coexpressed in Nicotiana benthamiana. Other maize HCT homologs are unable to confer the same level of suppression on Rp1-D21-induced HR. The metabolic activity of HCT1806 and HCT4918 is unlikely to be necessary for their role in suppressing HR. We show that the lignin pathway is activated by Rp1-D21 at both the transcriptional and metabolic levels. We derive a model to explain the roles of HCT1806 and HCT4918 in Rp1-mediated disease resistance.”
Via Christophe Jacquet
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Involvement of Arabidopsis Hexokinase1 in Cell Death Mediated by Myo-Inositol Accumulation

Involvement of Arabidopsis Hexokinase1 in Cell Death Mediated by Myo-Inositol Accumulation | plant-microbe interactions | Scoop.it

Programmed cell death (PCD) is essential for several aspects of plant life, including development and stress responses. We recently identified the mips1 mutant ofArabidopsis thaliana, which is deficient for the enzyme catalyzing the limiting step of myo-inositol (MI) synthesis. One of the most striking features of mips1 is the light-dependent formation of lesions on leaves due to salicylic acid (SA)-dependent PCD. Here, we identified a suppressor of PCD by screening for mutations that abolish the mips1 cell death phenotype. Our screen identified thehxk1 mutant, mutated in the gene encoding the hexokinase1 (HXK1) enzyme that catalyzes sugar phosphorylation and acts as a genuine glucose sensor. We show that HXK1 is required for lesion formation in mips1 due to alterations in MIcontent, via SA-dependant signaling. Using two catalytically inactive HXK1 mutants, we also show that hexokinase catalytic activity is necessary for the establishment of lesions in mips1. Gas chromatography-mass spectrometry analyses revealed a restoration of the MI content in mips1 hxk1 that it is due to the activity of the MIPS2 isoform, while MIPS3 is not involved. Our work defines a pathway of HXK1-mediated cell death in plants and demonstrates that two MIPSenzymes act cooperatively under a particular metabolic status, highlighting a novel checkpoint of MI homeostasis in plants.


Via Jennifer Mach
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Jennifer Mach's curator insight, June 10, 2015 8:25 AM

Hot topic alert! Myo-inositol is trending in my editing queue....

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Simultaneous editing of three homoeoalleles in hexaploid bread wheat confers heritable resistance to powdery mildew - Nature Biotech.

Simultaneous editing of three homoeoalleles in hexaploid bread wheat confers heritable resistance to powdery mildew - Nature Biotech. | plant-microbe interactions | Scoop.it

Wang et al, 2014

Sequence-specific nucleases have been applied to engineer targeted modifications in polyploid genomes1, but simultaneous modification of multiple homoeoalleles has not been reported. Here we use transcription activator–like effector nuclease (TALEN)2,3 and clustered, regularly interspaced, short palindromic repeats (CRISPR)-Cas9 (refs. 4,5) technologies in hexaploid bread wheat to introduce targeted mutations in the three homoeoalleles that encode MILDEW- RESISTANCE LOCUS (MLO) proteins6. Genetic redundancy has prevented evaluation of whether mutation of all three MLO alleles in bread wheat might confer resistance to powdery mildew, a trait not found in natural populations7. We show that TALEN-induced mutation of all three TaMLO homoeologs in the same plant confers heritable broad-spectrum resistanceto powdery mildew. We further use CRISPR-Cas9 technologyto generate transgenic wheat plants that carry mutations inthe TaMLO-A1 allele. We also demonstrate the feasibility of engineering targeted DNA insertion in bread wheat through nonhomologous end joining of the double-strand breaks caused by TALENs. Our findings provide a methodological framework to improve polyploid crops.


Via dromius
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Fesquet didier's curator insight, July 22, 2014 5:22 AM

this open the way for developping non toxic wheat species...good for celiac people...maybe one day...hopes for a slice of pizza :-)

 

Mary Williams's curator insight, July 31, 2014 6:33 AM

I'm trying to catch up with what I missed while traveling. I think this is one of the more exciting papers that came out in the past few weeks, and I'm a bit surprised that it didn't get more press coverage.

Rescooped by WeiGao from Emerging Research in Plant Cell Biology
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Annual Review of Phytopathology: Susceptibility Genes 101: How to Be a Good Host (2014)

Annual Review of Phytopathology: Susceptibility Genes 101: How to Be a Good Host (2014) | plant-microbe interactions | Scoop.it

To confer resistance against pathogens and pests in plants, typically dominant resistance genes are deployed. However, because resistance is based on recognition of a single pathogen-derived molecular pattern these narrowspectrum genes are usually readily overcome. Disease arises from a compatible interaction between plant and pathogen. Hence, altering a plant gene that critically facilitates compatibility could provide a more broad-spectrum and durable type of resistance. Here, such susceptibility (S) genes are reviewed with a focus on the mechanisms underlying loss of compatibility. We distinguish three groups of S genes acting during different stages of infection: early pathogen establishment, modulation of host defenses, and pathogen sustenance. The many examples reviewed here show that S genes have the potential to be used in resistance breeding. However, because S genes have a function other than being a compatibility factor for the pathogen, the side effects caused by their mutation demands a one-by-one assessment of their usefulness for application.


Via Kamoun Lab @ TSL, Jennifer Mach
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Rescooped by WeiGao from Plant Stress
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Science: Nonlegumes Respond to Rhizobial Nod Factors by Suppressing the Innate Immune Response

Science: Nonlegumes Respond to Rhizobial Nod Factors by Suppressing the Innate Immune Response | plant-microbe interactions | Scoop.it

Several nonleguminous plants, including Arabidopsis, tomato, and corn, were able to respond to the same Nod factors that initiate the microbial symbiosis in soybean.This figure shows that the addition of Nod Factor (NF) supresses the immune response triggered by the flg22 peptide. The authors also show that, "Plants defective in the LYK3 protein failed to suppress flg22-triggered ROS production upon Nod factor addition, whereas ectopic overexpression of LYK3 enhanced Nod factor–induced suppression of ROS production".


Via Mary Williams, R K Upadhyay
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MPMI: Single amino acid mutations in the potato immune receptor R3a expand response to Phytophthora effectors (2014)

MPMI: Single amino acid mutations in the potato immune receptor R3a expand response to Phytophthora effectors (2014) | plant-microbe interactions | Scoop.it

Both plants and animals rely on nucleotide-binding domain and leucine-rich repeat-containing proteins (NB-LRRs or NLRs) to respond to invading pathogens and activate immune responses. How plant NB-LRR proteins respond to pathogens is poorly understood. We undertook a gain-of-function random mutagenesis screen of the potato NB-LRR immune receptor R3a to study how this protein responds to the effector protein AVR3a from the oomycete pathogen Phytophthora infestans. R3a response can be extended to the stealthy AVR3aEM isoform of the effector while retaining recognition of AVR3aKI. Each one of 8 single amino acid mutations is sufficient to expand the R3a response to AVR3aEM and other AVR3a variants. These mutations occur across the R3a protein, from the N-terminus to different regions of the LRR domain. Further characterization of these R3a mutants revealed that at least one of them was sensitized, exhibiting a stronger response than the wild-type R3a protein to AVR3aKI. Remarkably, the N336Y mutation, near the R3a nucleotide-binding pocket, conferred response to the effector protein PcAVR3a4 from the vegetable pathogen Phytophthora capsici. This work contributes to understanding how NB-LRR receptor specificity can be modulated. Together with knowledge of pathogen effector diversity, this strategy can be exploited to develop synthetic immune receptors.


Via Kamoun Lab @ TSL
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Stephen Bolus's curator insight, March 30, 2014 2:09 AM

I just really love the idea of synthetic immune receptors!

Rescooped by WeiGao from Plants and Microbes
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MPMI: Transcriptome Sequencing Uncovers the Avr5 Avirulence Gene of the Tomato Leaf Mould Pathogen Cladosporium fulvum (2014)

MPMI: Transcriptome Sequencing Uncovers the Avr5 Avirulence Gene of the Tomato Leaf Mould Pathogen Cladosporium fulvum (2014) | plant-microbe interactions | Scoop.it

The Cf-5 gene of tomato confers resistance to strains of the fungal pathogen Cladosporium fulvum carrying the avirulence gene Avr5. Although Cf-5 has been cloned, Avr5 has remained elusive. We report the cloning of Avr5 using a combined bioinformatic and transcriptome sequencing approach. RNA-Seq was performed on the sequenced race 0 strain (0WU; carries Avr5), as well as a race 5 strain (IPO 1979; lacks a functional Avr5 gene), during infection of susceptible tomato. Forty-four in planta-induced C. fulvum Candidate Effector (CfCE) genes of 0WU were identified that putatively encode a secreted, small cysteine-rich protein. An expressed transcript sequence comparison between strains revealed two polymorphic CfCE genes in IPO 1979. One of these conferred avirulence to IPO 1979 on Cf-5 tomato following complementation with the corresponding 0WU allele, confirming identification of Avr5. Complementation also led to increased fungal biomass during infection of susceptible tomato, signifying a role for Avr5 in virulence. Seven of eight race 5 strains investigated escape Cf-5–mediated resistance through deletion of the Avr5 gene. Avr5 is heavily flanked by repetitive elements, suggesting that repeat instability, in combination with Cf-5–mediated selection pressure, has led to the emergence of race 5 strains deleted for the Avr5 gene.


Via Kamoun Lab @ TSL
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Plant Physiology: The plant membrane-associated REM1.3 remorin accumulates in discrete perihaustorial domains and enhances susceptibility to Phytophthora infestans (2014)

Plant Physiology: The plant membrane-associated REM1.3 remorin accumulates in discrete perihaustorial domains and enhances susceptibility to Phytophthora infestans (2014) | plant-microbe interactions | Scoop.it

Filamentous pathogens such as the oomycete Phytophthora infestans infect plants by developing specialized structures termed haustoria inside the host cells. Haustoria are thought to enable secretion of effector proteins into the plant cells. Haustorium biogenesis is therefore critical for pathogen accommodation in the host tissue. Haustoria are enveloped by a specialized host-derived membrane, the extrahaustorial membrane (EHM), which is distinct from the plant plasma membrane. The mechanisms underlying the biogenesis of the EHM are unknown. Remarkably, several plasma membrane localised proteins are excluded from the EHM but the remorin REM1.3 accumulates around P. infestans haustoria. Here, we used overexpression, co-localization with reporter proteins, and super-resolution microscopy in cells infected by P. infestans to reveal discrete EHM domains labelled by REM1.3 and P. infestans effector AVRblb2. Moreover, SYT1 synaptotagmin, another previously identified perihaustorial protein, localized to subdomains which are mainly not labelled by REM1.3 and AVRblb2. Functional characterization of REM1.3 revealed that it is a susceptibility factor that promotes infection by P. infestans. This activity, and REM1.3 recruitment to the EHM, require REM1.3 membrane binding domain. Our results implicate REM1.3 membrane micro-domains in plant susceptibility to an oomycete pathogen.


Via Kamoun Lab @ TSL
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Jean-Michel Ané's curator insight, May 14, 2014 4:17 PM

I know that it is not a symbiont but... some people will guess why I am scooping this :-)