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PLOS Pathogens: Virus-Encoded microRNAs: An Overview and a Look to the Future

PLOS Pathogens: Virus-Encoded microRNAs: An Overview and a Look to the Future | Plant-Microbe Interaction | Scoop.it

MicroRNAs (miRNAs) are small RNAs that play important roles in the regulation of gene expression. First described as posttranscriptional gene regulators in eukaryotic hosts, virus-encoded miRNAs were later uncovered. It is now apparent that diverse virus families, most with DNA genomes, but at least some with RNA genomes, encode miRNAs. While deciphering the functions of viral miRNAs has lagged behind their discovery, recent functional studies are bringing into focus these roles. Some of the best characterized viral miRNA functions include subtle roles in prolonging the longevity of infected cells, evading the immune response, and regulating the switch to lytic infection. Notably, all of these functions are particularly important during persistent infections. Furthermore, an emerging view of viral miRNAs suggests two distinct groups exist. In the first group, viral miRNAs mimic host miRNAs and take advantage of conserved networks of host miRNA target sites. In the larger second group, viral miRNAs do not share common target sites conserved for host miRNAs, and it remains unclear what fraction of these targeted transcripts are beneficial to the virus. Recent insights from multiple virus families have revealed new ways of interacting with the host miRNA machinery including noncanonical miRNA biogenesis and new mechanisms of posttranscriptional cis gene regulation. Exciting challenges await the field, including determining the most relevant miRNA targets and parlaying our current understanding of viral miRNAs into new therapeutic strategies. To accomplish these goals and to better grasp miRNA function, new in vivo models that recapitulate persistent infections associated with viral pathogens are required.

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Rescooped by Guogen Yang from Plant-microbe interactions (on the plant's side)
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Light intensity and temperature affect systemic spread of silencing signal in transient agro-infiltration studies

Light intensity and temperature affect systemic spread of silencing signal in transient agro-infiltration studies | Plant-Microbe Interaction | Scoop.it

RNA silencing is a sequence-specific post-transcriptional gene inactivation mechanism that operates in diverse organisms and which can extend beyond its site of initiation, owing to the movement of the silencing signal, called non-autonomous gene silencing. Previous studies have shown that several factors manifest the movement of silencing signal, such as, the size (21 or 24 nt) of secondary siRNA produced, or the steady-state concentration of siRNAs and their cognate mRNA, or as a result of change in the sink-source status of plant parts affecting the phloem translocation. Our studies show that, both light intensity and temperature have significant impact on systemic movement of silencing signal in transient agro-infiltration studies in Nicotiana benthamiana. At higher light intensities (≥450 μEm-2s-1) and higher temperatures (≥30°C), the gene silencing was localized to the leaf tissue that was infiltrated, without any systemic spread. Interestingly in these light and temperature conditions (≥450 μEm-2s-1 and ≥30°C) the N. benthamiana plants showed recovery from the viral symptoms. However reduced systemic silencing and the reduced viral symptom severity at higher light intensities were due to the change in the sink-source status of the plant, ultimately affecting the phloem translocation of small RNAs or the viral genome. Whereas at lower light intensities (<300 μEm-2s-1) with a constant temperature of 25°C, there was strong systemic movement of silencing signal in the N. benthamiana plants and also there was reduced recovery from virus infections. Accumulation of gene specific siRNAs were reduced at higher temperature as a result of reduction in the accumulation of transcript on transient agro-infiltration of RNAi constructs, mostly because of poor T-DNA transfer activity of Agrobacterium, possibly also accompanied by reduced phloem translocation.


Via Christophe Jacquet
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Genome-wide annotation of the soybean WRKY family and functional characterization of genes involved in response to Phakopsora pachyrhizi infection

Genome-wide annotation of the soybean WRKY family and functional characterization of genes involved in response to Phakopsora pachyrhizi infection | Plant-Microbe Interaction | Scoop.it

BackgroundMany previous studies have shown that soybean WRKY transcription factors are involved in the plant response to biotic and abiotic stresses. Phakopsora pachyrhizi is the causal agent of Asian Soybean Rust, one of the most important soybean diseases. There are evidences that WRKYs are involved in the resistance of some soybean genotypes against that fungus. The number of WRKY genes already annotated in soybean genome was underrepresented. In the present study, a genome-wide annotation of the soybean WRKY family was carried out and members involved in the response to P. pachyrhizi were identified.ResultsAs a result of a soybean genomic databases search, 182 WRKY-encoding genes were annotated and 33 putative pseudogenes identified. Genes involved in the response to P. pachyrhizi infection were identified using superSAGE, RNA-Seq of microdissected lesions and microarray experiments. Seventy-five genes were differentially expressed during fungal infection. The expression of eight WRKY genes was validated by RT-qPCR. The expression of these genes in a resistant genotype was earlier and/or stronger compared with a susceptible genotype in response to P. pachyrhizi infection. Soybean somatic embryos were transformed in order to overexpress or silence WRKY genes. Embryos overexpressing a WRKY gene were obtained, but they were unable to convert into plants. When infected with P. pachyrhizi, the leaves of the silenced transgenic line showed a higher number of lesions than the wild-type plants. ConclusionsThe present study reports a genome-wide annotation of soybean WRKY family. The participation of some members in response to P. pachyrhizi infection was demonstrated. The results contribute to the elucidation of gene function and suggest the manipulation of WRKYs as a strategy to increase fungal resistance in soybean plants.


Via Christophe Jacquet
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Rescooped by Guogen Yang from Plant Immunity And Microbial Effectors
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Nonsense-Mediated mRNA Decay Modulates Immune Receptor Levels to Regulate Plant Antibacterial Defense: Cell Host & Microbe

Nonsense-Mediated mRNA Decay Modulates Immune Receptor Levels to Regulate Plant Antibacterial Defense: Cell Host & Microbe | Plant-Microbe Interaction | Scoop.it

Highlights•Nonsense-mediated mRNA decay (NMD) prevents aberrant plant immune response activation•NMD posttranscriptionally regulates numerous TNL immune receptor transcripts•NMD is dampened upon pathogen infection as part of host-programmed immunity•Host-regulated NMD inhibition upon infection promotes disease resistance


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MPMI: The genome of the saprophytic fungus Verticillium tricorpus reveals a complex effector repertoire resembling that of its pathogenic relatives (2014)

MPMI: The genome of the saprophytic fungus Verticillium tricorpus reveals a complex effector repertoire resembling that of its pathogenic relatives (2014) | Plant-Microbe Interaction | Scoop.it

Vascular wilts caused by Verticillium spp. are destructive plant diseases, affecting hundreds of hosts. Only few Verticillium spp. are causal agents of vascular wilt diseases, of which V. dahliae is the most notorious pathogen, and several V. dahliae genomes are available. In contrast, V. tricorpus is mainly known as saprophyte and causal agent of opportunistic infections. Based on a hybrid approach that combines second and third generation sequencing, a near-gapless V. tricorpus genome assembly was obtained. With comparative genomics, we aimed to identify genomic features in V. dahliae that confer the ability to cause vascular wilt disease. Unexpectedly, both species encode similar effector repertoires and share a genomic structure with genes encoding secreted proteins clustered in genomic islands. Intriguingly, V. tricorpus contains significantly less repetitive elements and an extended spectrum of secreted carbohydrate-active enzymes when compared with V. dahliae. In conclusion, we highlight the technical advances of a hybrid sequencing and assembly approach and reveal that the saprophyte V. tricorpus shares many hallmark features with V. dahliae.


Via Kamoun Lab @ TSL, Francis Martin
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Rescooped by Guogen Yang from Plant Immunity And Microbial Effectors
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The Ins and Outs of Rust Haustoria

The Ins and Outs of Rust Haustoria | Plant-Microbe Interaction | Scoop.it
From molecules to physiology

Via IPM Lab
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Rescooped by Guogen Yang from Effectors and Plant Immunity
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Nature Biotech.: Field trial of Xanthomonas wilt disease-resistant bananas in East Africa (2014)

Nature Biotech.: Field trial of Xanthomonas wilt disease-resistant bananas in East Africa (2014) | Plant-Microbe Interaction | Scoop.it

Banana is a major staple crop in East Africa produced mostly by smallholder subsistence farmers. More bananas are produced and consumed in East Africa than in any region of the world. Uganda is the world’s second foremost grower with a total annual production of about 10.5 million tons. The average daily per capita consumption in Uganda ranges from 0.61 to over 1.6 kg, one of the highest in the world. In this Correspondence, we report preliminary results from a confined field trial in Uganda of transgenic bananas resistant to the deadly banana Xanthomonas wilt disease.

 

Leena Tripathi, Jaindra Nath Tripathi, Andrew Kiggundu, Sam Korie, Frank Shotkoski & Wilberforce Kateera Tushemereirwe


Via Nicolas Denancé
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Rescooped by Guogen Yang from Virology and Bioinformatics from Virology.ca
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A single vertebrate DNA virus protein disarms invertebrate immunity to RNA virus infection

A single vertebrate DNA virus protein disarms invertebrate immunity to RNA virus infection | Plant-Microbe Interaction | Scoop.it

Virus-host interactions drive a remarkable diversity of immune responses and countermeasures. We found that two RNA viruses with broad host ranges, vesicular stomatitis virus (VSV) and Sindbis virus (SINV), are completely restricted in their replication after entry into Lepidopteran cells. This restriction is overcome when cells are co-infected with vaccinia virus (VACV), a vertebrate DNA virus. Using RNAi screening, we show that Lepidopteran RNAi, Nuclear Factor-κB, and ubiquitin-proteasome pathways restrict RNA virus infection. Surprisingly, a highly conserved, uncharacterized VACV protein, A51R, can partially overcome this virus restriction. We show that A51R is also critical for VACV replication in vertebrate cells and for pathogenesis in mice. Interestingly, A51R colocalizes with, and stabilizes, host microtubules and also associates with ubiquitin. We show that A51R promotes viral protein stability, possibly by preventing ubiquitin-dependent targeting of viral proteins for destruction. Importantly, our studies reveal exciting new opportunities to study virus-host interactions in experimentally-tractable Lepidopteran systems.


Via natashai
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Rescooped by Guogen Yang from Plant Pathogenomics
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Scoop.it: Mycorrhizal fungal genomes (2014)

Scoop.it: Mycorrhizal fungal genomes (2014) | Plant-Microbe Interaction | Scoop.it

Genome and Transcriptome of Mycorrhizal fungi - by S. Ghignone & R. Balestrini


Via Kamoun Lab @ TSL
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Rescooped by Guogen Yang from Plant Biology Teaching Resources (Higher Education)
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Journal of Visualized Experiments (JOVE) Cell Specific Analysis of Arabidopsis Leaves using Fluorescently Activated Cell Sorting (FACS)

Journal of Visualized Experiments (JOVE) Cell Specific Analysis of Arabidopsis Leaves using Fluorescently Activated Cell Sorting (FACS) | Plant-Microbe Interaction | Scoop.it
A method for producing Arabidopsis leaf protoplasts that are compatible with fluorescence activated cell sorting (FACS),...

Via Mary Williams
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Mary Williams's curator insight, September 9, 3:50 AM

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Rescooped by Guogen Yang from Plant Biology Teaching Resources (Higher Education)
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Review (PLOS Genetics): Trans-kingdom Cross-Talk: Small RNAs on the Move

Review (PLOS Genetics): Trans-kingdom Cross-Talk: Small RNAs on the Move | Plant-Microbe Interaction | Scoop.it

"Mobility of sRNA molecules within organisms is a well-known phenomenon, facilitating gene silencing between cells and tissues. sRNA signals are also transmitted between organisms of the same species and of different species. Remarkably, in recent years many examples of RNA-signal exchange have been described to occur between organisms of different kingdoms. These examples are predominantly found in interactions between hosts and their pathogens, parasites, and symbionts. However, they may only represent the tip of the iceberg, since the emerging picture suggests that organisms in biological niches commonly exchange RNA-silencing signals."


Via Mary Williams
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Rescooped by Guogen Yang from Fungal|Oomycete Biology
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Fungal model systems and the elucidation of pathogenicity determinants

Fungal model systems and the elucidation of pathogenicity determinants | Plant-Microbe Interaction | Scoop.it

Fungi have the capacity to cause devastating diseases of both plants and animals, causing significant harvest losses that threaten food security and human mycoses with high mortality rates. As a consequence, there is a critical need to promote development of new antifungal drugs, which requires a comprehensive molecular knowledge of fungal pathogenesis. In this review, we critically evaluate current knowledge of seven fungal organisms used as major research models for fungal pathogenesis. These include pathogens of both animals and plants; Ashbya gossypii, Aspergillus fumigatus, Candida albicans, Fusarium oxysporum, Magnaporthe oryzae, Ustilago maydis and Zymoseptoria tritici. We present key insights into the virulence mechanisms deployed by each species and a comparative overview of key insights obtained from genomic analysis. We then consider current trends and future challenges associated with the study of fungal pathogenicity.


Via Alejandro Rojas
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Rescooped by Guogen Yang from Rice Blast
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System-wide characterization of bZIP transcription factor proteins involved in infection-related morphogenesis of Magnaporthe oryzae

System-wide characterization of bZIP transcription factor proteins involved in infection-related morphogenesis of Magnaporthe oryzae | Plant-Microbe Interaction | Scoop.it

The basic-leucine zipper (bZIP) domain-containing transcription factors (TFs) function as key regulators of cellular growth and differentiation in eukaryotic organisms including fungi. We have previously identified MoAp1 and MoAtf1 as bZIP TFs in Magnaporthe oryzae and demonstrated that they regulate the oxidative stress response and are critical in conidiogenesis and pathogenicity. Studies of bZIP proteins could provide a novel strategy for controlling rice blast, but a systematic examination of the bZIP proteins has not been carried out. Here, we identified 19 additional bZIP TFs and characterized their functions. We found that the majority of these TFs exhibit active functions, most notably, in conidiogenesis. We showed that MoHac1 regulates the endoplasmic reticulum (ER)-stress response through a conserved unfolded protein response (UPR) pathway, MoMetR controls amino acid metabolism to govern growth and differentiation, and MoBzip10 governs appressorium function and invasive hyphal growth. Moreover, MoBzip5 participates in appressorium formation through a pathway distinct from that MoBzip10, and MoMeaB appears to exert a regulatory role through nutrient uptake and nitrogen utilization. Collectively, our results provide insights into shared and specific functions associated with each of these TFs and link the regulatory roles to the fungal growth, conidiation, appressorium formation, host penetration, and pathogenicity


Via Elsa Ballini
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Rescooped by Guogen Yang from Plant Biology Teaching Resources (Higher Education)
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Special Issue: Functional-Structural Plant Modelling

Special Issue: Functional-Structural Plant Modelling | Plant-Microbe Interaction | Scoop.it

A number of research groups in various areas of plant biology as well as computer science and applied mathematics have addressed modelling the spatiotemporal dynamics of growth and development of plants. This has resulted in development of functional–structural plant models (FSPMs). In FSPMs, the plant structure is always explicitly represented in terms of a network of elementary units. In this respect, FSPMs are different from more abstract models in which a simplified representation of the plant structure is frequently used (e.g. spatial density of leaves, total biomass, etc.). This key feature makes it possible to build modular models and creates avenues for efficient exchange of model components and experimental data. They are being used to deal with the complex 3-D structure of plants and to simulate growth and development occurring at spatial scales from cells to forest areas, and temporal scales from seconds to decades and many plant generations. The plant types studied also cover a broad spectrum, from algae to trees. This special issue of Annals of Botany features selected papers on FSPM topics such as models of morphological development, models of physical and biological processes, integrated models predicting dynamics of plants and plant communities, modelling platforms, methods for acquiring the 3-D structures of plants using automated measurements, and practical applications for agronomic purposes.


Via Jennifer Mach, Mary Williams
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Rescooped by Guogen Yang from Plant Biology Teaching Resources (Higher Education)
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Plant Physiology: Efficient gene editing in tomato in the first generation using the CRISPR/Cas9 system (2014)

Plant Physiology: Efficient gene editing in tomato in the first generation using the CRISPR/Cas9 system (2014) | Plant-Microbe Interaction | Scoop.it

To test the efficacy of CRISPR/Cas9 in tomato, we chose to target a gene that, when function was disrupted, would result in a distinctive, immediately recognizable phenotype early in the plant tissue culture phase of Agrobacterium-mediated transformation. A CRISPR/Cas9 construct was designed to target neighboring sequences in the second exon of the tomato homolog of Arabidopsis ARGONAUTE7 (SlAGO7), because loss-of-function mutations are recessive and result in plants whose typical compound flat leaves become needle-like, or “wiry” (Fig. 1) (Lesley, 1928; Yifhar et al., 2012). SlAGO7 is required for the biogenesis of a class of small RNAs known as trans-acting short interfering RNAs (ta-siRNAs), which regulate organ polarity through post-transcriptional silencing of AUXIN RESPONSE FACTOR (ARF) genes (Husbands et al., 2009). Strong alleles of slago7 thus produce lower levels of ta-siRNAs and reduced ARF mRNA degradation, resulting in the first leaves of mutant plants having leaflets without petioles, and later formed leaves lacking laminae (Fig. 1C). These distinctive phenotypes allowed us to immediately identify first generation transformed (T0) plants in which both alleles of SlAGO7 might be mutated.


Via Kamoun Lab @ TSL, Mary Williams
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Rescooped by Guogen Yang from Publications
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PLOS ONE: Variation in Capsidiol Sensitivity between Phytophthora infestans and Phytophthora capsici Is Consistent with Their Host Range (2014)

PLOS ONE: Variation in Capsidiol Sensitivity between Phytophthora infestans and Phytophthora capsici Is Consistent with Their Host Range (2014) | Plant-Microbe Interaction | Scoop.it

Plants protect themselves against a variety of invading pathogenic organisms via sophisticated defence mechanisms. These responses include deployment of specialized antimicrobial compounds, such as phytoalexins, that rapidly accumulate at pathogen infection sites. However, the extent to which these compounds contribute to species-level resistance and their spectrum of action remain poorly understood. Capsidiol, a defense related phytoalexin, is produced by several solanaceous plants including pepper and tobacco during microbial attack. Interestingly, capsidiol differentially affects growth and germination of the oomycete pathogensPhytophthora infestans and Phytophthora capsici, although the underlying molecular mechanisms remain unknown. In this study we revisited the differential effect of capsidiol on P. infestans and P. capsici, using highly pure capsidiol preparations obtained from yeast engineered to express the capsidiol biosynthetic pathway. Taking advantage of transgenicPhytophthora strains expressing fluorescent markers, we developed a fluorescence-based method to determine the differential effect of capsidiol on Phytophtora growth. Using these assays, we confirm major differences in capsidiol sensitivity between P. infestans and P. capsiciand demonstrate that capsidiol alters the growth behaviour of both Phytophthora species. Finally, we report intraspecific variation within P. infestans isolates towards capsidiol tolerance pointing to an arms race between the plant and the pathogens in deployment of defence related phytoalexins.


Via Kamoun Lab @ TSL
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J Exp Bot: Expression patterns of FLAGELLIN SENSING 2 map to bacterial entry sites in plant shoots and roots (2014)

J Exp Bot: Expression patterns of FLAGELLIN SENSING 2 map to bacterial entry sites in plant shoots and roots (2014) | Plant-Microbe Interaction | Scoop.it

Pathogens can colonize all plant organs and tissues. To prevent this, each cell must be capable of autonomously triggering defence. Therefore, it is generally assumed that primary sensors of the immune system are constitutively present. One major primary sensor against bacterial infection is the FLAGELLIN SENSING 2 (FLS2) pattern recognition receptor (PRR). To gain insights into its expression pattern, the FLS2 promoter activity in β-glucuronidase (GUS) reporter lines was monitored. The data show that pFLS2::GUS activity is highest in cells and tissues vulnerable to bacterial entry and colonization, such as stomata, hydathodes, and lateral roots. GUS activity is also high in the vasculature and, by monitoring Ca2+responses in the vasculature, it was found that this tissue contributes to flg22-induced Ca2+ burst. The FLS2 promoter is also regulated in a tissue- and cell type-specific manner and is responsive to hormones, damage, and biotic stresses. This results in stimulus-dependent expansion of the FLS2 expression domain. In summary, a tissue- and cell type-specific map of FLS2 expression has been created correlating with prominent entry sites and target tissues of plant bacterial pathogens.


Via The Sainsbury Lab, Suayib Üstün
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The Sainsbury Lab's curator insight, September 11, 1:09 AM

Pathogens can colonize all plant organs and tissues. To prevent this, each cell must be capable of autonomously triggering defence. Therefore, it is generally assumed that primary sensors of the immune system are constitutively present. One major primary sensor against bacterial infection is the FLAGELLIN SENSING 2 (FLS2) pattern recognition receptor (PRR). To gain insights into its expression pattern, the FLS2 promoter activity in β-glucuronidase (GUS) reporter lines was monitored. The data show that pFLS2::GUS activity is highest in cells and tissues vulnerable to bacterial entry and colonization, such as stomata, hydathodes, and lateral roots. GUS activity is also high in the vasculature and, by monitoring Ca2+responses in the vasculature, it was found that this tissue contributes to flg22-induced Ca2+ burst. The FLS2 promoter is also regulated in a tissue- and cell type-specific manner and is responsive to hormones, damage, and biotic stresses. This results in stimulus-dependent expansion of the FLS2 expression domain. In summary, a tissue- and cell type-specific map of FLS2 expression has been created correlating with prominent entry sites and target tissues of plant bacterial pathogens.

Rescooped by Guogen Yang from MycorWeb Plant-Microbe Interactions
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Frontiers | Control of arbuscular mycorrhiza development by nutrient signals | Plant Physiology

Inorganic phosphate (Pi), the main form of phosphorus used by plants, is one of the most important limiting factors for plant growth. In the soil soluble Pi that is readily available for uptake, occurs at very low concentrations (Schachtman et al., 1998). One adaptation of plants to low Pi availability is the symbiosis with arbuscular mycorrhiza fungi (AMF) of the phylum Glomeromycota. The fungi efficiently take up phosphate and other mineral nutrients and deliver them to the host, in exchange for carbohydrates. Thereby, arbuscular-mycorrhiza compatible plants have two Pi uptake pathways, which are defined by different sets of phosphate transporters: a direct uptake pathway through the epidermis and root hairs, and a symbiotic uptake pathway for the Pi provided by the fungus (Smith and Smith, 2011).


Via Francis Martin
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Rescooped by Guogen Yang from Plant Biology Teaching Resources (Higher Education)
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Cell Host Microbes: Convergent Targeting of a Common Host Protein-Network by Pathogen Effectors from Three Kingdoms of Life (2014)

Cell Host Microbes: Convergent Targeting of a Common Host Protein-Network by Pathogen Effectors from Three Kingdoms of Life (2014) | Plant-Microbe Interaction | Scoop.it

While conceptual principles governing plant immunity are becoming clear, its systems-level organization and the evolutionary dynamic of the host-pathogen interface are still obscure. We generated a systematic protein-protein interaction network of virulence effectors from the ascomycete pathogen Golovinomyces orontii and Arabidopsis thaliana host proteins. We combined this data set with corresponding data for the eubacterial pathogen Pseudomonas syringae and the oomycete pathogen Hyaloperonospora arabidopsidis. The resulting network identifies host proteins onto which intraspecies and interspecies pathogen effectors converge. Phenotyping of 124 Arabidopsis effector-interactor mutants revealed a correlation between intraspecies and interspecies convergence and several altered immune response phenotypes. Several effectors and the most heavily targeted host protein colocalized in subnuclear foci. Products of adaptively selected Arabidopsis genes are enriched for interactions with effector targets. Our data suggest the existence of a molecular host-pathogen interface that is conserved across Arabidopsis accessions, while evolutionary adaptation occurs in the immediate network neighborhood of effector targets.

 

Ralf Weßling, Petra Epple, Stefan Altmann,Yijian He, Li Yang, Stefan R. Henz, Nathan McDonald, Kristin Wiley, Kai Christian Bader, Christine Glaßer, M. Shahid Mukhtar, Sabine Haigis, Lila Ghamsari, Amber E. Stephens, Joseph R. Ecker, Marc Vidal, Jonathan D.G. Jones,Klaus F.X. Mayer, Emiel Ver Loren van Themaat, Detlef Weigel, Paul Schulze-Lefert, Jeffery L. Dangl, Ralph Panstruga, and Pascal Braun


Via Nicolas Denancé, Suayib Üstün, Mary Williams
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CP's curator insight, September 12, 1:04 AM

add your insight...

Suayib Üstün's comment, September 12, 1:45 AM
HopBF1 is HopZ4!
Suayib Üstün's curator insight, September 12, 2:14 AM

HopBF1 is HopZ4...

Rescooped by Guogen Yang from TAL effector science
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Wheat rescued from fungal disease - Nature Biotechnol.

Wheat rescued from fungal disease - Nature Biotechnol. | Plant-Microbe Interaction | Scoop.it

(via T. Lahaye, thx)

GIl-Humanes & Voytas 2014

Wang et al. targeted the MLO loci using an SSN known as a transcription activator–like effector nuclease (TALEN), which effectively recognized the MLO loci and created targeted mutations at high efficiency. Wang et al.2 owed their success to the large scale of their experiments: by generating a remarkable 687 transgenic wheat lines containing the TALEN-encoding construct, they were able to recover 35 mlo mutant plants with one, two or three MLO genes modified. After self-fertilization of the triply mutant plants, lines were recovered with knockouts of all six MLO alleles. The mutations were typical of those generated by imprecise double-strand break repair, namely the loss or gain of a small number of bases at the target site. After segregation of the TALEN-encoding transgene, the resultant powdery mildew resistance line had no foreign DNA in its genome, and relative to the 17.1-Gb genome of its susceptible parent, differed by a mere 530 base pairs. This achievement highlights the remarkable power of SSNs to simultaneously modify multiple targets in complex genomes.


Via dromius
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Rescooped by Guogen Yang from Plants and Microbes
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PNAS: Four hundred-million-year-old vesicular arbuscular mycorrhizae (2004)

PNAS: Four hundred-million-year-old vesicular arbuscular mycorrhizae (2004) | Plant-Microbe Interaction | Scoop.it

The discovery of arbuscules in Aglaophyton major, an Early Devonian land plant, provides unequivocal evidence that mycorrhizae were established >400 million years ago. Nonseptate hyphac and arbuscules occur in a specialized meristematic region of the cortex that continually provided new cells for fungal infection. Arbuscules are morphologically identical to those of living arbuscular mycorrhizae in consisting of a basal trunk and repeatedly branched bush-like tuft within the plant cell. Although interpretations of the evolution of mycorrhizal mutualisms continue to be speculative, the existence of arbuscules in the Early Devonian indicates that nutrient transfer mutualism may have been in existence when plants invaded the land.


Via Kamoun Lab @ TSL
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Rescooped by Guogen Yang from Effectors and Plant Immunity
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Curr. Biol.: Type III secretion system (2014)

Curr. Biol.: Type III secretion system (2014) | Plant-Microbe Interaction | Scoop.it

The type III secretion system (T3SS) is a membrane-embedded nanomachine found in several Gram-negative bacteria. Upon contact between bacteria and host cells, the syringe-like T3SS transfers proteins termed effectors from the bacterial cytosol to the cytoplasm or the plasma membrane of a single target cell. This is a major difference from secretion systems that merely release molecules into the extracellular milieu, where they act on potentially distant target cells expressing the relevant surface receptors. The syringe architecture is conserved at the structural and functional level and supports injection into a great variety of hosts and tissues. However, the pool of effectors is species specific and determines the outcome of the interaction, via modulation of target-cell function.

 

Andrea Puhar & Philippe J. Sansonetti


Via Nicolas Denancé
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Rescooped by Guogen Yang from Virology and Bioinformatics from Virology.ca
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Genomic analysis of vaccinia virus strain TianTan provides new insights into the evolution and evolutionary relationships between Orthopoxviruses

Genomic analysis of vaccinia virus strain TianTan provides new insights into the evolution and evolutionary relationships between Orthopoxviruses | Plant-Microbe Interaction | Scoop.it

Vaccinia virus (VACV) strain TianTan was used for much of China's modern history to vaccinate against smallpox, however the only genome sequence contains errors. We have sequenced additional examples of TianTan to obtain a better picture of this important virus. We detected two different subclones. One (TP03) encodes large deletions in the terminal repeats that extend into both VEGF genes and create a small plaque variant. The second clone (TP05) encodes a nearly intact complement of genes in the terminal repeats, except for an insertion of sequences resembling the telomeric 69 bp repeats. The TP05 genome spans 196,260 bp and encodes 219 genes. The revised sequence documents the integrity of all the genes in the conserved virus core. Phylogenetic methods show that TianTan belongs to a unique clade of VACV, but probably also share a common origin with strains belonging to the Copenhagen/Lister lineage and distinct from the Wyeth/Dryvax lineage.


Via natashai
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Rescooped by Guogen Yang from MycorWeb Plant-Microbe Interactions
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eLIFE: Active invasion of bacteria into living fungal cells

eLIFE: Active invasion of bacteria into living fungal cells | Plant-Microbe Interaction | Scoop.it

The rice seedling blight fungus Rhizopus microsporus and its endosymbiont Burkholderia rhizoxinica form an unusual, highly specific alliance to produce the highly potent antimitotic phytotoxin rhizoxin. Yet, it has remained a riddle how bacteria invade into the fungal cells. Genome mining for potential symbiosis factors and functional analyses revealed that a type 2 secretion system (T2SS) of the bacterial endosymbiont is required for the formation of the endosymbiosis. Comparative proteome analyses show that the T2SS releases chitinolytic enzymes (chitinase, chitosanase) and chitin-binding proteins. The genes responsible for chitinolytic proteins and T2SS components are highly expressed during infection. Through targeted gene knock-outs, sporulation assays and microscopic investigations we found that chitinase is essential for bacteria to enter hyphae. Unprecedented snapshots of the traceless bacterial intrusion were obtained using cryo-electron microscopy. Beyond unveiling the pivotal role of chitinolytic enzymes in the active invasion of a fungus by bacteria, these findings grant unprecedented insight into the fungal cell wall penetration and symbiosis formation.


Via Stéphane Hacquard, Francis Martin
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Evidence for a Transketolase-Mediated Metabolic Checkpoint Governing Biotrophic Growth in Rice Cells by the Blast Fungus Magnaporthe oryzae

Evidence for a Transketolase-Mediated Metabolic Checkpoint Governing Biotrophic Growth in Rice Cells by the Blast Fungus Magnaporthe oryzae | Plant-Microbe Interaction | Scoop.it

Here, using molecular genetics and live-cell imaging, we dismantled M. oryzae glucose-metabolizing pathways to reveal that the transketolase enzyme, encoded by TKL1, plays an essential role in facilitating host colonization during rice blast disease. In the absence of transketolase, Δtkl1 mutant strains formed functional appressoria that penetrated rice cuticles successfully and developed invasive hyphae (IH) in rice cells from primary hyphae. However, Δtkl1 could not undertake sustained biotrophic growth or cell-to-cell movement. Transcript data and observations using fluorescently labeled histone H1:RFP fusion proteins indicated Δtkl1 mutant strains were alive in host cells but were delayed in mitosis. Mitotic delay could be reversed and IH growth restored by the addition of exogenous ATP, a metabolite depleted in Δtkl1 mutant strains. We show that ATP might act via the TOR signaling pathway, and TOR is likely a downstream target of activation for TKL1. TKL1is also involved in controlling the migration of appressorial nuclei into primary hyphae in host cells. When taken together, our results indicate transketolase has a novel role in mediating - via ATP and TOR signaling - an in planta-specific metabolic checkpoint that controls nuclear migration from appressoria into primary hyphae, prevents mitotic delay in early IH and promotes biotrophic growth. This work thus provides new information about the metabolic strategies employed by M. oryzae to enable rice cell colonizatio


Via Elsa Ballini
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Rescooped by Guogen Yang from Plant-Microbe Symbioses
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Ectomycorrhizal fungi have larger fruit bodies than saprotrophic fungi

Ectomycorrhizal fungi have larger fruit bodies than saprotrophic fungi | Plant-Microbe Interaction | Scoop.it

Currently we have only a limited understanding of the evolutionary and ecological significance of reproductive traits of fungi. We compared data on fruit body size, spore size and shape between saprotrophic and mutualistic (ectomycorrhizal) fungi in Northern and Central Europe. Lifestyle and reproductive traits showed strong phylogenetic signals. A phylogenetically informed analysis demonstrated that saprotrophs produce on average smaller fruit bodies than mutualistic species. The two guilds, however, do not differ in spore size. Overall this suggests that fruit bodies of ectomycorrhizal fungi produce on average more spores than saprotrophic fungi. We argue that this difference is related to resource availability: ectomycorrhizal fungi receive carbon from their hosts and, therefore, evolution favours large fruit bodies, whereas the fruit body size of saprotrophic fungi might have responded to resource availability and the distribution and size of resource patches.


Via Jean-Michel Ané
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