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PLOS Genetics: Plant Vascular Cell Division Is Maintained by an Interaction between PXY and Ethylene Signalling

PLOS Genetics: Plant Vascular Cell Division Is Maintained by an Interaction between PXY and Ethylene Signalling | Plant-Microbe Interaction | Scoop.it
Plants transport water and nutrients throughout their bodies using a specialised vascular system. Vascular tissue is also responsible for providing structural support to plants; for example, wood is made up of specialised vascular cells. Consequently, the vascular system constitutes the majority of plant biomass. Chemicals from plant biomass could be used to make the next generation of biofuels in order to reduce dependence on fossil fuels. Vascular tissue is derived from a group of dividing cells present in a structure called the procambium, but mechanisms controlling cell division in this structure remain poorly understood. Understanding the events that occur in the procambium may help us to understand how we can best utilise plants for increased plant biomass, for example, for biofuel and wood production. We have identified a number of genes that regulate cell division in the procambium that are controlled by the gaseous plant hormone ethylene. We show that ethylene signalling, in turn, interacts with PXY, a gene encoding a signalling component that also controls vascular cell division. Our results demonstrate that the interaction between ethylene and PXY signalling is responsible for maintaining the plant vascular system.

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Rescooped by Guogen Yang from Plant Immunity And Microbial Effectors
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Secretory Function of Autophagy in Innate Immune Cells

Secretory Function of Autophagy in Innate Immune Cells | Plant-Microbe Interaction | Scoop.it
Summary
Eukaryotic cells utilize two main secretory pathways to transport proteins to the extracellular space.

Via IPM Lab
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Rescooped by Guogen Yang from Plant Immunity And Microbial Effectors
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Frontiers | Diversifying selection in the wheat stem rust fungus acts predominantly on pathogen-associated gene families and reveals candidate effectors | Plant-Microbe Interaction

Plant pathogens cause severe losses to crop plants and threaten global food production. One striking example is the wheat stem rust fungus, Puccinia graminis f. sp. tritici, which can rapidly evolve new virulent pathotypes in response to resistant host lines. Like several other filamentous fungal and oomycete plant pathogens, its genome features expanded gene families that have been implicated in host-pathogen interactions, possibly encoding effector proteins that interact directly with target host defence proteins. Previous efforts to understand virulence largely relied on the prediction of secreted, small and cysteine-rich proteins as candidate effectors and thus delivered an overwhelming number of candidates. Here, we implement an alternative analysis strategy that uses the signal of adaptive evolution as a line of evidence for effector function, combined with comparative information and expression data. We demonstrate that in planta up-regulated genes that are rapidly evolving are found almost exclusively in pathogen-associated gene families, affirming the impact of host-pathogen co-evolution on genome structure and the adaptive diversification of specialised gene families. In particular, we predict 42 effector candidates that are conserved only across pathogens, induced during infection and rapidly evolving. One of our top candidates has recently been shown to induce genotype-specific hypersensitive cell death in wheat. This shows that comparative genomics incorporating the evolutionary signal of adaptation is powerful for predicting effector candidates for laboratory verification. Our system can be applied to a wide range of pathogens and will give insight into host-pathogen dynamics, ultimately leading to progress in strategies for disease control.

Via IPM Lab
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Rescooped by Guogen Yang from MycorWeb Plant-Microbe Interactions
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Ancient human genomes suggest three ancestral populations for present-day Europeans : Nature

Ancient human genomes suggest three ancestral populations for present-day Europeans : Nature | Plant-Microbe Interaction | Scoop.it
We sequenced the genomes of a [sim]7,000-year-old farmer from Germany and eight [sim]8,000-year-old hunter-gatherers from Luxembourg and Sweden. We analysed these and other ancient genomes with 2,345 contemporary humans to show that most present-day Europeans derive from at least three highly differentiated populations: west European hunter-gatherers, who contributed ancestry to all Europeans but not to Near Easterners; ancient north Eurasians related to Upper Palaeolithic Siberians, who contributed to both Europeans and Near Easterners; and early European farmers, who were mainly of Near Eastern origin but also harboured west European hunter-gatherer related ancestry. We model these populations/' deep relationships and show that early European farmers had [sim]44% ancestry from a /`basal Eurasian/' population that split before the diversification of other non-African lineages.

Via Francis Martin
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Rescooped by Guogen Yang from Plant-microbe interactions (on the plant's side)
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A procedure for the transient expression of genes by agroinfiltration above the permissive threshold to study temperature-sensitive processes in plant–pathogen interactions

A procedure for the transient expression of genes by agroinfiltration above the permissive threshold to study temperature-sensitive processes in plant–pathogen interactions | Plant-Microbe Interaction | Scoop.it

Localized expression of genes in plants from T-DNAs delivered into plant cells by Agrobacterium tumefaciens is an important tool in plant research. The technique, known as agroinfiltration, provides fast, efficient ways to transiently express or silence a desired gene without resorting to the time-consuming, challenging stable transformation of the host, the use of less efficient means of delivery, such as bombardment, or the use of viral vectors, which multiply and spread within the host causing physiological alterations themselves. A drawback of the agroinfiltration technique is its temperature dependence: early studies have shown that temperatures above 29 °C are nonpermissive to tumour induction by the bacterium as a result of failure in pilus formation. However, research in plant sciences is interested in studying processes at these temperatures, above the 25 °C experimental standard, common to many host–environment and host–pathogen interactions in nature, and agroinfiltration is an excellent tool for this purpose. Here, we measured the efficiency of agroinfiltration for the expression of reporter genes in plants from T-DNAs at the nonpermissive temperature of 30 °C, either transiently or as part of viral amplicons, and envisaged procedures that allow and optimize its use for gene expression at this temperature. We applied this technical advance to assess the performance at 30 °C of two viral suppressors of silencing in agropatch assays [Potato virus Y helper component proteinase (HCPro) and Cucumber mosaic virus 2b protein] and, within the context of infection by a Potato virus X (PVX) vector, also assessed indirectly their effect on the overall response of the host Nicotiana benthamiana to the virus.


Via Christophe Jacquet
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Rescooped by Guogen Yang from MycorWeb Plant-Microbe Interactions
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Cell Research - A DELLA protein complex controls the arbuscular mycorrhizal symbiosis in plants

Plants establish beneficial symbiotic associations with arbuscular mycorrhizal fungi, which colonize the root cortex, building specialized structures called arbuscules that facilitate nutrient exchange. The association occurs following plant recognition of lipochitooligosaccharides (LCOs) from mycorrhizal fungi, which activates the symbiosis signaling pathway prior to mycorrhizal colonization. Here we show that SLR1/DELLA, a repressor of gibberellic acid (GA) signaling, and its interacting partner protein are required for the mycorrhizal symbiosis. GA treatment inhibits mycorrhizal colonization and leads to the degradation of DELLAs. Consistently, rice lines mutated in DELLA are unable to be colonized by mycorrhizal fungi. DELLAs are members of the GRAS family of transcription factors. We further show that rice DELLA interacts with a second GRAS protein, DIP1 (DELLA Interacting Protein 1). DIP1 is also required for mycorrhizal colonization and in turn interacts with a previously characterized mycorrhizal GRAS protein, RAM1, that has been shown to directly regulate mycorrhizal-associated gene expression. We conclude that a complex of GRAS proteins, including DELLAs, is necessary for regulation of mycorrhizal-associated gene expression and thus colonization.


Via Francis Martin
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Rescooped by Guogen Yang from MycorWeb Plant-Microbe Interactions
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The role of forest trees and their mycorrhizal fungi in carbonate rock weathering and its significance for global carbon cycling

The role of forest trees and their mycorrhizal fungi in carbonate rock weathering and its significance for global carbon cycling | Plant-Microbe Interaction | Scoop.it

On million-year timescales, carbonate rock weathering exerts no net effect on atmospheric CO2 concentration. However, on timescales of decades-to-centuries it can contribute to sequestration of anthropogenic CO2 and increase land-ocean alkalinity flux, counteracting ocean acidification. Historical evidence indicates this flux is sensitive to land-use change, and recent experimental evidence suggests that trees and their associated soil microbial communities are major drivers of continental mineral weathering. Here, we review key physical and chemical mechanisms by which the symbiotic mycorrhizal fungi of forest tree roots potentially enhance carbonate rock weathering. Evidence from our ongoing field study at the UK's national pinetum confirms increased weathering of carbonate rocks by a wide range of gymnosperm and angiosperm tree species that form arbuscular (AM) or ectomycorrhizal (EM) fungal partnerships. We demonstrate that calcite-containing rock grains under EM tree species weather significantly faster than those under AM trees, an effect linked to greater soil acidification by EM trees. Weathering and corresponding alkalinity export is likely to increase with rising atmospheric CO2 and associated climate change. Our analyses suggest that strategic planting of fast growing EM angiosperm taxa on calcite-and dolomite rich terrain might accelerate the transient sink for atmospheric CO2 and slow rates of ocean acidification.


Via Christophe Jacquet, Francis Martin
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Rescooped by Guogen Yang from Rice Blast
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Large scale germplasm screening for identification of novel rice blast resistance sources

Large scale germplasm screening for identification of novel rice blast resistance sources | Plant-Microbe Interaction | Scoop.it

We conducted a large-scale screen for new rice blast resistance sources in 4246 geographically diverse rice accessions originating from 13 major rice-growing countries. The accessions were selected from a total collection of over 120’000 accessions based on their annotated rice blast resistance information in the International Rice Genebank. A two-step resistance screening protocol was used involving natural infection in a rice uniform blast nursery and subsequent artificial infections with five single rice blast isolates. 289 accessions showed broad-spectrum resistance against all five single rice blast isolates.


Via Elsa Ballini
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Rescooped by Guogen Yang from Plant-microbe interactions (on the plant's side)
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Roles of Plant Hormones in Regulating Host-Virus Interactions

Roles of Plant Hormones in Regulating Host-Virus Interactions | Plant-Microbe Interaction | Scoop.it

Abstract

Hormones are tuners of plant responses to biotic and abiotic stresses. They are involved in various complicated networks, through which they modulate responses to different stimuli. Four hormones primarily regulate plant defense to pathogens: salicylic acid (SA), jasmonic acid (JA), ethylene (Et), and abscisic acid (ABA). In susceptible plants, viral infections result in hormonal disruption, which manifests as simultaneous induction of few antagonistic hormones. However, these antagonistic hormones may exhibit some sequential accumulation in resistant lines. Virus propagation is usually restricted by activation of the small interfering RNA (siRNA) antiviral machinery and/or SA signaling pathway. Several studies have investigated these two systems, using different model viruses. However, the roles of hormones other than SA, especially those with antagonistic properties, such as ABA, have been neglected. Increasing evidence indicates that hormones control components of the small RNA system, which regulates many processes (including the siRNA antiviral machinery and the microRNA system) at the transcriptional or post-transcriptional level. Consequently, cross-talk between the antagonistic SA and ABA pathways modulates plant responses at multiple levels. In this review, we summarize recent findings on the different roles of hormones in regulating plant-virus interactions, which are helping us elucidate the fine-tuning of viral and plant systems by hormones.

 

 


Via Christophe Jacquet
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Rescooped by Guogen Yang from Plant-microbe interactions (on the plant's side)
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Virus infection triggers widespread silencing of host genes by a distinct class of endogenous siRNAs in Arabidopsis

Virus infection triggers widespread silencing of host genes by a distinct class of endogenous siRNAs in Arabidopsis | Plant-Microbe Interaction | Scoop.it

Significance

RNAi-mediated antiviral immunity directs specific virus resistance by virus-derived siRNAs in contrast to broad-spectrum resistance triggered in innate immunity by host pattern recognition receptors. Here we show that induction of antiviral RNAi in Arabidopsis is associated with production of a genetically distinct class of virus-activated siRNAs (vasiRNAs) by RNA-dependent RNA polymerase-1 to target hundreds of host genes for RNA silencing by Argonaute-2. Production of vasiRNAs is induced by viruses from two different supergroups of RNA virus families, targeted for inhibition by Cucumber mosaic virus, and correlated with virus resistance independently of viral siRNAs. We propose that antiviral RNAi activates broad-spectrum antiviral activity via widespread silencing of host genes directed by vasiRNAs in addition to specific antiviral defense by viral siRNAs.

Abstract

Antiviral immunity controlled by RNA interference (RNAi) in plants and animals is thought to specifically target only viral RNAs by the virus-derived small interfering RNAs (siRNAs). Here we show that activation of antiviral RNAi in Arabidopsis plants is accompanied by the production of an abundant class of endogenous siRNAs mapped to the exon regions of more than 1,000 host genes and rRNA. These virus-activated siRNAs (vasiRNAs) are predominantly 21 nucleotides long with an approximately equal ratio of sense and antisense strands. Genetically, vasiRNAs are distinct from the known plant endogenous siRNAs characterized to date and instead resemble viral siRNAs by requiring Dicer-like 4 and RNA-dependent RNA polymerase 1 (RDR1) for biogenesis. However, loss of EXORIBONUCLEASE4/THYLENE-INSENSITIVE5 enhances vasiRNA biogenesis and virus resistance without altering the biogenesis of viral siRNAs. We show that vasiRNAs are active in directing widespread silencing of the target host genes and that Argonaute-2 binds to and is essential for the silencing activity of vasiRNAs. Production of vasiRNAs is readily detectable in Arabidopsis after infection by viruses from two distinct supergroups of plant RNA virus families and is targeted for inhibition by the silencing suppressor protein 2b of Cucumber mosaic virus. These findings reveal RDR1 production of Arabidopsis endogenous siRNAs and identify production of vasiRNAs to direct widespread silencing of host genes as a conserved response of plants to infection by diverse viruses. A possible function for vasiRNAs to confer broad-spectrum antiviral activity distinct to the virus-specific antiviral RNAi by viral siRNAs is discussed.


Via Christophe Jacquet
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Rescooped by Guogen Yang from Virology and Bioinformatics from Virology.ca
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How to bury your academic writing

How to bury your academic writing | Plant-Microbe Interaction | Scoop.it
Book chapters can allow freedom to think about your work in line with broader theoretical issues, but if you're tempted to write a book chapter for an edited collection, it might be best to reconsi...

Via Chris Upton + helpers
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Rescooped by Guogen Yang from Plants and Microbes
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Scientific Reports: Secret lifestyles of Neurospora crassa: can it be a plant pathogen? (2014)

Scientific Reports: Secret lifestyles of Neurospora crassa: can it be a plant pathogen? (2014) | Plant-Microbe Interaction | Scoop.it

Neurospora crassa has a long history as an excellent model for genetic, cellular, and biochemical research. Although this fungus is known as a saprotroph, it normally appears on burned vegetations or trees after forest fires. However, due to a lack of experimental evidence, the nature of its association with living plants remains enigmatic. Here we report that Scots pine (Pinus sylvestris) is a host plant for N. crassa. The endophytic lifestyle of N. crassa was found in its interaction with Scots pine. Moreover, the fungus can switch to a pathogenic state when its balanced interaction with the host is disrupted. Our data reveal previously unknown lifestyles of N. crassa, which are likely controlled by both environmental and host factors. Switching among the endophytic, pathogenic, and saprotrophic lifestyles confers upon fungi phenotypic plasticity in adapting to changing environments and drives the evolution of fungi and associated plants.


Via Kamoun Lab @ TSL
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Rescooped by Guogen Yang from Plant-microbe interactions (on the plant's side)
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The mannose‐binding lectin gene FaMBL1 is involved in the resistance of unripe strawberry fruits to Colletotrichum acutatum

The mannose‐binding lectin gene FaMBL1 is involved in the resistance of unripe strawberry fruits to Colletotrichum acutatum | Plant-Microbe Interaction | Scoop.it

The fungal pathogen Colletotrichum acutatum is the causal agent of strawberry (Fragaria × ananassa) anthracnose. Although the fungus can infect strawberry fruits at both unripe and ripe stages, the symptoms appear only on red ripe fruits. On white unripe fruits, the pathogen becomes quiescent as melanized appressoria after 24 h of interaction. Previous transcriptome analysis has indicated that a mannose-binding lectin (MBL) gene is the most up-regulated gene in 24-h-infected white strawberries, suggesting a role for this gene in the low susceptibility of unripe stages. A time course analysis of the expression of this MBL gene, named FaMBL1 (Fragaria × ananassa MBL 1a), was undertaken to monitor its expression profile in white and red fruits at early interaction times: FaMBL1 was expressed exclusively in white fruit after 24 h, when the pathogen was quiescent. Agrobacterium-mediated transient transformation was used to silence and overexpress the FaMBL1 gene in 24-h-infected white and red strawberries, respectively. FaMBL1-silenced unripe fruits showed an increase in susceptibility to C. acutatum. These 24-h-infected tissues contained subcuticular hyphae, indicating pathogen penetration and active growth. In contrast, overexpression of FaMBL1 in ripe fruits decreased susceptibility; here, 24-h-infected tissues showed a high percentage of ungerminated appressoria, suggesting that the growth of the pathogen had slowed. These data suggest that FaMBL1 plays a crucial role in the resistance of unripe strawberry fruits to C. acutatum.


Via Christophe Jacquet
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Rescooped by Guogen Yang from MycorWeb Plant-Microbe Interactions
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Challenges and opportunities for quantifying roots and rhizosphere interactions through imaging and image analysis

Challenges and opportunities for quantifying roots and rhizosphere interactions through imaging and image analysis | Plant-Microbe Interaction | Scoop.it

The morphology of roots and root systems influences the efficiency by which plants acquire nutrients and water, anchor themselves and provide stability to the surrounding soil. Plant genotype and the biotic and abiotic environment significantly influence root morphology, growth and ultimately crop yield. The challenge for researchers interested in phenotyping root systems is, therefore, not just to measure roots and link their phenotype to the plant genotype, but also to understand how the growth of roots is influenced by their environment. This review discusses progress in quantifying root system parameters (e.g. in terms of size, shape and dynamics) using imaging and image analysis technologies and also discusses their potential for providing a better understanding of root:soil interactions. Significant progress has been made in image acquisition techniques, however trade-offs exist between sample throughput, sample size, image resolution and information gained. All of these factors impact on downstream image analysis processes. While there have been significant advances in computation power, limitations still exist in statistical processes involved in image analysis. Utilizing and combining different imaging systems, integrating measurements and image analysis where possible, and amalgamating data will allow researchers to gain a better understanding of root:soil interactions.


Via Christophe Jacquet, Stéphane Hacquard, Francis Martin
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Rescooped by Guogen Yang from Plant-microbe interactions (on the plant's side)
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Frontiers | Extracellular ATP acts as a damage-associated molecular pattern (DAMP) signal in plants | Plant-Microbe Interaction

Frontiers | Extracellular ATP acts as a damage-associated molecular pattern (DAMP) signal in plants | Plant-Microbe Interaction | Plant-Microbe Interaction | Scoop.it
As sessile organisms, plants have evolved effective mechanisms to protect themselves from environmental stresses. Damaged (i.e., wounded) plants recognize a variety of endogenous molecules as danger signals, referred to as damage-associated molecular patterns (DAMPs). ATP is among the molecules that are released by cell damage, and recent evidence suggests that ATP can serve as a DAMP. Although little studied in plants, extracellular ATP is well known for its signaling role in animals, including acting as a DAMP during the inflammatory response and wound healing. If ATP acts outside the cell, then it is reasonable to expect that it is recognized by a plasma membrane-localized receptor. Recently, DORN1, a lectin receptor kinase, was shown to recognize extracellular ATP in Arabidopsis. DORN1 is the founding member of a new purinoceptor subfamily, P2K (P2 receptor Kinase), which is plant-specific. P2K1 (DORN1) is required for ATP-induced cellular responses (e.g., cytosolic Ca2+ elevation, MAPK phosphorylation, and gene expression). Genetic analysis of loss-of-function mutants and overexpression lines showed that P2K1 participates in the plant wound response, consistent with the role of ATP as a DAMP. In this review, we summarize past research on the roles and mechanisms of extracellular ATP signaling in plants, and discuss the direction of the future research of extracellular ATP as a DAMP signal.

Via Christophe Jacquet
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Cytochrome P450 Monooxygenase CYP53 Family in Fungi: Comparative Structural and Evolutionary Analysis and Its Role as a Common Alternative Anti-Fungal Drug Target

Cytochrome P450 Monooxygenase CYP53 Family in Fungi: Comparative Structural and Evolutionary Analysis and Its Role as a Common Alternative Anti-Fungal Drug Target | Plant-Microbe Interaction | Scoop.it

Cytochrome P450 monooxygenases (CYPs/P450s) are heme-thiolate proteins whose role as a drug target against pathogenic microbes has been explored because of their stereo- and regio-specific oxidation activity. We aimed to assess the CYP53 family's role as a common alternative drug target against animal (including human) and plant pathogenic fungi and its role in fungal-mediated wood degradation. Genome-wide analysis of fungal species revealed the presence of CYP53 members in ascomycetes and basidiomycetes. Basidiomycetes had a higher number of CYP53 members in their genomes than ascomycetes. Only two CYP53 subfamilies were found in ascomycetes and six subfamilies in basidiomycetes, suggesting that during the divergence of phyla ascomycetes lost CYP53 P450s. According to phylogenetic and gene-structure analysis, enrichment of CYP53 P450s in basidiomycetes occurred due to the extensive duplication of CYP53 P450s in their genomes. Numerous amino acids (103) were found to be conserved in the ascomycetes CYP53 P450s, against only seven in basidiomycetes CYP53 P450s. 3D-modelling and active-site cavity mapping data revealed that the ascomycetes CYP53 P450s have a highly conserved protein structure whereby 78% amino acids in the active-site cavity were found to be conserved. Because of this rigid nature of ascomycetes CYP53 P450s' active site cavity, any inhibitor directed against this P450 family can serve as a common anti-fungal drug target, particularly toward pathogenic ascomycetes. The dynamic nature of basidiomycetes CYP53 P450s at a gene and protein level indicates that these P450s are destined to acquire novel functions. Functional analysis of CYP53 P450s strongly supported our hypothesis that the ascomycetes CYP53 P450s ability is limited for detoxification of toxic molecules, whereas basidiomycetes CYP53 P450s play an additional role, i.e. involvement in degradation of wood and its derived components. This study is the first report on genome-wide comparative structural (gene and protein structure-level) and evolutionary analysis of a fungal P450 family.


Via Christophe Jacquet, Steve Marek, Carla Garzon, Elsa Ballini
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First evidence of mutualism between ancient plant lineages (Haplomitriopsida liverworts) and Mucoromycotina fungi and its response to simulated Palaeozoic changes in atmospheric CO2

First evidence of mutualism between ancient plant lineages (Haplomitriopsida liverworts) and Mucoromycotina fungi and its response to simulated Palaeozoic changes in atmospheric CO2 | Plant-Microbe Interaction | Scoop.it

SummaryThe discovery that Mucoromycotina, an ancient and partially saprotrophic fungal lineage, associates with the basal liverwort lineage Haplomitriopsida casts doubt on the widely held view that Glomeromycota formed the sole ancestral plant–fungus symbiosis. Whether this association is mutualistic, and how its functioning was affected by the fall in atmospheric CO2 concentration that followed plant terrestrialization in the Palaeozoic, remains unknown.We measured carbon-for-nutrient exchanges between Haplomitriopsida liverworts and Mucoromycotina fungi under simulated mid-Palaeozoic (1500 ppm) and near-contemporary (440 ppm) CO2 concentrations using isotope tracers, and analysed cytological differences in plant–fungal interactions. Concomitantly, we cultured both partners axenically, resynthesized the associations in vitro, and characterized their cytology.We demonstrate that liverwort–Mucoromycotina symbiosis is mutualistic and mycorrhiza-like, but differs from liverwort–Glomeromycota symbiosis in maintaining functional efficiency of carbon-for-nutrient exchange between partners across CO2 concentrations. Inoculation of axenic plants with Mucoromycotina caused major cytological changes affecting the anatomy of plant tissues, similar to that observed in wild-collected plants colonized by Mucoromycotina fungi.By demonstrating reciprocal exchange of carbon for nutrients between partners, our results provide support for Mucoromycotina establishing the earliest mutualistic symbiosis with land plants. As symbiotic functional efficiency was not compromised by reduced CO2, we suggest that other factors led to the modern predominance of the Glomeromycota symbiosis.


Via Pierre-Marc Delaux, Francis Martin
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Antifungal drug resistance evoked via RNAi-dependent epimutations

Antifungal drug resistance evoked via RNAi-dependent epimutations | Plant-Microbe Interaction | Scoop.it

Microorganisms evolve via a range of mechanisms that may include or involve sexual/parasexual reproduction, mutators, aneuploidy, Hsp90 and even prions. Mechanisms that may seem detrimental can be repurposed to generate diversity. Here we show that the human fungal pathogen Mucor circinelloides develops spontaneous resistance to the antifungal drug FK506 (tacrolimus) via two distinct mechanisms. One involves Mendelian mutations that confer stable drug resistance; the other occurs via an epigenetic RNA interference (RNAi)-mediated pathway resulting in unstable drug resistance. The peptidylprolyl isomerase FKBP12 interacts with FK506 forming a complex that inhibits the protein phosphatase calcineurin1. Calcineurin inhibition by FK506 blocksM. circinelloides transition to hyphae and enforces yeast growth2. Mutations in the fkbAgene encoding FKBP12 or the calcineurin cnbR or cnaA genes confer FK506 resistance and restore hyphal growth. In parallel, RNAi is spontaneously triggered to silence thefkbA gene, giving rise to drug-resistant epimutants. FK506-resistant epimutants readily reverted to the drug-sensitive wild-type phenotype when grown without exposure to the drug. The establishment of these epimutants is accompanied by generation of abundantfkbA small RNAs and requires the RNAi pathway as well as other factors that constrain or reverse the epimutant state. Silencing involves the generation of a double-stranded RNA trigger intermediate using the fkbA mature mRNA as a template to produce antisensefkbA RNA. This study uncovers a novel epigenetic RNAi-based epimutation mechanism controlling phenotypic plasticity, with possible implications for antimicrobial drug resistance and RNAi-regulatory mechanisms in fungi and other eukaryotes.

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Microbes ride the current

Microbes ride the current | Plant-Microbe Interaction | Scoop.it

How do differences in marine bacterial populations arise in the ocean? On page 1346 of this Science issue, Hellweger et al. (1) investigate this question with a model based on ocean currents, parameterized with data from the most ubiquitous and abundant ocean bacterium, Pelagibacter. The model assumes that mutations are neutral—that is, they cause no change in the fitness of organisms, so that selection cannot act on them. The results show that neutral processes are enough to generate biogeographical patterns in marine bacteria without any adaptive evolution taking place.


Via Francis Martin
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The Clavibacter michiganensis subsp. michiganensis–Tomato Interactome Reveals the Perception of Pathogen by the Host and Suggests Mechanisms of Infection

The Clavibacter michiganensis subsp. michiganensis–Tomato Interactome Reveals the Perception of Pathogen by the Host and Suggests Mechanisms of Infection | Plant-Microbe Interaction | Scoop.it

The Gram-positive bacterium Clavibacter michiganensis subsp. michiganensis (Cmm) causes wilt and canker disease of tomato (Solanum lycopersicum). Mechanisms of Cmm pathogenicity and tomato response to Cmm infection are not well understood. To explore the interaction between Cmm and tomato, multidimensional protein identification technology (MudPIT) and tandem mass spectrometry were used to analyze in vitro and in planta generated samples. The results show that during infection Cmm senses the plant environment, transmits signals, induces, and then secretes multiple hydrolytic enzymes, including serine proteases of the Pat-1, Ppa, and Sbt familes, the CelA, XysA, and NagA glycosyl hydrolases, and other cell wall-degrading enzymes. Tomato induction of pathogenesis-related (PR) proteins, LOX1, and other defense-related proteins during infection indicates that the plant senses the invading bacterium and mounts a basal defense response, although partial with some suppressed components including class III peroxidases and a secreted serine peptidase. The tomato ethylene-synthesizing enzyme ACC-oxidase was induced during infection with the wild-typeCmm but not during infection with an endophytic Cmm strain, identifying Cmm-triggered host synthesis of ethylene as an important factor in disease symptom development. The proteomic data were also used to improve Cmm genome annotation, and thousands of Cmm gene models were confirmed or expanded.


Via Freddy Monteiro
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The cryptic role of biodiversity in the emergence of host–microbial mutualisms

The cryptic role of biodiversity in the emergence of host–microbial mutualisms | Plant-Microbe Interaction | Scoop.it

The persistence of mutualisms in host-microbial – or holobiont – systems is difficult to explain because microbial mutualists, who bear the costs of providing benefits to their host, are always prone to being competitively displaced by non-mutualist ‘cheater’ species. This disruptive effect of competition is expected to be particularly strong when the benefits provided by the mutualists entail costs such as reduced competitive ability. Using a metacommunity model, we show that competition between multiple cheaters within the host's microbiome, when combined with the spatial structure of host–microbial interactions, can have a constructive rather than a disruptive effect by allowing the emergence and maintenance of mutualistic microorganisms within the host. These results indicate that many of the microorganisms inhabiting a host's microbiome, including those that would otherwise be considered opportunistic or even potential pathogens, play a cryptic yet critical role in promoting the health and persistence of the holobiont across spatial scales.


Via Jean-Michel Ané, Francis Martin
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Genomic and transcriptomic characterization of the transcription factor family R2R3-MYB in soybean and its involvement in the resistance responses to Phakopsora pachyrhizi

Genomic and transcriptomic characterization of the transcription factor family R2R3-MYB in soybean and its involvement in the resistance responses to Phakopsora pachyrhizi | Plant-Microbe Interaction | Scoop.it

Highlights•

Identification of 264 R2R3-MYBs, classified into 42 subgroups in Glycine max.

Approximately 32–40.8% of GmMYBs are induced in response to pathogens.

GmMYBs exercises control over important defense responses in soybean.

Abstract

Myb genes constitute one of the largest transcription factor families in the plant kingdom. Soybean MYB transcription factors have been related to the plant response to biotic stresses. Their involvement in response to Phakopsora pachyrhizi infection has been reported by several transcriptional studies. Due to their apparently highly diverse functions, these genes are promising targets for developing crop varieties resistant to diseases. In the present study, the identification and phylogenetic analysis of the soybean R2R3-MYB (GmMYB) transcription factor family was performed and the expression profiles of these genes under biotic stress were determined. GmMYBs were identified from the soybean genome using bioinformatic tools, and their putative functions were determined based on the phylogenetic tree and classified into subfamilies using guides AtMYBs describing known functions. The transcriptional profiles of GmMYBs upon infection with different pathogen were revealed by in vivo and in silico analyses. Selected target genes potentially involved in disease responses were assessed by RT-qPCR after different times of inoculation with P. pachyrhizi using different genetic backgrounds related to resistance genes (Rpp2 and Rpp5). R2R3-MYB transcription factors related to lignin synthesis and genes responsive to chitin were significantly induced in the resistant genotypes.


Via Christophe Jacquet
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Rescooped by Guogen Yang from Virology and Bioinformatics from Virology.ca
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Genetically Modified Mosquitoes Pave the Way for Dengue Fever Prevention | Viruses101 | Learn Science at Scitable

Genetically Modified Mosquitoes Pave the Way for Dengue Fever Prevention | Viruses101 | Learn Science at Scitable | Plant-Microbe Interaction | Scoop.it
Over 40% of the word's population is at risk of contracting Dengue Fever, a mosquito borne virus. Scientists are now using genetically modified mosquitoes to try and prevent the spread of Dengue Fever.

Via Julia Paoli
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Rescooped by Guogen Yang from TAL effector science
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Comparison of TALE designer transcription factors and the CRISPR/dCas9 in regulation of gene expression by targeting enhancers - Nucl. Acids. Res.

(via T. Lahaye, thx)

Gao et al, 2014

The transcription activator–like effectors (TALEs) and the RNA-guided clustered regularly interspaced short palindromic repeat (CRISPR) associated protein (Cas9) utlilize distinct molecular mechanisms in targeting site recognition. The two proteins can be modified to carry additional functional domains to regulate expression of genomic loci in mammalian cells. In this study, we have compared the two systems in activation and suppression of the Oct4 and Nanog loci by targeting their enhancers. Although both are able to efficiently activate the luciferase reporters, the CRISPR/dCas9 system is much less potent in activating the endogenous loci and in the application of reprogramming somatic cells to iPS cells. Nevertheless, repression by CRISPR/dCas9 is comparable to or even better than TALE repressors. We demonstrated that dCas9 protein binding results in significant physical interference to binding of native transcription factors at enhancer, less efficient active histone markers induction or recruitment of activating complexes in gene activation. This study thus highlighted the merits and drawbacks of transcription regulation by each system. A combined approach of TALEs and CRISPR/dCas9 should provide an optimized solution to regulate genomic loci and to study genetic elements such as enhancers in biological processes including somatic cell reprogramming and guided differentiation.


Via dromius
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dromius's curator insight, September 16, 4:21 AM

CRISPR/dCas9 system much less potent in activating the endogenous loci


repression by CRISPR/dCas9 is comparable to or better than TALE repressors

Rescooped by Guogen Yang from Plant-microbe interactions (on the plant's side)
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Eggplant and related species are promising genetic resources to dissect the plant immune response to Pseudomonas syringae and Xanthomonas euvesicatoria and to identify new resistance determinants -...

Eggplant and related species are promising genetic resources to dissect the plant immune response to Pseudomonas syringae and Xanthomonas euvesicatoria and to identify new resistance determinants -... | Plant-Microbe Interaction | Scoop.it

The apparent lack of durability of many resistance (R) genes highlights the need for the constant identification of new genetic sources of resistance for the breeding of new disease-resistant crop cultivars. To this end, we screened a collection of accessions of eggplant and close relatives for resistance against Pseudomonas syringae pv. tomato (Pto) and Xanthomonas euvesicatoria (Xeu), foliar plant pathogens of many solanaceous crops. Both pathogens caused substantial disease on most genotypes of eggplant and its relatives. Promisingly, however, some of the genotypes were fully or partially resistant to either of the pathogens, suggesting the presence of effective resistance determinants in these genotypes. Segregation of resistance to the growth of Xeu following infiltration in F2 progeny from a cross of a resistant and susceptible genotype suggests that resistance to Xeu is inherited as a multigenic trait. With regard to Pto, a mutant strain lacking all 28 functional type III secreted effectors, and a Pseudomonas fluorescens strain expressing a P. syringae type III secretion system (T3SS), both elicit a strong cell death response on most eggplant lines. Several genotypes thus appear to harbour a mechanism for the direct recognition of a component of the T3SS. Therefore, eggplant and its close relatives are promising resources to unravel novel aspects of plant immunity and to identify new candidate R genes that could be employed in other Solanaceae in which Xeu and Pto cause agriculturally relevant diseases.


Via Christophe Jacquet
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Rescooped by Guogen Yang from Plant-microbe interactions (on the plant's side)
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From Chitin to Bioactive Chitooligosaccharides and Conjugates: Access to Lipochitooligosaccharides and the TMG-chitotriomycin

From Chitin to Bioactive Chitooligosaccharides and Conjugates: Access to Lipochitooligosaccharides and the TMG-chitotriomycin | Plant-Microbe Interaction | Scoop.it

The direct and chemoselective N-transacylation of peracetylated chitooligosaccharides (COSs), readily obtained from chitin, to give per-N-trifluoroacetyl derivatives offers an attractive route to size-defined COSs and derived glycoconjugates. It involves the use of various acceptor building blocks and trifluoromethyl oxazoline dimer donors prepared with efficiency and highly reactive in 1,2-trans glycosylation reactions. This method was applied to the preparation of the important symbiotic glycolipids which are highly active on plants and to the TMG-chitotriomycin, a potent and specific inhibitor of insect, fungal, and bacterial N-acetylglucosaminidases.

 


Via Jean-Michel Ané, Christophe Jacquet
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