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The Magnaporthe oryzae Effector AvrPiz-t Targets the RING E3 Ubiquitin Ligase APIP6 to Suppress Pathogen-Associated Molecular Pattern–Triggered Immunity in Rice

The Magnaporthe oryzae Effector AvrPiz-t Targets the RING E3 Ubiquitin Ligase APIP6 to Suppress Pathogen-Associated Molecular Pattern–Triggered Immunity in Rice | Plant-Microbe Interaction | Scoop.it

Although the functions of a few effector proteins produced by bacterial and oomycete plant pathogens have been elucidated in recent years, information for the vast majority of pathogen effectors is still lacking, particularly for those of plant-pathogenic fungi. Here, we show that the avirulence effector AvrPiz-t from the rice blast fungus Magnaporthe oryzae preferentially accumulates in the specialized structure called the biotrophic interfacial complex and is then translocated into rice (Oryza sativa) cells. Ectopic expression of AvrPiz-t in transgenic rice suppresses the flg22- and chitin-induced generation of reactive oxygen species (ROS) and enhances susceptibility to M. oryzae, indicating that AvrPiz-t functions to suppress pathogen-associated molecular pattern (PAMP)-triggered immunity in rice. Interaction assays show that AvrPiz-t suppresses the ubiquitin ligase activity of the rice RING E3 ubiquitin ligase APIP6 and that, in return, APIP6 ubiquitinates AvrPiz-t in vitro. Interestingly, agroinfection assays reveal that AvrPiz-t and AvrPiz-t Interacting Protein 6 (APIP6) are both degraded when coexpressed in Nicotiana benthamiana. Silencing of APIP6 in transgenic rice leads to a significant reduction of flg22-induced ROS generation, suppression of defense-related gene expression, and enhanced susceptibility of rice plants to M. oryzae. Taken together, our results reveal a mechanism in which a fungal effector targets the host ubiquitin proteasome system for the suppression of PAMP-triggered immunity in plants.


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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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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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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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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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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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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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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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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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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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Signaling in cells and organisms — calcium holds the line

Signaling in cells and organisms — calcium holds the line | Plant-Microbe Interaction | Scoop.it

Previous research has established calcium (Ca2+) and reactive oxygen species (ROS) as important cellular second messengers in eukaryotes. Recently, the occurrence of cell-to-cell moving Ca2+ and ROS waves was reported in plants. This was paralleled by the discovery of long-distance wound-activated surface potential changes (WASPs) that require the function of putatively Ca2+-releasing glutamate receptor-like channels (GLRs) in Arabidopsis. Although the functional interconnection of Ca2+-dependent phosphorylation and ROS waves via NADPH oxidase activation has been clearly established, potential further interconnections between these long-distance signaling processes are less clear. In this review we cover emerging concepts and existing open questions that interconnect cellular and global signaling via Ca2+, ROS and WASPs.


Via Christophe Jacquet
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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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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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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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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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Rescooped by Guogen Yang from Plant-microbe interaction
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The mitochondrial outer membrane AAA ATPase AtOM66 affects cell death and pathogen resistance in Arabidopsis thaliana

The mitochondrial outer membrane AAA ATPase AtOM66 affects cell death and pathogen resistance in Arabidopsis thaliana | Plant-Microbe Interaction | Scoop.it

One of the most stress-responsive genes encoding a mitochondrial protein in Arabidopsis (At3g50930) has been annotated as AtBCS1 (cytochrome bc1 synthase 1), but was previously functionally uncharacterised. Here, we show that the protein encoded by At3g50930 is present as a homo-multimeric protein complex on the outer mitochondrial membrane and lacks the BCS1 domain present in yeast and mammalian BCS1 proteins, with the sequence similarity restricted to the AAA ATPase domain. Thus we propose to re-annotate this protein as AtOM66 (Outer Mitochondrial membrane protein of 66 kDa). While transgenic plants with reduced AtOM66 expression appear phenotypically normal, AtOM66 over-expression lines have a distinct phenotype, showing strong leaf curling and increased starch content. Analysis of mitochondrial protein content demonstrated no detectable changes in mitochondrial respiratory complex protein abundance. Consistent with the stress inducible expression pattern, overexpression lines of AtOM66 are more tolerant to drought stress but undergo stress-induced senescence earlier than wild type. Genome-wide expression analysis revealed a constitutive induction of salicylic acid-related (SA) pathogen defence and cell death genes in over-expression lines. Conversely, expression of SA marker gene PR-1 was reduced in atom66 plants, while jasmonic acid response genes PDF1.2 and VSP2 have increased transcript abundance. In agreement with the expression profile, AtOM66 over-expression plants show increased SA content, accelerated cell death rates and are more tolerant to the biotrophic pathogen Pseudomonas syringae, but more susceptible to the necrotrophic fungus Botrytis cinerea. In conclusion, our results demonstrate a role for AtOM66 in cell death and amplifying SA signalling.


Via Christophe Jacquet, Suayib Üstün
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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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