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pH Signaling in Human Fungal Pathogens: a New Target for Antifungal Strategies

pH Signaling in Human Fungal Pathogens: a New Target for Antifungal Strategies | Plant pathogenic fungi | Scoop.it

Fungi are exposed to broadly fluctuating environmental conditions, to which adaptation is crucial for their survival. An ability to respond to a wide pH range, in particular, allows them to cope with rapid changes in their extracellular settings. PacC/Rim signaling elicits the primary pH response in both model and pathogenic fungi and has been studied in multiple fungal species. In the predominant human pathogenic fungi, namely, Candida albicans, Aspergillus fumigatus, and Cryptococcus neoformans, this pathway is required for many functions associated with pathogenesis and virulence. Aspects of this pathway are fungus specific and do not exist in mammalian cells. In this review, we highlight recent advances in our understanding of PacC/Rim-mediated functions and discuss the growing interest in this cascade and its factors as potential drug targets for antifungal strategies. We focus on both conserved and distinctive features in model and pathogenic fungi, highlighting the specificities of PacC/Rim signaling in C. albicans, A. fumigatus, and C. neoformans. We consider the role of this pathway in fungal virulence, including modulation of the host immune response. Finally, as now recognized for other signaling cascades, we highlight the role of pH in adaptation to antifungal drug pressure. By acting on the PacC/Rim pathway, it may therefore be possible (i) to ensure fungal specificity and to limit the side effects of drugs, (ii) to ensure broad-spectrum efficacy, (iii) to attenuate fungal virulence, (iv) to obtain additive or synergistic effects with existing antifungal drugs through tolerance inhibition, and (v) to slow the emergence of resistant mutants.

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Primary transcripts of microRNAs encode regulatory peptides : Nature

Primary transcripts of microRNAs encode regulatory peptides : Nature | Plant pathogenic fungi | Scoop.it
MicroRNAs (miRNAs) are small regulatory RNA molecules that inhibit the expression of specific target genes by binding to and cleaving their messenger RNAs or otherwise inhibiting their translation into proteins. miRNAs are transcribed as much larger primary transcripts (pri-miRNAs), the function of which is not fully understood. Here we show that plant pri-miRNAs contain short open reading frame sequences that encode regulatory peptides. The pri-miR171b of Medicago truncatula and the pri-miR165a of Arabidopsis thaliana produce peptides, which we term miPEP171b and miPEP165a, respectively, that enhance the accumulation of their corresponding mature miRNAs, resulting in downregulation of target genes involved in root development. The mechanism of miRNA-encoded peptide (miPEP) action involves increasing transcription of the pri-miRNA. Five other pri-miRNAs of A. thaliana and M. truncatula encode active miPEPs, suggesting that miPEPs are widespread throughout the plant kingdom. Synthetic miPEP171b and miPEP165a peptides applied to plants specifically trigger the accumulation of miR171b and miR165a, leading to reduction of lateral root development and stimulation of main root growth, respectively, suggesting that miPEPs might have agronomical applications.

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The Fungal Quorum-Sensing Molecule Farnesol Activates Innate Immune Cells but Suppresses Cellular Adaptive Immunity

The Fungal Quorum-Sensing Molecule Farnesol Activates Innate Immune Cells but Suppresses Cellular Adaptive Immunity | Plant pathogenic fungi | Scoop.it

IMPORTANCE Farnesol is a quorum-sensing molecule which controls morphological plasticity of the pathogenic yeast Candida albicans. As such, it is a major mediator of intraspecies communication. Here, we investigated the impact of farnesol on human innate immune cells known to be important for fungal clearance and protective immunity. We show that farnesol is able to enhance inflammation by inducing activation of neutrophils and monocytes. At the same time, farnesol impairs differentiation of monocytes into immature dendritic cells (iDC) by modulating surface phenotype, cytokine release and migrational behavior. Consequently, iDC generated in the presence of farnesol are unable to induce proper T cell responses and fail to secrete Th1 promoting interleukin 12 (IL-12). As farnesol induced down-regulation of the granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor, desensitization to GM-CSF could potentially explain transcriptional reprofiling of iDC effector molecules. Taken together, our data show that farnesol can also mediate Candida-host communication and is able to act as a virulence factor.

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Flow cytometry reveals that the rust fungus Uromyces bidentis (Pucciniales) possesses the largest fungal genome reported, 2,489 Mbp

Flow cytometry reveals that the rust fungus Uromyces bidentis (Pucciniales) possesses the largest fungal genome reported, 2,489 Mbp | Plant pathogenic fungi | Scoop.it
Among the Eukaryotes, Fungi have relatively small genomes (average 44.2 Mbp across 1850 species). The order Pucciniales (Basidiomycota) has the largest average genome size among fungi (305 Mbp), and includes the two largest fungal genomes reported so far (Puccinia chrysanthemi and Gymnosporangium confusum, with 806.5 and 893.2 Mbp, respectively). In this work flow cytometry was employed to determine the genome size of the Bidens pilosa rust pathogen, Uromyces bidentis. The results obtained revealed that U. bidentis presents a surprisingly large haploid genome size of 2,489 Mbp. This value is almost three times larger than the previous largest fungal genome reported and over 50x larger than the average fungal genome size. Microscopic examination of U. bidentis nuclei also shows that they are not as different in size from the B. pilosa nuclei, as compared to the differences between other rusts and their host plants. This result further reinforces the position of the Pucciniales as the fungal group with the largest genomes, prompting studies addressing the role of repetitive elements and polyploidy on evolution, pathological specialisation and diversity of fungal species.

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Unexpected diversity of basidiomycetous endophytes in sapwood and leaves of Hevea

Unexpected diversity of basidiomycetous endophytes in sapwood and leaves of Hevea | Plant pathogenic fungi | Scoop.it

Research on fungal endophytes has expanded dramatically in recent years, but little is known about the diversity and ecological roles of endophytic basidiomycetes. Here we report the analysis of 310 basidiomycetous endophytes isolated from wild and planted populations of the rubber tree genus, Hevea. Species accumulation curves were nonasymptotic, as in the majority of endophyte surveys, indicating that more sampling is needed to recover the true diversity of the community. One hundred eighteen OTUs were delimited, representing nine orders of Basidiomycota (Agaricales, Atheliales, Auriculariales, Cantharellales, Hymenochaetales, Polyporales, Russulales, Septobasidiales, Tremellales). The diversity of basidiomycetous endophytes found inhabiting wild populations of Hevea was comparable to that present in plantations. However, when samples were segregated by tissue type, sapwood of wild populations was found to contain a higher number of species than sapwood of planted trees. Seventy-five percent of isolates were members of the Polyporales, the majority in the phlebioid clade. Most of the species belong to clades known to cause a white-rot type of wood decay. Two species in the insect-associated genus Septobasidium were isolated. The most frequently isolated genera included Bjerkandera, Ceriporia,Phanerochaete, Phlebia, Rigidoporus, Tinctoporellus, Trametes (Polyporales),Peniophora, Stereum (Russulales) and Coprinellus (Agaricales), all of which have been reported as endophytes from a variety of hosts, across wide geographic locations. Literature records on the geographic distribution and host association of these genera revealed that their distribution and substrate affinity could be extended if the endophytic niche was investigated as part of fungal biodiversity surveys.

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Suppression of RNAi by dsRNA-Degrading RNaseIII Enzymes of Viruses in Animals and Plants

Suppression of RNAi by dsRNA-Degrading RNaseIII Enzymes of Viruses in Animals and Plants | Plant pathogenic fungi | Scoop.it
RNA interference (RNAi) is a cellular mechanism activated by double-stranded RNA (dsRNA). Cellular dsRNA-specific RNaseIII enzymes (Dicer) recognize dsRNA and process it into double-stranded small interfering RNAs (ds-siRNAs) of 21–25 nucleotides (nt). siRNAs guide RNAi to degrade also single-stranded RNA homologous to the trigger. RNAi regulates gene expression, controls transposons, and represents an important antiviral defense mechanism. Therefore, viruses encode proteins dedicated to countering RNAi. In this study, the RNaseIII enzymes of a fish DNA virus (PPIV) and a plant RNA virus (SPCSV) were compared for suppression of RNAi in non-host organisms. The fish iridovirus RNaseIII suppressed RNAi in a plant and a nematode. It also enhanced accumulation of an RNAi suppressor deficient virus in plants, and suppressed antiviral RNAi and could rescue multiplication of an unrelated, RNAi suppressor-defective virus in nematodes. In contrast, the plant virus RNaseIII could suppress RNAi only in plants. Our results underscore that the active viral RNaseIII enzymes suppress RNAi. Their activity in suppression of RNAi seems to differ for the spectrum of unrelated organisms. Understanding of this novel mechanism of RNAi suppression may inform means of controlling the diseases and economic losses which the RNaseIII-containing viruses cause in animal and plant production.

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Dynamics of the Establishment of Multinucleate Compartments in Fusarium oxysporum

Dynamics of the Establishment of Multinucleate Compartments in Fusarium oxysporum | Plant pathogenic fungi | Scoop.it

Nuclear dynamics can vary widely between fungal species and between stages of development of fungal colonies. Here we compared nuclear dynamics and mitotic patterns between germlings and mature hyphae in Fusarium oxysporum. Using fluorescently labeled nuclei and live-cell imaging, we show that F. oxysporum is subject to a developmental transition from a uninucleate to a multinucleate state after completion of colony initiation. We observed a special type of hypha that exhibits a higher growth rate, possibly acting as a nutrient scout. The higher growth rate is associated with a higher nuclear count and mitotic waves involving 2 to 6 nuclei in the apical compartment. Further, we found that dormant nuclei of intercalary compartments can reenter the mitotic cycle, resulting in multinucleate compartments with up to 18 nuclei in a single compartment.

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Single-step fermentative production of the cholesterol-lowering drug pravastatin via reprogramming of Penicillium chrysogenum

Single-step fermentative production of the cholesterol-lowering drug pravastatin via reprogramming of Penicillium chrysogenum | Plant pathogenic fungi | Scoop.it

Statins are successful widely used drugs that decrease the risk of coronary heart disease and strokes by lowering cholesterol levels. They selectively inhibit the key regulatory enzyme of the cholesterol synthesis pathway, thus lowering levels of plasma LDL (bad) cholesterol. Pravastatin is one of the leading and most effective statins, derived from the natural product compactin. However, pravastatin production involves a costly dual-step fermentation and biotransformation process. Here we present a single-step fermentative method for production of the active drug pravastatin. Reprogramming of the antibiotics-producing fungus Penicillium chrysogenum, with discovery and engineering of an enzyme involved in the hydroxylation of compactin, enables high level fermentation of the correct form of pravastatin to facilitate efficient industrial-scale statin drug production.

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PLOS Collections : The Missing Pieces: A Collection of Negative, Null and Inconclusive Results

PLOS Collections : The Missing Pieces: A Collection of Negative, Null and Inconclusive Results | Plant pathogenic fungi | Scoop.it
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A high-sensitivity optical device for the early monitoring of plant pathogen attack via the in vivo detection of ROS bursts

A high-sensitivity optical device for the early monitoring of plant pathogen attack via the in vivo detection of ROS bursts | Plant pathogenic fungi | Scoop.it

Biotic stressors, especially pathogenic microorganisms, are rather difficult to detect. In plants, one of the earliest cellular responses following pathogen infection is the production of reactive oxygen species (ROS). In this study, a novel optical device for the early monitoring of Pseudomonas attack was developed; this device measures the ROS level via oxidation-sensitive 2′, 7′-dichlorodihydrofluorescein diacetate (H2DCFDA)-mediated fluorescence, which could provide early monitoring of attacks by a range of plant pathogen; ROS bursts were detected in vivo in Arabidopsis thaliana with higher sensitivity and accuracy than those of a commercial luminescence spectrophotometer. Additionally, the DCF fluorescence truly reflected early changes in the ROS level, as indicated by an evaluation of the H2O2 content and the tight association between the ROS andPseudomonas concentration. Moreover, compared with traditional methods for detecting plant pathogen attacks based on physiological and biochemical measurements, our proposed technique also offers significant advantages, such as low cost, simplicity, convenient operation and quick turnaround. These results therefore suggest that the proposed optical device could be useful for the rapid monitoring of attacks by plant pathogen and yield results considerably earlier than the appearance of visual changes in plant morphology or growth.


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Nuclear rRNA transcript processing versus internal transcribed spacer secondary structure

Nuclear rRNA transcript processing versus internal transcribed spacer secondary structure | Plant pathogenic fungi | Scoop.it

Highlights
•Nuclear rRNA ITSs are not just cut and degraded randomly.
•The secondary structure of ITSs correlates with cleavage sites during the processing of these regions.
•I present predicted cut sites based on experimental data, sequence alignments, and secondary structure.
•Processomes induce 3D associations of RNA transcripts and may position the leads for further scission.

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It's not just a DNA barcode

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An update to polyketide synthase and non-ribosomal synthetase genes and nomenclature in Fusarium

An update to polyketide synthase and non-ribosomal synthetase genes and nomenclature in Fusarium | Plant pathogenic fungi | Scoop.it

Highlights
•52 different PKSs and 52 different NRPSs were identified in 22 Fusarium strains.
•PKS3, 7 and 8 were conserved in all sequenced.
•NRPS2–4, 6 and 10–13 were conserved in all sequenced strains.
•Fusarium avenaceum has the highest number of PKSs (24) and NRPSs (24).

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The parade of Fusarium's secondary metabolism continues...

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Recognition of seven species in the Cryptococcus gattii/Cryptococcus neoformans species complex

Recognition of seven species in the Cryptococcus gattii/Cryptococcus neoformans species complex | Plant pathogenic fungi | Scoop.it

Highlights
•Cryptococcus neoformans is a complex of important human pathogens.
•We provide evidence that at least seven species occur in the species complex.
•The seven species are described, together with information on occurrence, epidemiology, virulence and host ranges.
•MALDI-TOF MS can identify all seven species.

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Tracking the best reference genes for RT-qPCR data normalization in filamentous fungi

Tracking the best reference genes for RT-qPCR data normalization in filamentous fungi | Plant pathogenic fungi | Scoop.it

A critical step in the RT-qPCR workflow for studying gene expression is data normalization, one of the strategies being on the use of reference genes. This study aimed to identify and validate a selection of reference genes for relative quantification in Talaromyces versatilis, a relevant industrial filamentous fungus. Beyond T. versatilis, this study also aimed to propose reference genes that are applicable more widely for RT-qPCR data normalization in filamentous fungi.ResultsA selection of stable, potential reference genes was carried out in silico from RNA-seq based transcriptomic data obtained from T. versatilis. A dozen functionally unrelated candidate genes were analysed by RT-qPCR assays over more than 30 relevant culture conditions. By using geNorm, we showed that most of these candidate genes had stable transcript levels in most of the conditions, from growth environments to conidial germination. The overall robustness of these genes was explored further by showing that any combination of 3 of them led to minimal normalization bias. To extend the relevance of the study beyond T. versatilis, we challenged their stability together with sixteen other classically used genes such as beta-tubulin or actin, in a representative sample of about 100 RNA-seq datasets. These datasets were obtained from 18 phylogenetically distant filamentous fungi exposed to prevalent experimental conditions. Although this wide analysis demonstrated that each of the chosen genes exhibited sporadic up- or down-regulation, their hierarchical clustering allowed the identification of a promising group of 6 genes, which presented weak expression changes and no tendency to up- or down-regulation over the whole set of conditions. This group included ubcB, sac7, fis1 and sarA genes, as well as TFC1 and UBC6 that were previously validated for their use in S. cerevisiae.ConclusionsWe propose a set of 6 genes that can be used as reference genes in RT-qPCR data normalization in any field of fungal biology. However, we recommend that the uniform transcription of these genes is tested by systematic experimental validation and to use the geometric averaging of at least 3 of the best ones. This will minimize the bias in normalization and will support trustworthy biological conclusions.


Via Elsa Ballini, Jean-Michel Ané, Francis Martin
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a most useful paper

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Elsa Ballini's curator insight, February 19, 3:30 AM

For Magnaporthe

MGG_04150 AP-2 β
MGG_03041 glkA
MGG_09926 g6pdh
MGG_03982 act
MGG_09574 TAF10
MGG_03188 coxV
MGG_01084 gapdh
MGG_06158 spo7-like
MGG_00604 β-tub
MGG_09249 apsC
MGG_03641 tef1a
MGG_04019 TFC1
MGG_06075 fis1
MGG_06145 DUF500
MGG_12822 pgiA
MGG_07268 icdA
MGG_02653 pfkA
MGG_01766 spt3
MGG_06362 sarA
MGG_03378 psm1
MGG_14835 alg9
MGG_09977 UBC6
MGG_05320 npl1
MGG_01756 ubcB
MGG_08731 DUF221
MGG_10941 Cu-ATPase
MGG_00770 ADA
MGG_06390 sac7

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A Comprehensive, Automatically Updated Fungal ITS Sequence Dataset for Reference-Based Chimera Control in Environmental Sequencing Efforts

The nuclear ribosomal internal transcribed spacer (ITS) region is the most commonly chosen genetic marker for the molecular identification of fungi in environmental sequencing and molecular ecology studies. Several analytical issues complicate such efforts, one of which is the formation of chimeric—artificially joined—DNA sequences during PCR amplification or sequence assembly. Several software tools are currently available for chimera detection, but rely to various degrees on the presence of a chimera-free reference dataset for optimal performance. However, no such dataset is available for use with the fungal ITS region. This study introduces a comprehensive, automatically updated reference dataset for fungal ITS sequences based on the UNITE database for the molecular identification of fungi. This dataset supports chimera detection throughout the fungal kingdom and for full-length ITS sequences as well as partial (ITS1 or ITS2 only) datasets. The performance of the dataset on a large set of artificial chimeras was above 99.5%, and we subsequently used the dataset to remove nearly 1,000 compromised fungal ITS sequences from public circulation. The dataset is available at http://unite.ut.ee/repository.php and is subject to web-based third-party curation.

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Looks incredibly useful and timely

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Unearthing America's truffle trove a lucrative niche - KOCO Oklahoma City

Unearthing America's truffle trove a lucrative niche - KOCO Oklahoma City | Plant pathogenic fungi | Scoop.it
Jim Sanford and his dog Tom can be found on the hunt in Tennessee's foothills, searching for the highly prized underground fungus known as the truffle.
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Circadian Control Sheds Light on Fungal Bioluminescence: Current Biology

Circadian Control Sheds Light on Fungal Bioluminescence: Current Biology | Plant pathogenic fungi | Scoop.it

Bioluminescence in Neonothopanus gardneri, a basidiomycete, is regulated by the circadian clock.

Luciferin, reductase, and luciferase, which together make light, all peak at night.

Prosthetic LED-illuminated acrylic mushrooms can be used to study insect behavior.

Insects that can disperse fungal spores are attracted to light at night.

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Polyploidy can drive rapid adaptation in yeast : Nature : Nature Publishing Group

Polyploidy can drive rapid adaptation in yeast : Nature : Nature Publishing Group | Plant pathogenic fungi | Scoop.it
Polyploidy is observed across the tree of life, yet its influence on evolution remains incompletely understood. Polyploidy, usually whole-genome duplication, is proposed to alter the rate of evolutionary adaptation. This could occur through complex effects on the frequency or fitness of beneficial mutations. For example, in diverse cell types and organisms, immediately after a whole-genome duplication, newly formed polyploids missegregate chromosomes and undergo genetic instability. The instability following whole-genome duplications is thought to provide adaptive mutations in microorganisms and can promote tumorigenesis in mammalian cells. Polyploidy may also affect adaptation independently of beneficial mutations through ploidy-specific changes in cell physiology. Here we perform in vitro evolution experiments to test directly whether polyploidy can accelerate evolutionary adaptation. Compared with haploids and diploids, tetraploids undergo significantly faster adaptation. Mathematical modelling suggests that rapid adaptation of tetraploids is driven by higher rates of beneficial mutations with stronger fitness effects, which is supported by whole-genome sequencing and phenotypic analyses of evolved clones. Chromosome aneuploidy, concerted chromosome loss, and point mutations all provide large fitness gains. We identify several mutations whose beneficial effects are manifest specifically in the tetraploid strains. Together, these results provide direct quantitative evidence that in some environments polyploidy can accelerate evolutionary adaptation.
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A novel intracellular nitrogen-fixing symbiosis made by Ustilago maydis and Bacillus spp.

A novel intracellular nitrogen-fixing symbiosis made by Ustilago maydis and Bacillus spp. | Plant pathogenic fungi | Scoop.it
We observed that the maize pathogenic fungus Ustilago maydis grew in nitrogen (N)-free media at a rate similar to that observed in media containing ammonium nitrate, suggesting that it was able to fix atmospheric N2. Because only prokaryotic organisms have the capacity to reduce N2, we entertained the possibility that U. maydis was associated with an intracellular bacterium.
The presence of nitrogenase in the fungus was analyzed by acetylene reduction, and capacity to fix N2 by use of 15N2. Presence of an intracellular N2-fixing bacterium was analyzed by PCR amplification of bacterial 16S rRNA and nifH genes, and by microscopic observations.
Nitrogenase activity and 15N incorporation into the cells proved that U. maydis fixed N2. Light and electron microscopy, and fluorescence in situ hybridization (FISH) experiments revealed the presence of intracellular bacteria related to Bacillus pumilus, as evidenced by sequencing of the PCR-amplified fragments.
These observations reveal for the first time the existence of an endosymbiotic N2-fixing association involving a fungus and a bacterium.

Via Jean-Michel Ané
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Jean-Michel Ané's curator insight, March 9, 12:39 PM

Huge... so cool...

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Frontiers | The “sensor domains” of plant NLR proteins: more than decoys? | Plant-Microbe Interaction

Frontiers | The “sensor domains” of plant NLR proteins: more than decoys? | Plant-Microbe Interaction | Plant pathogenic fungi | Scoop.it
Figure 1. A genetic test to inform whether NLR-SD proteins have retained a biochemical activity independent of perception of an avirulence effector. In the top panel, isogenic plants either carrying or lacking the NLR-SD display differential resistance to a pathogen strain carrying the AVR (avirulence) effector (top panel, NLR-SD plants displaying full resistance to the avirulent pathogen strain). To challenge the decoy hypothesis, the differential NLR-SD lines are challenged with a pathogen strain that lacks the AVR effector (avr) and is isogenic to the AVR strain. In these experiments, three outcomes can be expected. (1) No differences between the NLR-SD lines are observed resulting in inconclusive results—the null decoy hypothesis cannot be rejected. The reason the result is inconclusive is because it is now accepted that effectors have other activities than suppression of immunity (nutrition, development, epigenetics etc.), and therefore the targeted host proteins do not necessarily modulate susceptibility/resistance phenotypes. (2) The plants carrying the NLR-SD are more resistant to the avr pathogen strain that lacks the AVR effector. (3) The plants carrying the NLR-SD are more susceptible to the avr pathogen strain that lacks the AVR effector. In these two cases, the SD is likely to have retained the biochemical activity of its ancestral host protein and the decoy hypothesis can be rejected. In scenario (2), the higher levels of resistance to the avr pathogen conferred by the NLR-SD are consistent with a role of the SD in basal immunity analogous to the ancestral target. In scenario (3), however, the NLR-SD is more susceptible to its isogenic line possibly because the SD is targeted by another (unrecognized) effector. In such a case, the NLR-SD resistance (R) gene becomes a susceptibility (S) gene depending on the genotype of the pathogen it is challenged with.
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Genome Biology | Full text | Field pathogenomics reveals the emergence of a diverse wheat yellow rust population

Genome Biology | Full text | Field pathogenomics reveals the emergence of a diverse wheat yellow rust population | Plant pathogenic fungi | Scoop.it
Emerging and re-emerging pathogens imperil public health and global food security. Responding to these threats requires improved surveillance and diagnostic systems. Despite their potential, genomic tools have not been readily applied to emerging or re-emerging plant pathogens such as the wheat yellow (stripe) rust pathogen Puccinia striiformis f. sp. tritici (PST). This is due largely to the obligate parasitic nature of PST, as culturing PST isolates for DNA extraction remains slow and tedious.

To counteract the limitations associated with culturing PST, we developed and applied a field pathogenomics approach by transcriptome sequencing infected wheat leaves collected from the field in 2013. This enabled us to rapidly gain insights into this emerging pathogen population. We found that the PST population across the United Kingdom (UK) underwent a major shift in recent years. Population genetic structure analyses revealed four distinct lineages that correlated to the phenotypic groups determined through traditional pathology-based virulence assays. Furthermore, the genetic diversity between members of a single population cluster for all 2013 PST field samples was much higher than that displayed by historical UK isolates, revealing a more diverse population of PST.

Our field pathogenomics approach uncovered a dramatic shift in the PST population in the UK, likely due to a recent introduction of a diverse set of exotic PST lineages. The methodology described herein accelerates genetic analysis of pathogen populations and circumvents the difficulties associated with obligate plant pathogens. In principle, this strategy can be widely applied to a variety of plant pathogens.

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Effector discovery in the fungal wheat pathogen Zymoseptoria tritici

Effector discovery in the fungal wheat pathogen Zymoseptoria tritici | Plant pathogenic fungi | Scoop.it

Fungal plant pathogens such as Zymoseptoria tritici (formerly known as Mycosphaerella graminicola) secrete repertoires of effectors facilitating infection or triggering host defence mechanisms. Discovery and functional characterization of effectors renders valuable knowledge that contributes to designing new and effective disease management strategies. Here, we combined bioinformatics approaches with  expression profiling during pathogenesis to identify candidate effectors of Z. tritici. Additionally, a genetic approach was conducted to map quantitative trait loci (QTL) carrying putative effectors enabling the validation of both complementary strategies for effector discovery. In planta expression profiling revealed that candidate effectors were up-regulated in successive waves corresponding with consecutive stages of pathogenesis, contrary to candidates identified by QTL mapping that were overall lowly expressed. Functional analyses of two top candidate effectors (SSP15 and SSP18) showed their dispensability for Z. tritici pathogenesis. These analyses reveal that generally adopted criteria such as protein size, cysteine residues and expression during pathogenesis may preclude an unbiased effector discovery. Indeed, genetic mapping of genomic regions involved in specificity render alternative effector candidates that do not match the aforementioned criteria, but should nevertheless be considered as promising new leads for effectors that are crucial for the Z. tritici-wheat pathosystem.


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FEMS Microbiol. Rev.: The battle for chitin recognition in plant-microbe interactions (2015)

FEMS Microbiol. Rev.: The battle for chitin recognition in plant-microbe interactions (2015) | Plant pathogenic fungi | Scoop.it

Fungal cell walls play dynamic functions in interaction of fungi with their surroundings. In pathogenic fungi, the cell wall is the first structure to make physical contact with host cells. An important structural component of fungal cell walls is chitin, a well-known elicitor of immune responses in plants. Research into chitin perception has sparked since the chitin receptor from rice was cloned nearly a decade ago. Considering the widespread nature of chitin perception in plants, pathogens evidently evolved strategies to overcome detection, including alterations in the composition of cell walls, modification of their carbohydrate chains and secretion of effectors to provide cell wall protection or target host immune responses. Also non-pathogenic fungi contain chitin in their cell walls and are recipients of immune responses. Intriguingly, various mutualists employ chitin-derived signaling molecules to prepare their hosts for the mutualistic relationship. Research on the various types of interactions has revealed different molecular components that play crucial roles and, moreover, that various chitin-binding proteins contain dissimilar chitin-binding domains across species that differ in affinity and specificity. Considering the various strategies from microbes and hosts focused on chitin recognition, it is evident that this carbohydrate plays a central role in plant–fungus interactions.

 

Andrea Sánchez-Vallet , Jeroen R. Mesters , Bart P.H.J. Thomma


Via Nicolas Denancé
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Fighting Colorado potato beetle with RNA interference

Fighting Colorado potato beetle with RNA interference | Plant pathogenic fungi | Scoop.it
Colorado potato beetles are a dreaded pest of potatoes. Since they do not have natural enemies in most regions, farmers try to control them with pesticides. However, this strategy is often ineffective because the pest has developed resistances against nearly all insecticides. Now, scientists have shown that potato plants can be protected from herbivory using RNA interference.
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HIGS against insects

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Current Opinion in Insect Science: Disruption of insect transmission of plant viruses (2015)

Current Opinion in Insect Science: Disruption of insect transmission of plant viruses (2015) | Plant pathogenic fungi | Scoop.it

Plant-infecting viruses are transmitted by a diverse array of organisms including insects, mites, nematodes, fungi, and plasmodiophorids. Virus interactions with these vectors are diverse, but there are some commonalities. Generally the infection cycle begins with the vector encountering the virus in the plant and the virus is acquired by the vector. The virus must then persist in or on the vector long enough for the virus to be transported to a new host and delivered into the plant cell. Plant viruses rely on their vectors for breaching the plant cell wall to be delivered directly into the cytosol. In most cases, viral capsid or membrane glycoproteins are the specific viral proteins that are required for transmission and determinants of vector specificity. Specific molecules in vectors also interact with the virus and while there are few-identified to no-identified receptors, candidate recognition molecules are being further explored in these systems. Due to the specificity of virus transmission by vectors, there are defined steps that represent good targets for interdiction strategies to disrupt the disease cycle. This review focuses on new technologies that aim to disrupt the virus–vector interaction and focuses on a few of the well-characterized virus–vector interactions in the field. In closing, we discuss the importance of integration of these technologies with current methods for plant virus disease control.


Via Kamoun Lab @ TSL
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Not fungal, but still an excellent review with great insights on important plant pathosystems.

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Rescooped by Steve Marek from Plant-Microbe Symbioses
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The interaction of Arabidopsis with Piriformospora indica shifts from initial transient stress induced by fungus-released chemical mediators to a mutualistic interaction after physical contact of t...

The interaction of Arabidopsis with Piriformospora indica shifts from initial transient stress induced by fungus-released chemical mediators to a mutualistic interaction after physical contact of t... | Plant pathogenic fungi | Scoop.it
Background Piriformospora indica, an endophytic fungus of Sebacinales, colonizes the roots of many plant species including Arabidopsis thaliana. The symbiotic interaction promotes plant performance, growth and resistance/tolerance against abiotic and biotic stress. Results We demonstrate that exudated compounds from the fungus activate stress and defense responses in the Arabidopsis roots and shoots before the two partners are in physical contact. They induce stomata closure, stimulate reactive oxygen species (ROS) production, stress-related phytohormone accumulation and activate defense and stress genes in the roots and/or shoots. Once a physical contact is established, the stomata re-open, ROS and phytohormone levels decline, and the number and expression level of defense/stress-related genes decreases. Conclusions We propose that exudated compounds from P. indica induce stress and defense responses in the host. Root colonization results in the down-regulation of defense responses and the activation of genes involved in promoting plant growth, metabolism and performance.

Via Jean-Michel Ané
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