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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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Evidence of ancient horizontal gene transfer between fungi and the terrestrial alga Trebouxia - Springer

Evidence of ancient horizontal gene transfer between fungi and the terrestrial alga Trebouxia - Springer | Plant pathogenic fungi | Scoop.it

Intimate and long-lasting relationships of fungi and algae have been known for centuries by scientists, and these ancient symbioses might have provided excellent opportunities for horizontal gene transfer (HGT) of protein encoding genes between the two organismal partners. In this study, we sequenced and assembled 451 Mbp of novel genomic DNA from Trebouxia decolorans(Trebouxiaceae, Chlorophyta), the green algal photobiont of the lichen Xanthoria parietina(Teloschistaceae, Lecanoromycetes, Ascomycota). This alga also occurs as a free-living terrestrial organism. The aim of our work was to search for candidate genes pointing to HGT between lichenized fungi and lichen algae. We found evidence for three putative HGT events of fungal genes into the Trebouxia genome, but these are likely more ancient (over 600 mya) than the origin of lichenization within the fungal Ascomycetes. The three transferred genes are part of gene groups that in other species encode a tellurite-resistance dicarboxylate transporter (TDT) family protein, a class-1 nitrilase/cyanide hydratase (CH), and an oxidoreductase/retinol dehydrogenase. In each case, our phylogenomic analyses show orthologs from Trebouxia as sister to orthologs from all fungi or basally placed within Ascomycetes, while the orthologs from green algae and land plants form separate, independent evolutionary lineages. Alternative hypothesis tests significantly support these HGT events. The presence of these genes in Trebouxia was validated by PCR amplification of separately isolated Trebouxia DNA. The ancient incorporation of fungal genes in the genomes of these particular green algae are intriguing and could be early evidence for symbiotic and co-evolutionary relationships among the major eukaryotic branches of algae and fungi present in early terrestrial life on Earth. These genes could have played a pre-disposition role for some fungi and algae in the origin of lichen symbiosis, but further studies are needed to evaluate this in detail.

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The Plasmodiophora brassicae genome reveals insights in its life cycle and ancestry of chitin synthases

The Plasmodiophora brassicae genome reveals insights in its life cycle and ancestry of chitin synthases | Plant pathogenic fungi | Scoop.it

Plasmodiophora brassicae causes clubroot, a major disease of Brassica oil and vegetable crops worldwide. P. brassicae is a Plasmodiophorid, obligate biotrophic protist in the eukaryotic kingdom of Rhizaria. Here we present the 25.5 Mb genome draft of P. brassicae, developmental stage-specific transcriptomes and a transcriptome of Spongospora subterranea, the Plasmodiophorid causing powdery scab on potato. Like other biotrophic pathogens both Plasmodiophorids are reduced in metabolic pathways. Phytohormones contribute to the gall phenotypes of infected roots. We report a protein (PbGH3) that can modify auxin and jasmonic acid. Plasmodiophorids contain chitin in cell walls of the resilient resting spores. If recognized, chitin can trigger defense responses in plants. Interestingly, chitin-related enzymes of Plasmodiophorids built specific families and the carbohydrate/chitin binding (CBM18) domain is enriched in the Plasmodiophorid secretome. Plasmodiophorids chitin synthases belong to two families, which were present before the split of the eukaryotic Stramenopiles/Alveolates/Rhizaria/Plantae and Metazoa/Fungi/Amoebozoa megagroups, suggesting chitin synthesis to be an ancient feature of eukaryotes. This exemplifies the importance of genomic data from unexplored eukaryotic groups, such as the Plasmodiophorids, to decipher evolutionary relationships and gene diversification of early eukaryotes.


Via Francis Martin
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Alejandro Rojas's curator insight, June 25, 9:44 AM

This is an special case since it is not a fungal or oomycete pathogen.  However, it is interesting case on pathogenesis and the resemblance of other pathogens.  In this case the oomycetes, specially pathogens like the Pythium species.  

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Identification of a New Class of Antifungals Targeting the Synthesis of Fungal Sphingolipids

Identification of a New Class of Antifungals Targeting the Synthesis of Fungal Sphingolipids | Plant pathogenic fungi | Scoop.it

Recent estimates suggest that >300 million people are afflicted by serious fungal infections worldwide. Current antifungal drugs are static and toxic and/or have a narrow spectrum of activity. Thus, there is an urgent need for the development of new antifungal drugs. The fungal sphingolipid glucosylceramide (GlcCer) is critical in promoting virulence of a variety of human-pathogenic fungi. In this study, we screened a synthetic drug library for compounds that target the synthesis of fungal, but not mammalian, GlcCer and found two compounds [N′-(3-bromo-4-hydroxybenzylidene)-2-methylbenzohydrazide (BHBM) and its derivative, 3-bromo-N′-(3-bromo-4-hydroxybenzylidene) benzohydrazide (D0)] that were highly effective in vitro and in vivo against several pathogenic fungi. BHBM and D0 were well tolerated in animals and are highly synergistic or additive to current antifungals. BHBM and D0 significantly affected fungal cell morphology and resulted in the accumulation of intracellular vesicles. Deep-sequencing analysis of drug-resistant mutants revealed that four protein products, encoded by genes APL5, COS111, MKK1, and STE2, which are involved in vesicular transport and cell cycle progression, are targeted by BHBM.

IMPORTANCE Fungal infections are a significant cause of morbidity and mortality worldwide. Current antifungal drugs suffer from various drawbacks, including toxicity, drug resistance, and narrow spectrum of activity. In this study, we have demonstrated that pharmaceutical inhibition of fungal glucosylceramide presents a new opportunity to treat cryptococcosis and various other fungal infections. In addition to being effective against pathogenic fungi, the compounds discovered in this study were well tolerated by animals and additive to current antifungals. These findings suggest that these drugs might pave the way for the development of a new class of antifungals.

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Ecological impacts of parasitic chytrids, syndiniales and perkinsids on populations of marine photosynthetic dinoflagellates

Ecological impacts of parasitic chytrids, syndiniales and perkinsids on populations of marine photosynthetic dinoflagellates | Plant pathogenic fungi | Scoop.it

Highlights
• Marine dinoflagellates may be infected by a diverse suite of parasitoids.
• These parasitoids are either true-fungi, or exhibit fungi-like properties.
• The interactions of these organisms may be viewed as a pathosystem.
• Human activity can potentially render these pathosystems unstable.
• Increasing aquacultural activity may be severely affected by marine pathosystems.

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Impact of plant domestication on rhizosphere microbiome assembly and functions

Impact of plant domestication on rhizosphere microbiome assembly and functions | Plant pathogenic fungi | Scoop.it
The rhizosphere microbiome is pivotal for plant health and growth, providing defence against pests and diseases, facilitating nutrient acquisition and helping plants to withstand abiotic stresses. Plants can actively recruit members of the soil microbial community for positive feedbacks, but the underlying mechanisms and plant traits that drive microbiome assembly and functions are largely unknown. Domestication of plant species has substantially contributed to human civilization, but also caused a strong decrease in the genetic diversity of modern crop cultivars that may have affected the ability of plants to establish beneficial associations with rhizosphere microbes. Here, we review how plants shape the rhizosphere microbiome and how domestication may have impacted rhizosphere microbiome assembly and functions via habitat expansion and via changes in crop management practices, root exudation, root architecture, and plant litter quality. We also propose a “back to the roots” framework that comprises the exploration of the microbiome of indigenous plants and their native habitats for the identification of plant and microbial traits with the ultimate goal to reinstate beneficial associations that may have been undermined during plant domestication.

Via Jean-Michel Ané
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MicroRNA-mediated regulation of gene expression in the response of rice plants to fungal elicitors

MicroRNA-mediated regulation of gene expression in the response of rice plants to fungal elicitors | Plant pathogenic fungi | Scoop.it
MicroRNAs (miRNAs) are small non-coding RNAs that have important regulatory functions in plant growth, development, and response to abiotic stress. Increasing evidence also supports that plant miRNAs contribute to immune responses to pathogens. Here, we used deep sequencing of small RNA libraries for global identification of rice miRNAs that are regulated by fungal elicitors. We also describe 9 previously uncharacterized miRNAs in rice. Combined small RNA and degradome analyses revealed regulatory networks enriched in elicitor-regulated miRNAs supported by the identification of their corresponding target genes. Specifically, we identified an important number of miRNA/target gene pairs involved in small RNA pathways, including miRNA, heterochromatic and trans-acting siRNA pathways. We present evidence for miRNA/target gene pairs implicated in hormone signaling and cross-talk among hormone pathways having great potential in regulating rice immunity. Furthermore, we describe miRNA-mediated regulation of Conserved-Peptide upstream Open Reading Frame (CPuORF)-containing genes in rice, which suggests the existence of a novel regulatory network that integrates miRNA and CPuORF functions in plants. The knowledge gained in this study will help in understanding the underlying regulatory mechanisms of miRNAs in rice immunity and develop appropriate strategies for rice protection.

Via Elsa Ballini
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RNA–protein interactions in plant disease: hackers at the dinner table

RNA–protein interactions in plant disease: hackers at the dinner table | Plant pathogenic fungi | Scoop.it
Plants are the source of most of our food, whether directly or as feed for the animals we eat. Our dinner table is a trophic level we share with the microbes that also feed on the primary photosynthetic producers. Microbes that enter into close interactions with plants need to evade or suppress detection and host immunity to access nutrients. They do this by deploying molecular tools – effectors – which target host processes. The mode of action of effector proteins in these events is varied and complex. Recent data from diverse systems indicate that RNA-interacting proteins and RNA itself are delivered by eukaryotic microbes, such as fungi and oomycetes, to host plants and contribute to the establishment of successful interactions. This is evidence that pathogenic microbes can interfere with the host software. We are beginning to see that pathogenic microbes are capable of hacking into the plants' immunity programs.

Via Francis Martin
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Functional Operons in Secondary Metabolic Gene Clusters in Glarea lozoyensis (Fungi, Ascomycota, Leotiomycetes)

Functional Operons in Secondary Metabolic Gene Clusters in Glarea lozoyensis (Fungi, Ascomycota, Leotiomycetes) | Plant pathogenic fungi | Scoop.it

IMPORTANCE Operons are multigene transcriptional units which occur mostly in prokaryotes but rarely in eukaryotes. Three operon-like gene structures for secondary metabolism that were discovered in the filamentous fungus Glarea lozoyensis are the first examples of protein-coding operons identified in a member of the Fungi. Among them, the glpks3-glnrps7 operon is responsible for the biosynthesis of xenolozoyenone, which is a novel tetramic acid-containing compound. Although structurally similar to prokaryotic operons, the glpks3-glnrps7 operon locus did not result from horizontal gene transfer from prokaryotes. In addition, operon like structures have been predicted in silico to be common in other fungi. The common occurrence and operon like structure in fungi provide evolutionary insight and essential data for eukaryotic gene transcription.

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PLOS ONE (2015): Novel Introner-Like Elements in fungi Are Involved in Parallel Gains of Spliceosomal Introns

PLOS ONE (2015): Novel Introner-Like Elements in fungi Are Involved in Parallel Gains of Spliceosomal Introns | Plant pathogenic fungi | Scoop.it

Spliceosomal introns are key components of the eukaryotic gene structure. Although they contributed to the emergence of eukaryotes, their origin remains elusive. In fungi, they might originate from the multiplication of invasive introns named Introner-Like Elements (ILEs). However, so far ILEs have been observed in six fungal species only, including Fulvia fulva and Dothistroma septosporum (Dothideomycetes), arguing against ILE insertion as a general mechanism for intron gain. Here, we identified novel ILEs in eight additional fungal species that are phylogenetically related to F. fulva and D. septosporum using PCR amplification with primers derived from previously identified ILEs. The ILE content appeared unique to each species, suggesting independent multiplication events. Interestingly, we identified four genes each containing two gained ILEs. By analysing intron positions in orthologues of these four genes in Ascomycota, we found that three ILEs had inserted within a 15 bp window that contains regular spliceosomal introns in other fungal species. These three positions are not the result of intron sliding because ILEs are newly gained introns. Furthermore, the alternative hypothesis of an inferred ancestral gain followed by independent losses contradicts the observed degeneration of ILEs. These observations clearly indicate three parallel intron gains in four genes that were randomly identified. Our findings suggest that parallel intron gain is a phenomenon that has been highly underestimated in ILE-containing fungi, and likely in the whole fungal kingdom.


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Endocytosis and exocytosis in hyphal growth

Endocytosis and exocytosis in hyphal growth | Plant pathogenic fungi | Scoop.it

Highlights
• Knowledge of the exocytic and endocytic machinery in filamentous fungi is detailed.
• Methods used by the cell to polarize endocytosis and exocytosis are discussed.
• Evidence for the importance of endocytic recycling in hyphae is presented.
• The roles for endocytosis and exocytosis in host-pathogen interactions are discussed.

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Genome-Wide Analysis of Simple Sequence Repeats and Efficient Development of Polymorphic SSR Markers Based on Whole Genome Re-Sequencing of Multiple Isolates of the Wheat Stripe Rust Fungus

Genome-Wide Analysis of Simple Sequence Repeats and Efficient Development of Polymorphic SSR Markers Based on Whole Genome Re-Sequencing of Multiple Isolates of the Wheat Stripe Rust Fungus | Plant pathogenic fungi | Scoop.it

The biotrophic parasitic fungus Puccinia striiformis f. sp. tritici (Pst) causes stripe rust, a devastating disease of wheat, endangering global food security. Because the Pst population is highly dynamic, it is difficult to develop wheat cultivars with durable and highly effective resistance. Simple sequence repeats (SSRs) are widely used as molecular markers in genetic studies to determine population structure in many organisms. However, only a small number of SSR markers have been developed for Pst. In this study, a total of 4,792 SSR loci were identified using the whole genome sequences of six isolates from different regions of the world, with a marker density of one SSR per 22.95 kb. The majority of the SSRs were di- and tri-nucleotide repeats. A database containing 1,113 SSR markers were established. Through in silico comparison, the previously reported SSR markers were found mainly in exons, whereas the SSR markers in the database were mostly in intergenic regions. Furthermore, 105 polymorphic SSR markers were confirmed in silico by their identical positions and nucleotide variations with INDELs identified among the six isolates. When 104 in silico polymorphic SSR markers were used to genotype 21 Pst isolates, 84 produced the target bands, and 82 of them were polymorphic and revealed the genetic relationships among the isolates. The results show that whole genome re-sequencing of multiple isolates provides an ideal resource for developing SSR markers, and the newly developed SSR markers are useful for genetic and population studies of the wheat stripe rust fungus.


Via IPM Lab
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Nice genomic analysis and development of SSRs for stripe rust fungus.

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Differences in the responses of melon accessions to fusarium root and stem rot and their colonization by Fusarium oxysporum f. sp. radicis-cucumerinum

Differences in the responses of melon accessions to fusarium root and stem rot and their colonization by Fusarium oxysporum f. sp. radicis-cucumerinum | Plant pathogenic fungi | Scoop.it

Fusarium root and stem rot caused by the fungus Fusarium oxysporum f. sp. radicis-cucumerinum is a major disease in greenhouse cucumbers. Over the past decade, the disease has been documented in melon greenhouses in Greece, and recently it has been sporadically recorded in greenhouse melons in Israel. Variations in disease response were found among 41 melon accessions artificially inoculated with the pathogen: 10 accessions were highly susceptible (90–100% mortality), 23 exhibited an intermediate response (20–86%) and eight were resistant (0–4%). Two melon accessions – HEM (highly resistant) and TAD (partially resistant) – were crossed with the susceptible accession DUL. The responses of the three accessions and F1 crosses between the resistant and susceptible parents were evaluated. HEM contributed higher resistance to the F1 hybrid than TAD. Roots of susceptible and resistant accessions were 100 and 79% colonized, respectively, following artificial inoculation. However, only susceptible plants showed colonization of the upper plant tissues. Microscopic evaluation of cross sections taken from the crown region of the susceptible DUL revealed profuse fungal growth in the intercellular spaces of the parenchyma and in xylem vessels. In the resistant cultivar HEM, very little fungal growth was detected in the intercellular spaces of the parenchyma, and none in the xylem or any other vascular tissue. Finding resistant accessions may create an opportunity to study the genetics of resistance inheritance and to develop molecular markers that will facilitate breeding resistant melon cultivars.

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Novel pathways for fuels and lubricants from biomass optimized using life-cycle greenhouse gas assessment

Novel pathways for fuels and lubricants from biomass optimized using life-cycle greenhouse gas assessment | Plant pathogenic fungi | Scoop.it

Decarbonizing the transportation sector is critical to achieving global climate change mitigation. Although biofuels will play an important role in conventional gasoline and diesel applications, bioderived solutions are particularly important in jet fuels and lubricants, for which no other viable renewable alternatives exist. Producing compounds for jet fuel and lubricant base oil applications often requires upgrading fermentation products, such as alcohols and ketones, to reach the appropriate molecular-weight range. Ketones possess both electrophilic and nucleophilic functionality, which allows them to be used as building blocks similar to alkenes and aromatics in a petroleum refining complex. Here, we develop a method for selectively upgrading biomass-derived alkyl methyl ketones with >95% yields into trimer condensates, which can then be hydrodeoxygenated in near-quantitative yields to give a new class of cycloalkane compounds. The basic chemistry developed here can be tailored for aviation fuels as well as lubricants by changing the production strategy. We also demonstrate that a sugarcane biorefinery could use natural synergies between various routes to produce a mixture of lubricant base oils and jet fuels that achieve net life-cycle greenhouse gas savings of up to 80%.

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Fungal Traits That Drive Ecosystem Dynamics on Land

Fungal Traits That Drive Ecosystem Dynamics on Land | Plant pathogenic fungi | Scoop.it

Fungi contribute extensively to a wide range of ecosystem processes, including decomposition of organic carbon, deposition of recalcitrant carbon, and transformations of nitrogen and phosphorus. In this review, we discuss the current knowledge about physiological and morphological traits of fungi that directly influence these processes, and we describe the functional genes that encode these traits. In addition, we synthesize information from 157 whole fungal genomes in order to determine relationships among selected functional genes within fungal taxa. Ecosystem-related traits varied most at relatively coarse taxonomic levels. For example, we found that the maximum amount of variance for traits associated with carbon mineralization, nitrogen and phosphorus cycling, and stress tolerance could be explained at the levels of order to phylum. Moreover, suites of traits tended to co-occur within taxa. Specifically, the genetic capacities for traits that improve stress tolerance—β-glucan synthesis, trehalose production, and cold-induced RNA helicases—were positively related to one another, and they were more evident in yeasts. Traits that regulate the decomposition of complex organic matter—lignin peroxidases, cellobiohydrolases, and crystalline cellulases—were also positively related, but they were more strongly associated with free-living filamentous fungi. Altogether, these relationships provide evidence for two functional groups: stress tolerators, which may contribute to soil carbon accumulation via the production of recalcitrant compounds; and decomposers, which may reduce soil carbon stocks. It is possible that ecosystem functions, such as soil carbon storage, may be mediated by shifts in the fungal community between stress tolerators and decomposers in response to environmental changes, such as drought and warming.

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Evolution of virulence in fungal plant pathogens: exploiting fungal genomics to control plant disease

Evolution of virulence in fungal plant pathogens: exploiting fungal genomics to control plant disease | Plant pathogenic fungi | Scoop.it

The propensity of a fungal pathogen to evolve virulence depends on features of its biology (e.g. mode of reproduction) and of its genome (e.g. amount of repetitive DNA). Populations of Leptosphaeria maculans, a pathogen ofBrassica napus (canola), can evolve and overcome disease resistance bred into canola within three years of commercial release of a cultivar. Avirulence effector genes are key fungal genes that are complementary to resistance genes. In L. maculans these genes are embedded within inactivated transposable elements in genomic regions where they are readily mutated or deleted. The risk of resistance breakdown in the field can be minimised by monitoring disease severity of canola cultivars and virulence of fungal populations using high throughput molecular assays and by sowing canola cultivars with different resistance genes in subsequent years. This strategy has been exploited to avert yield losses due to blackleg disease in Australia.

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Nice summation of lots of work.

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Complete Genome Sequence of Sporisorium scitamineum and Biotrophic Interaction Transcriptome with Sugarcane

Complete Genome Sequence of  Sporisorium scitamineum  and Biotrophic Interaction Transcriptome with Sugarcane | Plant pathogenic fungi | Scoop.it
Sporisorium scitamineum is a biotrophic fungus responsible for the sugarcane smut, a worldwide spread disease. This study provides the complete sequence of individual chromosomes of S. scitamineum from telomere to telomere achieved by a combination of PacBio long reads and Illumina short reads sequence data, as well as a draft sequence of a second fungal strain. Comparative analysis to previous available sequences of another strain detected few polymorphisms among the three genomes. The novel complete sequence described herein allowed us to identify and annotate extended subtelomeric regions, repetitive elements and the mitochondrial DNA sequence. The genome comprises 19,979,571 bases, 6,677 genes encoding proteins, 111 tRNAs and 3 assembled copies of rDNA, out of our estimated number of copies as 130. Chromosomal reorganizations were detected when comparing to sequences of S. reilianum, the closest smut relative, potentially influenced by repeats of transposable elements. Repetitive elements may have also directed the linkage of the two mating-type loci. The fungal transcriptome profiling from in vitro and from interaction with sugarcane at two time points (early infection and whip emergence) revealed that 13.5% of the genes were differentially expressed in planta and particular to each developmental stage. Among them are plant cell wall degrading enzymes, proteases, lipases, chitin modification and lignin degradation enzymes, sugar transporters and transcriptional factors. The fungus also modulates transcription of genes related to surviving against reactive oxygen species and other toxic metabolites produced by the plant. Previously described effectors in smut/plant interactions were detected but some new candidates are proposed. Ten genomic islands harboring some of the candidate genes unique to S. scitamineum were expressed only in planta. RNAseq data was also used to reassure gene predictions.

Via Christophe Jacquet, Francis Martin, Guogen Yang, Rey Thomas
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The natural history, ecology, and epidemiology of Ophidiomyces ophiodiicola and its potential impact on free-ranging snake populations

The natural history, ecology, and epidemiology of Ophidiomyces ophiodiicola and its potential impact on free-ranging snake populations | Plant pathogenic fungi | Scoop.it

Highlights
• Some pathotypes in Ophidiomyces ophiodiicola cause serious disease in free range snakes.
• These fungi usually kill their hosts resulting in large declines in population sizes of hosts.
• It is possible that these fungi can be spread internationally through the animal trade.
• Molecular tests for this disease, prevention strategies, and therapeutic options are needed.

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Mutual Exclusion between Fungal Species of the Fusarium Head Blight Complex in a Wheat Spike

Mutual Exclusion between Fungal Species of the Fusarium Head Blight Complex in a Wheat Spike | Plant pathogenic fungi | Scoop.it

Fusarium head blight (FHB) is one of the most damaging diseases of wheat. FHB is caused by a species complex that includes two genera of Ascomycetes:  Microdochium and Fusarium. Fusarium graminearum, Fusarium culmorum, Fusarium poae, and Microdochium nivale are among the most common FHB species in Europe and were chosen for these experiments. Field studies and surveys show that two or more species often coexist within the same field or grain sample. In this study, we investigated the competitiveness of isolates of different species against isolates of F. graminearum at the scale of a single spike. By performing point inoculations of a single floret, we ensured that each species was able to establish independent infections and competed for spike colonization only. The fungal colonization was assessed in each spike by quantitative PCR. After establishing that the spike colonization was mainly downwards, we compared the relative colonization of each species in coinoculations. Classical analysis of variance suggested a competitive interaction but remained partly inconclusive because of a large between-spike variance. Further data exploration revealed a clear exclusion of one of the competing species and the complete absence of coexistence at the spike level.

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Molecular Signatures of Nicotinoid-Pathogen Synergy in the Termite Gut

Molecular Signatures of Nicotinoid-Pathogen Synergy in the Termite Gut | Plant pathogenic fungi | Scoop.it

Previous studies in lower termites revealed unexpected synergies between nicotinoid insecticides and fungal entomopathogens. The present study investigated molecular mechanisms of nicotinoid-pathogen synergy in the lower termite Reticulitermes flavipes, using the nicotinoid, imidacloprid, in combination with fungal and bacterial entomopathogens. Particular focus was placed on metatranscriptome composition and microbial dynamics in the symbiont-rich termite gut, which houses diverse mixes of protists and bacteria. cDNA microarrays containing a mix of host and protist symbiont oligonucleotides were used to simultaneously assess termite and protist gene expression. Five treatments were compared that included single challenges with sublethal doses of fungi (Metharizium anisopliae), bacteria (Serratia marcescens) or imidacloprid, and dual challenges with fungi + imidacloprid or bacteria + imidacloprid. Our findings point towards protist dysbiosis and compromised social behavior, rather than suppression of stereotypical immune defense mechanisms, as the dominant factors underlying nicotinoid-pathogen synergy in termites. Also, greater impacts observed for the fungal pathogen than for the bacterial pathogen suggest that the rich bacterial symbiont community in the R. flavipes gut (>5000 species-level phylotypes) exists in an ecological balance that effectively excludes exogenous bacterial pathogens. These findings significantly advance our understanding of antimicrobial defenses in this important eusocial insect group, as well as provide novel insights into how nicotinoids can exert deleterious effects on social insect colonies.

Steve Marek's insight:

Insecticide and pathogens alter termite bacterial and protist symbionts, disrupting social behavior and increasing mortality.

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Septoria tritici blotch disease of wheat: Tools and techniques to study the pathogen Zymoseptoria tritici

Septoria tritici blotch disease of wheat: Tools and techniques to study the pathogen Zymoseptoria tritici | Plant pathogenic fungi | Scoop.it

Fungi pose an increasing threat to our health, wealth, food security and ecosystem (Fisher et al., 2012. Nature 484, 186). A major challenge to wheat crops is the fungal pathogen Zymoseptoria tritici (=Mycosphaerella graminicola or Septoria tritici), the causal agent of Septoria tritici leaf Blotch (STB). This special issue in Fungal Genetics and Biology focuses on this important disease, with an emphasis on the fungal pathogen. It aims to provide an overview and entry portal into research on this disease in wheat. The special issue combines 27 focussed papers, provided by 65 authors, located in 25 institutions, both in academia and industry, from 10 countries all over the world (United Kingdom, USA, Netherlands, Iran, Tunisia, Germany, France, Ireland, Switzerland, and Australia).

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Nontoxic antimicrobials that evade drug resistance

Nontoxic antimicrobials that evade drug resistance | Plant pathogenic fungi | Scoop.it
An amphotericin antifungal that is less toxic to human cells due to its increased capacity for binding the fungal ergosterol over the human cholesterol can still evade resistance mechanisms, challenging the resistance-toxicity yin-yang of antimicrobials.
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Microbial and biochemical basis of a Fusarium wilt-suppressive soil

Microbial and biochemical basis of a Fusarium wilt-suppressive soil | Plant pathogenic fungi | Scoop.it
Crops lack genetic resistance to most necrotrophic pathogens. To compensate for this disadvantage, plants recruit antagonistic members of the soil microbiome to defend their roots against pathogens and other pests. The best examples of this microbially based defense of roots are observed in disease-suppressive soils in which suppressiveness is induced by continuously growing crops that are susceptible to a pathogen, but the molecular basis of most is poorly understood. Here we report the microbial characterization of a Korean soil with specific suppressiveness to Fusarium wilt of strawberry. In this soil, an attack on strawberry roots by Fusarium oxysporum results in a response by microbial defenders, of which members of the Actinobacteria appear to have a key role. We also identify Streptomyces genes responsible for the ribosomal synthesis of a novel heat-stable antifungal thiopeptide antibiotic inhibitory to F. oxysporum and the antibiotic’s mode of action against fungal cell wall biosynthesis. Both classical- and community-oriented approaches were required to dissect this suppressive soil from the field to the molecular level, and the results highlight the role of natural antibiotics as weapons in the microbial warfare in the rhizosphere that is integral to plant health, vigor and development.

Via Jean-Michel Ané
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Sr36- and Sr5-Mediated Resistance Response to Puccinia graminis f. sp. tritici Is Associated with Callose Deposition in Wheat Guard Cells

Sr36- and Sr5-Mediated Resistance Response to Puccinia graminis f. sp. tritici Is Associated with Callose Deposition in Wheat Guard Cells | Plant pathogenic fungi | Scoop.it

Race-specific resistance of wheat to Puccinia graminis f. sp. tritici is primarily posthaustorial and often involves the induction of a hypersensitive response (HR). The aim of this study was to investigate host defense responses induced in interactions between P. graminis f. sp. tritici races and wheat lines carrying different race-specific stem rust resistance (Sr) genes. In incompatible interactions between wheat lines carrying Sr36 in three genetic backgrounds (LMPG, Prelude, or W2691) and avirulent P. graminis f. sp.tritici races MCCFC or RCCDM, callose accumulated within 24 h in wheat guard cells contacted by a P. graminis f. sp. tritici appressorium, and P. graminis f. sp. tritici ingress was inhibited following appressorium formation. Accordingly, the expression of transcripts encoding a callose synthase increased in the incompatible interaction between LMPG-Sr36and avirulent P. graminis f. sp. tritici race MCCFC. Furthermore, the inhibition of callose synthesis through the infiltration of 2-deoxy-D-glucose (DDG) increased the ability of P. graminis f. sp. tritici race MCCFC to infect LMPG-Sr36. A similar induction of callose deposition in wheat guard cells was also observed within 24 h after inoculation (hai) with avirulent P. graminis f. sp. tritici race HKCJC on LMPG-Sr5 plants. In contrast, this defense response was not induced in incompatible interactions involving Sr6, Sr24, or Sr30. Instead, the induction of an HR and cellular lignification were noted. The manifestation of the HR and cellular lignification was induced earlier (24 hai) and was more extensive in the resistance response mediated by Sr6 compared with those mediated by Sr24 or Sr30.These results indicate that the resistance mediated by Sr36 is similar to that mediated bySr5 but different from those triggered by Sr6, Sr24, or Sr30. Resistance responses mediated by Sr5 and Sr36 are prehaustorial, and are a result of very rapid recognition of molecules derived from avirulent isolates of P. graminis f. sp. tritici, in contrast to the responses triggered in lines with Sr6, Sr24, and Sr30.

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The dispersal of alien species redefines biogeography in the Anthropocene

The dispersal of alien species redefines biogeography in the Anthropocene | Plant pathogenic fungi | Scoop.it
Emerging patterns in species distribution

Human influences are leading to a shift in the geographical distribution of animal species. Capinha et al.compared the distributions of native mollusk species with those introduced to new areas by human activities. The ranges of native species are still broadly constrained by limitations on their capacity for dispersal, whereas those of the introduced aliens are affected more by climate and patterns of human movement. As humans continue to break down barriers to dispersal, more species' distributions will come to be limited by their environmental tolerances.

Science, this issue p. 1248

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Humans aid invasive snails.

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