Plant pathogenic fungi
27.0K views | +34 today
Follow
 
Rescooped by Steve Marek from Plants and Microbes
onto Plant pathogenic fungi
Scoop.it!

Your input requested for Top 10 oomycete pathogens in molecular plant pathology

Your input requested for Top 10 oomycete pathogens in molecular plant pathology | Plant pathogenic fungi | Scoop.it

We are writing to seek your input to generate a list of the Top 10 oomycete pathogens in molecular plant pathology to use as the basis for an article in the Top 10 reviews series to be published in Molecular Plant Pathology.

 

Several of you must be familiar with the Top 10 reviews, which have covered so far fungi, viruses, bacteria and nematodes. These articles are available free to download from the journal website.

 

Yes, it is about time to cover our cherished oomycetes so please do vote and indicate your favourite by emailing the ballot to diane.hird@bristol.ac.uk. Each of you can vote for up to 5 species. The criteria we would like to cover are both the scientific and economic importance of the taxa. Feel free to draft a brief justification.

 

Please send your responses before October 20, 2013. The voting ballot is available at http://kamounlab.dreamhosters.com/Top10oomycetes_Ballot.docx

 

Also, feel free to forward this message to relevant colleagues.

 

Many thanks,

 

Sophien Kamoun and Diane Hird

 


Via Kamoun Lab @ TSL
Steve Marek's insight:

Your opinion needed!

more...
dromius's comment, September 30, 2013 4:21 AM
Phytophthora palmivora is the best ;)
Plant pathogenic fungi
Your new post is loading...
Your new post is loading...
Scooped by Steve Marek
Scoop.it!

Engineered gray mold resistance, antioxidant capacity, and pigmentation in betalain-producing crops and ornamentals

Engineered gray mold resistance, antioxidant capacity, and pigmentation in betalain-producing crops and ornamentals | Plant pathogenic fungi | Scoop.it
In plants, three major classes of pigments are generally responsible for colors seen in fruits and flowers: anthocyanins, carotenoids, and betalains. Betalains are red-violet and yellow plant pigments that have been reported to possess strong antioxidant and health-promoting properties, including anticancer, antiinflammatory, and antidiabetic activity. Here, heterologous betalain production was achieved for the first time in three major food crops: tomato, potato, and eggplant. Remarkably, betalain production in tobacco resulted in significantly enhanced resistance toward gray mold (Botrytis cinerea), a plant pathogen responsible for major crop losses. Considering the significant characteristics of these molecules, heterologous betalain production now offers exciting opportunities for creating new value for consumers, producers, and suppliers of food crops and ornamental plants.

Abstract
Betalains are tyrosine-derived red-violet and yellow plant pigments known for their antioxidant activity, health-promoting properties, and wide use as food colorants and dietary supplements. By coexpressing three genes of the recently elucidated betalain biosynthetic pathway, we demonstrate the heterologous production of these pigments in a variety of plants, including three major food crops: tomato, potato, and eggplant, and the economically important ornamental petunia. Combinatorial expression of betalain-related genes also allowed the engineering of tobacco plants and cell cultures to produce a palette of unique colors. Furthermore, betalain-producing tobacco plants exhibited significantly increased resistance toward gray mold (Botrytis cinerea), a pathogen responsible for major losses in agricultural produce. Heterologous production of betalains is thus anticipated to enable biofortification of essential foods, development of new ornamental varieties, and innovative sources for commercial betalain production, as well as utilization of these pigments in crop protection.
more...
No comment yet.
Scooped by Steve Marek
Scoop.it!

Investigating the diversity of effector genes in the banana pathogen, Fusarium oxysporum f.sp. cubense, reveals evidence of horizontal gene transfer

Investigating the diversity of effector genes in the banana pathogen, Fusarium oxysporum f.sp. cubense, reveals evidence of horizontal gene transfer | Plant pathogenic fungi | Scoop.it
It is hypothesised that the virulence of phytopathogenic fungi is mediated through the secretion of small effector proteins that interfere with the defence responses of the host plant. In Fusarium oxysporum, one family of effectors, the secreted in xylem (SIX) genes, have been identified. We sought to characterise the diversity and evolution of the SIX genes in the banana-infecting lineages of F. oxysporum f.sp. cubense (Foc).

Whole-genome sequencing data was generated for the 23 genetic lineages of Foc, which were subsequently queried for the 14 known SIX genes (SIX1-SIX14). The sequences of the identified SIX genes were confirmed in a larger collection of Foc isolates. Genealogies were generated for each of the SIX genes identified in Foc to further investigate the evolution of the SIX genes in Foc.

Within Foc, variation of the SIX gene profile, including the presence of specific SIX homologues, correlated with the pathogenic race structure of Foc. Furthermore, the topologies of the SIX gene trees were discordant with the topology of an infraspecies phylogeny inferred from EF-1α/RPB1/RPB2. A series of topological constraint models provided strong evidence for the horizontal transmission of SIX genes in Foc.

The horizontal inheritance of pathogenicity genes in Foc counters previous assumptions that convergent evolution has driven the polyphyletic phylogeny of Foc. This work has significant implications for the management of Foc, including the improvement of diagnostics and breeding programs.
Steve Marek's insight:
Share your insight
more...
No comment yet.
Scooped by Steve Marek
Scoop.it!

Read quality-based trimming of the distal ends of public fungal DNA sequences is nowhere near satisfactory

Read quality-based trimming of the distal ends of public fungal DNA sequences is nowhere near satisfactory | Plant pathogenic fungi | Scoop.it
DNA sequences are increasingly used for taxonomic and functional assessment of environmental communities. In mycology, the nuclear ribosomal internal transcribed spacer (ITS) region is the most commonly chosen marker for such pursuits. Molecular identification is associated with many challenges, one of which is low read quality of the reference sequences used for inference of taxonomic and functional properties of the newly sequenced community (or single taxon). This study investigates whether public fungal ITS sequences are subjected to sufficient trimming in their distal (5’ and 3’) ends prior to deposition in the public repositories. We examined 86 species (and 10,584 sequences) across the fungal tree of life, and we found that on average 13.1% of the sequences were poorly trimmed in one or both of their 5’ and 3’ ends. Deposition of poorly trimmed entries was found to continue through 2016. Poorly trimmed reference sequences add noise and mask biological signal in sequence similarity searches and phylogenetic analyses, and we provide a set of recommendations on how to manage the sequence trimming problem.
more...
Scooped by Steve Marek
Scoop.it!

Mating-type genes of the anamorphic fungus Ulocladium botrytis affect both asexual sporulation and sexual reproduction

Mating-type genes of the anamorphic fungus Ulocladium botrytis affect both asexual sporulation and sexual reproduction | Plant pathogenic fungi | Scoop.it
Ulocladium was thought to be a strictly asexual genus of filamentous fungi. However, Ulocladium strains were shown to possess both MAT1-1-1 and MAT1-2-1 genes as observed in homothallic filamentous Ascomycetes. Here, we demonstrate that the U. botrytis MAT genes play essential roles for controlling asexual traits (conidial size and number). Using reciprocal genetic transformation, we demonstrate that MAT genes from the related heterothallic species Cochliobolus heterostrophus can also influence U. botrytis colony growth, conidial number and size, and have a strong effect on the range of the number of septa/conidium. Moreover, U. botrytis MAT genes can also affect similar aspects of asexual reproduction when expressed in C. heterostrophus. Heterologous complementation using C. heterostrophus MAT genes shows that they have lost the ability to regulate sexual reproduction in U. botrytis, under the conditions we employed, while the reciprocal heterologous complementation demonstrates that U. botrytis MAT genes have the ability to partially induce sexual reproduction in C. heterostrophus. Thus, the genetic backgrounds of C. heterostrophus and U. botrytis play significant roles in determining the function of MAT genes on sexual reproduction in these two fungi species. These data further support the role of MAT genes in controlling asexual growth in filamentous Ascomycetes but also confirm that heterothallic and homothallic Dothideomycete fungi can be interconverted by the exchange of MAT genes.

Steve Marek's insight:
Mating type loci deletions and swaps with those of Cochliobolus
more...
No comment yet.
Scooped by Steve Marek
Scoop.it!

Chickpea-Fusarium oxysporum interaction transcriptome reveals differential modulation of plant defense strategies

Chickpea-Fusarium oxysporum interaction transcriptome reveals differential modulation of plant defense strategies | Plant pathogenic fungi | Scoop.it
Fusarium wilt is one of the major biotic stresses reducing chickpea productivity. The use of wilt-resistant cultivars is the most appropriate means to combat the disease and secure productivity. As a step towards understanding the molecular basis of wilt resistance in chickpea, we investigated the transcriptomes of wilt-susceptible and wilt-resistant cultivars under both Fusarium oxysporum f.sp. ciceri (Foc) challenged and unchallenged conditions. Transcriptome profiling using LongSAGE provided a valuable insight into the molecular interactions between chickpea and Foc, which revealed several known as well as novel genes with differential or unique expression patterns in chickpea contributing to lignification, hormonal homeostasis, plant defense signaling, ROS homeostasis, R-gene mediated defense, etc. Similarly, several Foc genes characteristically required for survival and growth of the pathogen were expressed only in the susceptible cultivar with null expression of most of these genes in the resistant cultivar. This study provides a rich resource for functional characterization of the genes involved in resistance mechanism and their use in breeding for sustainable wilt-resistance. Additionally, it provides pathogen targets facilitating the development of novel control strategies.

more...
No comment yet.
Rescooped by Steve Marek from MycorWeb Plant-Microbe Interactions
Scoop.it!

Comparative analysis of basidiomycete transcriptomes reveals a core set of expressed genes encoding plant biomass degrading enzymes

Comparative analysis of basidiomycete transcriptomes reveals a core set of expressed genes encoding plant biomass degrading enzymes | Plant pathogenic fungi | Scoop.it
Basidiomycete fungi can degrade a wide range of plant biomass, including living and dead trees, forest litter, crops, and plant matter in soils. Understanding the process of plant biomass decay by basidiomycetes could facilitate their application in various industrial sectors such as food & feed, detergents and biofuels, and also provide new insights into their essential biological role in the global carbon cycle. The fast expansion of basidiomycete genomic and functional genomics data (e.g. transcriptomics, proteomics) has facilitated exploration of key genes and regulatory mechanisms of plant biomass degradation. In this study, we comparatively analyzed 22 transcriptome datasets from basidiomycetes related to plant biomass degradation, and identified 328 commonly induced genes and 318 repressed genes, and defined a core set of carbohydrate active enzymes (CAZymes), which was shared by most of the basidiomycete species. High conservation of these CAZymes in genomes and similar regulation pattern in transcriptomics data from lignocellulosic substrates indicate their key role in plant biomass degradation and need for their further biochemical investigation.

Via Francis Martin
more...
No comment yet.
Rescooped by Steve Marek from Plant-Microbe Interactions: Pathogenesis & Symbiosis
Scoop.it!

The cereal pathogen Fusarium pseudograminearum produces a new class of active cytokinins during infection

The cereal pathogen Fusarium pseudograminearum produces a new class of active cytokinins during infection | Plant pathogenic fungi | Scoop.it
The fungal pathogen Fusarium pseudograminearum causes important diseases of wheat and barley. During a survey of secondary metabolites produced by this fungus, a novel class of cytokinins, herein termed Fusarium cytokinins, was discovered. Cytokinins are known for their growth promoting and anti-senescence activities and the production of a cytokinin mimic by what was once considered a necrotrophic pathogen that promotes cell death and senescence challenges the simple view that this pathogen invades its hosts by employing a barrage of lytic enzymes and toxins. Through genome mining, a gene cluster in the F. pseudograminearum genome for the production of Fusarium cytokinins was identified and the biosynthetic pathway established using gene knockouts. The Fusarium cytokinins could activate plant cytokinin signalling, demonstrating their genuine hormone mimicry. In planta analysis of the transcriptional response to one Fusarium cytokinin suggests extensive reprogramming of the host environment by these molecules, possibly through crosstalk with defence hormone signalling pathways. This article is protected by copyright. All rights reserved.

Via Philip Carella
more...
No comment yet.
Rescooped by Steve Marek from Adaptive Evolution and Speciation
Scoop.it!

Fungal genome and mating system transitions facilitated by chromosomal translocations involving intercentromeric recombination - PLoS Biology

Fungal genome and mating system transitions facilitated by chromosomal translocations involving intercentromeric recombination - PLoS Biology | Plant pathogenic fungi | Scoop.it
Species within the human pathogenic Cryptococcus species complex are major threats to public health, causing approximately 1 million infections globally annually. Cryptococcus amylolentus is the most closely known related species of the pathogenic Cryptococcus species complex, and it is non-pathogenic. Additionally, while pathogenic Cryptococcus species have bipolar mating systems with a single large mating type (MAT) locus that represents a derived state in Basidiomycetes, C. amylolentus has a tetrapolar mating system with 2 MAT loci (P/R and HD) located on different chromosomes. Thus, studying C. amylolentus will shed light on the transition from tetrapolar to bipolar mating systems in the pathogenic Cryptococcus species, as well as its possible link with the origin and evolution of pathogenesis. In this study, we sequenced, assembled, and annotated the genomes of 2 C. amylolentus isolates, CBS6039 and CBS6273, which are sexual and interfertile. Genome comparison between the 2 C. amylolentus isolates identified the boundaries and the complete gene contents of the P/R and HD MAT loci. Bioinformatic and chromatin immunoprecipitation sequencing (ChIP-seq) analyses revealed that, similar to those of the pathogenic Cryptococcus species, C. amylolentus has regional centromeres (CENs) that are enriched with species-specific transposable and repetitive DNA elements. Additionally, we found that while neither the P/R nor the HD locus is physically closely linked to its centromere in C. amylolentus, and the regions between the MAT loci and their respective centromeres show overall synteny between the 2 genomes, both MAT loci exhibit genetic linkage to their respective centromere during meiosis, suggesting the presence of recombinational suppressors and/or epistatic gene interactions in the MAT-CEN intervening regions. Furthermore, genomic comparisons between C. amylolentus and related pathogenic Cryptococcus species provide evidence that multiple chromosomal rearrangements mediated by intercentromeric recombination have occurred during descent of the 2 lineages from their common ancestor. Taken together, our findings support a model in which the evolution of the bipolar mating system was initiated by an ectopic recombination event mediated by similar repetitive centromeric DNA elements shared between chromosomes. This translocation brought the P/R and HD loci onto the same chromosome, and further chromosomal rearrangements then resulted in the 2 MAT loci becoming physically linked and eventually fusing to form the single contiguous MAT locus that is now extant in the pathogenic Cryptococcus species.

Via Ronny Kellner
more...
No comment yet.
Scooped by Steve Marek
Scoop.it!

Human presence impacts fungal diversity of inflated lunar/Mars analog habitat

Human presence impacts fungal diversity of inflated lunar/Mars analog habitat | Plant pathogenic fungi | Scoop.it
Background
An inflatable lunar/Mars analog habitat (ILMAH), simulated closed system isolated by HEPA filtration, mimics International Space Station (ISS) conditions and future human habitation on other planets except for the exchange of air between outdoor and indoor environments. The ILMAH was primarily commissioned to measure physiological, psychological, and immunological characteristics of human inhabiting in isolation, but it was also available for other studies such as examining its microbiological aspects. Characterizing and understanding possible changes and succession of fungal species is of high importance since fungi are not only hazardous to inhabitants but also deteriorate the habitats. Observing the mycobiome changes in the presence of human will enable developing appropriate countermeasures with reference to crew health in a future closed habitat.

Results
Succession of fungi was characterized utilizing both traditional and state-of-the-art molecular techniques during the 30-day human occupation of the ILMAH. Surface samples were collected at various time points and locations to observe both the total and viable fungal populations of common environmental and opportunistic pathogenic species. To estimate the cultivable fungal population, potato dextrose agar plate counts method was utilized. The internal transcribed spacer region-based iTag Illumina sequencing was employed to measure the community structure and fluctuation of the mycobiome over time in various locations. Treatment of samples with propidium monoazide (PMA; a DNA intercalating dye for selective detection of viable microbial populations) had a significant effect on the microbial diversity compared to non-PMA-treated samples. Statistical analysis confirmed that viable fungal community structure changed (increase in diversity and decrease in fungal burden) over the occupation time. Samples collected at day 20 showed distinct fungal profiles from samples collected at any other time point (before or after). Viable fungal families like Davidiellaceae, Teratosphaeriaceae, Pleosporales, and Pleosporaceae were shown to increase during the occupation time.

Conclusions
The results of this study revealed that the overall fungal diversity in the closed habitat changed during human presence; therefore, it is crucial to properly maintain a closed habitat to preserve it from deteriorating and keep it safe for its inhabitants. Differences in community profiles were observed when statistically treated, especially of the mycobiome of samples collected at day 20. On a genus level Epiccocum, Alternaria, Pleosporales, Davidiella, and Cryptococcus showed increased abundance over the occupation time.
more...
No comment yet.
Scooped by Steve Marek
Scoop.it!

Complementation of CTB7 in the Maize Pathogen Cercospora zeina Overcomes the Lack of In Vitro Cercosporin Production | Molecular Plant-Microbe Interactions

Complementation of CTB7 in the Maize Pathogen Cercospora zeina Overcomes the Lack of In Vitro Cercosporin Production | Molecular Plant-Microbe Interactions | Plant pathogenic fungi | Scoop.it
Gray leaf spot (GLS), caused by the sibling species Cercospora zeina or Cercospora zeae-maydis, is cited as one of the most important diseases threatening global maize production. C. zeina fails to produce cercosporin in vitro and, in most cases, causes large coalescing lesions during maize infection, a symptom generally absent from cercosporin-deficient mutants in other Cercospora spp. Here, we describe the C. zeina cercosporin toxin biosynthetic (CTB) gene cluster. The oxidoreductase gene CTB7 contained several insertions and deletions as compared with the C. zeae-maydis ortholog. We set out to determine whether complementing the defective CTB7 gene with the full-length gene from C. zeae-maydis could confer in vitro cercosporin production. C. zeina transformants containing C. zeae-maydis CTB7 were generated by Agrobacterium tumefaciens–mediated transformation and were evaluated for in vitro cercosporin production. When grown on nitrogen-limited medium in the light—conditions conducive to cercosporin production in other Cercospora spp.—one transformant accumulated a red pigment that was confirmed to be cercosporin by the KOH assay, thin-layer chromatography, and ultra performance liquid chromatography-quadrupole-time-of-flight mass spectrometry. Our results indicated that C. zeina has a defective CTB7, but all other necessary machinery required for synthesizing cercosporin-like molecules and, thus, C. zeina may produce a structural variant of cercosporin during maize infection.

more...
No comment yet.
Scooped by Steve Marek
Scoop.it!

Quantitative iTRAQ-based secretome analysis reveals species-specific and temporal shifts in carbon utilization strategies among manganese(II)-oxidizing Ascomycete fungi - ScienceDirect

Quantitative iTRAQ-based secretome analysis reveals species-specific and temporal shifts in carbon utilization strategies among manganese(II)-oxidizing Ascomycete fungi - ScienceDirect | Plant pathogenic fungi | Scoop.it

• We investigated the carbon utilization strategies of four filamentous Ascomycetes.
• These fungi are environmental isolates with cellulose-degrading capability.
• iTRAQ proteomics identified over 1200 proteins in the secretome of each species.
• Carbon utilization patterns varied with each species over a 21-day period.
• Extracellular enzyme activity assays supported major carbon utilization patterns.

more...
No comment yet.
Rescooped by Steve Marek from Colletotrichum
Scoop.it!

Differential gene expression in tomato fruit and Colletotrichum gloeosporioides during colonization of the RNAi –SlPH tomato line with reduced fruit acidity and higher pH

Differential gene expression in tomato fruit and Colletotrichum gloeosporioides during colonization of the RNAi –SlPH tomato line with reduced fruit acidity and higher pH | Plant pathogenic fungi | Scoop.it

Background The destructive phytopathogen Colletotrichum gloeosporioides causes anthracnose disease in fruit. During host colonization, it secretes ammonia, which modulates environmental pH and regulates gene expression, contributing to pathogenicity. However, the effect of host pH environment on pathogen colonization has never been evaluated. Development of an isogenic tomato line with reduced expression of the gene for acidity, SlPH (Solyc10g074790.1.1), enabled this analysis. Total RNA from C. gloeosporioides colonizing wild-type (WT) and RNAi–SlPH tomato lines was sequenced and gene-expression patterns were compared. 


Results C. gloeosporioides inoculation of the RNAi–SlPH line with pH 5.96 compared to the WT line with pH 4.2 showed 30% higher colonization and reduced ammonia accumulation. Large-scale comparative transcriptome analysis of the colonized RNAi–SlPH and WT lines revealed their different mechanisms of colonization-pattern activation: whereas the WT tomato upregulated 13-LOX (lipoxygenase), jasmonic acid and glutamate biosynthesis pathways, it downregulated processes related to chlorogenic acid biosynthesis II, phenylpropanoid biosynthesis and hydroxycinnamic acid tyramine amide biosynthesis; the RNAi–SlPH line upregulated UDP-D-galacturonate biosynthesis I and free phenylpropanoid acid biosynthesis, but mainly downregulated pathways related to sugar metabolism, such as the glyoxylate cycle and L-arabinose degradation II. Comparison of C. gloeosporioides gene expression during colonization of the WT and RNAi–SlPH lines showed that the fungus upregulates ammonia and nitrogen transport and the gamma-aminobutyric acid metabolic process during colonization of the WT, while on the RNAi–SlPH tomato, it mainly upregulates the nitrate metabolic process. 


 Conclusions Modulation of tomato acidity and pH had significant phenotypic effects on C. gloeosporioides development. The fungus showed increased colonization on the neutral RNAi–SlPH fruit, and limited colonization on the WT acidic fruit. The change in environmental pH resulted in different defense responses for the two tomato lines. Interestingly, the WT line showed upregulation of jasmonate pathways and glutamate accumulation, supporting the reduced symptom development and increased ammonia accumulation, as the fungus might utilize glutamate to accumulate ammonia and increase environmental pH for better expression of pathogenicity factors. This was not found in the RNAi–SlPH line which downregulated sugar metabolism and upregulated the phenylpropanoid pathway, leading to host susceptibility.


Via Serenella A Sukno
more...
No comment yet.
Scooped by Steve Marek
Scoop.it!

Bark and wood tissues of American elm exhibit distinct responses to Dutch elm disease

Bark and wood tissues of American elm exhibit distinct responses to Dutch elm disease | Plant pathogenic fungi | Scoop.it
Tolerance to Dutch elm disease (DED) has been linked to the rapid and/or high induction of disease-responsive genes after infection with the fungus Ophiostoma novo-ulmi. Although the fungal infection by O. novo-ulmi primarily takes places in xylem vessels, it is still unclear how xylem contributes to the defense against DED. Taking advantage of the easy separation of wood and bark tissues in young American elm saplings, here we show that most disease-responsive genes exhibited higher expression in wood compared to bark tissues after fungal infection. On the other hand, the stress-related phytohormones were generally more abundant in the bark compared to wood tissues. However, only endogenous levels of jasmonates (JAs), but not salicylic acid (SA) and abscisic acid (ABA) increased in the inoculated tissues. This, along with the upregulation of JA-biosynthesis genes in inoculated bark and core tissues further suggest that phloem and xylem might contribute to the de novo biosynthesis of JA after fungal infection. The comparison between two tolerant elm varieties, ‘Valley Forge’ and ‘Princeton,’ also indicated that tolerance against DED might be mediated by different mechanisms in the xylem. The present study sheds some light on the amplitude and kinetics of defense responses produced in the xylem and phloem in response to DED.

more...
No comment yet.
Scooped by Steve Marek
Scoop.it!

ASMscience | Fungal Diversity Revisited: 2.2 to 3.8 Million Species

ASMscience | Fungal Diversity Revisited: 2.2 to 3.8 Million Species | Plant pathogenic fungi | Scoop.it

The question of how many species of Fungi there are has occasioned much speculation, with figures mostly posited from around half a million to 10 million, and in one extreme case even a sizable portion of the spectacular number of 1 trillion. Here we examine new evidence from various sources to derive an updated estimate of global fungal diversity. The rates and patterns in the description of new species from the 1750s show no sign of approaching an asymptote and even accelerated in the 2010s after the advent of molecular approaches to species delimitation. Species recognition studies of (semi-)cryptic species hidden in morpho-species complexes suggest a weighted average ratio of about an order of magnitude for the number of species recognized after and before such studies. New evidence also comes from extrapolations of plant:fungus ratios, with information now being generated from environmental sequence studies, including comparisons of molecular and fieldwork data from the same sites. We further draw attention to undescribed species awaiting discovery in biodiversity hot spots in the tropics, little-explored habitats (such as lichen-inhabiting fungi), and material in collections awaiting study. We conclude that the commonly cited estimate of 1.5 million species is conservative and that the actual range is properly estimated at 2.2 to 3.8 million. With 120,000 currently accepted species, it appears that at best just 8%, and in the worst case scenario just 3%, are named so far. Improved estimates hinge particularly on reliable statistical and phylogenetic approaches to analyze the rapidly increasing amount of environmental sequence data.

more...
No comment yet.
Rescooped by Steve Marek from Host-Microbe Interactions. Plant Biology.
Scoop.it!

A plant effector‐triggered immunity signaling sector is inhibited by pattern‐triggered immunity

A plant effector‐triggered immunity signaling sector is inhibited by pattern‐triggered immunity | Plant pathogenic fungi | Scoop.it

Since signaling machineries for two modes of plant‐induced immunity, pattern‐triggered immunity (PTI) and effector‐triggered immunity (ETI), extensively overlap, PTI and ETI signaling likely interact. In an Arabidopsis quadruple mutant, in which four major sectors of the signaling network, jasmonate, ethylene, PAD4, and salicylate, are disabled, the hypersensitive response (HR) typical of ETI is abolished when the Pseudomonas syringae effector AvrRpt2 is bacterially delivered but is intact when AvrRpt2 is directly expressed in planta . These observations led us to discovery of a network‐buffered signaling mechanism that mediates HR signaling and is strongly inhibited by PTI signaling. We named this mechanism the ETI‐Mediating and PTI‐Inhibited Sector (EMPIS). The signaling kinetics of EMPIS explain apparently different plant genetic requirements for ETI triggered by different effectors without postulating different signaling machineries. The properties of EMPIS suggest that information about efficacy of the early immune response is fed back to the immune signaling network, modulating its activity and limiting the fitness cost of unnecessary immune responses.


Via Tatsuya Nobori
more...
No comment yet.
Rescooped by Steve Marek from MycorWeb Plant-Microbe Interactions
Scoop.it!

Crystal structure of the Melampsora lini effector AvrP reveals insights into a possible nuclear function and recognition by the flax disease resistance protein P.

Crystal structure of the Melampsora lini effector AvrP reveals insights into a possible nuclear function and recognition by the flax disease resistance protein P. | Plant pathogenic fungi | Scoop.it
The effector protein AvrP is secreted by the flax rust fungal pathogen (Melampsora lini) and recognized specifically by the flax (Linum usitatissimum) P disease resistance protein, leading to effector-triggered immunity. To investigate the biological function of this effector and mechanisms of specific recognition by the P resistance protein, we determined the crystal structure of AvrP. The structure reveals an elongated zinc-finger-like structure with a novel interleaved zinc-binding topology. The residues responsible for zinc binding are conserved in AvrP effector variants and mutations of these motifs result in loss of P-mediated recognition. The first zinc-coordinating region of the structure displays a positively-charged surface and has some limited similarities to nucleic acid-binding and chromatin-associated proteins. We show that the majority of the AvrP protein accumulates in the plant nucleus when transiently expressed in Nicotiana benthamiana cells, suggesting a nuclear pathogenic function. Polymorphic residues in AvrP and its allelic variants map to the protein surface and could be associated with differences in recognition specificity. Several point mutations of residues on the non-conserved surface patch result in a loss-of-recognition by P, suggesting that these residues are required for recognition.

Via Francis Martin
more...
No comment yet.
Scooped by Steve Marek
Scoop.it!

Small secreted proteins from the necrotrophic conifer pathogen Heterobasidion annosum s.l . (HaSSPs) induce cell death in Nicotiana benthamiana

Small secreted proteins from the necrotrophic conifer pathogen Heterobasidion annosum s.l . (HaSSPs) induce cell death in Nicotiana benthamiana | Plant pathogenic fungi | Scoop.it
The basidiomycete Heterobasidion annosum sensu lato (s.l.) is considered to be one of the most destructive conifer pathogens in the temperate forests of the northern hemisphere. H. annosum is characterized by a dual fungal lifestyle. The fungus grows necrotrophically on living plant cells and saprotrophically on dead wood material. In this study, we screened the H. annosum genome for small secreted proteins (HaSSPs) that could potentially be involved in promoting necrotrophic growth during the fungal infection process. The final list included 58 HaSSPs that lacked predictable protein domains. The transient expression of HaSSP encoding genes revealed the ability of 8 HaSSPs to induce cell chlorosis and cell death in Nicotiana benthamiana. In particular, one protein (HaSSP30) could induce a rapid, strong, and consistent cell death within 2 days post-infiltration. HaSSP30 also increased the transcription of host-defence-related genes in N. benthamiana, which suggested a necrotrophic-specific immune response. This is the first line of evidence demonstrating that the H. annosum genome encodes HaSSPs with the capability to induce plant cell death in a non-host plant.

more...
No comment yet.
Scooped by Steve Marek
Scoop.it!

First Report of Virulence to Sr25 in Race TKTTF of Puccinia graminis f. sp. tritici Causing Stem Rust on Wheat | Plant Disease

First Report of Virulence to Sr25 in Race TKTTF of Puccinia graminis f. sp. tritici Causing Stem Rust on Wheat | Plant Disease | Plant pathogenic fungi | Scoop.it
Puccinia graminis f. sp. tritici (Pgt) race TKTTF was reported as the dominant race in the wheat stem rust epidemics in Ethiopia during 2014–15 (Olivera et al. 2015). The race and variants hereof have also been recorded elsewhere in Africa, the Middle East, and Europe (www.wheatrust.org/stem-rust-tools-maps-and-charts/race-frequency-map). Here, we report the presence of additional virulence to Sr25 in the TKTTF population, a resistance gene transferred to several Australian and CIMMYT wheat genotypes. At the seedling stage, Sr25 confers infection type (IT) 2 or lower for isolates in the Ug99 race group and up to IT 2+ toward race TKTTF (Newcomb et al. 2016; Olivera et al. 2015). Our results are based on Pgt isolates of the TKTTF race from Ethiopia (2012, 2013, 2015), Egypt (2014), Azerbaijan (2014), Iran (2009, 2011, 2014), Iraq (2014), Lebanon, Sudan, and Turkey (2012), Denmark and Germany (2013), and Sweden (2014). Race typing was carried out at the Global Rust Reference Center according to Jin et al. (2008), except that we scored IT on both leaf 1 and 2; additional single pustule isolates of each sample were raised and stored in liquid nitrogen (–196°C). Sr25 response was assayed using seedling leaves and stems of adult plants of Misr1 (Oasis/Skauz//4*BCN/3/2*Pastor) and Agatha/9*LMPG (Sr25 carriers) along with two reference lines, Triumph 64 (SrTmp) and NA101/MqSr7a (Sr7a), and Morocco as a control. Seedling ITs were scored 17 days post-inoculation at 18 ± 2°C using a 0 to 4 scale (McIntosh et al. 1995). Isolates showing ITs of 33+ to 4 on Misr1, Agatha/9*LMPG, and susceptible check were considered Sr25 virulent, and clearly different from ITs conferred by Sr25 avirulent isolates. Results were confirmed for each isolate by race typing additional single-pustule isolates derived from cultivars Misr1 and/or Agatha, along with avirulent reference isolates. Virulence for Sr25 was observed in race TKTTF isolates from Azerbaijan, Egypt, Ethiopia, Iran, Iraq, and Sweden, collected in 2014 or 2015, but not in any sample collected earlier than 2014. The results were confirmed on adult plants of Misr1 and Agatha/9*LMPG by Sr25 virulent and avirulent isolates of TKTTF, TTKSK, and TTKST, respectively. Spore suspensions of ∼0.5 ml at concentration of ∼3 × 105 spores/ml were injected into the stem internodes at Zadoks 45. The adult plant and seedling tests were carried out concurrently using the environmental conditions described above. The plants containing Sr25 were susceptible to the Sr25 virulent isolate and moderately resistant to moderately susceptible to the Sr25-avirulent isolates of TKTTF, TTKSK, and TTKST. The experiments were repeated two times with three replicates, using cv. Morocco as a susceptible check. Emergence of virulence to Sr25 in the race TKTTF is considered significant due to its spread into new areas and the potential loss of a significant source of resistance against Ug99.

more...
No comment yet.
Scooped by Steve Marek
Scoop.it!

A genome Tree of Life for the Fungi kingdom

A genome Tree of Life for the Fungi kingdom | Plant pathogenic fungi | Scoop.it
Fungi belong to one of the largest and most diverse groups of living organisms. The evolutionary kinship within a fungal population has so far been inferred mostly from the gene-information–based trees (“gene trees”) constructed using a small number of genes. Since each gene evolves under different evolutionary pressure and time scale, it has been known that one gene tree for a population may differ from other gene trees for the same population, depending on the selection of the genes. We present whole-genome information-based trees (“genome trees”) using a variation of a computational algorithm developed to find plagiarism in two books, where we represent a whole-genomic information of an organism as a book of words without spaces.

Abstract
Fungi belong to one of the largest and most diverse kingdoms of living organisms. The evolutionary kinship within a fungal population has so far been inferred mostly from the gene-information–based trees (“gene trees”), constructed commonly based on the degree of differences of proteins or DNA sequences of a small number of highly conserved genes common among the population by a multiple sequence alignment (MSA) method. Since each gene evolves under different evolutionary pressure and time scale, it has been known that one gene tree for a population may differ from other gene trees for the same population depending on the subjective selection of the genes. Within the last decade, a large number of whole-genome sequences of fungi have become publicly available, which represent, at present, the most fundamental and complete information about each fungal organism. This presents an opportunity to infer kinship among fungi using a whole-genome information-based tree (“genome tree”). The method we used allows comparison of whole-genome information without MSA, and is a variation of a computational algorithm developed to find semantic similarities or plagiarism in two books, where we represent whole-genomic information of an organism as a book of words without spaces. The genome tree reveals several significant and notable differences from the gene trees, and these differences invoke new discussions about alternative narratives for the evolution of some of the currently accepted fungal groups.
more...
Steve Marek's comment, August 17, 12:55 PM
I would have liked to have seen how this approach places Fungi in the broader eukaryotic tree of life; first within the opisthokonts (w/ Metazoa and Amoebozoa) and then with representatives of the other main euk lineages.
Bridget Barker's comment, August 17, 1:02 PM
Good point Steve, I think that is the major issue with the analysis. I'm going to look into the scripts closer too. I think it's an interesting idea, and I'm always open to new approaches that can lead us to a better understanding of deeper phylogenetic relationships. But yeah, I won't be changing my FTOL slide just yet ;)
WillistonPlantPath's comment, August 17, 5:00 PM
Intuitively I think it makes more sense to use the whole proteome or genome to construct phylogenetic trees rather than single genes, or even a few genes in combination. Whether this is the best way to go about it remains to be seen.
Rescooped by Steve Marek from Host-Microbe Interactions. Plant Biology.
Scoop.it!

Membrane Trafficking in Plant Immunity

Membrane Trafficking in Plant Immunity | Plant pathogenic fungi | Scoop.it
Plants use sophisticated immune mechanisms to confer resistance against pathogens.
Targeted protein transport and coordinated membrane dynamics are involved in almost
every key step of plant immunity, including pathogen perception, receptor signaling,
and defense execution. We provide a critical analysis on the essential roles of two
major membrane trafficking pathways, the secretory and the endocytic pathways, in
activation of plant immunity.

Via Tatsuya Nobori
more...
No comment yet.
Scooped by Steve Marek
Scoop.it!

Molecular Characterization of Australian Isolates of Puccinia graminis f. sp. tritici Supports Long-Term Clonality but also Reveals Cryptic Genetic Variation | Phytopathology

Molecular Characterization of Australian Isolates of Puccinia graminis f. sp. tritici Supports Long-Term Clonality but also Reveals Cryptic Genetic Variation | Phytopathology | Plant pathogenic fungi | Scoop.it
Long-term surveys of pathogenicity in Puccinia graminis f. sp. tritici in Australia have implicated mutation as a major source of virulence, at times leading to the demise of stem-rust-resistant wheat cultivars and substantial yield losses. Since 1925, these surveys have identified at least four occasions on which exotic isolates of P. graminis f. sp. tritici appeared in Australia, with each acting as a founding isolate that gave rise sequentially to derivative pathotypes via presumed single-step mutation. The current study examined the relationship between virulence and molecular patterns using simple-sequence repeat (SSR) markers on selected isolates of P. graminis f. sp. tritici collected in Australia during a 52-year period in order to propose an evolutionary pathway involving these isolates. Studies of SSR variability among this collection of isolates within a putative clonal lineage based on pathotype 21-0, first detected in 1954 (the “21/34 lineage”), provided compelling evidence of clonality over the 52-year period, coupled with single-step acquisition of virulence for resistance genes. It also supported the postulation that two triticale-attacking pathotypes (34-2,12 and 34-2,12,13) detected in the early 1980s were derived from pathotype 21-0 via stepwise sequential acquisition of virulence for Sr5, Sr11, Sr27, and then SrSatu. Some of the isolates examined that were regarded as members of the race 21/34 lineage based on pathogenicity differed significantly in their SSR genotypes, indicating that they may have originated from processes more complex than simple mutation. This included two isolates of pathotype 21-0, which were collected in 1994 and 2006. Given that sexual recombination in P. graminis is rare or absent in Australia, the cryptic complexity observed could indicate that one or more of these isolates arose as a consequence of asexual recombination.

more...
No comment yet.
Rescooped by Steve Marek from Human Fungal Pathogens
Scoop.it!

Evolution and genome architecture in fungal plant pathogens - Nature Reviews Microbiology

Evolution and genome architecture in fungal plant pathogens - Nature Reviews Microbiology | Plant pathogenic fungi | Scoop.it
The fungal kingdom comprises some of the most devastating plant pathogens. Sequencing the genomes of fungal pathogens has shown a remarkable variability in genome size and architecture. Population genomic data enable us to understand the mechanisms and the history of changes in genome size and adaptive evolution in plant pathogens. Although transposable elements predominantly have negative effects on their host, fungal pathogens provide prominent examples of advantageous associations between rapidly evolving transposable elements and virulence genes that cause variation in virulence phenotypes. By providing homogeneous environments at large regional scales, managed ecosystems, such as modern agriculture, can be conducive for the rapid evolution and dispersal of pathogens. In this Review, we summarize key examples from fungal plant pathogen genomics and discuss evolutionary processes in pathogenic fungi in the context of molecular evolution, population genomics and agriculture.

Via Ronny Kellner, Bridget Barker
more...
No comment yet.
Scooped by Steve Marek
Scoop.it!

Ethylene Signaling Is Important for Isoflavonoid-Mediated Resistance to Rhizoctonia solani in Roots of Medicago truncatula | Molecular Plant-Microbe Interactions

Ethylene Signaling Is Important for Isoflavonoid-Mediated Resistance to Rhizoctonia solani in Roots of Medicago truncatula | Molecular Plant-Microbe Interactions | Plant pathogenic fungi | Scoop.it
The root-infecting necrotrophic fungal pathogen Rhizoctoniasolani causes significant disease to all the world’s major food crops. As a model for pathogenesis of legumes, we have examined the interaction of R. solani AG8 with Medicago truncatula. RNAseq analysis of the moderately resistant M. truncatula accession A17 and highly susceptible sickle (skl) mutant (defective in ethylene sensing) identified major early transcriptional reprogramming in A17. Responses specific to A17 included components of ethylene signaling, reactive oxygen species metabolism, and consistent upregulation of the isoflavonoid biosynthesis pathway. Mass spectrometry revealed accumulation of the isoflavonoid-related compounds liquiritigenin, formononetin, medicarpin, and biochanin A in A17. Overexpression of an isoflavone synthase in M. truncatula roots increased isoflavonoid accumulation and resistance to R. solani. Addition of exogenous medicarpin suggested this phytoalexin may be one of several isoflavonoids required to contribute to resistance to R. solani. Together, these results provide evidence for the role of ethylene-mediated accumulation of isoflavonoids during defense against root pathogens in legumes. The involvement of ethylene signaling and isoflavonoids in the regulation of both symbiont-legume and pathogen-legume interactions in the same tissue may suggest tight regulation of these responses are required in the root tissue.

more...
No comment yet.
Rescooped by Steve Marek from MycorWeb Plant-Microbe Interactions
Scoop.it!

Evolutionary biology through the lens of budding yeast comparative genomics

Evolutionary biology through the lens of budding yeast comparative genomics | Plant pathogenic fungi | Scoop.it
The budding yeast Saccharomyces cerevisiae is a highly advanced model system for studying genetics, cell biology and systems biology. Over the past decade, the application of high-throughput sequencing technologies to this species has contributed to this yeast also becoming an important model for evolutionary genomics. Indeed, comparative genomic analyses of laboratory, wild and domesticated yeast populations are providing unprecedented detail about many of the processes that govern evolution, including long-term processes, such as reproductive isolation and speciation, and short-term processes, such as adaptation to natural and domestication-related environments.

Via Francis Martin
more...
No comment yet.
Scooped by Steve Marek
Scoop.it!

Plant response to butterfly eggs: inducibility, severity and success of egg-killing leaf necrosis depends on plant genotype and egg clustering

Plant response to butterfly eggs: inducibility, severity and success of egg-killing leaf necrosis depends on plant genotype and egg clustering | Plant pathogenic fungi | Scoop.it
Plants employ various defences killing the insect attacker in an early stage. Oviposition by cabbage white butterflies (Pieris spp.) on brassicaceous plants, including Brassica nigra, induces a hypersensitive response (HR) - like leaf necrosis promoting desiccation of eggs. To gain a deeper insight into the arms race between butterflies and plants, we conducted field and greenhouse experiments using different B. nigra genotypes. We investigated variation in HR and consequent survival of P. brassicae egg clusters. Impact of egg density, distribution type and humidity on HR formation and egg survival was tested. HR differed among plant genotypes as well as plant individuals. Egg density per plant did not affect HR formation. Remarkably, egg survival did not depend on the formation of HR, unless butterflies were forced to lay single eggs. Larval hatching success from single eggs was lower on plants expressing HR. This may be due to increased vulnerability of single eggs to low humidity conditions at necrotic leaf sites. We conclude that effectiveness of HR-like necrosis in B. nigra varies with plant genotype, plant individual and the type of egg laying behaviour (singly or clustered). By clustering eggs, cabbage white butterflies can escape the egg-killing, direct plant defence trait.

more...
No comment yet.