Fusarium and wheat
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Fungal pathogen uses sex pheromone receptor for chemotropic sensing of host plant signals : Nature

Fungal pathogen uses sex pheromone receptor for chemotropic sensing of host plant signals : Nature | Fusarium and wheat | Scoop.it
For more than a century, fungal pathogens and symbionts have been known to orient hyphal growth towards chemical stimuli from the host plant. However, the nature of the plant signals as well as the mechanisms underlying the chemotropic response have remained elusive. Here we show that directed growth of the soil-inhabiting plant pathogen Fusarium oxysporum towards the roots of the host tomato (Solanum lycopersicum) is triggered by the catalytic activity of secreted class III peroxidases, a family of haem-containing enzymes present in all land plants. The chemotropic response requires conserved elements of the fungal cell integrity mitogen-activated protein kinase (MAPK) cascade and the seven-pass transmembrane protein Ste2, a functional homologue of the Saccharomyces cerevisiae sex pheromone α receptor. We further show that directed hyphal growth of F. oxysporum towards nutrient sources such as sugars and amino acids is governed by a functionally distinct MAPK cascade. These results reveal a potentially conserved chemotropic mechanism in root-colonizing fungi, and suggest a new function for the fungal pheromone-sensing machinery in locating plant hosts in a complex environment such as the soil.

Via Francis Martin
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Transgenic Wheat Expressing a Barley UDP-Glucosyltransferase Detoxifies Deoxynivalenol and Provides High Levels of Resistance to Fusarium graminearum — Molecular Plant-Microbe Interactions

Fusarium head blight (FHB), mainly caused by Fusarium graminearum, is a devastating disease of wheat that results in economic losses worldwide. During infection, F. graminearum produces trichothecene mycotoxins, including deoxynivalenol (DON), that increase fungal virulence and reduce grain quality. Transgenic wheat expressing a barley UDP-glucosyltransferase (HvUGT13248) were developed and evaluated for FHB resistance, DON accumulation, and the ability to metabolize DON to the less toxic DON-3-O-glucoside (D3G). Point-inoculation tests in the greenhouse showed that transgenic wheat carrying HvUGT13248 exhibited significantly higher resistance to disease spread in the spike (type II resistance) compared with nontransformed controls. Two transgenic events displayed complete suppression of disease spread in the spikes. Expression of HvUGT13248 in transgenic wheat rapidly and efficiently conjugated DON to D3G, suggesting that the enzymatic rate of DON detoxification translates to type II resistance. Under field conditions, FHB severity was variable; nonetheless, transgenic events showed significantly less-severe disease phenotypes compared with the nontransformed controls. In addition, a seedling assay demonstrated that the transformed plants had a higher tolerance to DON-inhibited root growth than nontransformed plants. These results demonstrate the utility of detoxifying DON as a FHB control strategy in wheat.

Via Christophe Jacquet
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Fusarium graminearum produces different xylanases causing host cell death that is prevented by the xylanase inhibitors XIP-I and TAXI-III in wheat

Fusarium graminearum produces different xylanases causing host cell death that is prevented by the xylanase inhibitors XIP-I and TAXI-III in wheat | Fusarium and wheat | Scoop.it
Highlights



Fusarium graminearum xylanases induce cell death in wheat cell cultures and in planta.


F. graminearum xylanases of GH 10 and GH 11 families induce host cell death.


The capacity to induce cell death and catalytic activity are unrelated features.


TAXI-III and XIP-I inhibit catalytic activity and host cell death caused by xylanases.


TAXI-III and XIP-I plants prevent cell death symptoms caused by xylanases.

Abstract

To shed light on the role of Xylanase Inhibitors (XIs) during Fusarium graminearum infection, we first demonstrated that three out of four F. graminearum xylanases, in addition to their xylan degrading activity, have also the capacity to cause host cell death both in cell suspensions and wheat spike tissue.

Subsequently, we demonstrated that TAXI-III and XIP-I prevented both the enzyme and host cell death activities of F. graminearum xylanases. In particular, we showed that the enzymatic inhibition by TAXI-III and XIP-I was competitive and only FGSG_11487 escaped inhibition.

The finding that TAXI-III and XIP-I prevented cell death activity of heat inactivated xylanases and that XIP-I precluded the cell death activity of FGSG_11487 – even if XIP-I does not inhibit its enzyme activity – suggests that the catalytic and the cell death activities are separated features of these xylanases.

Finally, the efficacy of TAXI-III or XIP-I to prevent host cell death caused by xylanases was confirmed in transgenic plants expressing separately these inhibitors, suggesting that the XIs could limit F. graminearum infection via direct inhibition of xylanase activity and/or by preventing host cell death.

Via Christophe Jacquet
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Thyme essential oil as a defense inducer of tomato against gray mold and Fusarium wilt

Thyme essential oil as a defense inducer of tomato against gray mold and Fusarium wilt | Fusarium and wheat | Scoop.it
“ Highlights • Thyme oil highly reduced 64% of gray mold incidence in tomato plants. • Thyme oil reduced Fusarium wilt severity to 30.76% in tomato plants grown in hydroponic system. • Thyme oil induced plant defense system which was mostly attributed to peroxidases accumulation. • Thyme oil seems to be more effective when applied to the roots. Abstract The potential of thyme essential oil in controlling gray mold and Fusarium wilt and inducing systemic acquired resistance in tomato seedlings and tomato grown in hydroponic system was evaluated. Thyme oil highly reduced 64% of Botrytis cinerea colonization on pretreated detached leaves compared to untreated control. Also, it played a significant decrease in Fusarium wilt severity especially at7 days post treatment when it was reduced to 30.76%. To explore the plant pathways triggered in response to thyme oil, phenolic compounds accumulation and peroxidase activity was investigated. Plant response was observed either after foliar spray or root feeding in hydroponics which was mostly attributed to peroxidases accumulation rather than phenolic compounds accumulation, and thyme oil seems to be more effective when applied to the roots.”
Via Christophe Jacquet
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The omics era of Fusarium graminearum: opportunities and challenges

The omics era of Fusarium graminearum: opportunities and challenges | Fusarium and wheat | Scoop.it
“ How do plant pathogens colonize their hosts is a key question in the field of plant pathology. Secreted effectors, hydrolytic enzymes, toxins and even small RNAs can be deployed as the virulence or pathogenicity factors to interfere with the host immune responses. But still there are more complicated systems to command and coordinate in their arsenal. The plant pathogen Fusarium graminearum can have devastating effects causing yield loss of various cereal crops and contaminating grain with mycotoxins that are harmful to the health of humans and livestock (Rocha et al., 2005). Given the economic importance of this pathogen, F. graminearum is currently under intense investigation and is becoming a model organism to study filamentous fungal cell biology, fungal–plant interactions and secondary metabolism. In this issue of New Phytologist, Yun et al. (pp. 119–134) contribute to our knowledge of the function of the F. graminearum phosphatome in hyphal growth, development, virulence and secondary metabolism by the omics level gene deletion and phenomic description (in line with the definition of kinome, phosphatome is the complete set of phosphatases of an organism, and the reversible protein phosphorylation is involved in the regulation of various life processes). Three phosphatases were identified as negative regulators of mitogen-activated protein kinase (MAPK) pathways.”
Via Francis Martin
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Reduced susceptibility to Fusarium head blight in Brachypodium distachyon through priming with the Fusarium mycotoxin deoxynivalenol

Reduced susceptibility to Fusarium head blight in Brachypodium distachyon through priming with the Fusarium mycotoxin deoxynivalenol | Fusarium and wheat | Scoop.it
“ The fungal cereal pathogen Fusarium graminearum produces deoxynivalenol (DON) during infection. The mycotoxin DON is associated with Fusarium head blight (FHB), a disease that can cause vast grain losses. Whilst investigating the suitability of Brachypodium distachyon as a model for spreading resistance to F. graminearum, we unexpectedly discovered that DON pretreatment of spikelets could reduce susceptibility to FHB in this model grass. We started to analyse the cell wall changes in spikelets after infection with F. graminearum wild-type and defined mutants: the DON-deficient Δtri5 mutant and the DON-producing lipase disruption mutant Δfgl1, both infecting only directly inoculated florets, and the mitogen-activated protein (MAP) kinase disruption mutant Δgpmk1, with strongly decreased virulence but intact DON production. At 14 days post-inoculation, the glucose amounts in the non-cellulosic cell wall fraction were only increased in spikelets infected with the DON-producing strains wild-type, Δfgl1 and Δgpmk1. Hence, we tested for DON-induced cell wall changes in B. distachyon, which were most prominent at DON concentrations ranging from 1 to 100 ppb. To test the involvement of DON in defence priming, we pretreated spikelets with DON at a concentration of 1 ppm prior to F. graminearum wild-type infection, which significantly reduced FHB disease symptoms. The analysis of cell wall composition and plant defence-related gene expression after DON pretreatment and fungal infection suggested that DON-induced priming of the spikelet tissue contributed to the reduced susceptibility to FHB.”
Via Christophe Jacquet
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Frontiers | FocVel1 influences asexual production, filamentous growth, biofilm formation, and virulence in Fusarium oxysporum f. sp. cucumerinum | Plant-Microbe Interaction

Frontiers | FocVel1 influences asexual production, filamentous growth, biofilm formation, and virulence in Fusarium oxysporum f. sp. cucumerinum | Plant-Microbe Interaction | Fusarium and wheat | Scoop.it
“ Velvet genes play critical roles in the regulation of diverse cellular processes. In current study, we identified the gene FocVel1, a homolog of Fusarium graminearum VelA, in the plant pathogenic fungus F. oxysporum f. sp. cucumerinum. This pathogen causes the destructive disease called cucumber Fusarium wilt, which severely affects the production and marketing of this vegetable worldwide. Transcript analyses revealed high expression of FocVel1 during conidiophore development. Disruption of the FocVel1 gene led to several phenotypic defects, including reduction in aerial hyphal formation and conidial production. The deletion mutant ⊿FocVel1 showed increased resistance to both osmotic stress and cell wall-damaging agents, but increased sensitivity to iprodione and prochloraz fungicides, which may be related to changes in cell wall components. In the process of biofilm formation in vitro, the mutant strain ⊿FocVel1 displayed not only a reduction in spore aggregation but also a delay in conidial germination on the polystyrene surface, which may result in defects in biofilm formation. Moreover, pathogenicity assays showed that the mutant ⊿FocVel1 exhibited impaired virulence in cucumber seedlings. And the genetic complementation of the mutant with the wild-type FocVel1 gene restored all the defects of the ⊿FocVel1. Taken together, the results of this study indicated that FocVel1 played a critical role in the regulation of various cellular processes and pathogenicity in F. oxysporum f. sp. cucumerinum.”
Via Christophe Jacquet
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Brachypodium distachyon–Cochliobolus sativus Pathosystem is a New Model for Studying Plant–Fungal ...

Brachypodium distachyon–Cochliobolus sativus Pathosystem is a New Model for Studying Plant–Fungal  ... | Fusarium and wheat | Scoop.it
“ Cochliobolus sativus (anamorph: Bipolaris sorokiniana) causes spot blotch, common root rot, and kernel blight or black point in barley and wheat. However, little is known about the molecular mechanisms underlying the pathogenicity of C. sativus or the molecular basis of resistance and susceptibility in the hosts. This study aims to establish the model grass Brachypodium distachyon as a new model for studying plant–fungus interactions in cereal crops. Six B. distachyon lines were inoculated with five C. sativus isolates. The results indicated that all six B. distachyon lines were infected by the C. sativus isolates, with their levels of resistance varying depending on the fungal isolates used. Responses ranging from hypersensitive response-mediated resistance to complete susceptibility were observed in a large collection of B. distachyon (2n = 2x = 10) and B. hybridum (2n = 4x = 30) accessions inoculated with four of the C. sativus isolates. Evaluation of an F2 population derived from the cross between two of the B. distachyon lines, Bd1-1 and Bd3-1, with isolate Cs07-47-1 showed quantitative and transgressive segregation for resistance to C. sativus, suggesting that the resistance may be governed by quantitative trait loci from both parents. The availability of whole-genome sequences of both the host (B. distachyon) and the pathogen (C. sativus) makes this pathosystem an attractive model for studying this important disease of cereal crops.”
Via Christophe Jacquet
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New Phytologist: The tomato I-3 gene: a novel gene for resistance to Fusarium wilt disease - Catanzariti (2015)

New Phytologist: The tomato I-3 gene: a novel gene for resistance to Fusarium wilt disease - Catanzariti (2015) | Fusarium and wheat | Scoop.it
- Plant resistance proteins provide race-specific immunity through the recognition of pathogen effectors. The resistance genes I, I-2 and I-3 have been incorporated into cultivated tomato (Solanum lycopersicum) from wild tomato species to confer resistance against Fusarium oxysporum f. sp. lycopersici (Fol) races 1, 2 and 3, respectively. Although the Fol effectors corresponding to these resistance genes have all been identified, only the I-2 resistance gene has been isolated from tomato. - To isolate the I-3 resistance gene, we employed a map-based cloning approach and used transgenic complementation to test candidate genes for resistance to Fol race 3. - Here, we describe the fine mapping and sequencing of genes at the I-3 locus, which revealed a family of S-receptor-like kinase (SRLK) genes. Transgenic tomato lines were generated with three of these SRLK genes and one was found to confer Avr3-dependent resistance to Fol race 3, confirming it to be I-3. - The finding that I-3 encodes an SRLK reveals a new pathway for Fol resistance and a new class of resistance genes, of which Pi-d2from rice is also a member. The identification of I-3 also allows the investigation of the complex effector–resistance protein interaction involving Avr1-mediated suppression of I-2- and I-3-dependent resistance in tomato.
Via Kamoun Lab @ TSL
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Functional analysis of the Fusarium graminearum phosphatome

Phosphatases are known to play important roles in the regulation of various cellular processes in eukaryotes. However, systematic characterization of the phosphatome has not been reported in phytopathogenic fungi.The wheat scab fungus Fusarium graminearum contains 82 putative phosphatases. The biological functions of each phosphatase were investigated in this study.Although 11 phosphatase genes appeared to be essential, deletion mutants of the other 71 phosphatase genes were obtained and characterized for changes in 15 phenotypes, including vegetative growth, nutrient response and virulence. Overall, the deletion of 63 phosphatase genes resulted in changes in at least one of the phenotypes assayed. Interestingly, the deletion of four genes (Fg06297,Fg03333, Fg03826 and Fg07932) did not dramatically affect hyphal growth, but led to strongly reduced virulence. Western blot analyses showed that three phosphatases (Fg10516, Fg03333 and Fg12867) functioned as negative regulators of the mitogen-activated protein kinase signaling pathways. In addition, we found, for the first time, that FgCdc14 is dispensable for growth, but plays an important role in ribosome biogenesis.Overall, in this first functional characterization of the fungal phosphatome, phosphatases important for various aspects of hyphal growth, development, plant infection and secondary metabolism were identified in the phytopathogenic fungus F. graminearum.
Via Francis Martin
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The F-box protein Fbp1 functions in the invasive growth and cell wall integrity MAPK pathways in Fusarium oxysporum -

The F-box protein Fbp1 functions in the invasive growth and cell wall integrity MAPK pathways in Fusarium oxysporum - | Fusarium and wheat | Scoop.it
“ F-box proteins determine substrate specificity of the ubiquitin-proteasome sytem. Previous work demonstrated that the F-box protein Fbp1, a component of the SCFFbp1 E3 ligase complex, is essential for invasive growth and virulence of the fungal plant pathogen Fusarium oxysporum. Here we show that besides invasive growth, Fbp1 also contributes to vegetative hyphal fusion and fungal adhesion to tomato roots. All these functions were previously shown to require the mitogen-activated protein kinase (MAPK) Fmk1. We found that Fbp1 is required for full phosphorylation of Fmk1, indicating that Fbp1 regulates virulence and invasive growth via the Fmk1 pathway. Moreover the Δfbp1 mutant was hypersensitive to sodium dodecyl sulfate (SDS) and calcofluor white (CFW) and showed reduced phosphorylation levels of the cell wall integrity MAPK Mpk1 after SDS treatment. Collectively, these results suggest that Fbp1 contributes both to the invasive growth and the cell wall integrity MAPK pathways of F. oxysporum.”
Via Christophe Jacquet
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Fusarium oxysporum Triggers Tissue-Specific Transcriptional Reprogramming in Arabidopsis thaliana

Fusarium oxysporum  Triggers Tissue-Specific Transcriptional Reprogramming in  Arabidopsis thaliana | Fusarium and wheat | Scoop.it
“ Some of the most devastating agricultural diseases are caused by root-infecting pathogens, yet the majority of studies on these interactions to date have focused on the host responses of aerial tissues rather than those belowground. Fusarium oxysporum is a root-infecting pathogen that causes wilt disease on several plant species including Arabidopsis thaliana. To investigate and compare transcriptional changes triggered by F. oxysporum in different Arabidopsis tissues, we infected soil-grown plants with F. oxysporum and subjected root and leaf tissue harvested at early and late timepoints to RNA-seq analyses. At least half of the genes induced or repressed by F. oxysporum showed tissue-specific regulation. Regulators of auxin and ABA signalling, mannose binding lectins and peroxidases showed strong differential expression in root tissue. We demonstrate that ARF2 and PRX33, two genes regulated in the roots, promote susceptibility to F. oxysporum. In the leaves, defensins and genes associated with the response to auxin, cold and senescence were strongly regulated while jasmonate biosynthesis and signalling genes were induced throughout the plant.”
Via Christophe Jacquet
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Brachypodium as an emerging model for cereal–pathogen interactions

Brachypodium as an emerging model for cereal–pathogen interactions | Fusarium and wheat | Scoop.it
“ Abstract Background Cereal diseases cause tens of billions of dollars of losses annually and have devastating humanitarian consequences in the developing world. Increased understanding of the molecular basis of cereal host–pathogen interactions should facilitate development of novel resistance strategies. However, achieving this in most cereals can be challenging due to large and complex genomes, long generation times and large plant size, as well as quarantine and intellectual property issues that may constrain the development and use of community resources. Brachypodium distachyon (brachypodium) with its small, diploid and sequenced genome, short generation time, high transformability and rapidly expanding community resources is emerging as a tractable cereal model. Scope Recent research reviewed here has demonstrated that brachypodium is either susceptible or partially susceptible to many of the major cereal pathogens. Thus, the study of brachypodium–pathogen interactions appears to hold great potential to improve understanding of cereal disease resistance, and to guide approaches to enhance this resistance. This paper reviews brachypodium experimental pathosystems for the study of fungal, bacterial and viral cereal pathogens; the current status of the use of brachypodium for functional analysis of cereal disease resistance; and comparative genomic approaches undertaken using brachypodium to assist characterization of cereal resistance genes. Additionally, it explores future prospects for brachypodium as a model to study cereal–pathogen interactions. Conclusions The study of brachypodium–pathogen interactions appears to be a productive strategy for understanding mechanisms of disease resistance in cereal species. Knowledge obtained from this model interaction has strong potential to be exploited for crop improvement.”
Via Christophe Jacquet
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The exocyst complex: delivery hub for morphogenesis and pathogenesis in filamentous fungi

The exocyst complex: delivery hub for morphogenesis and pathogenesis in filamentous fungi | Fusarium and wheat | Scoop.it

Highlights



Localization of exocyst components differs at the point of polarized growth.


The Spitzenkörper has evolved during speciation to optimize hyphal growth.


The exocyst is used in different pathways to deliver effectors to plant cells.


Fungi have evolved different secretory routes and/or regulatory mechanisms.

Regulated by several small GTPases, the octameric exocyst complex directs the docking and tethering of exocytic vesicles to the destined plasma membrane sites, providing the precise spatiotemporal control of exocytosis. Although the exocyst components are well conserved among various fungal species, the mechanisms for the regulation of its assembly and activity are diverse. Exocytosis is crucial for the generation of cell polarity as well as the delivery of effector proteins in filamentous fungi, and thus plays an important role for fungal morphogenesis and pathogenicity on plant hosts. This review focuses on current findings about the roles of the exocyst complex in the morphogenesis and pathogenesis of filamentous fungi.


Via Christophe Jacquet
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Intraspecies Interaction of Fusarium graminearum Contributes to Reduced Toxin Production and Virulence — Molecular Plant-Microbe Interactions

Fusarium graminearum is a pathogenic fungus that causes Fusarium head blight in wheat and lowers the yield and quality of grains by contamination with the trichothecene mycotoxin deoxynivalenol. The fungi coexist and interact with several different fusaria as well as other plant pathogenic fungi and bacteria in the field. In Canada, F. graminearum exists as two main trichothecene chemotypes: 3-acetyldeoxynivalenol and 15-acetyldeoxynivalenol. To understand the potential interactions between two isolates of these chemotypes, we conducted coinoculation studies both in culture and in planta. The studies showed that intraspecies interaction reduces trichothecene yield in culture and disease symptoms in wheat. To elucidate the genes involved in the intraspecies interaction, expression profiling was performed on RNA samples isolated from coinoculated cultures, and potential genes were identified by using the genome sequences of the respective isolates.

Via Christophe Jacquet
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The omics era of Fusarium graminearum: opportunities and challengesNew Phytologist

The omics era of Fusarium graminearum: opportunities and challengesNew Phytologist | Fusarium and wheat | Scoop.it
“ How do plant pathogens colonize their hosts is a key question in the field of plant pathology. Secreted effectors, hydrolytic enzymes, toxins and even small RNAs can be deployed as the virulence or pathogenicity factors to interfere with the host immune responses. But still there are more complicated systems to command and coordinate in their arsenal. The plant pathogen Fusarium graminearum can have devastating effects causing yield loss of various cereal crops and contaminating grain with mycotoxins that are harmful to the health of humans and livestock (Rocha et al., 2005). Given the economic importance of this pathogen, F. graminearum is currently under intense investigation and is becoming a model organism to study filamentous fungal cell biology, fungal–plant interactions and secondary metabolism. In this issue of New Phytologist, Yun et al. (pp. 119–134) contribute to our knowledge of the function of the F. graminearum phosphatome in hyphal growth, development, virulence and secondary metabolism by the omics level gene deletion and phenomic description (in line with the definition of kinome, phosphatome is the complete set of phosphatases of an organism, and the reversible protein phosphorylation is involved in the regulation of various life processes). Three phosphatases were identified as negative regulators of mitogen-activated protein kinase (MAPK) pathways. ‘Although many genes are involved in fungal–plant interactions, gene redundancy and functional comple-mentation make assigning definitive roles in virulence to be a challenging task.’”
Via Christophe Jacquet
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The omics era of Fusarium graminearum: opportunities and challenges

The omics era of Fusarium graminearum: opportunities and challenges | Fusarium and wheat | Scoop.it
“ How do plant pathogens colonize their hosts is a key question in the field of plant pathology. Secreted effectors, hydrolytic enzymes, toxins and even small RNAs can be deployed as the virulence or pathogenicity factors to interfere with the host immune responses. But still there are more complicated systems to command and coordinate in their arsenal. The plant pathogen Fusarium graminearum can have devastating effects causing yield loss of various cereal crops and contaminating grain with mycotoxins that are harmful to the health of humans and livestock (Rocha et al., 2005). Given the economic importance of this pathogen, F. graminearum is currently under intense investigation and is becoming a model organism to study filamentous fungal cell biology, fungal–plant interactions and secondary metabolism. In this issue of New Phytologist, Yun et al. (pp. 119–134) contribute to our knowledge of the function of the F. graminearum phosphatome in hyphal growth, development, virulence and secondary metabolism by the omics level gene deletion and phenomic description (in line with the definition of kinome, phosphatome is the complete set of phosphatases of an organism, and the reversible protein phosphorylation is involved in the regulation of various life processes). Three phosphatases were identified as negative regulators of mitogen-activated protein kinase (MAPK) pathways.”
Via Francis Martin
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PLOS Pathogens: Advances and Challenges in Computational Prediction of Effectors from Plant Pathogenic Fungi

PLOS Pathogens: Advances and Challenges in Computational Prediction of Effectors from Plant Pathogenic Fungi | Fusarium and wheat | Scoop.it

With the rising number of sequenced pathogen genomes, computational prediction of effector proteins holds promise as a fast and economical technique to define candidates for subsequent laboratory work. Bacterial effectors delivered to the host via dedicated pathogen-derived delivery mechanisms, such as the type III secretion system, can be predicted using machine learning approaches based on protein sequence information. In oomycetes, consensus sequence motifs implicated in host translocation, such as RXLR, can be exploited for effector prediction. However, computational effector prediction in fungi is challenging due to a lack of known protein features that are common to fungal effectors and the low number of characterized effectors for individual species, which limits the use of machine learning approaches.


Via Bradford Condon, Francis Martin
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Molecular Plant Pathology: Effector discovery in the fungal wheat pathogen Zymoseptoria tritici (2015)

Molecular Plant Pathology: Effector discovery in the fungal wheat pathogen Zymoseptoria tritici (2015) | Fusarium and wheat | Scoop.it

Fungal plant pathogens, such as Zymoseptoria tritici (formerly known as Mycosphaerella graminicola), secrete repertoires of effectors to facilitate infection or trigger host defence mechanisms. The discovery and functional characterization of effectors provides valuable knowledge that can contribute to the design of new and effective disease management strategies. Here, we combined bioinformatics approaches with expression profiling during pathogenesis to identify candidate effectors of Z. tritici. In addition, a genetic approach was conducted to map quantitative trait loci (QTLs) 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 to consecutive stages of pathogenesis, contrary to candidates identified by QTL mapping that were, overall, expressed at low levels. 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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Global Genome and Transcriptome Analyses of Magnaporthe oryzae Epidemic Isolate 98-06 Uncover Novel Effectors and Pathogenicity-Related Genes, Revealing Gene Gain and Lose Dynamics in Genome Evol...

Global Genome and Transcriptome Analyses of  Magnaporthe oryzae  Epidemic Isolate 98-06 Uncover Novel Effectors and Pathogenicity-Related Genes, Revealing Gene Gain and Lose Dynamics in Genome Evol... | Fusarium and wheat | Scoop.it
“ Genome dynamics of pathogenic organisms are driven by pathogen and host co-evolution, in which pathogen genomes are shaped to overcome stresses imposed by hosts with various genetic backgrounds through generation of a variety of isolates. This same principle applies to the rice blast pathogen Magnaporthe oryzae and the rice host; however, genetic variations among different isolates of M. oryzae remain largely unknown, particularly at genome and transcriptome levels. Here, we applied genomic and transcriptomic analytical tools to investigate M. oryzae isolate 98-06 that is the most aggressive in infection of susceptible rice cultivars. A unique 1.4 Mb of genomic sequences was found in isolate 98-06 in comparison to reference strain 70-15. Genome-wide expression profiling revealed the presence of two critical expression patterns of M. oryzae based on 64 known pathogenicity-related (PaR) genes. In addition, 134 candidate effectors with various segregation patterns were identified. Five tested proteins could suppress BAX-mediated programmed cell death in Nicotiana benthamiana leaves. Characterization of isolate-specific effector candidates Iug6 and Iug9 and PaR candidate Iug18 revealed that they have a role in fungal propagation and pathogenicity. Moreover, Iug6 and Iug9 are located exclusively in the biotrophic interfacial complex (BIC) and their overexpression leads to suppression of defense-related gene expression in rice, suggesting that they might participate in biotrophy by inhibiting the SA and ET pathways within the host. Thus, our studies identify novel effector and PaR proteins involved in pathogenicity of the highly aggressive M. oryzae field isolate 98-06, and reveal molecular and genomic dynamics in the evolution of M. oryzae and rice host interactions.”
Via Francis Martin
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Molecular mechanism of resistance of Fusarium fujikuroi to benzimidazole fungicides - FEMS MicroBiol Lett - Chen et al.

Molecular mechanism of resistance of Fusarium fujikuroi to benzimidazole fungicides - FEMS MicroBiol Lett - Chen et al. | Fusarium and wheat | Scoop.it

Although carbendazim (MBC) and other benzimidazole fungicides have effectively controlled bakanae disease of rice (which is caused by Fusarium fujikuroi, F. proliferatum, and F. verticillioides) in the past, MBC resistance has become common. Previous research has shown that MBC resistance results from a mutation in the β1-tubulin (β1tub) gene in F. verticillioides. However, MBC resistance in F. fujikuroi, a predominant species in China, does not result from a mutation in the β1tub. The molecular mechanism of F. fujikuroi resistance against benzimidazole fungicides is poorly understood. In this study, we determined that although β1tub and β2-tubulin (β2tub) in F. fujikuroi have high homology with β1tub andβ2tub in F. verticillioides, MBC resistance in F. fujikuroi results from mutations in β2tub[GAG(Glu)→GTG(Val) at codon 198, TTC(Phe)→TAC(Tyr) at codon 200, and GGC(Gly)→GGT(Gly) at codon 235] but not in β1tub. Δβ2tub (β2tub deletion) mutants were highly sensitive to MBC, produced fewer conidia and were less virulent than parental strains. Complementation of the Δβ2tub mutants with a copy of the whole β2tub locus from their parental strains restored the level of MBC resistance (or sensitivity) to that of the parental strain.


Via Melvin Bolton
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Examining the Evolution of the Regulatory Circuit Controlling Secondary Metabolism and Development in the Fungal Genus Aspergillus

Examining the Evolution of the Regulatory Circuit Controlling Secondary Metabolism and Development in the Fungal Genus  Aspergillus | Fusarium and wheat | Scoop.it
“ Author Summary Filamentous fungi produce a highly diverse cadre of secondary metabolites, small molecules whose potent toxic activities are integral to the fungal lifestyle. Most secondary metabolites are narrowly taxonomically distributed, whereas the transcriptional regulators that control their production, alongside with controlling other key processes such as development, are broadly conserved. To gain insight into the evolution of the regulatory circuit governing secondary metabolism and development, we examined the evolution of the genes and pathways underlying these processes as well as the evolution of their transcriptional regulation in the filamentous fungal genus Aspergillus , a prolific and important producer of secondary metabolites. We discovered that although secondary metabolic genes and pathways are poorly conserved across Aspergillus , their regulation is largely conserved. In contrast, the regulation of highly conserved developmental genes is divergent. These results point to a new type of rewiring that has occurred during the evolution of the regulatory circuit governing secondary metabolism and development in Aspergillus in which conserved regulators control a conserved biological process (secondary metabolism), even though the underlying genes and pathways that make up the biological process are not themselves conserved.”
Via Pierre-Marc Delaux
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RNA-Seq Transcriptome Analysis of Maize Inbred Carrying Nicosulfuron-Tolerant and Nicosulfuron-Susceptible Alleles.

RNA-Seq Transcriptome Analysis of Maize Inbred Carrying Nicosulfuron-Tolerant and Nicosulfuron-Susceptible Alleles. | Fusarium and wheat | Scoop.it
“ Postemergence applications of nicosulfuron can cause great damage to certain maize inbred lines and hybrids. Variation among different responses to nicosulfuron may be attributed to differential rates of herbicide metabolism. We employed RNA-Seq analysis to compare transcriptome responses between nicosulfuron-treated and untreated in both tolerant and susceptible maize plants. A total of 71.8 million paired end Illumina RNA-Seq reads were generated, representing the transcription of around 40,441 unique reads. About 345,171 gene ontology (GO) term assignments were conducted for the annotation in terms of biological process, cellular component and molecular function categories, and 6413 sequences with 108 enzyme commission numbers were assigned to 134 predicted Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathways. Digital gene expression profile (DGE) analysis using Solexa sequencing was performed within the susceptible and tolerant maize between the nicosulfuron-treated and untreated conditions, 13 genes were selected as the candidates most likely involved in herbicide metabolism, and quantitative RT-PCR validated the RNA-Seq results for eight genes. This transcriptome data may provide opportunities for the study of sulfonylurea herbicides susceptibility emergence of Zea mays.”
Via Biswapriya Biswavas Misra
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Biswapriya Biswavas Misra's curator insight, April 6, 2015 2:00 AM

Bipolaris zeicola is a fungal pathogen that causes Northern corn leaf spot (NCLS), which is a serious foliar disease in maize and one of the most significant pathogens affecting global food security. Here, we report a genome-wide transcriptional profile analysis using next-generation sequencing (NGS) of maize leaf development after inoculation with B. zeicola. We performed High-Throughput Digital Gene Expression analysis to identify differentially expressed genes (DEGs) in resistant inbred Mo17 lines after infection with B. zeicola at four successive disease development stages-CP (contact period), PP (penetration period), IP (incubation period), and DP (disease period); the expression of the genes was compared with those in a CK (mock-treatment) control. In addition, a sensitive maize line (Zheng58) was used for the comparisons with the Mo17. Among all tested genes, 466 differentially expressed genes were identified in all libraries, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of these genes suggested that they are involved in many biological processes related to systemic symptom development, such as plant hormone signal transduction, starch and sucrose metabolism, phenylpropanoid biosynthesis and photosynthesis. Our systematic analysis provides comprehensive transcriptomic information regarding systemic symptom development in fungal-infected plants. This information will help in furthering our understanding of the detailed mechanisms of plant responses to fungal infection.

  
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Mitogen-Activated Protein Kinases Are Associated with the Regulation of Physiological Traits and Virulence in Fusarium oxysporum f. sp. cubense

Mitogen-Activated Protein Kinases Are Associated with the Regulation of Physiological Traits and Virulence in Fusarium oxysporum f. sp. cubense | Fusarium and wheat | Scoop.it

Fusarium oxysporum f. sp. cubense (FOC) is an important soil-borne fungal pathogen causing devastating vascular wilt disease of banana plants and has become a great concern threatening banana production worldwide. However, little information is known about the molecular mechanisms that govern the expression of virulence determinants of this important fungal pathogen. In this study, we showed that null mutation of three mitogen-activated protein (MAP) kinase genes, designated as FoSlt2, FoMkk2 and FoBck1, respectively, led to substantial attenuation in fungal virulence on banana plants. Transcriptional analysis revealed that the MAP kinase signaling pathway plays a key role in regulation of the genes encoding production of chitin, peroxidase, beauvericin and fusaric acid. Biochemical analysis further confirmed the essential role of MAP kinases in modulating the production of fusaric acid, which was a crucial phytotoxin in accelerating development of Fusarium wilt symptoms in banana plants. Additionally, we found that the MAP kinase FoSlt2 was required for siderophore biosynthesis under iron-depletion conditions. Moreover, disruption of the MAP kinase genes resulted in abnormal hypha and increased sensitivity to Congo Red, Calcofluor White and H2O2. Taken together, these results depict the critical roles of MAP kinases in regulation of FOC physiology and virulence.


Via Christophe Jacquet
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New Phytologist: Plants, fungi and oomycetes: a 400-million year affair that shapes the biosphere (2015)

New Phytologist: Plants, fungi and oomycetes: a 400-million year affair that shapes the biosphere (2015) | Fusarium and wheat | Scoop.it

In a rare gathering, genomics met palaeontology at the 10th New Phytologist Workshop on the ‘Origin and evolution of plants and their interactions with fungi’. An eclectic group of 17 experts met at The Natural History Museum (London, UK) on 9–10 September 2014 to discuss the latest findings on plant interactions with fungi (Eumycota) and oomycetes (Oomycota = Peronosporomycota), with topics ranging from the fossil record and comparative genomics to symbiosis and phytopathology. The discussions were largely disseminated via social media (Box 1). Highly diverse plant–fungal interactions have formed the backbone of land ecosystems and biogeochemical cycles since the Palaeozoic (see Fig. 1 for geological timeframe). As summarized by Christine Strullu-Derrien and Paul Kenrick (The Natural History Museum, London, UK) the first land plants arose c. 470 million years (Myr) ago (Kenrick et al., 2012; Edwards et al., 2014), at which time fungi and oomycetes had already colonized terrestrial ecosystems. Following their terrestrialization, these microbes began to abound within plant fossils (Taylor et al., 2014, and references therein). Ultimately, biological interactions sculpted the genomes of plants, fungi and oomycetes (e.g. Schmidt & Panstruga, 2011; Kohler et al., 2015). Here we illustrate the picture that has emerged from the discussions at the 10th New Phytologist Workshop, and point to some pending questions.


Via Francis Martin, Kamoun Lab @ TSL
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Pierre-Marc Delaux's curator insight, March 23, 2015 5:54 AM

It was a great workshop indeed!

Peter Buckland's curator insight, March 23, 2015 9:01 AM

The importance of plant-fungal interactions