Rice Blast
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Scientific articles on rice blast and wheat blast 20 new articles each month !
Curated by Elsa Ballini
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Advances in Molecular Mechanism Toward Understanding Plant-Microbe Interaction: A Study of M. oryzae Versus Rice

Advances in Molecular Mechanism Toward Understanding Plant-Microbe Interaction: A Study of M. oryzae Versus Rice | Rice Blast | Scoop.it
Rice blast, caused by the fungus Magnaporthe oryzae, is the most devastating disease of rice which causes considerable economic loss worldwide. The interaction between rice and M. oryzae is an important model system for studying host-pathogen interactions. Since genomes of both species are sequenced, research is more focused by exploiting modern genetics, genomics, proteomics and bioinformatics. Recent research on functional genomics and candidate gene identification has helped to elucidate the role of resistance (R) and avirulence (Avr) genes and their interactions. Over the years, many avirulence genes (Avr) involved in pathogenicity and resistance genes (R) of rice involved in pathogen signaling molecules and defence response have been identified and characterized. Recent development in cloning of Avr genes (13) and R genes (22) and identification of many quantitative trait loci (QTL) has improved our understanding of rice-M. oryzae interaction at molecular level. This chapter is focusses on the current R and Avr genes cloned and characterized their structure, function and co-evolution, and the future research directions to study and understand the molecular mechanism of rice-M. oryzae interactions for better targeting and exploitation of host plant resistance towards management of this disease.
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Novel aspects of hydrophobins in wheat isolate of Magnaporthe oryzae: Mpg1, but not Mhp1, is essential for adhesion and pathogenicity

Novel aspects of hydrophobins in wheat isolate of Magnaporthe oryzae: Mpg1, but not Mhp1, is essential for adhesion and pathogenicity | Rice Blast | Scoop.it
The adhesive ability of spores is important for fungal pathogens to manifest pathogenicity. Hydrophobins found on the outer surface of conidia and hyphae may be involved in adhesion or communication between the fungus and its environment. The effects of two hydrophobins, class I Mpg1 and class II Mhp1, on adhesion, germling differentiation, and pathogenicity of a wheat isolate of Magnaporthe oryzae were evaluated. We conducted gene knockdown or knockout experiments to obtain hydrophobin mutants. We found several discrepancies from previous studies. The Mpg1-silenced mutants had various levels of Mpg1 transcription, and Mpg1 expression was correlated with adhesion, germling differentiation, and pathogenicity. We also obtained mhp1 null mutants that had full pathogenicity on wheat and barley leaves. These results suggest that Mpg1 is directly contributing to adhesion, but Mhp1 is not essential for the infection process in the wheat isolate of M. oryzae.
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METHOD FOR PREDICTING GENE CLUSTER INCLUDING SECONDARY METABOLISM-RELATED GENES, PREDICTION PROGRAM, AND PREDICTION DEVICE - NATIONAL INSTITUTE OF ADVANCED INDUSTRIAL SCIENCEAND TECHNOLGOY

This invention provides a method for predicting a gene cluster including secondary metabolism-related genes with high accuracy, independent of information concerning core genes. Such method comprises: a step of identifying a region the gene arrangement of which is conserved in nucleotide sequence information of another genome as a gene cluster on the basis of the results of homology search conducted with the use of nucleotide sequence information of at least a pair of genomes; and a step of determining whether or not the gene cluster of interest includes secondary metabolism-related gems on the basis of the proportion of synteny-like regions within the gene cluster identified by the above step.
Elsa Ballini's insight:

In Example 1, 8 types of genomic data sets were used. The data of Aspergillus fumigatas, Aspergillus nidulans, Aspergillus terreus, Magnaporthe grisea, Fusarium graminearum, and Chaetomium globosum were downloaded from the Broad Institute.

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Epigenetic mechanisms: an emerging player in plant-microbe interactions

Epigenetic mechanisms: an emerging player in plant-microbe interactions | Rice Blast | Scoop.it
Plants have developed diverse molecular and cellular mechanisms to cope with a life time of exposure to a variety of pathogens. Host transcriptional reprogramming is a central part of plant defence upon pathogen recognition. Recent studies link DNA methylation and demethylation, as well as chromatin remodelling by post translational histone modifications, including acetylation, methylation and ubiquitination, to changes in the expression levels of defence genes upon pathogen challenge. Remarkably these inducible defence mechanisms can be primed prior to pathogen attack by epigenetic modifications and this heightened resistance state can be transmitted to subsequent generations by inheritance of these modification patterns. Beside the plant host, epigenetic mechanisms have also been implicated in virulence development of pathogens. This review highlights recent findings and insights into epigenetic mechanisms associated with interactions between plants and pathogens, in particular bacterial and fungal pathogens, and demonstrates the positive role they can have in promoting plant defence.
Elsa Ballini's insight:

"The expression level of Pib is usually low in uninfected rice plants due to heavy CG-methylation at two critical regions of the Pib promoter but strongly induced by the blast disease-causing fungal pathogen Magnaporthe grisea, which presumably helps promote resistance to this pathogen. Surprisingly, the methylation level at the two critical promoter regions of Pib was unaffected by M. grisea infection. In fact, partial demethylation by 5-azacytidine-treatment actually reduced Pib expression and compromised blast disease-resistance (Li et al. 2011). This result suggests that DNA methylation at the promoter of Pib has a positive role in the M. grisea-induced expression of Pib. Thus, DNA methylation may play both a positive and negative role in regulating plant defence gene expression."

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Detection of Magnaporthe oryzae chrysovirus 1 in Japan and establishment of a rapid, sensitive and direct diagnostic method based on reverse transcription loop-mediated isothermal amplification

Detection of Magnaporthe oryzae chrysovirus 1 in Japan and establishment of a rapid, sensitive and direct diagnostic method based on reverse transcription loop-mediated isothermal amplification | Rice Blast | Scoop.it
Magnaporthe oryzae chrysovirus 1 (MoCV1) is a mycovirus with a dsRNA genome that infects the rice blast fungus Magnaporthe oryzae and impairs its growth. To date, MoCV1 has only been found in Vietnamese isolates of M. oryzae, and the distribution of this virus in M. oryzae isolates from other parts of the world remains unknown. In this study, using a one-step reverse transcription PCR (RT-PCR) assay, we detected a MoCV1-related virus in M. oryzae in Japan (named MoCV1-AK) whose sequence shares considerable similarity with that of the MoCV1 Vietnamese isolate. To establish a system for a comprehensive survey of MoCV1 infection in the field, we developed a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for direct detection of the virus. The sensitivity of the RT-LAMP assay was at least as high as that of the one-step RT-PCR assay. In addition, we detected MoCV1-AK in M. oryzae-infected oatmeal agar plates and lesions on rice leaves using the RT-LAMP assay without dsRNA extraction, by simple sampling with a toothpick. Preliminary screening of MoCV1 in Japanese M. oryzae isolates indicated that MoCV1 is currently distributed in rice fields in Japan. Our results provide a first example of the application of RT-LAMP for the detection of mycoviruses, which will accelerate surveys for mycovirus infection.
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METALLOENZYME INHIBITOR COMPOUNDS AS FUNGICIDES - DOW AGROSCIENCES LLC

The instant invention describes compounds of Formula I having metalloenzyme modulating activity, and methods of treating diseases, disorders or symptoms thereof mediated by such metalloenzymes.
Elsa Ballini's insight:

The compositions according to claim 28 wherein the fungal pathogen is one of Leaf Blotch of Wheat (Mycosphaerella graminicola; anamorph: Septoria tritici), Wheat Brown Rust (Puccinia triticina), Stripe Rust (Puccinia striiformis), Scab of Apple (Venturia inaequalis), Blister Smut of Maize (Ustilago maydis), Powdery Mildew of Grapevine (Uncinula necator), Barley Scald (Rhynchosporium secalis), Blast of Rice (Magnaporthe grisea), Rust of Soybean (Phakopsora pachyrhizi), Glume Blotch of Wheat (Leptosphaeria nodorum), Powdery Mildew of Wheat (Blumeria graminis f. sp. tritici), Powdery Mildew of Barley (Blumeria graminis f. sp. hordei), Powdery Mildew of Cucurbits (Erysiphe cichoracearum), Anthracnose of Cucurbits (Glomerella lagenarium), Leaf Spot of Beet (Cercospora beticola), Early Blight of Tomato (Alternaria solani), and Net Blotch of Barley (Pyrenophora teres). 

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Cloning of novel rice blast resistance genes from two rapidly evolving NBS-LRR gene families in rice

Cloning of novel rice blast resistance genes from two rapidly evolving NBS-LRR gene families in rice | Rice Blast | Scoop.it
Most rice blast resistance genes (R-genes) encode proteins with nucleotide-binding site (NBS) and leucine-rich repeat (LRR) domains. Our previous study has shown that more rice blast R-genes can be cloned in rapidly evolving NBS-LRR gene families. In the present study, two rapidly evolving R-gene families in rice were selected for cloning a subset of genes from their paralogs in three resistant rice lines. A total of eight functional blast R-genes were identified among nine NBS-LRR genes, and some of these showed resistance to three or more blast strains. Evolutionary analysis indicated that high nucleotide diversity of coding regions served as important parameters in the determination of gene resistance. We also observed that amino-acid variants (nonsynonymous mutations, insertions, or deletions) in essential motifs of the NBS domain contribute to the blast resistance capacity of NBS-LRR genes. These results suggested that the NBS regions might also play an important role in resistance specificity determination. On the other hand, different splicing patterns of introns were commonly observed in R-genes. The results of the present study contribute to improving the effectiveness of R-gene identification by using evolutionary analysis method and acquisition of novel blast resistance genes.
Elsa Ballini's insight:

One of the gene is at Pi33 locus : Os08g10430 ... Is Pi33 cloned in this paper?

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The syntaxin protein (MoSyn8) mediates intracellular trafficking to regulate conidiogenesis and pathogenicity of rice blast fungus

The syntaxin protein (MoSyn8) mediates intracellular trafficking to regulate conidiogenesis and pathogenicity of rice blast fungus | Rice Blast | Scoop.it
Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) mediate cellular membrane fusion and intracellular vesicle trafficking in eukaryotic cells, and are critical in the growth and development of pathogenic fungi such as Magnaporthe oryzae which causes rice blast. Rice blast is thought to involve distinct SNARE-mediated transport and secretion of fungal effector proteins into the host to modulate rice immunity.
We have previously characterized two SNARE proteins, secretory protein (MoSec22) and vesicle-associated membrane protein (MoVam7), as being important in cellular transport and pathogenicity. Here, we show that syntaxin 8 (MoSyn8), a Qc-SNARE protein homolog, also plays important roles in growth, conidiation, and pathogenicity.
The MoSYN8 deletion mutant (∆Mosyn8) mutant exhibits defects in endocytosis and F-actin organization, appressorium turgor pressure generation, and host penetration. In addition, the ∆Mosyn8 mutant cannot elaborate biotrophic invasion of the susceptible rice host, or secrete avirulence factors Avr-Pia (corresponding to the rice resistance gene Pia) and Avrpiz-t (the cognate Avr gene for the resistance gene Piz-t) proteins.
Our study of MoSyn8 advances our understanding of SNARE proteins in effector secretion which underlies the normal physiology and pathogenicity of M. oryzae, and it sheds new light on the mechanism of the blight disease caused by M. oryzae.
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Sexual Reproduction in Pyricularia oryzae

Sexual Reproduction in Pyricularia oryzae | Rice Blast | Scoop.it

Blast is caused by the Ascomycete Pyricularia oryzae and is the most important disease affecting rice in the world. Besides rice, wheat is affected by blast caused by P. oryzae in Brazil, Paraguay and Bolivia. The high genetic-pathotypic variability observed in local populations of P. oryzae is probably responsible for the low resistance durability of rice and wheat cultivarsto this disease and may also be determinant in eventsof 'host shift' by the pathogen. This review aims to present important aspects of the sexual reproduction of P. oryzae, as well as information about the regulatory mechanisms of the pathogen sexual cycle by the genes mating type and pheromones in a specific recognition system. Understanding the reproductive biology and the importance of P. oryzae sexual cycle is essential for blast disease management based on durable resistance.

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Biosynthesis of the mycotoxin tenuazonic acid by a fungal NRPS-PKS hybrid enzyme

Biosynthesis of the mycotoxin tenuazonic acid by a fungal NRPS-PKS hybrid enzyme | Rice Blast | Scoop.it
Tenuazonic acid (TeA) is a well-known mycotoxin produced by various plant pathogenic fungi. However, its biosynthetic gene has been unknown to date. Here we identify the TeA biosynthetic gene from Magnaporthe oryzae by finding two TeA-inducing conditions of a low-producing strain. We demonstrate that TeA is synthesized from isoleucine and acetoacetyl-coenzyme A by TeA synthetase 1 (TAS1). TAS1 is a unique non-ribosomal peptide synthetase and polyketide synthase (NRPS–PKS) hybrid enzyme that begins with an NRPS module. In contrast to other NRPS/PKS hybrid enzymes, the PKS portion of TAS1 has only a ketosynthase (KS) domain and this domain is indispensable for TAS1 activity. Phylogenetic analysis classifies this KS domain as an independent clade close to type I PKS KS domain. We demonstrate that the TAS1 KS domain conducts the final cyclization step for TeA release. These results indicate that TAS1 is a unique type of NRPS–PKS hybrid enzyme.
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Diterpenoid Phytoalexin Factor, a bHLH Transcription Factor, Plays a Central Role in the Biosynthesis of Diterpenoid Phytoalexins in Rice

Diterpenoid Phytoalexin Factor, a bHLH Transcription Factor, Plays a Central Role in the Biosynthesis of Diterpenoid Phytoalexins in Rice | Rice Blast | Scoop.it
Rice (Oryza sativa) produces diterpenoid phytoalexins (DPs), momilactones (MLs) and phytocassanes (PCs) as major phytoalexins. Accumulation of DPs is induced in rice by blast fungus infection, copper chloride or ultraviolet light. Herein, we report a rice transcription factor (TF) – named DITERPENOID PHYTOALEXIN FACTOR (DPF), a basic/helix-loop-helix (bHLH) TF. DPF is expressed mainly in roots and panicles, and is inducible in leaves by blast infection, copper chloride, or UV. Expressions of all DP biosynthetic genes and accumulation of MLs and PCs were remarkably increased and decreased in DPF overexpressing and DPF-knockdown rice, respectively. These results clearly demonstrated that DPF positively regulates DP accumulation via transcriptional regulation of DP biosynthetic genes, and plays a central role in the biosynthesis of DPs in rice. Furthermore, DPF activated the promoters of COPALYL DIPHOSPHATE SYNTHASE2 (CPS2) and CYTOCHROME P450 MONOOXIGENASE (CYP) 99A2, which are implicated in the biosynthesis of PCs and MLs, respectively. Mutations in the N-boxes in the CPS2 upstream region, to which several animal bHLH TFs bind, remarkably decreased CPS2 transcription, indicating that DPF positively regulates CPS2 transcription through the N-boxes. In addition, DPF partly regulates CYP99A2 through the N-box. This study demonstrated that DPF acts as a master TF in DP biosynthesis.
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Molecular marker assisted gene stacking for biotic and abiotic stress resistance genes in an elite rice cultivar

Molecular marker assisted gene stacking for biotic and abiotic stress resistance genes in an elite rice cultivar | Rice Blast | Scoop.it
Severe yield loss due to various biotic stresses like bacterial blight (BB), gall midge (insect) and Blast (disease) and abiotic stresses like submergence and salinity are a serious constraint to the rice productivity throughout the world. The most effective and reliable method of management of the stresses is the enhancement of host resistance, through an economical and environmentally friendly approach. Through the application of marker assisted selection (MAS) technique, the present study reports a successful pyramidization of genes/QTLs to confer resistance/tolerance to blast (Pi2, Pi9), gall Midge (Gm1, Gm4), submergence (Sub1), and salinity (Saltol) in a released rice variety CRMAS2621-7-1 as Improved Lalat which had already incorporated with three BB resistance genes xa5, xa13, and Xa21 to supplement the Xa4 gene present in Improved Lalat. The molecular analysis revealed clear polymorphism between the donor and recipient parents for all the markers that are tagged to the target traits. The conventional backcross breeding approach was followed till BC3F1 generation and starting from BC1F1 onwards, marker assisted selection was employed at each step to monitor the transfer of the target alleles with molecular markers. The different BC3F1s having the target genes/QTLs were inter crossed to generate hybrids with all 10 stress resistance/tolerance genes/QTLs into a single plant/line. Homozygous plants for resistance/tolerance genes in different combinations were recovered. The BC3F3 lines were characterized for their agronomic and quality traits and promising progeny lines were selected. The SSR based background selection was done. Most of the gene pyramid lines showed a high degree of similarity to the recurrent parent for both morphological, grain quality traits and in SSR based background selection. Out of all the gene pyramids tested, two lines had all the 10 resistance/tolerance genes and showed adequate levels of resistance/tolerance against the five target stresses. The study demonstrates the potential of MAS for stacking of several genes into a single line with a high degree of parental genome recovery.
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Assessment of environmental variables conducive fo epidemiology of rice-blast pathosystem

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XIV Meeting of the Working Group Biological control of fungal and bacterial plant pathogens: IOBC

XIV Meeting of the Working Group Biological control of fungal and bacterial plant pathogens: IOBC | Rice Blast | Scoop.it
All Information and Details about XIV Meeting of the Working Group Biological control of fungal and bacterial plant pathogens - Biocontrol and Microbial Ecology (IOBC) on 12-15 September 2016 in Berlin
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Rmg8, a New Gene for Resistance to Triticum Isolates of Pyricularia oryzae in Hexaploid Wheat

Rmg8, a New Gene for Resistance to Triticum Isolates of Pyricularia oryzae in Hexaploid Wheat | Rice Blast | Scoop.it
Blast, caused by Pyricularia oryzae, is one of the major diseases of wheat in South America. We identified a new gene for resistance to Triticum isolates of P. oryzae in common wheat ‘S-615’, and designated it “resistance to Magnaporthe grisea 8” (Rmg8). Rmg8 was assigned to chromosome 2B through molecular mapping with simple-sequence repeat markers. To identify an avirulence gene corresponding to Rmg8, Triticum isolate Br48 (avirulent on S-615) was crossed with 200R29 (virulent on S-615), an F1 progeny derived from a cross between an Eleusine isolate (MZ5-1-6) and Br48. Segregation analysis of their progeny revealed that avirulence of Br48 on S-615 was conditioned by a single gene, which was designated AVR-Rmg8. AVR-Rmg8 was closely linked to AVR-Rmg7, which corresponded to Rmg7 located on chromosome 2A of tetraploid wheat.
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Plant Cell: Septin-Dependent Assembly of the Exocyst Is Essential for Plant Infection by Magnaporthe oryzae (2015)

Plant Cell: Septin-Dependent Assembly of the Exocyst Is Essential for Plant Infection by Magnaporthe oryzae (2015) | Rice Blast | Scoop.it

Via The Sainsbury Lab, CP, hunter chen
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The Sainsbury Lab's curator insight, November 14, 2015 6:06 AM

Magnaporthe oryzae is the causal agent of rice blast disease, the most devastating disease of cultivated rice (Oryza sativa) and a continuing threat to global food security. To cause disease, the fungus elaborates a specialized infection cell called an appressorium, which breaches the cuticle of the rice leaf, allowing the fungus entry to plant tissue. Here, we show that the exocyst complex localizes to the tips of growing hyphae during vegetative growth, ahead of the Spitzenkörper, and is required for polarized exocytosis. However, during infection-related development, the exocyst specifically assembles in the appressorium at the point of plant infection. The exocyst components Sec3, Sec5, Sec6, Sec8, and Sec15, and exocyst complex proteins Exo70 and Exo84 localize specifically in a ring formation at the appressorium pore. Targeted gene deletion, or conditional mutation, of genes encoding exocyst components leads to impaired plant infection. We demonstrate that organization of the exocyst complex at the appressorium pore is a septin-dependent process, which also requires regulated synthesis of reactive oxygen species by the NoxR-dependent Nox2 NADPH oxidase complex. We conclude that septin-mediated assembly of the exocyst is necessary for appressorium repolarization and host cell invasion.

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New and Improved Techniques for the Study of Pathogenic Fungi

Fungal pathogens pose serious threats to human, plant, and ecosystem health. Improved diagnostics and antifungal strategies are therefore urgently required. Here, we review recent developments in online bioinformatic tools and associated interactive data archives, which enable sophisticated comparative genomics and functional analysis of fungal pathogens in silico. Additionally, we highlight cutting-edge experimental techniques, including conditional expression systems, recyclable markers, RNA interference, genome editing, compound screens, infection models, and robotic automation, which are promising to revolutionize the study of both human and plant pathogenic fungi. These novel techniques will allow vital knowledge gaps to be addressed with regard to the evolution of virulence, host–pathogen interactions and antifungal drug therapies in both the clinic and agriculture. This, in turn, will enable delivery of improved diagnosis and durable disease-control strategies.
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Oncotarget: Plant immune receptor decoy: Pathogens in their own trap (2015)

Oncotarget: Plant immune receptor decoy: Pathogens in their own trap (2015) | Rice Blast | Scoop.it

Microbial pathogens have evolved sophisticated strategies to infect their hosts, often resulting in disease. The host, in turn, can produce novel proteins (receptors or antibodies) that recognize pathogen molecules to trigger defense. Unlike animals, plants do not possess any adaptive immunity to defend themselves against pathogens. Therefore, they rely entirely on their genetic resistance capability (innate immunity) conferred by a family of receptors expressed in individual cells. The plant innate immune system can be divided into two layers of defense. The first, known as pattern-triggered immunity (PTI) leading to basal defense, involves the recognition of microbe-associated molecular patterns (MAMPs) by corresponding plasma membrane pattern-recognition receptors (PRRs). PTI can be suppressed by specific pathogen virulence factors (known as effectors). To detect such pathogen molecules or their interference with host proteins, plants have evolved a second layer of defense, known as effector-triggered immunity (ETI) [1]. ETI is mediated by intracellular nucleotide-binding–leucine-rich repeat receptors (NLRs) that resemble mammalian NLRs [2]. The speed with which microbial populations can produce new effectors places enormous pressure on plant hosts to fight back with genetically new or altered receptor recognition modes.

 

Alice Delga, Clémentine Le Roux and Laurent Deslandes

 

 


Via Nicolas Denancé
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Transcription Factor SomA Is Required for Adhesion, Development and Virulence of the Human Pathogen Aspergillus fumigatus

Transcription Factor SomA Is Required for Adhesion, Development and Virulence of the Human Pathogen  Aspergillus fumigatus | Rice Blast | Scoop.it
The transcription factor Flo8/Som1 controls filamentous growth in Saccharomyces cerevisiae and virulence in the plant pathogen Magnaporthe oryzae. Flo8/Som1 includes a characteristic N-terminal LUG/LUH-Flo8-single-stranded DNA binding (LUFS) domain and is activated by the cAMP dependent protein kinase A signaling pathway. Heterologous SomA from Aspergillus fumigatus rescued in yeast flo8 mutant strains several phenotypes including adhesion or flocculation in haploids and pseudohyphal growth in diploids, respectively. A. fumigatus SomA acts similarly to yeast Flo8 on the promoter of FLO11 fused with reporter gene (LacZ) in S. cerevisiae. FLO11 expression in yeast requires an activator complex including Flo8 and Mfg1. Furthermore, SomA physically interacts with PtaB, which is related to yeast Mfg1. Loss of the somA gene in A. fumigatus resulted in a slow growth phenotype and a block in asexual development. Only aerial hyphae without further differentiation could be formed. The deletion phenotype was verified by a conditional expression of somA using the inducible Tet-on system. A adherence assay with the conditional somA expression strain indicated that SomA is required for biofilm formation. A ptaB deletion strain showed a similar phenotype supporting that the SomA/PtaB complex controls A. fumigatus biofilm formation. Transcriptional analysis showed that SomA regulates expression of genes for several transcription factors which control conidiation or adhesion of A. fumigatus. Infection assays with fertilized chicken eggs as well as with mice revealed that SomA is required for pathogenicity. These data corroborate a complex control function of SomA acting as a central factor of the transcriptional network, which connects adhesion, spore formation and virulence in the opportunistic human pathogen A. fumigatus.
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Rice was domesticated three times across Asia, not once in China

Rice was domesticated three times across Asia, not once in China | Rice Blast | Scoop.it
Sticky rice hails from southern China, but basmati is a hybrid of rice domesticated in the Himalayas and near Bangladesh

Via Mary Williams
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Chitin-mediated plant–fungal interactions: catching, hiding and handshaking

Chitin-mediated plant–fungal interactions: catching, hiding and handshaking | Rice Blast | Scoop.it

Highlights•

Plants recognize infecting fungi through the perception of released chitin fragments by LysM receptor complexes.

Pathogenic fungi secrete effectors and change their cell walls to escape from the chitin-mediated immune system.

Chitin-related molecules also serve as symbiotic signals in rhizobium/AM symbiosis.

Dual function of OsCERK1 in both chitin-mediated immunity and AM symbiosis sheds a new light on the evolutionary relationships between these systems.

Plants can detect infecting fungi through the perception of chitin oligosaccharides by lysin motif receptors such as CEBiP and CERK1. A major function of CERK1 seems to be as a signaling molecule in the receptor complex formed with ligand-binding molecules and to activate downstream defense signaling. Fungal pathogens, however, have developed counter strategies to escape from the chitin-mediated detection by using effectors and/or changing their cell walls. Common structural features between chitin and Nod-/Myc-factors and corresponding receptors have suggested the close relationships between the chitin-mediated immunity and rhizobial/arbuscular mycorrhizal symbiosis. The recent discovery of the dual function of OsCERK1 in both plant immunity and mycorrhizal symbiosis sheds new light on the evolutionary relationships between defense and symbiotic systems in plants.

Current Opinion in Plant Biology 2015, 26:xx–


Via Christophe Jacquet, Giannis Stringlis
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Identification of novel alleles of the rice blast resistance gene Pi54

Identification of novel alleles of the rice blast resistance gene Pi54 | Rice Blast | Scoop.it
Rice blast is one of the most devastating rice diseases and continuous resistance breeding is required to control the disease. The rice blast resistance gene Pi54 initially identified in an Indian cultivar confers broad-spectrum resistance in India. We explored the allelic diversity of the Pi54 gene among 885 Indian rice genotypes that were found resistant in our screening against field mixture of naturally existing M. oryzae strains as well as against five unique strains. These genotypes are also annotated as rice blast resistant in the International Rice Genebank database. Sequence-based allele mining was used to amplify and clone the Pi54 allelic variants. Nine new alleles of Pi54 were identified based on the nucleotide sequence comparison to the Pi54 reference sequence as well as to already known Pi54 alleles. DNA sequence analysis of the newly identified Pi54 alleles revealed several single polymorphic sites, three double deletions and an eight base pair deletion. A SNP-rich region was found between a tyrosine kinase phosphorylation site and the nucleotide binding site (NBS) domain. Together, the newly identified Pi54 alleles expand the allelic series and are candidates for rice blast resistance breeding programs.
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Structure Analysis Uncovers a Highly Diverse but Structurally Conserved Effector Family in Phytopathogenic Fungi

Structure Analysis Uncovers a Highly Diverse but Structurally Conserved Effector Family in Phytopathogenic Fungi | Rice Blast | Scoop.it
Author Summary Fungal plant pathogens are of outstanding economic and ecological importance and cause destructive diseases on many cultivated and wild plants. Effector proteins that are secreted during infection to manipulate the host and to promote disease are a key element in fungal virulence. Phytopathogenic fungi possess huge effector repertoires that are dominated by hundreds of sequence-unrelated small secreted proteins. The molecular functions of this most important class of fungal effectors and the evolutionary mechanisms that generate this tremendous numbers of apparently unrelated proteins are largely unknown. By investigating the 3-dimensional structures of effectors from the rice blast fungus M . oryzae , we discovered an effector family comprising structurally conserved but sequence-unrelated effectors from M . oryzae and the phylogenetically distant wheat pathogen Pyrenophora tritici-repentis that we named MAX-effectors ( M . oryzae A vrs and To x B). Structure-informed searches of whole genome sequence databases suggest that MAX-effectors are present at low frequencies and with a patchy phylogenetic distribution in many ascomycete phytopathogens. They underwent strong lineage-specific expansion in fungi of the Pyriculariae family that contains M . oryzae where they seem particularly important during biotrophic plant colonization and account for 50% of the cloned Avr effectors and 5–10% of the effector repertoire. Based on our results on the MAX-effectors and the widely accepted concept that fungal effectors evolve according to a birth-and-death model we propose the hypothesis that the majority of the immense numbers of different ascomycete effectors could in fact belong to a limited set of structurally defined families whose members are phylogenetically related.

Via Tatsuya Nobori
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Steve Marek's curator insight, October 29, 2015 3:21 PM

MAX-effectors expressed during biotrophic phase of hemibiotrophic ascomycetes in Dothideomycetes and Sordariomycetes. 

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Abiotic Stresses Antagonize the Rice Defence Pathway through the Tyrosine-Dephosphorylation of OsMPK6

Abiotic Stresses Antagonize the Rice Defence Pathway through the Tyrosine-Dephosphorylation of OsMPK6 | Rice Blast | Scoop.it
Chemical defence inducers make plants resistant to diseases such as rice blast. However, plants sometimes become more pathogen susceptible under abiotic stresses even in their presence. Because such regulation prioritizes the responses to the most life-threatening stress, it could be necessary for plants to survive in nature. However, it seems dispensable or even disadvantageous for crops cultivated under fertile conditions. Here, we show the molecular mechanism underlying one of such phenomena in rice. WRKY45 is a central transcription factor that regulates strong defence signalling mediated by salicylic acid. We found that WRKY45 is activated through phosphorylation by a protein kinase, OsMPK6, which is activated by dual phosphorylation in response to the defence signalling. We also found that OsMPK6 can be inactivated by tyrosine dephosphorylation in response to abiotic stresses such as low temperature and high salinity probably mediated by abscisic acid, leading to reduction of WRKY45-dependent disease resistance. Moreover, we found that specific tyrosine protein phosphatases dephosphorylate/inactivate OsMPK6 in response to abiotic stresses. Knockdown of their genes rendered rice plants resistant against blast disease even under the abiotic stresses, pointing to the way to further improve rice.
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Characterization of field isolates of Magnaporthe oryzae with mating type, DNA fingerprinting, and pathogenicity assays

Characterization of field isolates of Magnaporthe oryzae with mating type, DNA fingerprinting, and pathogenicity assays | Rice Blast | Scoop.it
Due to the harmful nature of the rice blast fungus, Magnaporthe oryzae, it is beneficial to characterize field isolates to help aid in the deployment of resistance (R) genes in rice. In the present study, 252 field isolates of M. oryzae, collected from rice fields of Yunnan Province in China, were assessed for mating type, DNA fingerprinting, and disease reactions to differential rice lines. Ninety-four isolates (37.3%) were MAT1-1 and 158 (62.7%) were MAT1-2 based on polymerase chain reaction assays, and some of them were verified with the tester isolates. All MAT1-1 and MAT1-2 isolates were virulent to some of IRRI-JIRCAS monogenic lines harboring 22 major resistance genes as differential varieties. Three simple sequence repeat (SSR) markers were used to examine genetic diversity in all isolates. The existence of regional patterns of genetic diversity, sexual reproduction potential, and pathogenicity suggests that M. oryzae populations have been independently asexually adapted in rice fields during crop cultivation.
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