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Shigeyuki Mayama - One of the best experts on this subject based on the ideXlab platform.
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RNA Silencing in the Blast Fungus Magnaporthe Grisea
Rice Blast: Interaction with Rice and Control, 2020Co-Authors: Hitoshi Nakayshiki, Yukio Tosa, Naoki Kadotani, Shigeyuki MayamaAbstract:We have examined RNA silencing in the blast fungus Magnaporthe grisea using the green fluorescence protein (GFP) gene as a model. The fluorescence in the GFP transformants was efficiently silenced by introducing a plasmid expressing double-stranded GFP RNA. Consequently, GFP mRNA accumulation was drastically reduced in the silenced transformants. In addition, small interfering RNAs of GFP were observed only in the silenced transformants. These results indicate that RNA silencing operates in M. grisea through processes very similar to those reported in other eukaryotes.
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one of the two dicer like proteins in the filamentous fungi Magnaporthe oryzae genome is responsible for hairpin rna triggered rna silencing and related small interfering rna accumulation
Journal of Biological Chemistry, 2004Co-Authors: Naoki Kadotani, Yukio Tosa, Hitoshi Nakayashiki, Shigeyuki MayamaAbstract:Abstract Dicer is a ribonuclease III-like enzyme playing a key role in the RNA silencing pathway. Genome sequencing projects have demonstrated that eukaryotic genomes vary in the numbers of Dicer-like (DCL) proteins from one (human) to four (Arabidopsis). Two DCL genes, MDL-1 and -2 (Magnaporthe Dicer-like-1 and -2) have been identified in the genome of the filamentous fungus Magnaporthe oryzae. Here we show that the knockout of MDL-2 drastically impaired gene silencing of enhanced green fluorescence protein by hairpin RNA and reduced related small interfering RNA (siRNA) accumulation to nondetectable levels. In contrast, mutating the other DCL, MDL-1, exhibited a gene silencing frequency similar to wild type and accumulated siRNA normally. The silencing-deficient phenotype and loss of siRNA accumulation in the mdl-2 mutant was restored by genetic complementation with the wild-type MDL-2 allele. These results indicate that only MDL-2 is responsible for siRNA production, and no functional redundancy exists between MDL-1 and MDL-2 in the RNA silencing pathway in M. oryzae. Our findings contrast with a recent report in the filamentous fungus Neurospora crassa, where two DCL proteins are redundantly involved in the RNA silencing pathway, but are similar to the results obtained in a more distantly related organism, Drosophila melanogaster, where an individual DCL protein has a distinct role in the siRNA/micro-RNA pathways.
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rna silencing in the phytopathogenic fungus Magnaporthe oryzae
Molecular Plant-microbe Interactions, 2003Co-Authors: Naoki Kadotani, Yukio Tosa, Hitoshi Nakayashiki, Shigeyuki MayamaAbstract:Systematic analysis of RNA silencing was carried out in the blast fungus Magnaporthe oryzae (formerly Magnaporthe grisea) using the enhanced green fluorescence protein (eGFP) gene as a model. To assess the ability of RNA species to induce RNA silencing in the fungus, plasmid constructs expressing sense, antisense, and hairpin RNAs were introduced into an eGFP-expressing transformant. The fluorescence of eGFP in the transformant was silenced much more efficiently by hairpin RNA of eGFP than by other RNA species. In the silenced transformants, the accumulation of eGFP mRNA was drastically reduced, but no methylation of the promoter or coding region was involved in it. In addition, we found small interfering RNAs (siRNAs) only in the silenced transformants. Interestingly, the siRNAs consisted of RNA molecules with at least three different sizes ranging from 19 to 23 nucleotides, and all of them contained both sense and antisense strands of the eGFP gene. To our knowledge, this is the first demonstration in w...
Nicholas J. Talbot - One of the best experts on this subject based on the ideXlab platform.
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Identification of Pathogenicity Determinants in the Rice Blast Fungus Magnaporthe Grisea
Major Fungal Diseases of Rice, 2020Co-Authors: Nicholas J. Talbot, H. R. K. Mccafferty, M. J. Kershaw, K. P. DixonAbstract:Magnaporthe grisea, (Hebert) Barr [anamorph, Pyricularia grisea Sacc.], is a heterothallic ascomycete fungus (Rossman et al.,1990) capable of causing disease in more than fifty members of the Gramineae (Ou, 1985). These include many forage grasses and weeds, and a number of important crops such as wheat (Triticum aestivum), barley (Hordeum vulgare), millet (Pennisetum americanum),maize (Zea mays) and rice (Oryza sativa). Magnaporthe grisea is most widely known, however, as the causal agent of rice blast, the most devastating disease of cultivated rice. Rice blast is a persistent problem and in the past 20 years has caused average annual losses from 11 to 30% of the world rice harvest (Baker et al., 1997), equivalent to 157 million tons of rice.
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under pressure investigating the biology of plant infection by Magnaporthe oryzae
Nature Reviews Microbiology, 2009Co-Authors: Richard A Wilson, Nicholas J. TalbotAbstract:Almost one-quarter of the calories consumed by the global human population is derived from rice. Epidemics of rice blast disease, which are caused by the filamentous fungus Magnaporthe oryzae, therefore represent a major threat to global food stocks. This Review discusses how functional genomic approaches are shedding light on the mechanisms used by M. oryzae during plant infection.
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A Fungal Metallothionein Is Required for Pathogenicity of Magnaporthe grisea
The Plant Cell, 2004Co-Authors: Sara L. Tucker, Christopher R. Thornton, Karen M. Tasker, Claus Jacob, Greg Giles, Martin J. Egan, Nicholas J. TalbotAbstract:The causal agent of rice blast disease, the ascomycete fungus Magnaporthe grisea, infects rice (Oryza sativa) plants by means of specialized infection structures called appressoria, which are formed on the leaf surface and mechanically rupture the cuticle. We have identified a gene, Magnaporthe metallothionein 1 (MMT1), which is highly expressed throughout growth and development by M. grisea and encodes an unusual 22–amino acid metallothionein-like protein containing only six Cys residues. The MMT1-encoded protein shows a very high affinity for zinc and can act as a powerful antioxidant. Targeted gene disruption of MMT1 produced mutants that show accelerated hyphal growth rates and poor sporulation but had no effect on metal tolerance. Mmt1 mutants are incapable of causing plant disease because of an inability to bring about appressorium-mediated cuticle penetration. Mmt1 appears to be distributed in the inner side of the cell wall of the fungus. These findings indicate that Mmt1-like metallothioneins may play a novel role in fungal cell wall biochemistry that is required for fungal virulence.
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A Magnaporthe grisea Cyclophilin Acts as a Virulence Determinant during Plant Infection
The Plant Cell, 2002Co-Authors: Muriel Viaud, Pascale V. Balhadère, Nicholas J. TalbotAbstract:Cyclophilins are peptidyl prolyl cis-trans isomerases that are highly conserved throughout eukaryotes and that are best known for being the cellular target of the immunosuppressive drug cyclosporin A (CsA). The activity of CsA is caused by the drug forming a complex with cyclophilin A and inhibiting the calmodulin-dependent phosphoprotein phosphatase calcineurin. We have investigated the role of CYP1, a cyclophilin-encoding gene in the phytopathogenic fungus Magnaporthe grisea, which is the causal agent of rice blast disease. CYP1 putatively encodes a mitochondrial and cytosolic form of cyclophilin, and targeted gene replacement has shown that CYP1 acts as a virulence determinant in rice blast. Cyp1 mutants show reduced virulence and are impaired in associated functions, such as penetration peg formation and appressorium turgor generation. CYP1 cyclophilin also is the cellular target for CsA in Magnaporthe, and CsA was found to inhibit appressorium development and hyphal growth in a CYP1-dependent manner. These data implicate cyclophilins as virulence factors in phytopathogenic fungi and also provide evidence that calcineurin signaling is required for infection structure formation by Magnaporthe.
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Having a blast: exploring the pathogenicity of Magnaporthe grisea
Trends in Microbiology, 1995Co-Authors: Nicholas J. TalbotAbstract:Abstract The rice blast fungus Magnaporthe grisea has an exquisite level of pathogenic specialization, allowing it to infect and colonize rice, subvert the metabolism of the host and spread to new hosts. Through a combination of cytology and moleculargenetic analysis, a picture is gradually emerging of the many interlinked processes that are required for successful infection of the plant.
Yukio Tosa - One of the best experts on this subject based on the ideXlab platform.
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RNA Silencing in the Blast Fungus Magnaporthe Grisea
Rice Blast: Interaction with Rice and Control, 2020Co-Authors: Hitoshi Nakayshiki, Yukio Tosa, Naoki Kadotani, Shigeyuki MayamaAbstract:We have examined RNA silencing in the blast fungus Magnaporthe grisea using the green fluorescence protein (GFP) gene as a model. The fluorescence in the GFP transformants was efficiently silenced by introducing a plasmid expressing double-stranded GFP RNA. Consequently, GFP mRNA accumulation was drastically reduced in the silenced transformants. In addition, small interfering RNAs of GFP were observed only in the silenced transformants. These results indicate that RNA silencing operates in M. grisea through processes very similar to those reported in other eukaryotes.
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Classification and parasitic specialization of blast fungi
Journal of General Plant Pathology, 2014Co-Authors: Yukio Tosa, Izumi ChumaAbstract:Pyricularia oryzae ( Magnaporthe oryzae ), a causal agent of blast diseases on staple gramineous crops, is a model organism listed as the most important economically and scientifically of the top 10 fungal pathogens by fungal molecular pathologists. Although we are now in an era of genome-enabled analysis, we need to understand the history of the pathogen’s taxonomy, classification, and parasitic specialization in addition to recent research advances. In this review, we focus on these rather fundamental topics. First, the history of classification, including the discovery of its sexual stage and designation, is overviewed. Based on recent results of phylogenetic analysis of Magnaporthaceae isolates, blast fungi are suggested to constitute a robust population that is not congeneric with Magnaporthe salvinii , the type species of Magnaporthe . Second, genetic mechanisms involved in its parasitic specialization into host-specific subgroups and races are outlined. Implications of recent molecular data for resistance breeding are discussed.
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Various species of Pyricularia constitute a robust clade distinct from Magnaporthe salvinii and its relatives in Magnaporthaceae
Journal of General Plant Pathology, 2014Co-Authors: Nobuaki Murata, Yukio Tosa, Takayuki Aoki, Motoaki Kusaba, Izumi ChumaAbstract:In a phylogenetic analysis of species of Magnaporthaceae based on nucleotide sequences of rDNA-ITS and the RPB1 gene, isolates of the tested species were divided into two clusters with high bootstrap support. One group was composed of Pyricularia spp.; the other was composed of Magnaporthe salvinii , M. rhizophila , M. poae , Gaeumannomyces graminis , and G. incrustans . On the basis of this result, we concluded that Pyricularia spp. constitute a large but distinct phylogenetic species group that is not congeneric with Magnaporthe salvinii , the type species of Magnaporthe .
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Is the Fungus Magnaporthe Losing DNA Methylation
Genetics, 2013Co-Authors: Kenichi Ikeda, Yukio Tosa, Izumi Chuma, Naoki Kadotani, Masaki Tanaka, Toshiki Murata, Kohta Shiina, Hitoshi NakayashikiAbstract:The long terminal repeat retrotransposon, Magnaporthe gypsy-like element (MAGGY), has been shown to be targeted for cytosine methylation in a subset of Magnaporthe oryzae field isolates. Analysis of the F1 progeny from a genetic cross between methylation-proficient (Br48) and methylation-deficient (GFSI1-7-2) isolates revealed that methylation of the MAGGY element was governed by a single dominant gene. Positional cloning followed by gene disruption and complementation experiments revealed that the responsible gene was the DNA methyltransferase, MoDMT1, an ortholog of Neurospora crassa Dim-2. A survey of MAGGY methylation in 60 Magnaporthe field isolates revealed that 42 isolates from rice, common millet, wheat, finger millet, and buffelgrass were methylation proficient while 18 isolates from foxtail millet, green bristlegrass, Japanese panicgrass, torpedo grass, Guinea grass, and crabgrass were methylation deficient. Phenotypic analyses showed that MoDMT1 plays no major role in development and pathogenicity of the fungus. Quantitative polymerase chain reaction analysis showed that the average copy number of genomic MAGGY elements was not significantly different between methylation-deficient and -proficient field isolates even though the levels of MAGGY transcript were generally higher in the former group. MoDMT1 gene sequences in the methylation-deficient isolates suggested that at least three independent mutations were responsible for the loss of MoDMT1 function. Overall, our data suggest that MoDMT1 is not essential for the natural life cycle of the fungus and raise the possibility that the genus Magnaporthe may be losing the mechanism of DNA methylation on the evolutionary time scale.
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one of the two dicer like proteins in the filamentous fungi Magnaporthe oryzae genome is responsible for hairpin rna triggered rna silencing and related small interfering rna accumulation
Journal of Biological Chemistry, 2004Co-Authors: Naoki Kadotani, Yukio Tosa, Hitoshi Nakayashiki, Shigeyuki MayamaAbstract:Abstract Dicer is a ribonuclease III-like enzyme playing a key role in the RNA silencing pathway. Genome sequencing projects have demonstrated that eukaryotic genomes vary in the numbers of Dicer-like (DCL) proteins from one (human) to four (Arabidopsis). Two DCL genes, MDL-1 and -2 (Magnaporthe Dicer-like-1 and -2) have been identified in the genome of the filamentous fungus Magnaporthe oryzae. Here we show that the knockout of MDL-2 drastically impaired gene silencing of enhanced green fluorescence protein by hairpin RNA and reduced related small interfering RNA (siRNA) accumulation to nondetectable levels. In contrast, mutating the other DCL, MDL-1, exhibited a gene silencing frequency similar to wild type and accumulated siRNA normally. The silencing-deficient phenotype and loss of siRNA accumulation in the mdl-2 mutant was restored by genetic complementation with the wild-type MDL-2 allele. These results indicate that only MDL-2 is responsible for siRNA production, and no functional redundancy exists between MDL-1 and MDL-2 in the RNA silencing pathway in M. oryzae. Our findings contrast with a recent report in the filamentous fungus Neurospora crassa, where two DCL proteins are redundantly involved in the RNA silencing pathway, but are similar to the results obtained in a more distantly related organism, Drosophila melanogaster, where an individual DCL protein has a distinct role in the siRNA/micro-RNA pathways.
Naoki Kadotani - One of the best experts on this subject based on the ideXlab platform.
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RNA Silencing in the Blast Fungus Magnaporthe Grisea
Rice Blast: Interaction with Rice and Control, 2020Co-Authors: Hitoshi Nakayshiki, Yukio Tosa, Naoki Kadotani, Shigeyuki MayamaAbstract:We have examined RNA silencing in the blast fungus Magnaporthe grisea using the green fluorescence protein (GFP) gene as a model. The fluorescence in the GFP transformants was efficiently silenced by introducing a plasmid expressing double-stranded GFP RNA. Consequently, GFP mRNA accumulation was drastically reduced in the silenced transformants. In addition, small interfering RNAs of GFP were observed only in the silenced transformants. These results indicate that RNA silencing operates in M. grisea through processes very similar to those reported in other eukaryotes.
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Is the Fungus Magnaporthe Losing DNA Methylation
Genetics, 2013Co-Authors: Kenichi Ikeda, Yukio Tosa, Izumi Chuma, Naoki Kadotani, Masaki Tanaka, Toshiki Murata, Kohta Shiina, Hitoshi NakayashikiAbstract:The long terminal repeat retrotransposon, Magnaporthe gypsy-like element (MAGGY), has been shown to be targeted for cytosine methylation in a subset of Magnaporthe oryzae field isolates. Analysis of the F1 progeny from a genetic cross between methylation-proficient (Br48) and methylation-deficient (GFSI1-7-2) isolates revealed that methylation of the MAGGY element was governed by a single dominant gene. Positional cloning followed by gene disruption and complementation experiments revealed that the responsible gene was the DNA methyltransferase, MoDMT1, an ortholog of Neurospora crassa Dim-2. A survey of MAGGY methylation in 60 Magnaporthe field isolates revealed that 42 isolates from rice, common millet, wheat, finger millet, and buffelgrass were methylation proficient while 18 isolates from foxtail millet, green bristlegrass, Japanese panicgrass, torpedo grass, Guinea grass, and crabgrass were methylation deficient. Phenotypic analyses showed that MoDMT1 plays no major role in development and pathogenicity of the fungus. Quantitative polymerase chain reaction analysis showed that the average copy number of genomic MAGGY elements was not significantly different between methylation-deficient and -proficient field isolates even though the levels of MAGGY transcript were generally higher in the former group. MoDMT1 gene sequences in the methylation-deficient isolates suggested that at least three independent mutations were responsible for the loss of MoDMT1 function. Overall, our data suggest that MoDMT1 is not essential for the natural life cycle of the fungus and raise the possibility that the genus Magnaporthe may be losing the mechanism of DNA methylation on the evolutionary time scale.
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one of the two dicer like proteins in the filamentous fungi Magnaporthe oryzae genome is responsible for hairpin rna triggered rna silencing and related small interfering rna accumulation
Journal of Biological Chemistry, 2004Co-Authors: Naoki Kadotani, Yukio Tosa, Hitoshi Nakayashiki, Shigeyuki MayamaAbstract:Abstract Dicer is a ribonuclease III-like enzyme playing a key role in the RNA silencing pathway. Genome sequencing projects have demonstrated that eukaryotic genomes vary in the numbers of Dicer-like (DCL) proteins from one (human) to four (Arabidopsis). Two DCL genes, MDL-1 and -2 (Magnaporthe Dicer-like-1 and -2) have been identified in the genome of the filamentous fungus Magnaporthe oryzae. Here we show that the knockout of MDL-2 drastically impaired gene silencing of enhanced green fluorescence protein by hairpin RNA and reduced related small interfering RNA (siRNA) accumulation to nondetectable levels. In contrast, mutating the other DCL, MDL-1, exhibited a gene silencing frequency similar to wild type and accumulated siRNA normally. The silencing-deficient phenotype and loss of siRNA accumulation in the mdl-2 mutant was restored by genetic complementation with the wild-type MDL-2 allele. These results indicate that only MDL-2 is responsible for siRNA production, and no functional redundancy exists between MDL-1 and MDL-2 in the RNA silencing pathway in M. oryzae. Our findings contrast with a recent report in the filamentous fungus Neurospora crassa, where two DCL proteins are redundantly involved in the RNA silencing pathway, but are similar to the results obtained in a more distantly related organism, Drosophila melanogaster, where an individual DCL protein has a distinct role in the siRNA/micro-RNA pathways.
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rna silencing in the phytopathogenic fungus Magnaporthe oryzae
Molecular Plant-microbe Interactions, 2003Co-Authors: Naoki Kadotani, Yukio Tosa, Hitoshi Nakayashiki, Shigeyuki MayamaAbstract:Systematic analysis of RNA silencing was carried out in the blast fungus Magnaporthe oryzae (formerly Magnaporthe grisea) using the enhanced green fluorescence protein (eGFP) gene as a model. To assess the ability of RNA species to induce RNA silencing in the fungus, plasmid constructs expressing sense, antisense, and hairpin RNAs were introduced into an eGFP-expressing transformant. The fluorescence of eGFP in the transformant was silenced much more efficiently by hairpin RNA of eGFP than by other RNA species. In the silenced transformants, the accumulation of eGFP mRNA was drastically reduced, but no methylation of the promoter or coding region was involved in it. In addition, we found small interfering RNAs (siRNAs) only in the silenced transformants. Interestingly, the siRNAs consisted of RNA molecules with at least three different sizes ranging from 19 to 23 nucleotides, and all of them contained both sense and antisense strands of the eGFP gene. To our knowledge, this is the first demonstration in w...
Barbara Valent - One of the best experts on this subject based on the ideXlab platform.
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MGOS: Development of a community annotation database for Magnaporthe oryzae
Molecular Plant-microbe Interactions, 2012Co-Authors: Anupreet Kour, Kevin A. Greer, Barbara Valent, Marc Joel Orbach, Carol SoderlundAbstract:Magnaporthe oryzae causes rice blast disease, which is the most serious disease of cultivated rice worldwide. We previously developed the Magnaporthe grisea–Orzya sativa (MGOS) database as a repository for the M. oryzae and rice genome sequences together with a comprehensive set of functional interaction data generated by a major consortium of U.S. researchers. The MGOS database has now undergone a major redesign to include data from the international blast research community, accessible with a new intuitive, easy-to-use interface. Registered database users can manually annotate gene sequences and features as well as add mutant data and literature on individual gene pages. Over 900 genes have been manually curated based on various biological databases and the scientific literature. Gene names and descriptions, gene ontology annotations, published and unpublished information on mutants and their phenotypes, responses in diverse microarray analyses, and related literature have been incorporated. Thus far, 3...
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Magnaporthe oryzae and Rice Blast Disease
Cellular and Molecular Biology of Filamentous Fungi, 2010Co-Authors: Chang Hyun Khang, Barbara ValentAbstract:The Magnaporthe grisea species complex includes pathogens of more than 50 grass species. Magnaporthe oryzae was recently segregated as a distinct species from M. grisea based on a multilocus phylogenetic analysis and on mating properties of the strains. M. grisea isolates are pathogenic on crabgrass, Digitaria sanguinalis, and related grasses, and M. oryzae is associated with pathogens of diverse grasses with agricultural significance. Evolution of host-specific populations is an important topic that can be addressed within the M. grisea species complex. The abundance of transposable elements in the rice isolates from the field suggests that M. oryzae lacks the repeat-induced point mutation (RIP) mechanism described in the related pyrenomycete Neurospora crassa. Fluorescent effectors remained localized to the biotrophic interfacial complex (BIC) region as long as invasive hyphae (IH) continued to grow in the rice cell. Secreted effector fusions partially colocalized with an aggregation of plant endocytotic membranes that labeled with FM4-64. Some of the blast fungal metabolites, such as tenuazonic acid (TA) and picolinic acid, were demonstrated to be hypersensitive-response elicitors, inducing resistance responses in rice. For rice blast disease, the increasing numbers of avirulence (AVR)-like genes that control host specificity and the large number of R proteins that are predicted to be localized in the rice cytoplasm are consistent with the hypothesis that M. oryzae translocates many effectors into the host cytoplasm.
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gain of virulence caused by insertion of a pot3 transposon in a Magnaporthe grisea avirulence gene
Molecular Plant-microbe Interactions, 2001Co-Authors: Seogchan Kang, Marc-henri Lebrun, Leonard Farrall, Barbara ValentAbstract:The avirulence gene AVR-Pita in Magnaporthe grisea prevents the fungus from infecting rice cultivars carrying the disease resistance gene Pi-ta. Insertion of Pot3 transposon into the promoter of AVR-Pita caused the gain of virulence toward Yashiro-mochi, a rice cultivar containing Pi-ta, which demonstrated the ability of Pot3 to move within the M. grisea genome. The appearance of Pot3 in M. grisea seems to predate the diversification of various host-specific forms of the fungus.
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The Rice Blast Fungus, Magnaporthe grisea
Plant Relationships Part B, 1997Co-Authors: Barbara ValentAbstract:Magnaporthe grisea (Hebert) Barr (Barr 1977; Yaegashi and Udagawa 1978) is a filamentous, heterothallic Ascomycotina that collectively causes disease on many species of the grass (Poaceae) family. M. grisea is the teleomorph corresponding to the previously distinct anamorphs Pyricularia oryzae, infecting rice (Oryza sativa), and P. grisea, infecting other grasses. However, P. oryzae and P. grisea have now been synonymized, with the earlier name, P. grisea, having priority (Rossman et al. 1990), because strains with diverse host specificities are interfertile and morphologically indistinguishable. Although the collective host range of M. grisea is broad, individual strains infect a limited number of grass species (Ou 1985; Borromeo et al. 1993; Urashima et al. 1993). A comprehensive description of the economically important rice blast disease has recently been published (Zeigler et al. 1994).
