Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Magnaporthe”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed2003

Identification of proteins that interact with two regulators of appressorium development, adenylate cyclase and cAMP-dependent protein kinase A, in the rice blast fungus Magnaporthe grisea.

Adenylate cyclase (MAC1) and the catalytic subunit of cAMP-dependent protein kinase A (CPKA) are required for appressorium development and pathogenesis in the rice blast pathogen Magnaporthe grisea. To identify new components in the cAMP signal transduction pathway, we used the yeast two-hybrid system to screen MAC1 and CPKA against an appressorium cDNA library. The cDNA library was constructed by GATEWAY recombinational cloning, enabling transfer of the library to various alternative vectors. The protein phosphatase domain in MAC1, which is unique to fungal adenylate cyclases, interacted with a MAP kinase kinase and a Ser/Thr kinase. Interactions of MAC1 with the kinases may prove to be part of feedback loops between the corresponding signaling pathways. A predicted membrane protein, ACI1, which is highly expressed under conditions that are conducive to appressorium formation, also interacted with MAC1. ACI1 has an extracellular domain containing eight-cysteines, which is also present in other fungal proteins implicated in pathogenesis. The N-terminal half of CPKA, which includes a glutamine-rich sequence unique to a group of fungal sequences, interacted with a putative transcriptional regulator and two different glycosyl hydrolases. Phosphorylation motifs in these sequences suggest that they could be CPKA substrates. The protein interaction assay employed here can now be scaled up to identify interactions between a larger set of proteins in the M. grisea interactome.

Adenylyl Cyclases↗
PubMed2005

High-resolution mapping, cloning and molecular characterization of the Pi-k ( h ) gene of rice, which confers resistance to Magnaporthe grisea.

In order to understand the molecular mechanisms involved in the gene-for-gene type of pathogen resistance, high-resolution genetic and physical mapping of resistance loci is required to facilitate map-based cloning of resistance genes. Here, we report the molecular mapping and cloning of a dominant gene (Pi-k ( h )) present in the rice line Tetep, which is associated with resistance to rice blast disease caused by Magnaporthe grisea. This gene is effective against M. grisea populations prevalent in the Northwestern Himalayan region of India. Using 178 sequence tagged microsatellite, sequence-tagged site, expressed sequence tag and simple sequence repeat (SSR) markers to genotype a population of 208 F(2) individuals, we mapped the Pi-k ( h ) gene between two SSR markers (TRS26 and TRS33) which are 0.7 and 0.5 cM away, respectively, and can be used in marker-assisted-selection for blast-resistant rice cultivars. We used the markers to identify the homologous region in the genomic sequence of Oryza sativa cv. Nipponbare, and a physical map consisting of two overlapping bacterial artificial chromosome and P1 artificial chromosome clones was assembled, spanning a region of 143,537 bp on the long arm of chromosome 11. Using bioinformatic analyses, we then identified a candidate blast-resistance gene in the region, and cloned the homologous sequence from Tetep. The putative Pi-k ( h ) gene cloned from Tetep is 1.5 kbp long with a single ORF, and belongs to the nucleotide binding site-leucine rich repeat class of disease resistance genes. Structural and expression analysis of the Pi-k ( h ) gene revealed that its expression is pathogen inducible.

Amino Acid Sequence↗
PubMed2006

Molecular mapping of two cultivar-specific avirulence genes in the rice blast fungus Magnaporthe grisea.

Rice blast, caused by the fungus Magnaporthe grisea, is a globally important disease of rice that causes annual yield losses. The segregation of genes controlling the virulence of M. grisea on rice was studied to establish the genetic basis of cultivar specificity in the interaction of rice and M. grisea. The segregation of avirulence and virulence was studied in 87 M. grisea F(1) progeny isolates from a cross of two isolates, Guy11 and JS153, using resistance-gene-differential rice cultivars. The segregation ratio indicated that avirulence and virulence in the rice cultivars Aichi-asahi and K59, respectively, are controlled by single major genes. Genetic analyses of backcrosses and full-sib crosses in these populations were also performed. The chi(2 )test of goodness-of-fitness for a 1:1 ratio indicated that one dominant gene controls avirulence in Aichi-asahi and K59 in this population. Based on the resistance reactions of rice differential lines harboring known resistance genes to the parental isolates, two genetically independent avirulence genes, AVR-Pit and AVR-Pia, were identified. Genetic linkage analysis showed that the SSR marker m355-356 is closely linked to AVR-Pit, on the telomere of chromosome 1 at a distance of approximately 2.3 cM. The RAPD marker S487, which was converted to a sequence-characterized amplified region (SCAR) marker, was found to be closely linked to AVR-Pia, on the chromosome 7 telomere at a distance of 3.5 cM. These molecular markers will facilitate the positional cloning of the two AVR genes, and can be applied to molecular-marker-assisted studies of M. grisea populations.

Chromosome Mapping↗
PubMed2000

The rice Rim2 transcript accumulates in response to Magnaporthe grisea and its predicted protein product shares similarity with TNP2-like proteins encoded by CACTA transposons.

A rice transcript, Rim2, was identified that accumulated in both incompatible and compatible interactions between rice and Magnaporthe grisea. The Rim2 transcript also accumulated in response to treatment with a cell wall elicitor derived from M. grisea. A 3.3-kb RIM2 cDNA clone was isolated and is predicted to encode a protein of 653 amino acids, which shares 32 55% identity with TNP2-like proteins encoded by CACTA transposons of other plants. A 1.05-kb segment of the Rim2 sequence shows 82% nucleotide sequence identity with sequences flanking the A1 and C members of the rice Xa21 disease resistance gene family. The 5'-upstream region of Rim2 was cloned and the transcriptional start sites were identified. The 5' and 3' noncoding termini of Rim2 are AT-rich. A cis-element showing similarity to a sequence that mediates defense-associated transcriptional activation of the tobacco retrotransposon Tnt1, and four motifs that fit the consensus sequence of the elicitor-responsive elements in the promoters of the parsley PR-1 genes were found in the 5'-upstream region. Four imperfect tandem repeats were identified in the 3' noncoding terminus. Southern analysis with genomic DNA from different rice species indicated that Rim2 is present in 3-4 copies per genome. These results suggest that Rim2 may be one component of a large CACTA-like element, whose transcript accumulates in response to attack by pathogens.

Amino Acid Sequence↗
PubMed2001

Heat shock, copper sulfate and oxidative stress activate the retrotransposon MAGGY resident in the plant pathogenic fungus Magnaporthe grisea.

MAGGY is a gypsy-like retrotransposon isolated from the plant pathogenic fungus Magnaporthe grisea. The ability of various stresses to activate MAGGY was tested in the original and in a heterologous host (Colletotrichum lagenarium), using beta-glucuronidase (GUS) as a reporter. The MAGGY promoter was activated in M. grisea by either heat shock, copper sulfate, or oxidative stress, but not by the antifungal substance p-coumaric acid. Transcriptional up-regulation of MAGGY RNA was also observed following heat shock and oxidative stress. The MAGGY promoter remained responsive to the above-mentioned stresses when transformed into a M. grisea isolate that had no endogenous MAGGY elements. In C. lagenarium, however, the MAGGY promoter showed only basal expression of GUS and no further up-regulation was induced by any of the stress treatments, suggesting that the stress-responding cis-element(s) in the MAGGY promoter is not functional in a wider range of fungi. The relationship between the activation of MAGGY by stress and phenotypic diversification in M. grisea, including variations in pathogenicity, is discussed.

Amino Acid Sequence↗
PubMed2005

Live-cell imaging of tubulin in the filamentous fungus Magnaporthe grisea treated with anti-microtubule and anti-microfilament agents.

Microtubule dynamics were examined in live cells of the fungal plant pathogen Magnaporthe grisea transformed for constitutive expression of a fusion protein containing enhanced yellow-fluorescent protein and a Neurospora crassa benomyl-resistant allele of beta-tubulin. Transformants retained their ability to differentiate appressoria and cause disease but remained sensitive to benomyl. Linear microtubule arrays and low-level cytoplasmic fluorescence were observed in vegetative hyphae, conidia, germ tubes, and developing appressoria. Fluorescence within nuclei was conspicuously absent during interphase but increased rapidly at the onset of mitosis. Treatment with either benomyl or griseofulvin resulted in the appearance of prominent brightly fluorescent aggregates, including a large aggregate near the apex, with the concomitant disappearance of most cytoplasmic microtubules. Electron microscope imaging of treated cells indicated that the aggregates lacked any obvious profiles of intact microtubules. During these treatments, hyphal tip cells continued to elongate in a nonlinear and aerial fashion at a much slower rate than untreated cells. With subsequent removal of griseofulvin, distal aggregates disappeared rapidly but the apical aggregates persisted longer. Treatment with latrunculin A caused hyphal tip swelling without apparent effect on linear microtubule arrays. Simultaneous treatment with griseofulvin and latrunculin A resulted in depolymerization of microtubules and a cessation of growth, but near-apical fluorescent aggregates were not observed.

Actin Cytoskeleton↗
PubMed2005

Mating-type distribution and fertility status in Magnaporthe grisea populations from Argentina.

Isolates of Magnaporthe grisea causing gray leaf spot on rice were collected in Argentina and analyzed for mating distribution and fertility. One hundred and twenty-five isolates of M. grisea were collected from rice plants between 2000 and 2003. Each isolate was tested for mating type through a polymerase chain reaction based assay. All M. grisea isolates from Argentina belonged to a single mating type, MAT1.1. The fertility status of isolates was determined using controlled crosses in vitro, pairing each isolate with GUY11 and KA9 (MAT1.2 standard hermaphroditic testers). Production of perithecia was scarce among isolates of the blast pathogen since a low percentage of them (7.2%) developed perithecia with only one of the fertile tester (KA9); all crosses failed with the other tester strain. Asci and ascospores were not observed. The presence of only one mating type and the absence of female fertile isolates indicate that sexual reproduction is rare or absent in M. grisea populations associated with rice in Argentina.

Argentina↗
PubMed2003

Linoleate diol synthase of the rice blast fungus Magnaporthe grisea.

Mycelia of two strains of Magnaporthe grisea, Guy 11 and TH3, were incubated with linoleic acid, and the metabolites were isolated and identified by GC-MS and LC-MS. The two main metabolites were identified as 8-hydroxylinoleic and 7,8-dihydroxylinoleic acids, and the former was further oxidized by n-2 and by n-3 hydroxylation to 8,16- and 8,17-dihydroxylinoleic acids. Lipoxygenase metabolites of linoleic acid could not be detected. The sequence of the genome of M. grisea has been released from the Whitehead Institute; it contains a gene with close homology to the linoleate diol synthase gene of the take-all fungus Gaeumannomyces graminis. Both genes appear to have the same organization, with four exons and three short introns, and the intron-exon borders were determined by reverse-transcription PCR and sequencing. The linoleate diol synthase precursor of G. graminis consists of 978 amino acids, whereas the putative diol synthase precursor of M. grisea contains 987 amino acids. The diol synthases of G. graminis and M. grisea can be aligned with 65% identical and 78% positive amino acid residues, and catalytically important amino acid residues were conserved.

Amino Acid Sequence↗
PubMed2005

Identification of mature appressorium-enriched transcripts in Magnaporthe grisea, the rice blast fungus, using suppression subtractive hybridization.

We have constructed a fungal subtractive suppressive library enriched in genes expressed during appressorium maturation in Magnaporthe grisea. Sequencing of 250 clones from the subtracted appressorium cDNA library revealed 142 unique genes, represented by 155 non-redundant ESTs (expressed sequence tags). Of these ESTs, 72 have not been previously isolated in M. grisea. RT-PCR analysis of 105 of the genes discovered found transcripts corresponding to 71 of the ESTs only in mature appressoria while transcripts corresponding to a further 34 of the isolated ESTs were expressed both in appressoria and conidia/mycelia. Genes specifically expressed in appressorium identified by SSH included a number that have been previously implicated in appressorium formation or function including GAS1, GAS3, and PTH11.

Expressed Sequence Tags↗
PubMed2003

The development of simple sequence repeat markers for Magnaporthe grisea and their integration into an established genetic linkage map.

Although microsatellite or simple sequence repeat (SSR) markers have several advantages, few have been developed in fungi. The goal of this study was to identify and characterize SSR-containing loci in the filamentous ascomycete Magnaporthe grisea, the causal agent of rice blast disease, and to add these markers to an integrated genetic map of this species [Theor. Appl. Genet. 95 (1997) 20]. We have constructed and screened a microsatellite-enriched small-insert genomic library as well as exploited both publicly available and one proprietary databases for identification of M. grisea SSR containing sequences. Twenty-four out of 49 primer pairs designed to amplify SSR, produced unambiguous polymorphic products in our test population of six isolates. The number of alleles at each locus ranged from two to six when assayed on 3% agarose gels. Twenty-three of the primer pairs amplified polymorphic products between Guy11 and 2539, the parents of a cross from which a genetic map for M. grisea has been established. Genetic analysis showed that all the markers segregated in the expected 1:1 ratio and map positions were determined for all 23 loci.

Base Sequence↗
PubMed2004

BAC end sequences and a physical map reveal transposable element content and clustering patterns in the genome of Magnaporthe grisea.

Transposable elements (TEs) are viewed as major contributors to the evolution of fungal genomes. Genomic resources such as BAC libraries are an underutilized resource for studying genome-wide TE distribution. Using the BAC end sequences and physical map that are available for the rice blast fungus, Magnaporthe grisea, we describe a likelihood ratio test designed to identify clustering of TEs in the genome. A significant variation in the distribution of three TEs, MAGGY, MGL, and Pot2 was observed among the fingerprint contigs of the physical map. We utilized a draft sequence of M. grisea chromosome 7 to validate our results and found a similar pattern of clustering. By examining individual BAC end sequences, we found evidence for 11 unique integrations of MAGGY or MGL into Pot2 but no evidence for the reciprocal integration of Pot2 into another TE. This suggests that: (a) the presence of Pot2 in the genome predates that of the other TEs, (b) Pot2 was less transpositionally active than other TEs, or (c) that MAGGY and MGL have integration site preference for Pot2. High transition/transversion mutation ratios as well as bias in transition site context was observed in MAGGY and MGL elements, but not in Pot2 elements. These features are consistent with the effects of a Repeat-Induced Point (RIP) mutation-like process occurring in MAGGY and MGL elements. This study illustrates the general utility of a physical map and BAC end sequences for the study of genome-wide repetitive DNA content and organization.

Chromosomes, Artificial, Bacterial↗
PubMed2004

A comparative genomic analysis of the calcium signaling machinery in Neurospora crassa, Magnaporthe grisea, and Saccharomyces cerevisiae.

A large number of Ca2+ -signaling proteins have been previously identified and characterized in Saccharomyces cerevisiae but relatively few have been discovered in filamentous fungi. In this study, a detailed, comparative genomic analysis of Ca2+ -signaling proteins in Neurospora crassa, Magnaporthe grisea, and S. cerevisiae has been made. Our BLAST analysis identified 48, 42, and 40 Ca2+ -signaling proteins in N. crassa, M. grisea, and S. cerevisiae, respectively. In N. crassa, M. grisea, and S. cerevisiae, 79, 100, and 13% of these proteins, respectively, were previously unknown. For N. crassa, M. grisea, and S. cerevisiae, respectively, we have identified: three Ca2+ -permeable channels in each species; 9, 12, and 5 Ca2+/cation-ATPases; eight, six, and four Ca2+ -exchangers; four, four, and two phospholipase C's; one calmodulin in each species; and 23, 21, and 29 Ca2+/calmodulin-regulated proteins. Homologs of a number of key proteins involved in the release of Ca2+ from intracellular stores, and in the sensing of extracellular Ca2+, in animal and plant cells, were not identified. The greater complexity of the Ca2+ -signaling machinery in N. crassa and M. grisea over that in S. cerevisiae probably reflects their more complex cellular organization and behavior, and the greater range of external signals which filamentous fungi have to respond to in their natural habitats. To complement the data presented in this paper, a comprehensive web-based database resource (http://www.fungalcell.org/fdf/) of all Ca2+ -signaling proteins identified in N. crassa, M. grisea, and S. cerevisiae has been provided.

Calcineurin↗
PubMed2005

A dual selection based, targeted gene replacement tool for Magnaporthe grisea and Fusarium oxysporum.

Rapid progress in fungal genome sequencing presents many new opportunities for functional genomic analysis of fungal biology through the systematic mutagenesis of the genes identified through sequencing. However, the lack of efficient tools for targeted gene replacement is a limiting factor for fungal functional genomics, as it often necessitates the screening of a large number of transformants to identify the desired mutant. We developed an efficient method of gene replacement and evaluated factors affecting the efficiency of this method using two plant pathogenic fungi, Magnaporthe grisea and Fusarium oxysporum. This method is based on Agrobacterium tumefaciens-mediated transformation with a mutant allele of the target gene flanked by the herpes simplex virus thymidine kinase (HSVtk) gene as a conditional negative selection marker against ectopic transformants. The HSVtk gene product converts 5-fluoro-2'-deoxyuridine to a compound toxic to diverse fungi. Because ectopic transformants express HSVtk, while gene replacement mutants lack HSVtk, growing transformants on a medium amended with 5-fluoro-2'-deoxyuridine facilitates the identification of targeted mutants by counter-selecting against ectopic transformants. In addition to M. grisea and F. oxysporum, the method and associated vectors are likely to be applicable to manipulating genes in a broad spectrum of fungi, thus potentially serving as an efficient, universal functional genomic tool for harnessing the growing body of fungal genome sequence data to study fungal biology.

Agrobacterium tumefaciens↗
PubMed2005

Transposition of MINE, a composite retrotransposon, in the avirulence gene ACE1 of the rice blast fungus Magnaporthe grisea.

The ACE1 avirulence gene allele from the rice blast fungus Magnaporthe grisea was characterized in virulent isolate 2/0/3, revealing the insertion of a 1.9 kb MINE retrotransposon in the last ACE1 exon. MINE is a novel chimeric element composed of a transcribed non-coding sequence of 1.1 kb (WEIRD) fused to a 5'-truncated MGL retrotransposon. MINEs were found in high copy number in M. grisea isolates from rice (68 copies) and as a single copy in isolate CD156 from Eleusine. MINEs vary in size (1.3-6.7 kb) with conserved 5' WEIRD sequences and variable 3' MGL sequences. MGLs fused to WEIRDs correspond to different 5'-truncated MGLs with conserved 3' ends. The organization and diversity of MINEs suggest that these retrotransposons result from independent fusions between WEIRD and 5'-truncated MGLs. Such chimera could be formed during MGL reverse transcription as proposed for human U6-LINE1 chimeric retrotransposons and integrated into M. grisea genome using MGL machinery.

DNA, Fungal↗
PubMed2006

Global gene expression during nitrogen starvation in the rice blast fungus, Magnaporthe grisea.

Efficient regulation of nitrogen metabolism likely plays a role in the ability of fungi to exploit ecological niches. To learn about regulation of nitrogen metabolism in the rice blast pathogen Magnaporthe grisea, we undertook a genome-wide analysis of gene expression under nitrogen-limiting conditions. Five hundred and twenty genes showed increased transcript levels at 12 and 48 h after shifting the fungus to media lacking nitrate as a nitrogen source. Thirty-nine of these genes have putative functions in amino acid metabolism and uptake, and include the global nitrogen regulator in M. grisea, NUT1. Evaluation of seven nitrogen starvation-induced genes revealed that all were expressed during rice infection. Targeted gene replacement on one such gene, the vacuolar serine protease, SPM1, resulted in decreased sporulation and appressorial development as well as a greatly attenuated ability to cause disease. Data are discussed in the context of nitrogen metabolism under starvation conditions, as well as conditions potentially encountered during invasive growth in planta.

Amino Acids↗
PubMed2006

Light regulation of asexual development in the rice blast fungus, Magnaporthe oryzae.

Light is a major environmental factor that influences many biological processes. We characterized the roles of light in asexual development (including the formation of aerial hyphae and conidiophore) in Magnaporthe oryzae, which is the causal agent of rice blast disease. Our data revealed a complex nature of light regulation in the asexual developments of M. oryzae. Asexual development of M. oryzae is suppressed by blue light in a light/dark cycling environment and asexual spore release is controlled by both blue and red light. We demonstrated that even very dim light, about 10 micromol m(-2), is sufficient to suppress spore-release behavior in M. oryzae. We also generated knockout strains of a blue light receptor, mgwc-1, the M. oryzae homolog of white collar-1 in Neurospora crassa, and demonstrated blue-light-specific regulation in the asexual development and spore release in M. oryzae. Our findings in this agriculturally important pathogen, M. oryzae, broaden our understanding of the roles of light in fungal development.

Blotting, Southern↗
PubMed2004

Transcript abundance of rml1, encoding a putative GT1-like factor in rice, is up-regulated by Magnaporthe grisea and down-regulated by light.

We isolated and sequenced both genomic DNA and cDNA clones, which encoded a putative GT1-like protein with 385 amino acids, from cultivated rice (Oryza sativa ssp. indica). This protein shows significant amino acid sequence similarities with trihelix DNA-binding GT-1a/B2F and GT-1 factors that were identified in dicot plants. Northern blotting analysis indicated that the transcript of the rice GT-1 factor in seedling was up-regulated by the rice blast fungus Magnaporthe grisea, down-regulated by various continuous light conditions and expressed rhythmically in light/dark cycles. This GT1-like factor gene was therefore designated as rml1 (rice gene regulated by M. grisea and light). The putative RML1 protein, encoded by this single copy gene, is thus identified as a new member of the plant-specific GT family of transcription factors in rice.

Amino Acid Sequence↗
PubMed2005

Biomechanical model for appressorial design in Magnaporthe grisea.

The fungus Magnaporthe grisea, commonly referred to as the rice blast fungus, is responsible for destroying from 10% to 30% of the world's rice crop each year. The fungus attaches to the rice leaf and forms a dome-shaped structure, the appressorium, in which enormous pressures are generated that are used to blast a penetration peg through the rice cell walls and infect the plant. We develop a model of the appressorial design in terms of a bioelastic shell that can explain the shape of the appressorium, and its ability to maintain that shape under the enormous increases in turgor pressure that can occur during the penetration phase.

Biomechanical Phenomena↗