池田 健一 | ![]() |
イケダ ケンイチ | |
大学院農学研究科 生命機能科学専攻 | |
准教授 | |
農学関係 |
2018年03月 日本植物病理学会, Journal of General Plant Pathology誌論文賞, Novel aspects of hydrophobins in wheat isolate of Magnaporthe oryzae: Mpg1, but not Mhp1, is essential for adhesion and pathogenicity
学会誌・学術雑誌による顕彰
2015年08月 日本植物病理学会, 植物感染生理談話会ポスター発表優秀賞, Ralstonia solanacearum OE1-1株のバイオフィルム形成にレクチンES-IILは必要である
日本国国内学会・会議・シンポジウム等の賞
2015年06月 医学生物学電子顕微鏡技術学会, 奨励賞, 電子顕微鏡分野における複数の優れた業績
日本国学会誌・学術雑誌による顕彰
2014年09月 日本育種学会, 第126回講演会日本育種学会優秀発表賞, 野生イネ(Oryza rufipogon)の遺伝的背景における種子脱粒性遺伝子座間の相互作用と離層形態
国内学会・会議・シンポジウム等の賞
2012年 日本土壌微生物学会, 日本土壌微生物学会優秀ポスター賞, ゼラチナーゼ活性を有する土壌微生物を利用した植物病害防除法の開発
国内学会・会議・シンポジウム等の賞
2012年 日本植物病理学会, The 2nd Korea-Japan Joint Symposium 2012 for Plant Pathology Excellent Poster Prize, Detachment control: importance of extracellular matrix (ECM) for pathogenicity and potential target for disease protection
国際学会・会議・シンポジウム等の賞
2011年 日本植物病理学会, 日本植物病理学会論文賞, Chuma, I., Shinogi, T., Hosogi, N., Ikeda, K., Nakayashiki, H., Park, P., and Tosa, Y. (2009) Cytological characteristics of microconidia of Magnaporthe oryzae. J. Gen. Plant Pathol. 75:353-358
学会誌・学術雑誌による顕彰
2006年 日本植物病理学会, 日本植物病理学会学術奨励賞, 紋羽病菌におけるdsRNAの多様性とその動態
国内学会・会議・シンポジウム等の賞
研究論文(学術雑誌)
Abstract Rice is the model C3 crop for investigating the starch biosynthesis mechanism in endosperm because of its importance in grain production. However, little is known about starch biosynthesis in the vegetative organs of rice. In this study, we used novel rice mutants by inserting Tos17 into the starch synthase (SS) IIIb gene, which is mainly expressed in the leaf sheath (LS) and leaf blade (LB), and an ss1 mutant to clarify the differences in roles among SS isozymes during starch biosynthesis. Native polyacrylamide gel electrophoresis (PAGE)/activity staining for SS, using LS and LB of ss mutants, revealed that the lowest migrating SS activity bands on the gel were derived from SSIIIb activity and those of two ss3b mutants were not detected. The apparent amylose content of LS starch of ss3b mutants increased. Moreover, the chain-length distribution and size-exclusion chromatography analysis using ss mutants showed that SSIIIb and SSI synthesize the B2–B3 chain and A–B1 chain of amylopectin in the LS and LB respectively. Interestingly, we also found that starch contents were decreased in the LS and LB of ss3b mutants, although SSI deficiency did not affect the starch levels. All these results indicated that SSIIIb synthesizes the long chain of amylopectin in the LS and LB similar to SSIIIa in the endosperm, while SSI synthesizes the short chain in the vegetative organ as the same in the endosperm.
Oxford University Press (OUP), 2022年10月12日, Plant and Cell Physiology, 64 (1), 94 - 106, 英語, 国内誌研究論文(学術雑誌)
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研究論文(学術雑誌)
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研究論文(学術雑誌)
CO2-responsive CCT protein (CRCT) is suggested to be a positive regulator of starch biosynthesis in the leaf sheaths of rice, regulating the expression levels of starch biosynthesis-related genes. In this study, the effects of CRCT expression levels on the expression of starch biosynthesis-related enzymes and the quality of starch were studied. Using native-PAGE/activity staining and immunoblotting, we found that the protein levels of starch synthase I, branching enzyme I, branching enzyme IIa, isoamylase 1 and phosphorylase 1 were largely correlated with the CRCT expression levels in the leaf sheaths of CRCT transgenic lines. In contrast, the CRCT expression levels largely did not affect the expression levels and/or activities of starch biosynthesis-related enzymes in the leaf blades and endosperm tissues. The analysis of the chain-length distribution of starch in the leaf sheaths showed that short chains with a degree of polymerization from 5 to 14 were increased in the overexpression lines but decreased in the knockdown lines. The amylose content of starch in the leaf sheath was greatly increased in the overexpression lines. In contrast, the molecular weight of the amylopectin of starch in the leaf sheath of overexpression lines did not change compared with those of the non-transgenic rice. These results suggest that CRCT can control the quality and the quantity of starch in the leaf sheath by regulating the expression of particular starch biosynthesis-related enzymes.
2019年05月, Plant and Cell Physiology, 60 (5), 961 - 972, 英語, 国内誌[査読有り]
研究論文(学術雑誌)
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研究論文(学術雑誌)
Three ourmia-like viruses, designated Pyricularia oryzae ourmia-like virus (PoOLV) 1 to 3, were identified in a wheat-infecting isolate of P. oryzae. The sizes of the full-length PoOLV1-3 genomes were determined to be 2,528, 1,671, and 2,557 nt. Interestingly, we also found two abundant single-stranded RNAs sharing their 5' terminal 25 and 255 nt with PoOLV1 RNA and PoOLV3 RNA, respectively. The PoOLV1- and PoOLV3-associated RNAs (ARNA1 and ARNA3) were 639 and 514 nt in length, and possessed one and two small ORFs, respectively. In the field isolates of P. oryzae, PoOLVs and ARNAs were detectable at varying levels, and the levels of PoOLV1 and ARNA1 as well as those of PoOLV3 and ARNA3, were tightly correlated. In addition, gene silencing of PoOLV1 and PoOLV3 resulted in a reduction of ARNA1 and ARNA3, respectively. There results indicated that replication of ARNA1 and ARNA3 was associated with PoOLV1 and PoOLV3, respectively.
2019年, Virology, 534, 25 - 35, 英語, 国際誌[査読有り]
研究論文(学術雑誌)
© 2017 BSPP AND JOHN WILEY & SONS LTD After invasion into intercellular spaces of tomato plants, the soil-borne, plant-pathogenic Ralstonia solanacearum strain OE1-1 forms mushroom-shaped biofilms (mushroom-type biofilms, mBFs) on tomato cells, leading to its virulence. The strain OE1-1 produces aryl-furanone secondary metabolites, ralfuranones (A, B, J, K and L), dependent on the quorum sensing (QS) system, with methyl 3-hydroxymyristate (3-OH MAME) synthesized by PhcB as a QS signal. Ralfuranones are associated with the feedback loop of the QS system. A ralfuranone productivity-deficient mutant (ΔralA) exhibited significantly reduced growth in intercellular spaces compared with strain OE1-1, losing its virulence. To analyse the function of ralfuranones in mBF formation by OE1-1 cells, we observed cell aggregates of R. solanacearum strains statically incubated in tomato apoplast fluids on filters under a scanning electron microscope. The ΔralA strain formed significantly fewer microcolonies and mBFs than strain OE1-1. Supplementation of ralfuranones A, B, J and K, but not L, significantly enhanced the development of mBF formation by ΔralA. Furthermore, a phcB- and ralA-deleted mutant (ΔphcB/ralA) exhibited less formation of mBFs than OE1-1, although a QS-deficient, phcB-deleted mutant formed mBFs similar to OE1-1. Supplementation with 3-OH MAME significantly reduced the formation of mBFs by ΔphcB/ralA. The application of each ralfuranone significantly increased the formation of mBFs by ΔphcB/ralA supplied with 3-OH MAME. Together, our findings indicate that ralfuranones are implicated not only in the development of mBFs by strain OE1-1, but also in the suppression of QS-mediated negative regulation of mBF formation.
2018年04月, Molecular Plant Pathology, 19 (4), 975 - 985, 英語[査読有り]
研究論文(学術雑誌)
Small RNA (sRNA)-mediated gene silencing phenomena, exemplified by RNA interference (RNAi), require a unique class of proteins called Argonautes (AGOs). An AGO protein typically forms a protein-sRNA complex that contributes to gene silencing using the loaded sRNA as a specificity determinant. Here, we show that MoAGO2, one of the three AGO genes in the fungus Pyricularia oryzae (Magnaporthe oryzae) interferes with RNAi. Gene knockout (KO) studies revealed that MoAGO1 and MoAGO3 additively or redundantly played roles in hairpin RNA- and retrotransposon (MAGGY)-triggered RNAi while, surprisingly, the KO mutants of MoAGO2 (Δmoago2) showed elevated levels of gene silencing. Consistently, transcript levels of MAGGY and mycoviruses were drastically reduced in Δmoago2, supporting the idea that MoAGO2 impeded RNAi against the parasitic elements. Deep sequencing analysis revealed that repeat- and mycovirus-derived small interfering RNAs were mainly associated with MoAGO2 and MoAGO3, and their populations were very similar based on their size distribution patterns and positional base preference. Site-directed mutagenesis studies indicated that sRNA binding but not slicer activity of MoAGO2 was essential for the ability to diminish the efficacy of RNAi. Overall, these results suggest a possible interplay between distinct sRNA-mediated gene regulation pathways through a competition for sRNA.
2018年03月, Nucleic Acids Research, 46 (5), 2495 - 2508, 英語, 国際誌[査読有り]
研究論文(学術雑誌)
Lettuce big-vein disease, caused by Mirafiori lettuce big-vein virus and Lettuce big-vein associated virus, is suppressed when the pH of field soil becomes acidic. Therefore, we evaluated the effect of soil pH on the activities of Olpidium virulentus, the vector of the viruses. We found that acidic soil, pH less than 6.0, significantly reduced O. virulentus infection of the root and influenced the detection rate of zoospores released in the surrounding water. We concluded that acidic soil suppresses zoospore release from zoosporangia.
SPRINGER JAPAN KK, 2017年07月, JOURNAL OF GENERAL PLANT PATHOLOGY, 83 (4), 240 - 243, 英語[査読有り]
研究論文(学術雑誌)
We conducted laboratory experiments to assess the disease control effects of pH-decreasing fertilizer as a new control material for lettuce big-vein disease. Results show that the occurrence of big-vein disease was suppressed in concomitance with the descent of soil pH by applying the fertilizer.
関西病虫害研究会, 2017年05月, 関西病虫害研究会報, 59 (59), 51 - 53, 日本語[査読有り]
研究論文(学術雑誌)
The Sclerotium is one of the most persistent organs in filamentous fungi. Control of sclerotial formation is promising in the prevention of sclerotial disease. In this study, cytological analyses of sclerotial development were conducted in Sclerotinia minor. Number and size of sclerotia were correlated with nutrient concentration of the media. Interruption of aeration by sealing with parafilm completely suppressed sclerotial formation. We also found that reactive oxygen species (ROS) generated two phases, i.e., hydrogen peroxide at sclerotial initial (SI) stage and O-2(-) at outer layer of sclerotial development/mature stages, during sclerotial formation. Ultrastructural analyses revealed that ROS was prominently produced at the outer layer of sclerotia in sclerotial mature (SM) phase. Although most of the inhibitors for ROS generation enzymes were ineffective for sclerotial formation, ascorbic acid, one of the scavengers of hydrogen peroxide, inhibited melanin biosynthesis during sclerotial maturation stage. The mycelia sealed with parafilm, when exogenously sprayed with hydrogen peroxide, could not produce sclerotium. These results indicated that ROS generation during sclerotial formation is mainly involved in the production of melanin layer. (C) 2016 British Mycological Society. Published by Elsevier Ltd. All rights reserved.
ELSEVIER SCI LTD, 2017年02月, FUNGAL BIOLOGY, 121 (2), 127 - 136, 英語[査読有り]
研究論文(学術雑誌)
Light and temperature affect state transitions through changes in the plastoquinone (PQ) redox state in photosynthetic organisms. We demonstrated that light and/or heat treatment induced preferential photosystem (PS) I excitation by binding light-harvesting complex II (LHCII) proteins. The photosystem of wheat was in state 1 after dark overnight treatment, wherein PQ was oxidized and most of LHCII was not bound to PSI. At the onset of the light treatment [25 A degrees C in the light (100 A mu mol photons m(-2) s(-1))], two major LHCIIs, Lhcb1 and Lhcb2 were phosphorylated, and the PSI-LHCII supercomplex formed within 5 min, which coincided with an increase in the PQ oxidation rate. Heat treatment at 40 A degrees C of light-adapted wheat led to further LHCII protein phosphorylation of, resultant cyclic electron flow promotion, which was accompanied by ultrafast excitation of PSI and structural changes of thylakoid membranes, thereby protecting PSII from heat damage. These results suggest that LHCIIs are required for the functionality of wheat plant PSI, as it keeps PQ oxidized by regulating photochemical electron flow, thereby helping acclimation to environmental changes.
SPRINGER, 2017年01月, PHOTOSYNTHESIS RESEARCH, 131 (1), 41 - 50, 英語[査読有り]
研究論文(学術雑誌)
CO2-responsive CCT protein (CRCT) is the suggested positive regulator of starch synthesis in vegetative organs, particularly the leaf sheath of rice. In this study, we analyzed the effects of the starch level in the leaf sheath on the photosynthetic rate in the leaf blade using CRCT overexpression and RNA interference (RNAi) knockdown transgenic rice grown under ambient (38 Pa) or elevated (100 Pa) CO2 conditions. In leaf sheath, the starch content was markedly changed in relation to CRCT expression levels under both CO2 conditions. In contrast, the soluble sugar and starch contents of the leaf blade were markedly increased in the knockdown line grown under elevated CO2 conditions. The overexpression or RNAi knockdown of CRCT did not cause large effects on the photosynthetic rate of the transgenic lines grown under ambient CO2 condition. However, the photosynthetic rate of the overexpression line was enhanced, while that of the knockdown line was substantially decreased under elevated CO2 conditions. These photosynthetic rates were weakly correlated with the nitrogen contents and negatively correlated with the total nonstructural carbohydrate contents. Thus, the capacity for starch synthesis in leaf sheath, which is controlled by CRCT, can indirectly affect the carbohydrate content, and then the photosynthetic rate in the leaf blade of rice grown under elevated CO2 conditions.
OXFORD UNIV PRESS, 2016年11月, PLANT AND CELL PHYSIOLOGY, 57 (11), 2334 - 2341, 英語[査読有り]
研究論文(学術雑誌)
The mechanism of colonization of intercellular spaces by the soil-borne and vascular plant-pathogenic bacterium Ralstonia solanacearum strain OE1-1 after invasion into host plants remains unclear. To analyse the behaviour of OE1-1 cells in intercellular spaces, tomato leaves with the lower epidermis layers excised after infiltration with OE1-1 were observed under a scanning electron microscope. OE1-1 cells formed microcolonies on the surfaces of tomato cells adjacent to intercellular spaces, and then aggregated surrounded by an extracellular matrix, forming mature biofilm structures. Furthermore, OE1-1 cells produced mushroom-type biofilms when incubated in fluids of apoplasts including intercellular spaces, but not xylem fluids from tomato plants. This is the first report of biofilm formation by R. solanacearum on host plant cells after invasion into intercellular spaces and mushroom-type biofilms produced by R. solanacearum in vitro. Sugar application led to enhanced biofilm formation by OE1-1. Mutation of lecM encoding a lectin, RS-IIL, which reportedly exhibits affinity for these sugars, led to a significant decrease in biofilm formation. Colonization in intercellular spaces was significantly decreased in the lecM mutant, leading to a loss of virulence on tomato plants. Complementation of the lecM mutant with native lecM resulted in the recovery of mushroom-type biofilms and virulence on tomato plants. Together, our findings indicate that OE1-1 produces mature biofilms on the surfaces of tomato cells after invasion into intercellular spaces. RS-IIL may contribute to biofilm formation by OE1-1, which is required for OE1-1 virulence.
WILEY-BLACKWELL, 2016年08月, MOLECULAR PLANT PATHOLOGY, 17 (6), 890 - 902, 英語[査読有り]
研究論文(学術雑誌)
Lipid-derived reactive carbonyl species (RCS) possess electrophilic moieties and cause oxidative stress by reacting with cellular components. Arabidopsis (Arabidopsis thaliana) has a chloroplast-localized alkenal/one oxidoreductase (AtAOR) for the detoxification of lipid-derived RCS, especially alpha,beta-unsaturated carbonyls. In this study, we aimed to evaluate the physiological importance of AtAOR and analyzed AtAOR (aor) mutants, including a transfer DNA knockout, aor (T-DNA), and RNA interference knockdown, aor (RNAi), lines. We found that both aor mutants showed smaller plant sizes than wild-type plants when they were grown under day/night cycle conditions. To elucidate the cause of the aor mutant phenotype, we analyzed the photosynthetic rate and the respiration rate by gas-exchange analysis. Subsequently, we found that both wildtype and aor (RNAi) plants showed similar CO2 assimilation rates; however, the respiration rate was lower in aor (RNAi) than in wild-type plants. Furthermore, we revealed that phosphoenolpyruvate carboxylase activity decreased and starch degradation during the night was suppressed in aor (RNAi). In contrast, the phenotype of aor (RNAi) was rescued when aor (RNAi) plants were grown under constant light conditions. These results indicate that the smaller plant sizes observed in aor mutants grown under day/night cycle conditions were attributable to the decrease in carbon utilization during the night. Here, we propose that the detoxification of lipid-derived RCS by AtAOR in chloroplasts contributes to the protection of dark respiration and supports plant growth during the night.
AMER SOC PLANT BIOLOGISTS, 2016年04月, PLANT PHYSIOLOGY, 170 (4), 2024 - 2039, 英語[査読有り]
研究論文(学術雑誌)
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研究論文(研究会,シンポジウム資料等)
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.
SPRINGER JAPAN KK, 2016年01月, JOURNAL OF GENERAL PLANT PATHOLOGY, 82 (1), 18 - 28, 英語[査読有り]
研究論文(学術雑誌)
We designed specific primers for Coniothyrium minitans, a sclerotia-parasitizing biocontrol agent (BCA), and quantified its biomass in the field by quantitative polymerase chain reaction. Because chemical properties of the soil can decrease the DNA extraction efficiency and DNA polymerase activity, standard curves were calibrated by adding known concentrations of BCA to sterilized field soil. The BCA biomass was monitored over time and after various treatments. Because the distribution of the BCA biomass was uneven in the field, a method to spread BCA uniformly in the field is needed.
SPRINGER JAPAN KK, 2016年01月, JOURNAL OF GENERAL PLANT PATHOLOGY, 82 (1), 51 - 56, 英語[査読有り]
研究論文(学術雑誌)
Hyphal interactions of 10 Rosellinia necatrix isolates were analyzed. Most incompatible pairings produced broad melanized barrage lines, with a few exceptions. The variation in barrage lines revealed using light microscopy might result from distinct frequencies of different hyphal interaction types. In incompatible pairings, hyphal anastomosis was rarely observed. Activated-charcoal treatment of oatmeal agar media prevented both incompatible and compatible reactions. FUN-1 staining showed vacuole dysfunction at hyphal interaction sites, and the localization of a Lifeact-GFP mutant revealed that actin dynamics was prominent in compatible pairings. These results suggested that self/nonself recognition commonly proceeded to vacuole dysfunction and that actin dynamics played a critical role in the restoration of vacuole integrity.
SPRINGER JAPAN KK, 2015年11月, JOURNAL OF GENERAL PLANT PATHOLOGY, 81 (6), 420 - 428, 英語[査読有り]
研究論文(学術雑誌)
Uranyl salts are toxic and radioactive; therefore, several studies have been conducted to screen for substitutes of electron stains. In this regard, the contrast evaluation process is time consuming and the results obtained are inconsistent. In this study, we developed a novel contrast evaluation method using affinity beads and a backscattered electron image (BSEI), obtained using scanning electron microscopy. The contrast ratios of BSEI in each electron stain treatment were correlated with those of transmission electron microscopic images. The affinity beads bound to cell components independently. Protein and DNA samples were enhanced by image contrast treated with electron stains; however, this was not observed for sugars. Protein-conjugated beads showed an additive effect of image contrast when double-stained with lead. However, additive effect of double staining was not observed in DNA-conjugated beads. The varying chemical properties of oligopeptides showed differences in image contrast when treated with each electron stain. This BSEI-based evaluation method not only enables screening for alternate electron stains, but also helps analyze the underlying mechanisms of electron staining of cellular structures.
OXFORD UNIV PRESS, 2015年10月, MICROSCOPY, 64 (5), 361 - 368, 英語[査読有り]
研究論文(学術雑誌)
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研究論文(研究会,シンポジウム資料等)
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研究論文(研究会,シンポジウム資料等)
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研究論文(学術雑誌)
Here we report the genetic analyses of histone lysine methyltransferase (KMT) genes in the phytopathogenic fungus Magnaporthe oryzae. Eight putative M. oryzae KMT genes were targeted for gene disruption by homologous recombination. Phenotypic assays revealed that the eight KMTs were involved in various infection processes at varying degrees. Moset1 disruptants (Delta moset1) impaired in histone H3 lysine 4 methylation (H3K4me) showed the most severe defects in infection-related morphogenesis, including conidiation and appressorium formation. Consequently,Delta moset1 lost pathogenicity on wheat host plants, thus indicating that H3K4me is an important epigenetic mark for infection-related gene expression in M. oryzae. Interestingly, appressorium formation was greatly restored in the Delta moset1 mutants by exogenous addition of cAMP or of the cutin monomer, 16-hydroxypalmitic acid. The Delta moset1 mutants were still infectious on the super-susceptible barley cultivar Nigrate. These results suggested that MoSET1 plays roles in various aspects of infection, including signal perception and overcoming host-specific resistance. However, since Delta moset1 was also impaired in vegetative growth, the impact of MoSET1 on gene regulation was not infection specific. ChIP-seq analysis of H3K4 di- and tri-methylation (H3K4me2/me3) and MoSET1 protein during infection-related morphogenesis, together with RNA-seq analysis of the Delta moset1 mutant, led to the following conclusions: 1) Approximately 5% of M. oryzae genes showed significant changes in H3K4-me2 or -me3 abundance during infection-related morphogenesis. 2) In general, H3K4-me2 and -me3 abundance was positively associated with active transcription. 3) Lack of MoSET1 methyltransferase, however, resulted in up-regulation of a significant portion of the M. oryzae genes in the vegetative mycelia (1,491 genes), and during infection-related morphogenesis (1,385 genes), indicating that MoSET1 has a role in gene repression either directly or more likely indirectly. 4) Among the 4,077 differentially expressed genes (DEGs) between mycelia and germination tubes, 1,201 and 882 genes were up- and down-regulated, respectively, in a Moset1-dependent manner. 5) The Moset1-dependent DEGs were enriched in several gene categories such as signal transduction, transport, RNA processing, and translation.
PUBLIC LIBRARY SCIENCE, 2015年07月, PLOS GENETICS, 11 (7), e1005385, 英語[査読有り]
研究論文(学術雑誌)
Loss of seed shattering was one of the key phenotypic changes selected for in the domestication of many crop species. Asian cultivated rice, Oryza sativa L., was domesticated from its wild ancestor, 0. rufipogon, and three seed-shattering loci, qSH1, sh4 and qSH3, have been reported to be involved in the loss of seed shattering in cultivated rice. Here, we analysed the seed-shattering behaviour of wild rice using introgression lines carrying the cultivated alleles from 0. sativa Nipponbare in the genetic background of wild rice, 0. rufipogon W630. We first carried out fine mapping of the qSH3 region and found that the qSH3 locus is localized in an 850-kb region on chromosome 3. We then analysed the effects of the Nipponbare alleles at sh4 and qSH3 on seed-shattering behaviour in wild rice, as a mutation at qSH1 was not commonly found in rice cultivars. Seed-shattering behaviour did not change in the two types of introgression line independently carrying the Nipponbare-homozygous alleles at sh4 or qSH3 in the genetic background of wild rice. However, the introgression lines having the Nipponbare-homozygous alleles at both sh4 and qSH3 showed a reduction in the degree of seed shattering. Histological and scanning electron microscopy analyses revealed that abscission layer formation was inhibited around the vascular bundles in these lines. Since the qSH3 region, as well as sh4, has been shown to be under artificial selection, the interaction of mutations at these two loci may have played a role in the initial loss of seed shattering during rice domestication.
GENETICS SOC JAPAN, 2015年02月, GENES & GENETIC SYSTEMS, 90 (1), 1 - 9, 英語[査読有り]
研究論文(学術雑誌)
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研究論文(学術雑誌)
Photosystems of higher plants alleviate heat-induced damage in the presence of light under moderate stressed conditions; however, in the absence of light (i.e., in the dark), the same plants are damaged more easily. (Yamauchi and Kimura, 2011) We demonstrate that regulating photochemical energy transfer in heat-treated wheat at 40 degrees C with light contributed to heat tolerance of the photosystem. Chlorophyll fluorescence analysis using heat-stressed wheat seedlings in light showed increased non-photochemical quenching (NPQ) of chlorophyll fluorescence, which was due to thermal dissipation that was increased by state 1 to state 2 transition. Transmission electron microscopy revealed structural changes in thylakoid membranes, including unstacking of grana regions under heat stress in light. It was accompanied by the phosphorylation of thylakoid proteins such as D1 and D2 proteins and the light harvesting complex II proteins Lhcb1 and Lhcb2. These results suggest that heat stress at 40 degrees C in light induces state 1 to state 2 transition for the preferential excitation of photosystem I (PSI) by phosphorylating thylakoid proteins more strongly. Structural changes of thylakoid membrane also assist the remodeling of photosystems and regulation of energy distribution by transition toward state 2 probably contributes to plastoquione oxidation; thus, light-driven electrons flowing through PSI play a protective role against PSII damage under heat stress.
MDPI AG, 2014年12月, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 15 (12), 23042 - 23058, 英語[査読有り]
研究論文(学術雑誌)
We had previously obtained collagenolytic/gelatinolytic bacteria, which degrade the fungal extracellular matrix, to establish a novel biological control measure that inhibits germling adhesion of airborne phytopathogenic fungi on the host plant surface. By using barley-Magnaporthe oryzae pathosystem, Chryseobacterium sp. was most effective biocontrol agents as tested. The selected bacteria were evaluated for durable disease protection against M. oryzae on barley leaves by using chloramphenicol-resistant mutants. Chryseobacterium sp. from the soil was less likely to settle on leaf surfaces. Therefore, we tried to manipulate Chryseobacterium sp. to inhabit the leaf's surface. The gelatin supplementation dramatically improved the settlement of gelatinolytic bacteria Chryseobacterium sp. from the soil, and the disease protection effect lasted for more than 2 weeks on barley. Moreover, exploitation of Chryseobacterium sp. for disease protection was extended against other airborne pathogens, Alternaria alternata Japanese pear pathotype on Japanese pear and Colletotrichum orbiculare on cucumber. (C) 2014 Elsevier Inc. All rights reserved.
ACADEMIC PRESS INC ELSEVIER SCIENCE, 2014年04月, BIOLOGICAL CONTROL, 71, 1 - 6, 英語[査読有り]
研究論文(学術雑誌)
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[査読有り]
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 F-1 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.
GENETICS SOC AM, 2013年11月, GENETICS, 195 (3), 845 - +, 英語[査読有り]
研究論文(学術雑誌)
Heterogenic incompatibility is considered a defense mechanism against deleterious intruders such as mycovirus. Rosellinia necatrix shows strong heterogenic incompatibility. In the heterogenic incompatibility reaction, the approaching hyphae hardly anastomosed, a distinctive barrage line formed, and green fluorescent protein (GFP)-labeled hyphae quickly lost their fluorescence when encountering incompatible hyphae. In this study, transmission of a hypovirulence-conferring mycovirus to strains with different genetic backgrounds was attempted. Various chemical reagents considered to affect the programmed cell death pathway or cell wall modification were examined. Treatment with zinc compounds was shown to aid in transmission of mycoviruses to strains with different genetic backgrounds. In incompatible pairings, treatment with zinc compounds accelerated hyphal anastomosis; moreover, cytosolic GFP was transmitted to the newly joined hyphae. These results suggest that zinc compounds not only increase hyphal anastomosis but also attenuate heterogenic incompatibility.
AMER SOC MICROBIOLOGY, 2013年06月, APPLIED AND ENVIRONMENTAL MICROBIOLOGY, 79 (12), 3684 - 3691, 英語[査読有り]
研究論文(学術雑誌)
Black spot disease, Alternaria alternataJapanese pear pathotype, produces the host-specific toxin AK-toxin, an important pathogenicity factor. Previously, we have found that hydrogen peroxide is produced in the hyphal cell wall at the plantpathogen interaction site, suggesting that the fungal reactive oxygen species (ROS) generation machinery is important for pathogenicity. In this study, we identified two NADPH oxidase (NoxA and NoxB) genes and produced nox disruption mutants. noxA and noxB disruption mutants showed increased hyphal branching and spore production per unit area. Surprisingly, only the noxB disruption mutant compromised disease symptoms. A fluorescent protein reporter assay revealed that only NoxB localized at the appressoria during pear leaf infection. In contrast, both NoxA and NoxB were highly expressed on the cellulose membrane, and these Nox proteins were also localized at the appressoria. In the noxB disruption mutant, we could not detect any necrotic lesions caused by AK-toxin. Moreover, the noxB disruption mutant did not induce papilla formation on pear leaves. Ultrastructural analysis revealed that the noxB disruption mutant also did not penetrate the cuticle layer. Moreover, ROS generation was not essential for penetration, suggesting that NoxB may have an unknown function in penetration. Taken together, our results suggest that NoxB is essential for aggressiveness and basal pathogenicity in A.alternata.
WILEY-BLACKWELL, 2013年05月, MOLECULAR PLANT PATHOLOGY, 14 (4), 365 - 378, 英語[査読有り]
研究論文(学術雑誌)
[招待有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
[査読有り]
[査読有り]
[査読有り]
生物防除を成功させるためには,病原菌とそれを取り巻く微生物群の生態的特徴を理解する必要がある。果樹類紋羽病菌は菌糸を伸展させて伝搬するタイプの病原菌であり,生物防除を利用するのに適している。さらに,土壌中の微生物分の影響を除去するために,病原菌細胞内で増殖・伝搬できる菌類ウイルスの利用(ヴァイロコントロール)が効果的であると考えられる。これまでに,白紋羽病菌を対象として,病原力低下作用を有する菌類ウイルスを明らかとし,それらを任意菌株へ伝搬させる手法の確立を進めている。
土壌微生物研究会, 2012年, 土と微生物, 66 (2), 55 - 57, 日本語研究論文(研究会,シンポジウム資料等)
病害防除においては,抵抗性品種の崩壊や薬剤耐性菌の出現など多くの困難に直面する.持続的な病害防除を実現するためには,病原菌の感染戦略や生存戦略を理解し,効果的な防除手段を多数用意する必要がある.植物病害抵抗性遺伝子は病原菌の侵入を感知する受容体として機能している.しかし,植物に認識される因子は病原菌にとって必須ではない場合が多く,その因子を変異させることにより容易に抵抗性品種の崩壊が起こると考えられている.病原菌が病原力を発揮するために必要不可欠な因子-言わば病原菌のアキレス腱部位-を認識できる病害抵抗性遺伝子を選抜育種あるいは進化分子工学的手法により創出することができれば,持続性の高い防除が実現可能となる.
近畿作物・育種研究会, 2012年, Journal of Crop Research, 57, 61 - 66, 日本語研究論文(研究会,シンポジウム資料等)
Azoxystrobin (AZ), a strobilurin-derived fungicide, is known to inhibit mitochondrial respiration in fungi by blocking the electron transport chain in the inner mitochondrial membrane. Germination was strongly inhibited when Botrytis cinerea spore suspension was treated with AZ and the alternative oxidase (AOX) inhibitors, salicylhydroxamic acid (SHAM) and n-propyl gallate. However, chemical death indicators trypan blue and propidium iodide showed that those spores were still alive. When the spore suspension in the AZ and SHAM solution was replaced with distilled water, the germination rate almost recovered, at least during the first 2 days of incubation with AZ and SHAM solution. No morphological alteration was detected in the cells treated with AZ and SHAM, especially in mitochondria, using transmission electron microscopy. Therefore, simultaneous application of AZ and AOX inhibitors has a fungistatic, rather than a fungicidal, action.
OXFORD UNIV PRESS, 2012年01月, FEMS MICROBIOLOGY LETTERS, 326 (1), 83 - 90, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
Magnaporthe oryzae germlings tightly attach to the host surface by producing extracellular matrix (ECM) from germ tubes and appressoria, which are important for the early infection process. To understand the adhesion mechanisms of ECM during differentiation of infection structure, we evaluated the effects of various enzymes on M. oryzae germlings and the disease symptoms of the host plant, wheat. Treatment with beta-mannosidase, collagenase N-2, collagenase S-1, or gelatinase B at 1-h postinoculation (hpi) resulted in germling detachment, although producing normal appressoria. Treatment with matrix metalloproteinases (MMPs) at 6 hpi also caused germling detachment. Furthermore, we confirmed by the inoculation tests and scanning electron microscopy that the germlings on the wheat plant were removed and did not manifest pathogenicity on treatment with MMPs. The most effective MMPs were crude collagenase, collagenase S-1, and gelatinase B, suggesting that the application of MMPs is promising for crop protection from fungal diseases by its detachment action.
OXFORD UNIV PRESS, 2011年10月, FEMS MICROBIOLOGY LETTERS, 323 (1), 13 - 19, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
This ultrastructural study showed that nonisotopic methanolic hafnium chloride and aqueous lead solution was an excellent new electron stain for enhancing TEM contrasts of fungal and plant cell structures. The ultrastructural definition provided by the new stain was often superior to that provided by conventional staining with uranyl acetate and lead. Definition of fine ultrastructure was also supported by quantitative data on TEM contrast ratios of organelles and components in fungal and plant cells. In particular, polysaccharides, which were localized in cell walls, glycogen particles, starch grains, and plant Golgi vesicle components, were much more reactive to the new stain than to the conventional one. The new nonisotopic stain is useful for enhancing the contrast of ultrastructure in biological tissues and is a safer alternative to uranyl acetate. Microsc. Res. Tech. 74: 825-830, 2011. (C) 2010 Wiley-Liss, Inc.
WILEY, 2011年09月, MICROSCOPY RESEARCH AND TECHNIQUE, 74 (9), 825 - 830, 英語[査読有り]
研究論文(学術雑誌)
When the mycelia of Helicobasidium mompa encounter mycelia with a different genetic background, distinct demarcation lines form. The hyphae of H. mompa induce heterogenic incompatibility accompanied by active programmed cell death (PCD) process. In this study, we observed hyphal interaction between compatible and incompatible H. mompa pairs by means of light and electron microscopy. PCD started with one of the two approaching hyphae. Heterochromatin condensation and genomic DNA laddering were not observed. Moreover, cell damage began with the tonoplast and continued with the plasma membrane and nuclear membrane, suggesting that the PCD observed in heterogenic incompatibility of H. mompa is a vacuole-mediated process.
OXFORD UNIV PRESS, 2011年02月, FEMS MICROBIOLOGY LETTERS, 315 (2), 94 - 100, 英語[査読有り]
研究論文(学術雑誌)
研究論文(研究会,シンポジウム資料等)
研究論文(研究会,シンポジウム資料等)
When mycelia of Rosellinia necatrix encounter mycelia of a different genetic strain, distinct barrage lines are formed between the two. These barrages have variable features such as pigmented pseudosclerotia structures, a clear zone, fuzzy hair-like mycelia, or tuft-like mycelia, suggesting that mycelial incompatibility triggers a number of cellular reactions. In this study, to evaluate cellular reactions we performed genetic analysis of mycelial incompatibility of R. nectarix, using 20 single ascospore isolates from single perithecia. Mycelial interaction zones were removed by spatula and cellular reactions studied on oatmeal agar media. The interaction zones were categorized into types such as sharp or wide lines, with or without melanin, and combinations of these. Although various reaction types were observed, we were able to identify a single genetic factor that appears to be responsible for the barrage line formation within oatmeal agar medium. DNA polymorphism analysis identified parental isolates and revealed that R. necatrix has a heterothallic life cycle. (C) 2010 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.
ELSEVIER SCI LTD, 2011年01月, FUNGAL BIOLOGY, 115 (1), 80 - 86, 英語[査読有り]
研究論文(学術雑誌)
When the mycelia of Rosellinia necatrix encounter mycelia with a different genetic background, distinct barrage lines form. In this study, we observed hyphal interactions between compatible and incompatible R. necatrix pairs by means of light and electron microscopy. Although we observed perfect hyphal anastomosis in compatible pairs of isolates, the hyphae never anastomosed in incompatible pairs (i.e., the hyphae remained parallel or crossed over without merging). These behaviours appeared to result from the detection of or failure to detect one or more diffusible factors. The attraction to other hyphae in pairs of incompatible isolates was increased by supplementation of the growing medium with activated charcoal, although no anastomosis was observed and ultrastructural observation confirmed a lack of hyphal anastomosis. Programmed cell death (PCD) started with one of the two approaching hyphae. Heterochromatin condensation and genomic DNA fragmentation were not observed. Moreover, cell damage began with the tonoplast and continued with the plasma and nuclear membranes, suggesting that the PCD observed in heterogenic incompatibility of R. necatrix was a vacuole-mediated process. (C) 2010 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.
ELSEVIER SCI LTD, 2011年01月, FUNGAL BIOLOGY, 115 (1), 87 - 95, 英語[査読有り]
研究論文(学術雑誌)
研究論文(研究会,シンポジウム資料等)
研究論文(研究会,シンポジウム資料等)
[査読有り]
We screened collagenolytic/gelatinolytic bacteria from rice leaves and soil which degraded the fungal extracellular matrix to establish a novel biological control measure inhibiting germling adhesion on the host plant surface against airborne fungal diseases such as rice blast disease Magnaporthe oryzae B. Coch. Two different screening methods, i.e., screening from the leaf-associated bacterial library and direct screening from leaf and soil with or without collagen incubation, were conducted. Screening from the collagen treated material resulted in a higher number of gelatinolytic isolates than without collagen treatment. The selected bacteria were identified as Acidovorax, Sphingomonas, Chryseobacterium, and Pseudomonas genera by 16S rDNA sequence. Based on treatment with EDTA and addition of divalent cations, four of the five screened isolates tested produced a metalloproteinase. Furthermore, the enzymes produced by Acidovorax and Sphingomonas sp. were categorized as calcium-dependent metalloproteinases, and the enzymes produced by Chryseobacterium sp. were categorized as calcium/zinc-dependent metalloproteinases. The screened bacterial culture showed inhibitory effects on spore adhesion on the plastic cover glass, and disease protective effects on rice. This study suggests that bacteria inhibiting germling adhesion by phytopathogenic fungi may have promise as a biological agent. (C) 2010 Elsevier Inc. All rights reserved.
ACADEMIC PRESS INC ELSEVIER SCIENCE, 2010年11月, BIOLOGICAL CONTROL, 55 (2), 85 - 91, 英語[査読有り]
研究論文(学術雑誌)
In the Japanese pear pathotype of Alternaria alternata, H(2)O(2) is generated solely from penetration pegs and not from other portions of subcuticular hyphae within the pectin layers of host leaves. A close association between H(2)O(2) generation and fungal aggressiveness is expected because the pegs are important for fungal penetration into the host epidermis. To determine the potential role of reactive oxygen species in microbial pathogenicity, we studied the inhibitory effects of the antioxidant reagent ascorbic acid and the NADPH oxidase inhibitor diphenylene iodonium on infection of the pathogen. In our study, we showed H(2)O(2) generation to be inhibited by inoculation with the mixture of ascorbic acid or diphenylene iodonium and spores at the pegs in the spore-inoculated host leaves. The decrease of generation in the pegs resulted in penetration failure, indicating that H(2)O(2) generation probably contributed to strengthening of the penetration and probably was recruited by NADPH oxidase.
AMER PHYTOPATHOLOGICAL SOC, 2010年09月, PHYTOPATHOLOGY, 100 (9), 840 - 847, 英語[査読有り]
研究論文(学術雑誌)
Aims: To isolate and characterize copper-resistant halophilic bacteria from the polluted Maruit Lake, Egypt and identify the role of plasmids in toxic metal resistance. Methods and Results: We isolated strain MA2, showing high copper resistance up to the 1 center dot 5 mmol l-1 concentration; it was also resistant to other metals such as nickel, cobalt and zinc and a group of antibiotics. Partial 16S rRNA analysis revealed that strain MA2 belonged to the genus Halomonas. Copper uptake, measured by atomic absorption spectrophotometery, was higher in the absence of NaCl than in the presence of 0 center dot 5-1 center dot 0 mol l-1 NaCl during 5-15 min of incubation. Cell fractionation and electron microscopic observation clarified that most of the copper accumulated in the outer membrane and periplasmic fractions of the cells. Plasmid screening yielded two plasmids: pMA21 (11 kb) and pMA22 (5 kb). Plasmid curing resulted in a strain that lost both the plasmids and was sensitive to cobalt and chromate but not copper, nickel and zinc. This cured strain also showed weak growth in the presence of 0 center dot 5-1 center dot 0 mol l-1 NaCl. Partial sequencing of both plasmids led to the identification of different toxic metals transporters but copper transporters were not identified. Conclusions: The highest cell viability was found in the presence of 1 center dot 0 mol l-1 NaCl at different copper concentrations, and copper uptake was optimal in the absence of NaCl. Plasmid pMA21 encoded chromate, cobalt, zinc and cadmium transporters, whereas pMA22 encoded specific zinc and RND (resistance, nodulation, cell division) efflux transporters as well as different kinds of metabolic enzymes. Copper resistance was mainly incorporated in the chromosome. Significance and Impact of the Study: Strain MA2 is a fast and efficient tool for copper bioremediation and the isolated plasmids show significant characteristics of both toxic metal and antibiotic resistance.
WILEY-BLACKWELL PUBLISHING, INC, 2010年04月, JOURNAL OF APPLIED MICROBIOLOGY, 108 (4), 1459 - 1470, 英語[査読有り]
研究論文(学術雑誌)
研究論文(国際会議プロシーディングス)
研究論文(国際会議プロシーディングス)
研究論文(研究会,シンポジウム資料等)
研究論文(国際会議プロシーディングス)
[査読有り]
研究論文(学術雑誌)
研究論文(国際会議プロシーディングス)
研究論文(国際会議プロシーディングス)
研究論文(国際会議プロシーディングス)
研究論文(国際会議プロシーディングス)
[査読有り]
研究論文(学術雑誌)
研究論文(研究会,シンポジウム資料等)
研究論文(国際会議プロシーディングス)
研究論文(研究会,シンポジウム資料等)
研究論文(国際会議プロシーディングス)
研究論文(国際会議プロシーディングス)
The inner cellular structure of microconidia of Magnaporthe oryzae was examined using fluorescent probes and electron microscopic techniques. The volume of the nucleus relative to the cell was significantly larger in microconidia than in macroconidia or vegetative hyphae, similar to observations for spermatia of other fungi. Selective fluorescent staining revealed that cytosolic RNA was less abundant in microconidia than in macroconidia and germ tubes, suggesting that general metabolic activity in microconidia is low. Consistently, GFP expression driven by the TrpC promoter was highly active during the formation of phialides and microconidia but gradually decreased as the microconidia matured. Such data suggest that microconidia are in a quiescent or dormant state.
SPRINGER TOKYO, 2009年10月, JOURNAL OF GENERAL PLANT PATHOLOGY, 75 (5), 353 - 358, 英語[査読有り]
研究論文(学術雑誌)
研究論文(研究会,シンポジウム資料等)
[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
研究論文(国際会議プロシーディングス)
研究論文(国際会議プロシーディングス)
[査読有り]
研究論文(学術雑誌)
研究論文(国際会議プロシーディングス)
研究論文(研究会,シンポジウム資料等)
[査読有り]
研究論文(学術雑誌)
The International Committee on Taxonomy of Viruses (ICTV) recently accepted Endornavirus as a new genus of plant dsRNA virus. We have determined the partial nucleotide sequences of the RNA-dependent RNA polymerase regions from the large dsRNAs (about 14 kbp) isolated from barley (Hordeum vulgare), kidney bean (Phaseolus vulgaris), melon (Cucumis melo), bottle gourd (Lagenaria siceraria), Malabar spinach (Basella alba), seagrass (Zostera marina), and the fungus Helicobasidium mompa. Phylogenetic analyses of these seven dsRNAs indicate that these dsRNAs are new members of the genus Endornavirus that are widely distributed over the plant and fungal kingdoms.
SPRINGER WIEN, 2006年05月, ARCHIVES OF VIROLOGY, 151 (5), 995 - 1002, 英語[査読有り]
研究論文(学術雑誌)
The white root rot fungus, Rosellinia necatrix, is a devastating soil-borne pathogen of many plant species. Biocontrol with the hypovirulence factor is promising, but disease symptoms, signs or culture morphology of the pathogen cannot be reliably used as markers for hypovirulence in this fungus. We attempted to obtain hypovirulent isolates from soil rather than from diseased roots, based on the hypothesis that hypovirulent isolates were more likely to persist in soil as saprobes. Sixteen isolates, belonging to eight mycelial compatibility groups (MCGs), were obtained from soil in two active and one abandoned Japanese pear orchards. Comparison of these isolates based on clonality revealed that six MCGs were commonly recovered from both diseased roots and soil and two MCGs exclusively from soil. No MCG was found in more than one orchard. With two exceptions, isolates within the same MCG were similar in virulence, competitive saprophytic ability (CSA) and mycelial growth rate whether or not they carried dsRNA. The two exceptional isolates recovered from soil had multiple dsRNA segments that caused hypovirulence, weakened CSA and restricted mycelial growth on nutrient-rich media. They belonged to different MCGs, each including dsRNA-free isolates. Isolates from soil contained various dsRNAs (44%), including the hypovirulence factor, more frequently than isolates from diseased roots in the same fields (25%), which is much higher than the proportion of isolates with dsRNA from diseased roots (19%) in a total of 424 isolates from Japan examined so far. These results suggest that isolation of R. necatrix from soil is an effective method to obtain isolates with dsRNAs, including the hypovirulence factor. (C) 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.
ELSEVIER SCIENCE BV, 2005年10月, FEMS MICROBIOLOGY ECOLOGY, 54 (2), 307 - 315, 英語[査読有り]
研究論文(学術雑誌)
Monokaryotic strains of Helicobasidium mompa were used as vectors of a mycovirus between various H. mompa isolates to examine the transmissibility of one of the mycoviruses, totivirus (HmTV1-17 virus) in the hypovirulent isolate V17 of H. mompa. The isolates that acquired HmTV1-17 virus were also examined for any alteration in the virulence. Twelve dikaryotic isolates of H. mompa, belonging to 11 mycelial compatibility groups (MCGs) and being mycelially incompatible with isolate V17, were used as recipients of HmTV1-17 virus. Two monokaryotic isolates that were mycelially incompatible with isolate V17 and all of the recipients were also used as vectors of HmTV1-17 virus between isolate V17 and the recipients. When isolate V17 and recipients were directly paired on plate media, HmTV1-17 virus was transmitted from isolate V17 into 2 of the 12 recipients (i.e., 2 of the 11 MCGs). Two monokaryotic strains were paired with isolate V17, and the monokaryotic strains that acquired HmTV1-17 virus were then used as new virus donors. When the monokaryotic strains containing HmTV1-17 virus were paired with the 12 recipients, HmTV1-17 virus was transmitted into 7 of the 12 recipients from the monokaryotic strains (i.e., 7 of 11 MCGs). Based on these results, we concluded that monokaryotic strains could act as vectors to transmit HmTV1-17 virus into H. mompa isolates. When four of the H. mompa isolates that acquired HmTV1-17 virus were used to inoculate apple rootstock Malus prunifolia, the virulence of all of the isolates was attenuated from that of their parental isolates. Moreover, because the DNA fingerprints of the fungal isolates that acquired HmTV1-17 virus were the same as those of their parental isolates, the infection with HmTV1-17 virus is considered the cause of virulence attenuation of H. mompa. © The Phytopathological Society of Japan and Springer-Verlag 2005.
2005年06月, Journal of General Plant Pathology, 71 (3), 161 - 168, 英語[査読有り]
研究論文(学術雑誌)
Eighty-three isolates of the violet root rot fungus, Helicobasidium mompa, were collected in a tulip tree plantation and analyzed for the dynamics of double-stranded (ds) RNA for five years. They were divided into eight mycelial compatibility groups (MCGs). Prevalent MCGs 60 and 68 included 61 and 11 isolates, respectively. Electrophoretic profiles of dsRNA in the first year collection of MCG 60 contained no or a single large dsRNA (more than 10 kb) with or without small dsRNAs (ca. 2.0-2.5 kb). Additional dsRNA fragments, i.e., a middle dsRNA (ca. 8.0 kb) or another type of small dsRNAs, became evident within MCG 60 isolates with time. Northern hybridization revealed the relatedness of all large and middle dsRNA fragments within MCG 60 but small fragments of dsRNA were variable. Large dsRNA fragment differed from that in other MCGs even in the same field. Correlation between specific dsRNA fragments and hypovirulence was not observed. Possible explanations for the accumulation of dsRNA fragments during the growth of disease patch by MCG 60 are discussed in terms of their internal changes such as evolution of novel dsRNA fragments from pre-existing viruses or fungal genomic DNA and horizontal transmissions. (C) 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.
ELSEVIER SCIENCE BV, 2005年01月, FEMS MICROBIOLOGY ECOLOGY, 51 (2), 293 - 301, 英語[査読有り]
研究論文(学術雑誌)
The diversity and vertical transmission of double-stranded (ds) RNA in Helicobasidium mompa and Rosellinia necatrix was examined by electrophoresis and Northern hybridization. These two fungi share the similar niche as root rot pathogens of trees in forests and orchards, and had diverse dsRNAs. The detection frequency of dsRNA in both fungi was different; in H. mompa, 68.4 % (132 out of 193 MCGs; mycelial compatibility groups) had dsRNA, whereas 20.9 % (53 out of 254 MCGs) in R. necatrix. dsRNA banding patterns and Northern blot analyses revealed the presence of various dsRNA elements in both fungi. Hyphal tip isolation was mostly unsuccessful to remove dsRNA with some exceptions. Sexual reproduction functioned to remove dsRNA in both fungi since dsRNA was not detected from single sexual spore cultures. Possible explanations for the difference in the detection frequency of dsRNA are discussed in terms of the differences in their sexual reproduction and other factors.
CAMBRIDGE UNIV PRESS, 2004年06月, MYCOLOGICAL RESEARCH, 108, 626 - 634, 英語[査読有り]
研究論文(学術雑誌)
White root rot, caused by Rosellinia necatrix, is a serious soilborne disease of fruit trees and other woody plants. R. necatrix isolate W370 contains 12 segments of double-stranded RNA (dsRNA) that is believed to represent a possible member of the family Reoviridae. W370 was weakly virulent and its hyphal-tip strains became dsRNA free and strongly virulent. The 12 segments of W370dsRNA were transmitted to hygromycin B-resistant strain RT37-1, derived from a dsRNA-free strain of W370 in all or none fashion through hyphal contact with W370. The W370dsRNA-transmitted strains were less virulent than their parent strain RT37-1 on apple seedlings, with mortality ranging between 0 to 16.7% in apple seedlings that were inoculated with the W370dsRNA-containing strains and 50 to 100% for seedlings inoculated with the dsRNA-free strains. Sonic W370dsRNA-containing strains killed greater than 16.7% of seedlings, but these were found to have lost the dsRNA in planta. These results indicate that W370dsRNA is a hypovirulence factor in R. necatrix. In addition, a strain lost one segment (S8) of W370dsRNA during subculture, and the S8-deficient mutant strain also exhibits hypovirulence in R. necatrix.
AMER PHYTOPATHOLOGICAL SOC, 2004年06月, PHYTOPATHOLOGY, 94 (6), 561 - 568, 英語[査読有り]
研究論文(学術雑誌)
A violet root rot fungus recently found in Japan was identified as Helicobasidium brebissonii. The fungus was compared with another violet root rot fungus, H. mompa, which is distributed throughout Japan, in terms of morphological characteristics of the basidiospores and the conidial state, sequences of rDNA ITS regions, and pathogenicity on carrot, sweet potato and apple rootstock. The two species were clearly discriminated by these features and the taxonomic status of both species is discussed.
CAMBRIDGE UNIV PRESS, 2004年06月, MYCOLOGICAL RESEARCH, 108, 641 - 648, 英語[査読有り]
研究論文(学術雑誌)
The RIP (repeat-induced point mutation) process introduces C:G to T:A transitions into duplicated sequences during a specific period in the sexual reproduction and has been reported in only two fungal species, Neurospora crassa and Podospora anserina. To investigate whether a RIP-like process operates in Magnaporthe grisea, the retrotransposon MAGGY and the hygromycin B phosphotransferase gene were introduced into the fungus as multiple transgenes and examined for sequence alterations after asexual growth and sexual crossing. Numerous C:G to T:A transitions were found in the transgenes, preferentially in (A/Tp)Cp(A/T) contexts, in the sexual progenies, suggesting that a RIP-like process functions in M. grisea. We also examined the sequence of another retrotransposon, Pyret, in field isolates of M. grisea. Even though the perfect stage rarely has been observed in M. grisea under field conditions, RIP-like transitions were found in all the field isolates tested and were correlated with the fertility of the isolates in Petri dishes. Analysis of RIP-like transitions in repetitive sequences may provide a tool to estimate the frequency of sexual recombination of M. grisea isolates.
SPRINGER, 2004年, RICE BLAST: INTERACTION WITH RICE AND CONTROL, 57 - 63, 英語[査読有り]
研究論文(国際会議プロシーディングス)
Helicobasidium mompa is a clampless basidiomycete and binucleate both in secondary and primary hyphae. Single basidiospore isolates were paired in sibling and non-sibling combinations. We did not observe any alterations in colony morphology, such as tuft formation, but mycelial incompatibility, as indicated by the presence of a dark demarcation line between colonies, occurred in a unifactorial manner. Techniques using DNA molecular markers, such as internal transcribed spacer-restriction fragment-length polymorphism (ITS-RFLP), inter-simple-sequence-repeat polymerase chain reaction (PCR), and universally primed PCR, failed to identify nuclear migration to opposite single basidiospore isolates in all but one of the 92 pairings. These results imply that single basidiospore isolates of H. mompa may be incompetent to mate under laboratory conditions and that a single mycelial incompatibility factor operates in single basidiospore isolates.
CAMBRIDGE UNIV PRESS, 2003年07月, MYCOLOGICAL RESEARCH, 107, 847 - 853, 英語[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
[査読有り]
研究論文(学術雑誌)
Repeat-induced point mutation (RIP) is a process that detects DNA duplications and peppers their sequences with C:G to T:A transitions in the sexual phase of the life cycle. So far, this unique mechanism has been identified as a currently active process in only two fungal species, Neurospora crassa and Podospora anserina. To determine whether a RIP-like process operates in the plant pathogenic fungus Magnaporthe grisea, the retrotransposon MAGGY and the hygromycin B phosphotransferase gene were introduced into the fungus as multiple transgenes and examined for sequence alterations after a cross. Frequent C:G to T:A transitions in the transgenes were found in the descendants, preferentially in (A/Tp)Cp(A/T)contexts, suggesting that a process similar to RIP functions in M. grisea. We also examined the sequence of another retrotransposon Pyret in six field isolates of M. grisea. Even though no perfect stage has been known in M. grisea under field conditions to date, RIP-like transitions were found in all the field isolates tested. Interestingly, the frequency of the transitions mostly correlated with the fertility of the isolates examined under laboratory conditions. These results imply that the sexual cycle of this fungus exists or existed in the natural field context.
WILEY-BLACKWELL, 2002年09月, MOLECULAR MICROBIOLOGY, 45 (5), 1355 - 1364, 英語[査読有り]
研究論文(学術雑誌)
Conidiomata of the white root rot fungus were produced in axenic culture under near-ultraviolet light radiation. Pieces of sterilized Japanese pear twigs were placed on 7-day-old oatmeal agar culture in plates. The plates were further incubated for 5 days and then illuminated by near-ultraviolet light. Synnemata developed on the twigs within 5 weeks in 19 of 20 isolates tested, and conidia were observed in 12 of the 19 isolates. The synnemata and conidia produced were morphologically identical to those of Dematophora necatrix.
Springer Japan, 2002年06月25日, Mycoscience, 43 (3), 251 - 254, 英語[査読有り]
研究論文(学術雑誌)
A novel Ty3/Gypsy retrotransposon, named Pyret, was identified in the plant pathogenic fungus Magnaporthe grisea (anamorph Pyricularia oryzae). Pyret-related elements were distributed in a wide range of Pyricularia isolates from various gramineous plants. The Pyret element is 7250 bp in length with a 475 bp LTR and one conceptual ORF. The ORF contains seven nonsense mutations in the reading frame, indicating that the Pyret clone is lightly degenerate. Comparative domain analysis among retroelements revealed that Pyret exhibits an extra domain (WCCH domain) beyond the basic components of LTR retrotransposons. The WCCH domain consists of similar to 300 amino acids and is located downstream of the nucleocapsid domain. The WCCH domain is so named because it contains two repeats of a characteristic amino acid sequence, W-X-2-C-X-4-C-X-2-H-X-3-K. A WCCH motif-like sequence is found in the precoat protein of some geminiviruses, viral RNA-dependent RNA polymerase and also in an Arabidopsis protein of unknown function. Interestingly, detailed sequence analysis of the gag protein revealed that Pyret, as well as some other chromodomain-containing LTR retrotransposons, displays significant sequence homology with members of the gammaretroviruses (MLV-related retroviruses) in the capsid and nucleocapsid domains. This suggests that chromodomain-containing LTR retrotransposons and gammaretroviruses may share a common ancestor with the gag protein.
OXFORD UNIV PRESS, 2001年10月, NUCLEIC ACIDS RESEARCH, 29 (20), 4106 - 4113, 英語[査読有り]
研究論文(学術雑誌)
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-elements) 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.
SPRINGER-VERLAG, 2001年10月, MOLECULAR GENETICS AND GENOMICS, 266 (2), 318 - 325, 英語[査読有り]
研究論文(学術雑誌)
We: have introduced the LTR-retrotransposon MAGGY into a naive genome of Magnaporthe grisea and estimated the copy number of MAGGY in a cell by serial isolation of fungal protoplasts at certain time intervals. The number of MAGGY elements rapidly-increased for a short period following introduction. However, it did not increase geometrically and reached equilibrium at 20-30 copies per genome, indicating that MAGGY was repressed or silenced during proliferation, De novo methylation of MAGGY occurred immediately following invasion into the genome but the degree of methylation was constant and did not correlate with the repression of MABGGY. 5-Azacytidine treatment demethylated and transcriptionally activated the MAGGY element in regenerants but did not affect transpositional frequency, suggesting that post-transcriptional suppression, not methylation, is the main force that represses MAGGY proliferation in M.grisea, Support for this conclusion was also obtained by examining the methylation status of MAGGY sequences in field isolates of M.grisea with active or inactive MAGGY elements. Methylation of the MAGGY sequences was detected in some isolates but not in others, However, the methylation status did not correlate with the copy numbers and activity of the elements.
OXFORD UNIV PRESS, 2001年03月, NUCLEIC ACIDS RESEARCH, 29 (6), 1278 - 1284, 英語[査読有り]
研究論文(学術雑誌)
We examined the distribution and activity of six transposable elements found in the blast fungus, Pyricularia spp. Sixty-eight isolates from various gramineous plants were used for the survey, and the elements were plotted on a dendrogram constructed on the basis of their rDNA-ITS2 sequences. MGR586 and Pot2 (Class II elements), Mg-SINE (SINE-like element) and MGR583 (LINE-like retrotransposon) were widely distributed among the Pyricularia isolates, suggesting that they are old elements which arose in, or invaded, the Pyricularia population at very early stages in its evolution. By contrast, the distribution of the LTR-retrotransposons MAGCY and Grasshopper was limited or sporadic, suggesting that they are relatively new elements which recently invaded the Pyricularia population by means of horizontal transfer events. The activity of these elements was evaluated by Southern analysis in progenies derived from a cross between a Setaria isolate and a Triticum isolate. Many new MAGGY signals were observed, which were absent in the parental isolates, at various stages of the sexual cycle and following vegetative growth. In contrast, the other elements yielded few, if any, such signals. Analysis of the sequences flanking the new MAGGY insertions revealed that they were each associated with a 5-bp target-site duplication at both ends of the insertion. These data suggested that MAGGY was the most active of the elements tested for transposition in Pyricularia.
SPRINGER-VERLAG, 2001年01月, MOLECULAR AND GENERAL GENETICS, 264 (5), 565 - 577, 英語[査読有り]
研究論文(学術雑誌)
The LTR-retrotransposon MAGGY is found sporadically in isolates of Pyricularia grisea (Magnaporthe grisea). Based on a dendrogram constructed by RFLP analysis of rDNA, isolates that carry MAGGY elements were classified into a single cluster that comprised four rDNA types. However, in a few members of this cluster, exemplified by isolates from common millet (Panicum miliaceum), the MAGGY element has distinct features. Southern analysis suggested that these isolates possessed a single copy of a MAGGY-related sequence whose restriction map differed from that of MAGGY itself. Sequence analysis revealed that the MAGGY-related sequence was a degenerate form of MAGGY, characterized by numerous C:G to T:A transitions, which have often been reported to result from RIP (Repeat-induced point mutation) or RIP-like processes. However, the favored target site for C:G to T:A transitions in this fungus, determined by examining a total of 501 sites, was (A/T)pCp(A/T), which differs from that for the RIP process originally reported in Neurospora (CpA), and from that reported in Aspergillus (CpC). The fact that certain members of the cluster of MAGGY carriers retain a single copy of a degenerate MAGGY element implies that the ancestor of these isolates successfully "captured" the invading MAGGY element.
SPRINGER VERLAG, 1999年07月, MOLECULAR AND GENERAL GENETICS, 261 (6), 958 - 966, 英語[査読有り]
研究論文(学術雑誌)
Pyricularia grisea, the blast fungus of many gramineous plants, includes several host-specific subgroups, A phenogram constructed from rDNA-RFLP data showed that subgroups pathogenic on crops (i.e., rice, foxtail millet, common millet; finger millet, and wheal) and the subgroup pathogenic on crabgrass were classified into different clusters and that this fungeal species has a high diversity. The distribution of MAGGY on the phenogram suggested that this retrotransposon was acquired by a common ancestor of four rDNA types including Oryza isolates (pathogenic oil rice) and Setaria isolates (pathogenic on foxtail millet). To elucidate mechanisms of the species-specific parasitism in gramineous crops classified as a subgroup; we crossed a Setaria isolate with a Triticum isolate (pathogenic on wheat and with no MAGGY), and produced an F-1 population which (i) showed segregation in pathogenicity, phytotoxic compounds, and MAGGY copies, (ii) included mutants in mycelial color: appressorium formation, pathogenicity, and phytotoxic compounds. and (iii) contained many transposed copies of MAGGY. The usefulness of this population for analyses of the species-specific parasitism was discussed.
SPRINGER, 1998年, MOLECULAR GENETICS OF HOST-SPECIFIC TOXINS IN PLANT DISEASES, 13, 211 - 221, 英語[査読有り]
研究論文(国際会議プロシーディングス)
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記事・総説・解説・論説等(学術雑誌)
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Cellular responses in fungi and in susceptible or resistant hosts during fungus-plant interactions have been studied ultrastructurally to examine their role in pathogenicity. Pathogenicity is determined in some saprophytic fungi by various factors: the production of disease determinants such as the production of host-specific toxins (HSTs) or the extracellular matrix (ECM) by fungal infection structures and H(2)O(2) generation from penetration pegs. Three different target sites for HSTs have been identified in host cells in many ultrastructural studies: plasma membranes, chloroplasts, and mitochondria. The mode of action of HSTs is characterized by the partial destruction of the target structures only in susceptible genotypes of host plants, with the result that the fungus can colonize the host. The infection structures of most fungal pathogen secrete ECM on plant surfaces during fungal differentiation, while the penetration pegs of some pathogens produce reactive oxygen species (ROS) in the cell walls and plasma membranes. The pathological roles of ECM and H(2)O(2) generation are discussed here in light of ultrastructural evidence. Host and fungal characteristics in the incompatible interactions include the rapid formation of lignin in host epidermal cell walls, failure of penetration pegs to invade lignin-fortified pectin layers, the inhibition of subcuticular hyphal proliferation and the collapse of hyphae that have degraded cell walls within pectin layers of the host. Apoptosis-like host resistant mechanism is also discussed.
SPRINGER TOKYO, 2008年02月, JOURNAL OF GENERAL PLANT PATHOLOGY, 74 (1), 2 - 14, 英語[査読有り]
書評論文,書評,文献紹介等
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記事・総説・解説・論説等(学術雑誌)
リンゴ園およびユリノキ植栽林では,紫紋羽病菌,Helicobasidium mompaの特定のMCG(Mycelial Compatibility Group)がパッチ状に大きな分布域を示し,これらのみが数年後さらに大きく進展していたことを報告した(中村ら,2001).今回,新たに茨城県のクワ園における個体群構造の経年変化を調査したところ,クワ園においても大きな分布域を示すMCGが存在し,それらは2年後さらに大きく進展していた.次に,上記の3調査地で認められた各MCGに属する菌株を用いて接種試験を行い,MCGの分布域の大きさと病原力との関係について調べた.1MCG当たり1-3菌株をリンゴ台木苗に接種した結果,大きな分布域を示すMCGは相対的に強い病原力を示し,一方分布域の小さなMCGの病原力は強弱様々であった.また接種苗根上での菌糸塊形成頻度と病原力との間には正の相関が認められた.以上から,MCGの病原力は各調査地内での各MCGの分布域の大きさあるいは進展程度を決定する要困の1つであると判断された.
日本植物病理学会, 2003年02月25日, 日本植物病理學會報, 69 (1), 44 - 45, 日本語学術書
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口頭発表(一般)
口頭発表(一般)
これまでの成果より、いもち病菌胞子懸濁液を接種した環境条件の違いにより細胞分裂の制御が大きく異なることが明らかとされた。この環境条件の違いに着目して、市販のカバーガラスを用いて付着器形成評価を進めたところ、製造ロットにより付着器形成率が変動することが明らかとなった。そこで、安定して付着器を形成する条件を検討するために、基板修飾技術を用いてガラス表面に様々な特性を付与して、付着器形成の頻度を評価した。 その結果、これまで疎水性表面において付着器が形成されるとされてきたが、十分に洗浄処理した親水性表面においては、付着器が形成され、化学的修飾により親水性を付与した表面においては、付着器形成が阻害された。一方、化学的修飾により疎水性を付与した表面においては、根において感染する際に形成されることで知られる菌足様の構造を有する新たな発芽様式が観察された。この結果は従来考えられてきたいもち病菌における付着器形成誘導条件に関する新たな知見をもたらすものであった。 また、タマネギ表皮においていもち病菌胞子懸濁液を接種し、植物細胞への侵入行動を観察した。この際にヒストンを蛍光タンパク質RFPにて標識した変異株を用いることにより核の挙動を観察することができる。一般的には、付着器を形成し、成熟する過程において胞子に存在する全ての核はオートファジー機構により分解されてしまう。しかし、タマネギ表皮における感染の際には、胞子に存在する核の一部は残存していた。このことは、人工基質における付着器形成と宿主植物細胞への侵入における付着器形成においてオートファジー活性や細胞周期制御機構が異なっている可能性を示唆している。これら違いについて次年度は解析を進めて行く予定である。
競争的資金
競争的資金
競争的資金
競争的資金
競争的資金
競争的資金