Publications by authors named "Satoshi T Ohki"

We investigated virus infection in the plant pathogenic oomycete Globisporangium splendens, formerly classified as Pythium splendens, in Japan. From 12 strains investigated, three strains contained virus-like double-stranded (dsRNA). Next-generation sequencing revealed that the G.

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We investigated virus infection in the oomycete Pythium polare from the Arctic. From 39 isolates investigated, 14 contained virus-like double-stranded RNA (dsRNA). Next generation sequencing revealed that the P.

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The mycoparasitic oomycete Pythium nunn isolate UZ415 contains two double-stranded RNAs (dsRNAs) of different sizes. The 1707-nt dsRNA1 and the 1475-nt dsRNA2 potentially encode an RNA-dependent RNA polymerase (RdRp) and a coat protein (CP), respectively, with sequence similarity to the RdRp and CP of gammapartitiviruses (< 57% and < 36%). Phylogenetic analysis of the deduced RdRp amino acid sequences indicated that the virus identified from P.

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We investigated the synergistic effects of co-infection by zucchini yellow mosaic virus (ZYMV) and cucumber mosaic virus (CMV) on viral distribution in the vascular tissues of cucumber. Immunohistochemical observations indicated that ZYMV was present in both the phloem and xylem tissues. ZYMV-RNA was detected in both the xylem wash and guttation fluid of ZYMV-inoculated cucumber.

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Most plant viruses do not infect the shoot apical meristem (SAM) of a host plant, and this virus-free region of meristem tissue has been used to obtain virus-free clones by meristem tip culture. Thus, the validation of viral distribution in meristem tissues is important for ensuring the appropriate excision of virus-free meristem tips. Although immunohistochemical microscopy and in situ hybridization are classical techniques, they allow us to determine the presence or absence of plant viruses in the shoot meristem tissues of a host plant.

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Asparagus virus 2 (AV-2) is a member of the genus Ilarvirus and thought to induce the asparagus decline syndrome. AV-2 is known to be transmitted by seed, and the possibility of pollen transmission was proposed 25 years ago but not verified. In AV-2 sequence analyses, we have unexpectedly found mixed infection by two distinct AV-2 isolates in two asparagus plants.

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In tobacco plants, the Cucumber mosaic virus (CMV) pepo strain induces mosaic symptoms, including pale green chlorosis and malformed tissues. Here, we characterized the involvement of 2b protein and coat protein (CP) in the development of mosaic symptoms. A 2b mutant (R46C) that lacks viral suppressor of RNA silencing (VSR) activity showed an asymptomatic phenotype with low levels of virus accumulation.

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Article Synopsis
  • Cucumber mosaic virus (CMV) causes mosaic disease in tobacco, with the coat protein (CP) influencing the severity of chlorosis observed in infected plants.
  • A study analyzed gene expression in chlorotic tissues from different CMV strains, revealing that while overall gene expression patterns were similar, the extent of expression changes varied with the severity of chlorosis.
  • Findings indicated that mutations in the CP affect the down-regulation of photosynthesis-related genes, correlating with the severity of chlorosis symptoms in the infected tobacco plants.
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The effect of synonymous substitutions in the melon necrotic spot virus p29 replicase gene on viral pathogenicity was investigated. The codons in the p29 gene were replaced by the least frequently used synonymous codons in Arabidopsis thaliana or melons. Mechanical inoculation of melon with p29 variants resulted in a loss of viral infectivity when all, one-half, or one-quarter of the gene was de-optimised.

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Taxonomic Relationships: Cucumber mosaic virus (CMV) is the type species of the genus Cucumovirus in the family Bromoviridae, which also encompasses the Peanut stunt virus (PSV) and the Tomato aspermy virus (TAV). Nucleotide sequence similarity among these three cucumoviruses is 60%-65%. CMV strains are divided into three subgroups, IA, IB and II, based on the sequence of the 5' untranslated region of the genomic RNA 3.

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The symptomatic effect of the amino acid type at residue 129 in the coat protein of cucumber mosaic virus was investigated in tobacco using coat protein mutants of the pepo strain in which proline 129 was substituted with 19 other amino acids. These mutants caused six types of symptoms: white mosaic, pale green mosaic, veinal chlorosis, veinal necrosis, systemic necrosis, and necrotic local lesions. Transmission electron microscopy revealed that the chloroplasts of plants showing the three former types of symptoms contained few thylakoid membranes.

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It has been reported previously that a 2b protein-defective mutant of the cucumber mosaic virus (CMV) Pepo strain (Delta 2b) induces only mild symptoms in systemically infected tobacco plants. To clarify further the role of the 2b protein as an RNA silencing suppressor in mosaic symptom expression during CMV infection, this study monitored the sequential distribution of Delta 2b in the shoot meristem and leaf primordia (LP) of inoculated tobacco. Time-course histochemical observations revealed that Delta 2b was distributed in the shoot meristem at 7 days post-inoculation (p.

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ABSTRACT A potential regulatory site for Cucumber mosaic virus (CMV, pepo strain) movement necessary to establish systemic infection was identified through immunological and hybridization studies on Tetragonia expansa, which was systemically infected by CMV at 36 degrees C but not at 24 degrees C. In inoculated leaves, cell-to-cell movement of CMV was enhanced at 36 degrees C compared with that observed at 24 degrees C. CMV was distributed in the phloem cells of minor veins as well as epidermal and mesophyll cells at both 36 and 24 degrees C.

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Tobacco plants (Nicotiana tabacum cv. Xanthi-nc) inoculated with a necrotic strain of Potato virus Y (PVY, T01 isolate) developed necrotic symptoms in some systemically infected leaves, but not in younger leaves. However, PVY expressed distinct symptoms not only in the older leaves, but also in the younger leaves, of plants that had been doubly inoculated with PVY and with Cucumber mosaic virus (CMV, strain Pepo).

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