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Toshihiro Omura - One of the best experts on this subject based on the ideXlab platform.

  • Electron microscopic imaging revealed the flexible filamentous structure of the cell attachment protein P2 of Rice dwarf virus located around the icosahedral 5-fold axes.
    Journal of Biochemistry, 2015
    Co-Authors: Naoyuki Miyazaki, Toshihiro Omura, Hiroyuki Hibino, Atsushi Nakagawa, Akifumi Higashiura, Fusamichi Akita, Tomoko Higashiura, Kenji Iwasaki
    Abstract:

    The minor outer capsid protein P2 of Rice dwarf virus (RDV), a member of the genus Phytoreovirus in the family Reoviridae, is essential for viral cell entry. Here, we clarified the structure of P2 and the interactions to host insect cells. Negative stain electron microscopy (EM) showed that P2 proteins are monomeric and flexible L-shaped filamentous structures of ∼20 nm in length. Cryo-EM structure revealed the spatial arrangement of P2 in the capsid, which was prescribed by the characteristic virion structure. The P2 proteins were visualized as partial rod-shaped structures of ∼10 nm in length in the cryo-EM map and accommodated in crevasses on the viral surface around icosahedral 5-fold axes with hydrophobic interactions. The remaining disordered region of P2 assumed to be extended to the radial direction towards exterior. Electron tomography clearly showed that RDV particles were away from the cellular membrane at a uniform distance and several spike-like densities, probably corresponding to P2, connecting a viral particle to the host cellular membrane during cell entry. By combining the in vitro and in vivo structural information, we could gain new insights into the detailed mechanism of the cell entry of RDV.

  • Hairpin RNA derived from the gene for Pns9, a viroplasm matrix protein of Rice gall dwarf virus, confers strong resistance to virus infection in transgenic rice plants.
    Journal of Biotechnology, 2012
    Co-Authors: Takumi Shimizu, Toshihiro Omura, Taiyun Wei, Takahide Sasaya, Eiko Nakazono-nagaoka, Fusamichi Akita, Tamaki Uehara-ichiki
    Abstract:

    The nonstructural Pns9 protein of Rice gall dwarf virus (RGDV) accumulates in viroplasm inclusions, which are structures that appear to play an important role in viral morphogenesis and are commonly found in host cells infected by viruses in the family Reoviridae. An RNA interference construct was designed to target the gene for Pns9 of RGDV, namely Trigger_G9. The resultant transgenic plants accumulated short interfering RNAs specific for the construct. All progenies from self-fertilized transgenic plants had strong and heritable resistance to RGDV infection and did not allow the propagation of RGDV. By contrast, our transgenic plants remained susceptible to Rice dwarf virus, another Phytoreovirus. There were no significant changes in the morphology of our transgenic plants compared with non-inoculated wild-type rice plants, suggesting that genes critical for the growth of rice plants were unaffected. Our results demonstrate that the resistance to RGDV of our transgenic rice plants is not due to resistance to the vector insects but to specific inhibition of RGDV replication and that the designed trigger sequence is functioning normally. Thus, our strategy to target a gene for viroplasm matrix protein should be applicable to plant viruses that belong to the family Reoviridae.

  • Pleomorphic Configuration of the Trimeric Capsid Proteins of Rice dwarf virus that Allows Formation of Both the Outer Capsid and Tubular Crystals
    Journal of Molecular Biology, 2008
    Co-Authors: Kenji Iwasaki, Toshihiro Omura, Yafeng Zhu, Lena Marmstål Hammar, Naoyuki Miyazaki, Fredrik Sjöborg, Koji Yonekura, Kazuyoshi Murata, Keiichi Namba
    Abstract:

    In the double-shelled capsid of Phytoreovirus, the outer capsid attaches firmly to the 3-fold axes of the T=1 core. It then forms a T=13 lattice via lateral interactions among the P8 trimers (Wu et al., 2000, Virology 271, 18-25). Purified P8 molecules also assemble into hexagonal monolayers as well as tubular crystals. To explore the mechanisms of formation of these structures, the configurations of P8 trimers were compared and verified in particles of Rice dwarf virus and in tubular crystals (tubes) whose structure was determined by cryoelectron microscopy using helical reconstruction technique. Remarkable variations in intertrimer contacts were observed in the tubes and in the surface lattice of Rice dwarf virus capsid. Superposition of the atomic structure of P8 trimers in the structures analyzed by cryoelectron microscopy allowed us to identify groups of specific and stable interactions, some of which were preserved in the tubes and the quasi-equivalent T=13 icosahedral lattice of the virion's shell. The flexible nature of the binding between P8 trimers, created via electrostatic interactions that hold radially inward, appears to allow the outer-capsid P8 trimers to envelop the ragged surface of the core, forming the double shell of an intact viral particle.

  • The P2 capsid protein of the nonenveloped rice dwarf Phytoreovirus induces membrane fusion in insect host cells
    Proceedings of the National Academy of Sciences, 2007
    Co-Authors: Feng Zhou, Chunhong Wei, Wulan Deng, Taiyuan Wei, Huijun Liu, Biao Ding, Toshihiro Omura
    Abstract:

    Insect transmission is an essential process of infection for numerous plant and animal viruses. How an insect-transmissible plant virus enters an insect cell to initiate the infection cycle is poorly understood, especially for nonenveloped plant and animal viruses. The capsid protein P2 of rice dwarf virus (RDV), which is nonenveloped, is necessary for insect transmission. Here, we present evidence that P2 shares structural features with membrane-fusogenic proteins encoded by enveloped animal viruses. When RDV P2 was ectopically expressed and displayed on the surface of insect Spodoptera frugiperda cells, it induced membrane fusion characterized by syncytium formation at low pH. Mutational analyses identified the N-terminal and a heptad repeat as being critical for the membrane fusion-inducing activity. These results are corroborated with results from RDV-infected cells of the insect vector leafhopper. We propose that the RDV P2-induced membrane fusion plays a critical role in viral entry into insect cells. Our report that a plant viral protein can induce membrane fusion has broad significance in studying the mechanisms of virus entry into insect cells and insect transmission of nonenveloped plant and animal viruses.

  • Pns12 protein of Rice dwarf virus is essential for formation of viroplasms and nucleation of viral-assembly complexes.
    The Journal of general virology, 2006
    Co-Authors: Taiyun Wei, Hongyan Chen, Yusuke Moriyasu, Akira Kikuchi, Nobuhiro Suzuki, Kyoji Hagiwara, Takumi Shimizu, Toshihiro Omura
    Abstract:

    Cytoplasmic inclusion bodies, known as viroplasms or viral factories, are assumed to be the sites of replication of members of the family Reoviridae. Immunocytochemical and biochemical analyses were carried out to characterize the poorly understood viroplasms of the Phytoreovirus Rice dwarf virus (RDV). Within 6 h of inoculation of cells, viroplasms, namely discrete cytoplasmic inclusions, were formed that contained the non-structural proteins Pns6, Pns11 and Pns12 of RDV, which appeared to be the constituents of the inclusions. Formation of similar inclusions in non-host insect cells upon expression of Pns12 in a baculovirus system and the association of molecules of Pns12 in vitro suggested that the inclusions observed in RDV-infected cells were composed basically of Pns12. Core proteins P1, P3, P5 and P7 and core virus particles were identified in the interior region of the inclusions. In contrast, accumulation of the outer capsid proteins P2, P8 and P9 and of intact virus particles was evident in the peripheral regions of the inclusions. These observations suggest that core particles were constructed inside the inclusions, whereas outer capsid proteins were assembled at the periphery of the inclusions. Viral inclusions were shown to be the sites of viral RNA synthesis by labelling infected cells with 5-bromouridine 5'-triphosphate. The number of viroplasms decreased with time post-inoculation as their sizes increased, suggesting that inclusions might fuse with one another during the virus-propagation process. Our results are consistent with a model, proposed for vertebrate reoviruses, in which viroplasms play a pivotal role in virus assembly.

Nobuhiro Suzuki - One of the best experts on this subject based on the ideXlab platform.

  • Downloaded from www.microbiologyresearch.org by
    2016
    Co-Authors: Nobuhiro Suzuki, Mariko Harada, Tomonobu Kusano
    Abstract:

    The complete nucleotide sequence of rice dwarf Phytoreovirus (RDV) genome segment S11 was deter-mined. S I 1 is 1067 nucleotides long. There is an inverted repeat of 10 bp adjacent o the conserved 5'-terminal hexanucleotide (5 ' GGUAAA 3') and 3'-terminal tetranucleotide (5 ' UAGU 3') sequences. A single large open reading frame found in the plus strand of $11 begins with the first AUG codon (bases 6 to 8) and extends for 567 bases. Evolutionary relatedness between RDV S11 and wound tumour Phytoreovirus S12 based on amino acid sequence similarity (25.8%) was found. In addition to the first AUG triplet, RDV S 11 possesses a second in-phase AUG triplet (positions 30 to 32) nearby, which conforms to the Kozak consensus equence. Two forms of the protein were identified by using an in vitro transcription and translation system in which a tailored full-length cDNA was the initial template. The abolition of the first AUG codon by site-directed mutagenesis resulted in disappearance of the larger translation product. These results trongly suggest that the two products are translated from the first and second AUG codons. Whether the two proteins are expressed in vivo is at present unclear

  • Pns12 protein of Rice dwarf virus is essential for formation of viroplasms and nucleation of viral-assembly complexes.
    The Journal of general virology, 2006
    Co-Authors: Taiyun Wei, Hongyan Chen, Yusuke Moriyasu, Akira Kikuchi, Nobuhiro Suzuki, Kyoji Hagiwara, Takumi Shimizu, Toshihiro Omura
    Abstract:

    Cytoplasmic inclusion bodies, known as viroplasms or viral factories, are assumed to be the sites of replication of members of the family Reoviridae. Immunocytochemical and biochemical analyses were carried out to characterize the poorly understood viroplasms of the Phytoreovirus Rice dwarf virus (RDV). Within 6 h of inoculation of cells, viroplasms, namely discrete cytoplasmic inclusions, were formed that contained the non-structural proteins Pns6, Pns11 and Pns12 of RDV, which appeared to be the constituents of the inclusions. Formation of similar inclusions in non-host insect cells upon expression of Pns12 in a baculovirus system and the association of molecules of Pns12 in vitro suggested that the inclusions observed in RDV-infected cells were composed basically of Pns12. Core proteins P1, P3, P5 and P7 and core virus particles were identified in the interior region of the inclusions. In contrast, accumulation of the outer capsid proteins P2, P8 and P9 and of intact virus particles was evident in the peripheral regions of the inclusions. These observations suggest that core particles were constructed inside the inclusions, whereas outer capsid proteins were assembled at the periphery of the inclusions. Viral inclusions were shown to be the sites of viral RNA synthesis by labelling infected cells with 5-bromouridine 5'-triphosphate. The number of viroplasms decreased with time post-inoculation as their sizes increased, suggesting that inclusions might fuse with one another during the virus-propagation process. Our results are consistent with a model, proposed for vertebrate reoviruses, in which viroplasms play a pivotal role in virus assembly.

  • structure function analysis of rice dwarf Phytoreovirus genome and its proteins
    Uirusu, 1997
    Co-Authors: Nobuhiro Suzuki
    Abstract:

    植物レオウイルスとしては初めてイネ萎縮ウイルスの全dsRNAゲノムセグメント (S1-S12) の一次構造が明らかになった。それぞれのセグメントは両末端の保存配列, 保存配列に隣接する逆反復配列をもっている。S1-S11は単一のORFを, 一方, S12は3つのORFを保有する。予想される翻訳産物が感染イネおよび感染ヨコバイ中に同定された。S1, S3, S5, S7がコア蛋白質 (P1, P3, P5, P7) を, S2, S8が外殼蛋白質 (P2, P8) を, S4, S6, S9-S12が非構造蛋白質 (Pns4, Pns6, Pns9-Pns12) をコードすることが明らかとなった。P1はRNA依存RNA合成酵素, P5はNTP結合蛋白質 (推定グアニル酸転移酵素), P7は核酸結合蛋白質であり, P1, P7は粒子中でゲノムセグメントと結合していることが明らかとなった。これらのコア蛋白質はウイルスRNAの複製に関与するものと考えられる。非構造蛋白質の機能については不明な点が多いが, Pns4が微細管封入体を構成する核酸結合蛋白質であること, Pns10が鞘状封入体蛋白質であること, Pns12が感染細胞内でリン酸化を受けること等が明らかとなった。感染性核酸-宿主細胞感染系の早急な確立が, 各ゲノムセグメントの機能分担の更なる解明に繋がるものと思われる。

  • The loss of outer capsid protein P2 results in nontransmissibility by the insect vector of rice dwarf Phytoreovirus.
    Journal of virology, 1997
    Co-Authors: Masatoshi Tomaru, Jin Yan, Ikuo Kimura, Akira Kikuchi, Nobuhiro Suzuki, Yafeng Zhu, Wakako Maruyama, Masamichi Isogai, Yuzuru Oguma, Toshihiro Omura
    Abstract:

    A transmission-defective (TD) isolate of rice dwarf Phytoreovirus lacked the ability to infect cells when derived from the virus-free insect vector Nephotettix cincticeps. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified virus showed that among six structural proteins, the P2 outer capsid protein (encoded by genome segment S2) was absent from the TD isolate, whereas all six proteins were present in the transmission-competent (TC) isolate. P2 was not detected on immunoblots of rice plants infected with the TD isolate. Genome segment S2 and its transcript were detected in both TD and TC isolates. Sequence analysis of the S2 segment of the TD isolate revealed the presence of a termination codon due to a point mutation in the open reading frame, which might explain the absence of P2 in the TD isolate. These results demonstrate that the P2 protein is one of the factors essential for infection by the virus of vector cells and, thus, influences transmissibility by vector insects.

  • Structure/function analysis of rice dwarf Phytoreovirus genome and its proteins
    Uirusu, 1997
    Co-Authors: Nobuhiro Suzuki
    Abstract:

    植物レオウイルスとしては初めてイネ萎縮ウイルスの全dsRNAゲノムセグメント (S1-S12) の一次構造が明らかになった。それぞれのセグメントは両末端の保存配列, 保存配列に隣接する逆反復配列をもっている。S1-S11は単一のORFを, 一方, S12は3つのORFを保有する。予想される翻訳産物が感染イネおよび感染ヨコバイ中に同定された。S1, S3, S5, S7がコア蛋白質 (P1, P3, P5, P7) を, S2, S8が外殼蛋白質 (P2, P8) を, S4, S6, S9-S12が非構造蛋白質 (Pns4, Pns6, Pns9-Pns12) をコードすることが明らかとなった。P1はRNA依存RNA合成酵素, P5はNTP結合蛋白質 (推定グアニル酸転移酵素), P7は核酸結合蛋白質であり, P1, P7は粒子中でゲノムセグメントと結合していることが明らかとなった。これらのコア蛋白質はウイルスRNAの複製に関与するものと考えられる。非構造蛋白質の機能については不明な点が多いが, Pns4が微細管封入体を構成する核酸結合蛋白質であること, Pns10が鞘状封入体蛋白質であること, Pns12が感染細胞内でリン酸化を受けること等が明らかとなった。感染性核酸-宿主細胞感染系の早急な確立が, 各ゲノムセグメントの機能分担の更なる解明に繋がるものと思われる。

T Omura - One of the best experts on this subject based on the ideXlab platform.

  • In vivo and in vitro phosphorylation of rice dwarf Phytoreovirus Pns12 cytoplasmic nonstructural protein
    Archives of Virology, 1999
    Co-Authors: N Suzuki, D. Hosokawa, Y. Matsuura, A. Kikuchi, T Omura
    Abstract:

    In vivo and in vitro phosphorylation and intracellular location of rice dwarf Phytoreovirus Pns12, which is encoded by one of the twelve dsRNA genome segments, S12, and comprises 312 amino acids, was investigated. When [^32P]phosphoric acid was incorporated into RDV-infected leafhopper cultured cells, labelled Pns12 was immunoprecipitated from the cells by a monospecific anti-Pns12 polyclonal antibody. Recombinant Pns12 was purified from Spodo-ptera frugiperda cells infected with AcRS12, a baculovirus recombinant carrying a full-length cDNA of RDV S12. Purified Pns12 was also demonstrated to be phosphorylated in vitro by a kinase activity present in host (rice, barley, wheat, leafhopper) cells and non-host (tobacco, spinach, white clover, S. frugiperda , mosquito, mammals) cells as well. Immunocytochemical studies showed Pns12 accumulated in the cytoplasm of infected cells, and frequently localized in a slightly electron-dense patch. These results demonstrated that RDV Pns12 was a cytoplasmic nonstructural phosphoprotein.

  • The minor outer capsid protein P2 of rice gall dwarf virus has a primary structure conserved with, yet is chemically dissimilar to, rice dwarf virus P2, a protein associated with virus infectivity
    Archives of Virology, 1997
    Co-Authors: W. Maruyama, Y Zhu, J Yan, K. Ichimi, Y. Fukui, H. Kamiunten, T Omura
    Abstract:

    The nucleotide sequence of the genome segment 2 (S2) of rice gall dwarf virus (RGDV), a Phytoreovirus, when compared with the amino acid sequence of a component protein of the virus, showed that S2 potentially encoded a 127K minor outer capsid protein. This 127K protein designated as P2 and the 127K minor outer capsid protein (also termed P2) of rice dwarf virus (RDV) are similar in size, located in the outer capsid, and have well-conserved predicted polypeptide sequences, suggesting similar functions. Infectivity to insect vector cell monolayers of RGDV was maintained and the P2 protein was retained irrespective of carbon tetrachloride (CCl_4) treatment. This is in contrast to the infectivity of RDV which is removed along with P2 protein following CCl_4 treatment. RGDV with P2 was acquired by vector insects and transmitted to host plants, although RDV lacking P2 could not be transmitted to plants as previously published. These results imply that RDV and RGDV require P2 proteins for virus infectivity to vector insects.

  • These include:
    1997
    Co-Authors: T Omura, Y Zhu, A M Hemmings, K Iwasaki, Y Fujiyoshi, B Zhong, J Yan
    Abstract:

    two-dimensional crystallography. of rice dwarf Phytoreovirus, as visualized by Details of the arrangement of the outer capsi

  • Effect of protectants in L-drying on the conformation and infectivity of rice dwarf Phytoreovirus
    Archives of Virology, 1996
    Co-Authors: F. Fukumoto, T Omura, I. Kimura
    Abstract:

    Purified rice dwarf Phytoreovirus preparations, after rehydration following drying without freezing (L-drying) and sucrose density gradient centrifugation, sedimented to the same position as untreated controls. Upon storage at 65 °C, virion conformation in L-dried preparations supplemented with 1% sucrose was maintained better than without additives. Moreover, during storage for 6 years at −70 °C, infectivity of L-dried preparations from crude extracts of infected rice plants containing 5% sucrose was higher than controls based on the number of count of infected foci on cell monolayers and transmission to rice seedlings by leafhopper of the vector Nephotettix cincticeps , which had been injected with such extracts.

Ichiro Uyeda - One of the best experts on this subject based on the ideXlab platform.

  • The C-terminal region of the P3 structural protein of rice dwarf Phytoreovirus is important for P3-P3 interaction
    Archives of Virology, 1999
    Co-Authors: Saori Uyeda, Chikara Masuta, Ichiro Uyeda
    Abstract:

    Using a random peptide library designed for the yeast two-hybrid system, we identified a peptide that binds strongly to the P3 structural protein of rice dwarf Phytoreovirus (RDV). The amino acid sequence of the peptide showed a high homology to the C-terminal region of P3. C-terminally truncated P3 lost its ability to interact with authentic P3. Our observations suggest that the C-terminal region of P3 is important for the P3-P3 interaction, which forms the core shell structure of RDV.

  • Hypothesis on particle structure and assembly of rice dwarf Phytoreovirus: interactions among multiple structural proteins.
    Journal of General Virology, 1997
    Co-Authors: Shigenori Ueda, Chikara Masuta, Ichiro Uyeda
    Abstract:

    To study the morphogenesis and packaging of rice dwarf Phytoreovirus (RDV), the interactions among multiple structural proteins were analysed using both the yeast two-hybrid system and far-Western blotting analysis. The following protein-protein interactions were observed. P3 (major core protein) bound to itself as well as to P7 (nucleic acid-binding protein) and P8 (major outer capsid protein). P7 bound to P1 (RNA-dependent RNA polymerase) and P8, in addition to P3. Based on these findings, we hypothesize that the core shell structure is based on P3-P3 interactions and that P7 has the ability to bind to multiple structural proteins as well as to genomic RNAs during viral particle assembly. Based on the observed protein-protein interactions and on computer-aided analysis of the numbers of structural proteins per particle, possible RDV assembly events are proposed.

  • Phylogenetic relationships between rice dwarf Phytoreovirus isolates from five countries
    European Journal of Plant Pathology, 1997
    Co-Authors: Bong-choon Lee, Kazunori Murao, M. Isogai, G. Dahal, Ichiro Uyeda
    Abstract:

    Rice dwarf virus isolates were collected from several locations in Japan, the Philippines, China, Nepal and Korea. Genomic dsRNA segment profiles in polyacrylamide gel electrophoresis differed among the isolates. There were less differences in the profiles between isolates from Japan and Korea than in those between these two Countries and others. Nucleic acid hybridization was used to examine the extent of genomic variation. Full-length cDNAs to all genomic segments encoding non-structural proteins (S4, S6, S9, S10, S11 and S12) were synthesized from two Japanese isolates, and were used for dot-blot hybridization. Hybridizations using probes generated from the full-length cDNA clones failed to differentiate isolates from different geographical areas. However, cDNA probes covering a variable region of S12 were able to distinguish Japanese and Korean isolates from those of other countries. Phylogenetic tree analysis based on the amino acid sequence of P12 encoded by S12 grouped Japanese and Korean isolates together. The Chinese isolates from two different locations (Yunnan and Fujian) were closely related to each other, and were the most distantly related to Japanese and Korean isolates.

  • Genomic Rearrangement in Genome Segment 12 of Rice Dwarf Phytoreovirus
    Virology, 1996
    Co-Authors: Kazunori Murao, Ichiro Uyeda, Ikuo Kimura, Yuko Ando, P. Q. Cabauatan, Hiroki Koganezawa
    Abstract:

    The genome segment 12 (S12) of rice dwarf Phytoreovirus (RDV) isolated from the Philippines (RDV-P) and of a variant (RDV-S-6) of RDV severe strain (RDV-S) migrated abnormally slower during polyacrylamide gel electrophoresis than that of the isolate maintained at Hokkaido University (RDV-H). Nucleotide sequence analysis revealed that rearrangement had occurred in these segments, affecting the open reading frame. A polypeptide encoded by S12 (Pns12) of RDV-P had a duplication of 28 amino acids while 1/3 of the carboxyl terminus of Pns12 was deleted in RDV-S-6 by premature termination due to a frameshift. RDV-S is always present in plants infected with the RDV-S-6 variant, suggesting that Pns12 of RDV-S-6 is defective. On the other hand, Pns12 of RDV-P was expressed and appeared to be functional in infected cells in spite of the duplication, as demonstrated by immunoblot analyses using antibody raised against Pns12 expressed in Escherichia coli.

  • Naturally Occurring Phenotypic Variants Differing in Symptom Severity of Rice Dwarf Phytoreovirus
    Japanese Journal of Phytopathology, 1996
    Co-Authors: Yuko Ando, Ichiro Uyeda, Kazunori Murao, Ikuo Kimura
    Abstract:

    Phenotypically distinct rice dwarf Phytoreovirus (RDV) variants which caused varying degree of stunt symptoms were segregated from three field sources after selective transfers using the insect vector. These variants were serologically identical. After the ninth transfer of a field source RDV-W, an extremely severe variant (RDV-W-M) and a mild variant (RDV-W-L) were isolated. Their structural proteins migrated identically in SDS-polyacrylamide gel electrophoresis (PAGE). Migration pattern of genomic dsRNAs in PAGE was different among the variants. Especially the mobility of genome segment 6 (S6) was different between severe and mild variants isolated from each of the three sources. The amount of viral antigen in plants infected with variants was correlated to their severity in symptomatology. These results may suggest that S6 is involved in efficiency of viral multiplication and symptom severity.

Jin Yan - One of the best experts on this subject based on the ideXlab platform.

  • Phytoreovirus t 1 core plays critical roles in organizing the outer capsid of t 13 quasi equivalence
    Virology, 2000
    Co-Authors: Lena Marmstål Hammar, Toshihiro Omura, Jin Yan, Kenji Iwasaki, Yoshinori Fujiyoshi, Li Xing, Sevak Markarian, Holland R Cheng
    Abstract:

    The structures of the double-shelled rice dwarf virus and of its single-shell core have been determined by cryoelectron microscopy and image reconstruction. The core carries a prominent density located at each of the icosahedral faces of its T = 1 lattice. These protrusions are formed by outer shell trimers, tightly inserted at the threefold positions of the core. Such configuration of the core may guide the assembly of the outer shell, aided by lateral interactions between its subunits, into a T = 13 lattice. The organization of the Phytoreovirus capsid elucidates for the first time a general model for assembling two unique T numbers of quasi-equivalence.

  • Phytoreovirus T = 1 Core Plays Critical Roles in Organizing the Outer Capsid of T = 13 Quasi-equivalence
    Virology, 2000
    Co-Authors: Lena Marmstål Hammar, Toshihiro Omura, Jin Yan, Kenji Iwasaki, Yoshinori Fujiyoshi, Li Xing, Sevak Markarian, R. Holland Cheng
    Abstract:

    The structures of the double-shelled rice dwarf virus and of its single-shell core have been determined by cryoelectron microscopy and image reconstruction. The core carries a prominent density located at each of the icosahedral faces of its T = 1 lattice. These protrusions are formed by outer shell trimers, tightly inserted at the threefold positions of the core. Such configuration of the core may guide the assembly of the outer shell, aided by lateral interactions between its subunits, into a T = 13 lattice. The organization of the Phytoreovirus capsid elucidates for the first time a general model for assembling two unique T numbers of quasi-equivalence.

  • role of outer capsid proteins in transmission of Phytoreovirus by insect vectors
    Advances in Virus Research, 1999
    Co-Authors: Toshihiro Omura, Jin Yan
    Abstract:

    Publisher Summary This chapter focuses on the role of outer capsid protein in the transmission of Phytoreoviru s by insect vectors. Using current research systems combined with reliable traditional experimental systems, the chapter discusses the viral proteins responsible for infection by Phytoreovirus of vector cells, with the goal of defining the mechanism of the vector transmission of such viruses. Clarification of the molecular mechanisms of viral multiplication in distinct hosts and of interkingdom differences in the expression of specific proteins should provide new insights into the roles of proteins that function in the virus–host relationship. Such investigations of the viral molecules that are essential for virus transmission by vectors and of the ways in which these molecules function should help develop measures for controling plant viruses that are transmitted by vectors. It might even be possible to generate transgenic plants that express proteins that interfere with the normal interactions between a virus and its vector.

  • The P2 protein of rice dwarf Phytoreovirus is required for adsorption of the virus to cells of the insect vector
    1998
    Co-Authors: Toshihiro Omura, Jin Yan, Akira Kikuchi, Boxiong Zhong, Masato Wada, Yafeng Zhu, Masatoshi Tomaru, Wakako Maruyama, Yasuo Watanabe
    Abstract:

    Intact particles of rice dwarf Phytoreovirus adsorbed to and entered monolayer-cultured cells of the insect vector Nephotettix cincticeps and multiplied within the cells. Particles that lacked the P2 protein neither attached to nor infected such cells. Furthermore, P2-free particles obtained from a transmission-competent isolate of the virus were unable to infect insect vectors that had been allowed to feed on these virus particles through a membrane. However, when such virus particles were injected into insects via a glass capillary tube they successfully infected the insects, which became able to transmit the virus. These results support the hypothesis that, while P2-free particles can neither interact with nor infect cells in the intestinal tract of the insect vector, they do retain the ability to infect such cells when physically introduced into the hemolymph by injection. Rice dwarf Phytoreovirus (RDV) is an icosahedral double-shelled particle approximately 70 nm in diameter (2, 5). The core particle, which is composed of 12 segments of double-stranded RNA and four different proteins, is enclosed by a capsid that consists of proteins designated P2 and P8 (18). RDV is not transmissible mechanically but is transmitted t

  • Details of the arrangement of the outer capsid of rice dwarf Phytoreovirus, as visualized by two-dimensional crystallography.
    Journal of virology, 1997
    Co-Authors: Yafeng Zhu, Jin Yan, Boxiong Zhong, Andrew Michael Hemmings, Kenji Iwasaki, Yoshinori Fujiyoshi, Masamichi Isogai, Toshihiro Omura
    Abstract:

    Two-dimensional crystals were obtained from purified P8, an outer capsid protein of rice dwarf Phytoreovirus. A filtered image of the two-dimensional crystal, in combination with the results of biochemical analysis, revealed the unit formation of the capsid protein, a capsomere structure, which appeared to be an approximately equilateral triangle with sides of approximately 6 nm and which was composed of a trimer of P8 protein. Details of the arrangements of the outer capsid of the virus are described.