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Masayuki Ishikawa - One of the best experts on this subject based on the ideXlab platform.
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Replication of Tobamovirus RNA
Annual review of phytopathology, 2016Co-Authors: Kazuhiro Ishibashi, Masayuki IshikawaAbstract:Tobacco mosaic virus and other Tobamoviruses have served as models for studying the mechanisms of viral RNA replication. In Tobamoviruses, genomic RNA replication occurs via several steps: (a) synthesis of viral replication proteins by translation of the genomic RNA; (b) translation-coupled binding of the replication proteins to a 5'-terminal region of the genomic RNA; (c) recruitment of the genomic RNA by replication proteins onto membranes and formation of a complex with host proteins TOM1 and ARL8; (d) synthesis of complementary (negative-strand) RNA in the complex; and (e) synthesis of progeny genomic RNA. This article reviews current knowledge on Tobamovirus RNA replication, particularly regarding how the genomic RNA is specifically selected as a replication template and how the replication proteins are activated. We also focus on the roles of the replication proteins in evading or suppressing host defense systems.
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Functions of the 5'- and 3'-untranslated regions of Tobamovirus RNA.
Virus research, 2015Co-Authors: Tetsuya Chujo, Kazuhiro Ishibashi, Shuhei Miyashita, Masayuki IshikawaAbstract:Abstract The Tobamovirus genome is a 5′-m 7 G-capped RNA that carries a tRNA-like structure at its 3′-terminus. The genomic RNA serves as the template for both translation and negative-strand RNA synthesis. The 5′- and 3′-untranslated regions (UTRs) of the genomic RNA contain elements that enhance translation, and the 3′-UTR also contains the elements necessary for the initiation of negative-strand RNA synthesis. Recent studies using a cell-free viral RNA translation–replication system revealed that a 70-nucleotide region containing a part of the 5′-UTR is bound cotranslationally by tobacco mosaic virus (TMV) replication proteins translated from the genomic RNA and that the binding leads the genomic RNA to RNA replication pathway. This mechanism explains the cis -preferential replication of TMV by the replication proteins. The binding also inhibits further translation to avoid a fatal ribosome–RNA polymerase collision, which might arise if translation and negative-strand synthesis occur simultaneously on a single genomic RNA molecule. Therefore, the 5′- and 3′-UTRs play multiple important roles in the life cycle of Tobamovirus.
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Interactions between Tobamovirus replication proteins and cellular factors: their impacts on virus multiplication.
Molecular plant-microbe interactions : MPMI, 2010Co-Authors: Kazuhiro Ishibashi, Masaki Nishikiori, Masayuki IshikawaAbstract:Most viral gene products function inside cells in the presence of various host proteins, nucleic acids, and lipids. Thus, viral gene products come into direct contact with these molecules. The replication proteins of Tobamovirus participate not only in viral genome replication but also in counterdefense mechanisms against RNA silencing and other plant defense systems. Accumulating evidence indicates that these functions are carried out through interactions with specific host components. Interactions with some cellular factors, however, are inhibitory to virus multiplication and contribute to host range restriction of Tobamovirus. The interactions that have positive and negative impacts on virus multiplication should have been maintained and lost, respectively, during adaptation of the viruses to their respective natural hosts. This review lists the host factors that interact with the replication proteins of Tobamovirus and discusses how they influence multiplication of the virus.
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Analysis of Tobamovirus multiplication in Arabidopsis thaliana mutants defective in TOM2A homologues.
Journal of General Virology, 2008Co-Authors: Koki Fujisaki, Satoshi Naito, Soko Kobayashi, Yayoi Tsujimoto, Masayuki IshikawaAbstract:The TOM2A gene of Arabidopsis thaliana encodes a four-pass transmembrane protein that is required for efficient multiplication of a Tobamovirus, TMV-Cg. In this study, the involvement of three TOM2A homologues in Tobamovirus multiplication in A. thaliana was examined. T-DNA insertion mutations in the three homologues, separately or in combination, did not affect TMV-Cg multiplication, whereas, in the tom2a genetic background, some combinations reduced it. This result suggests that the TOM2A homologues are functional in enhancing TMV-Cg multiplication, but their contribution is much less than TOM2A. Interestingly, the multiplication of another Tobamovirus, Tomato mosaic virus, was not drastically affected by any combinations of the mutations in TOM2A and its homologues as far as we examined.
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Involvement of THH1, an Arabidopsis thaliana homologue of the TOM1 gene, in Tobamovirus multiplication.
Journal of General Virology, 2006Co-Authors: Koki Fujisaki, Gerald B. Ravelo, Satoshi Naito, Masayuki IshikawaAbstract:The TOM1 and TOM3 genes of Arabidopsis thaliana encode homologous proteins that are required for Tobamovirus multiplication. Although the A. thaliana genome encodes another TOM1-like gene, THH1, the Tobamovirus coat protein (CP) does not accumulate to a detectable level in the tom1 tom3 double mutant. Here, double and triple mutants of tom1, tom3 and thh1 were generated to investigate whether THH1 functions to support Tobamovirus multiplication. In the tom1 thh1 double mutant, the Tobamovirus CP accumulated to a level that was detectable, but lower than that in the tom1 single mutant. In tom1 tom3 double-mutant lines overexpressing THH1, the Tobamovirus CP accumulated to a level similar to that observed in wild-type plants. These results suggest that THH1 supports Tobamovirus multiplication, but to a lesser extent than TOM1 and TOM3. The expression level of THH1 is lower than that of TOM1 and TOM3, which might explain the smaller contribution of THH1 to Tobamovirus multiplication.
Satoshi Naito - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Tobamovirus multiplication in Arabidopsis thaliana mutants defective in TOM2A homologues.
Journal of General Virology, 2008Co-Authors: Koki Fujisaki, Satoshi Naito, Soko Kobayashi, Yayoi Tsujimoto, Masayuki IshikawaAbstract:The TOM2A gene of Arabidopsis thaliana encodes a four-pass transmembrane protein that is required for efficient multiplication of a Tobamovirus, TMV-Cg. In this study, the involvement of three TOM2A homologues in Tobamovirus multiplication in A. thaliana was examined. T-DNA insertion mutations in the three homologues, separately or in combination, did not affect TMV-Cg multiplication, whereas, in the tom2a genetic background, some combinations reduced it. This result suggests that the TOM2A homologues are functional in enhancing TMV-Cg multiplication, but their contribution is much less than TOM2A. Interestingly, the multiplication of another Tobamovirus, Tomato mosaic virus, was not drastically affected by any combinations of the mutations in TOM2A and its homologues as far as we examined.
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Involvement of THH1, an Arabidopsis thaliana homologue of the TOM1 gene, in Tobamovirus multiplication.
Journal of General Virology, 2006Co-Authors: Koki Fujisaki, Gerald B. Ravelo, Satoshi Naito, Masayuki IshikawaAbstract:The TOM1 and TOM3 genes of Arabidopsis thaliana encode homologous proteins that are required for Tobamovirus multiplication. Although the A. thaliana genome encodes another TOM1-like gene, THH1, the Tobamovirus coat protein (CP) does not accumulate to a detectable level in the tom1 tom3 double mutant. Here, double and triple mutants of tom1, tom3 and thh1 were generated to investigate whether THH1 functions to support Tobamovirus multiplication. In the tom1 thh1 double mutant, the Tobamovirus CP accumulated to a level that was detectable, but lower than that in the tom1 single mutant. In tom1 tom3 double-mutant lines overexpressing THH1, the Tobamovirus CP accumulated to a level similar to that observed in wild-type plants. These results suggest that THH1 supports Tobamovirus multiplication, but to a lesser extent than TOM1 and TOM3. The expression level of THH1 is lower than that of TOM1 and TOM3, which might explain the smaller contribution of THH1 to Tobamovirus multiplication.
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Tobamovirus-resistant tobacco generated by RNA interference directed against host genes.
FEBS letters, 2005Co-Authors: Momoko Asano, Satoshi Naito, Shinya Tsuda, Takuya Yamanaka, Rena Satoh, Tetsuo Meshi, Atsuko Mochizuki, Masamichi Nishiguchi, Katsuyuki Hirai, Masayuki IshikawaAbstract:Two homologous Nicotiana tabacum genes NtTOM1 and NtTOM3 have been identified. These genes encode polypeptides with amino acid sequence similarity to Arabidopsis thaliana TOM1 and TOM3, which function in parallel to support Tobamovirus multiplication. Simultaneous RNA interference against NtTOM1 and NtTOM3 in N. tabacum resulted in nearly complete inhibition of the multiplication of Tomato mosaic virus and other Tobamoviruses, but did not affect plant growth or the ability of Cucumber mosaic virus to multiply. As TOM1 and TOM3 homologues are present in a variety of plant species, their inhibition via RNA interference should constitute a useful method for generating Tobamovirus-resistant plants.
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Arabidopsis Tobamovirus MULTIPLICATION (TOM) 2 locus encodes a transmembrane protein that interacts with TOM1
The EMBO journal, 2003Co-Authors: Yayoi Tsujimoto, Satoshi Naito, Takuro Numaga, Kiyoshi Ohshima, Masa‐aki Yano, Ryuji Ohsawa, Derek B. Goto, Masayuki IshikawaAbstract:The tom2-1 mutation of Arabidopsis thaliana reduces the efficiency of intracellular multiplication of Tobamoviruses. The tom2-1 mutant was derived from fast-neutron-irradiated seeds, and the original mutant line also carries ttm1, a dominant modifier that increases Tobamovirus multiplication efficiency in a Tobamovirus-strain-specific manner in the tom2-1 genetic background. Here, we show that the tom2-1 mutation involved a deletion of ∼20 kb in the nuclear genome. The deleted region included two genes named TOM2A and TOM2B that were both associated with the tom2-1 phenotype, whereas ttm1 corresponded to the translocation of part of the deleted region that included intact TOM2B but not TOM2A. TOM2A encodes a 280 amino acid putative four-pass transmembrane protein with a C-terminal farnesylation signal, while TOM2B encodes a 122 amino acid basic protein. The split-ubiquitin assay demonstrated an interaction of TOM2A both with itself and with TOM1, an integral membrane protein of A.thaliana presumed to be an essential constituent of Tobamovirus replication complex. The data presented here suggest that TOM2A is also an integral part of the Tobamovirus replication complex.
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Subcellular localization of host and viral proteins associated with Tobamovirus RNA replication
The EMBO journal, 2003Co-Authors: Yuka Hagiwara, Satoshi Naito, Takuya Yamanaka, Tetsuo Meshi, Keisuke Komoda, Atsushi Tamai, Ryo Funada, Tomohiro Tsuchiya, Masayuki IshikawaAbstract:Arabidopsis TOM1 (AtTOM1) and TOM2A (AtTOM2A) are integral membrane proteins genetically identified to be necessary for efficient intracellular multiplication of Tobamoviruses. AtTOM1 interacts with the helicase domain polypeptide of Tobamovirus-encoded replication proteins and with AtTOM2A, suggesting that both AtTOM1 and AtTOM2A are integral components of the Tobamovirus replication complex. We show here that AtTOM1 and AtTOM2A proteins tagged with green fluorescent protein (GFP) are targeted to the vacuolar membrane (tonoplast)-like structures in plant cells. In subcellular fractionation analyses, GFP–AtTOM2A, AtTOM2A and its tobacco homolog NtTOM2A were predominantly fractionated to low-density tonoplast-rich fractions, whereas AtTOM1–GFP, AtTOM1 and its tobacco homolog NtTOM1 were distributed mainly into the tonoplast-rich fractions and partially into higher-buoyant-density fractions containing membranes from several other organelles. The Tobamovirus-encoded replication proteins were co-fractionated with both NtTOM1 and viral RNA-dependent RNA polymerase activity. The replication proteins were also found in the fractions containing non-membrane-bound proteins, but neither NtTOM1 nor the polymerase activity was detected there. These observations suggest that the formation of tobamoviral RNA replication complex occurs on TOM1-containing membranes and is facilitated by TOM2A.
Yoshimi Okada - One of the best experts on this subject based on the ideXlab platform.
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Replication of Tobamovirus RNA
Proceedings of the Japan Academy Series B, 2004Co-Authors: Masayuki Ishikawa, Yoshimi OkadaAbstract:Tobamovirus is a positive-strand RNA virus of plants. Its single-stranded RNA genome replicates via the negative-strand RNA. In this review, we describe our current knowledge about viral and host factors associated with Tobamovirus RNA replication and discuss the replication mechanisms. We also mention the usefulness of Tobamovirus genomes as vectors. (Communicated by Eishiro SHIKATA, M.J.A.)
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A Single Amino Acid Substitution in the Virus-Encoded Replicase of Tomato Mosaic Tobamovirus Alters Host Specificity
Molecular Plant-Microbe Interactions®, 1997Co-Authors: Hiroshi Hamamoto, Yuichiro Watanabe, Hiroshi Kamada, Yoshimi OkadaAbstract:Introduction of a single amino acid substitution (Gln979 to Ile) into the 130- and 180-kDa proteins of tomato mosaic Tobamovirus (ToMV) rendered the mutant virtually unable to replicate in tomato cells while it replicated perfectly in tobacco cells. The mechanism of this change in host specificity is discussed.
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Nucleotide sequence of Tobamovirus Ob which can spread systemically in N gene tobacco.
Journal of General Virology, 1993Co-Authors: Ryoji Ikeda, Eijiro Watanabe, Yuichiro Watanabe, Yoshimi OkadaAbstract:The genomic RNA sequence of Tobamovirus Ob (Ob), which can spread systemically in tobacco carrying the N gene, was determined. It consists of 6507 nucleotides and contains four open reading frames, exactly corresponding to the genomic organization of Tobamoviruses known so far, i.e. encoding the 130K, 180K, 30K and coat proteins. There were no nucleotide overlaps between any open reading frames. The Ob nucleic acid sequence, predicted protein sequences and gene organization were compared with those of other Tobamoviruses reported previously. This virus was originally reported as a tomato mosaic virus; however, the nucleotide sequence data given here refute this classification. The determinants that allow Tobamovirus Ob to overcome the N gene, a feature peculiar to this virus, were not identified apart from sequence data. This virus should be regarded as a new Tobamovirus. The determinants interacting with the tentative N gene product have not yet been analysed.
Takuya Yamanaka - One of the best experts on this subject based on the ideXlab platform.
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Tobamovirus-resistant tobacco generated by RNA interference directed against host genes.
FEBS letters, 2005Co-Authors: Momoko Asano, Satoshi Naito, Shinya Tsuda, Takuya Yamanaka, Rena Satoh, Tetsuo Meshi, Atsuko Mochizuki, Masamichi Nishiguchi, Katsuyuki Hirai, Masayuki IshikawaAbstract:Two homologous Nicotiana tabacum genes NtTOM1 and NtTOM3 have been identified. These genes encode polypeptides with amino acid sequence similarity to Arabidopsis thaliana TOM1 and TOM3, which function in parallel to support Tobamovirus multiplication. Simultaneous RNA interference against NtTOM1 and NtTOM3 in N. tabacum resulted in nearly complete inhibition of the multiplication of Tomato mosaic virus and other Tobamoviruses, but did not affect plant growth or the ability of Cucumber mosaic virus to multiply. As TOM1 and TOM3 homologues are present in a variety of plant species, their inhibition via RNA interference should constitute a useful method for generating Tobamovirus-resistant plants.
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Subcellular localization of host and viral proteins associated with Tobamovirus RNA replication
The EMBO journal, 2003Co-Authors: Yuka Hagiwara, Satoshi Naito, Takuya Yamanaka, Tetsuo Meshi, Keisuke Komoda, Atsushi Tamai, Ryo Funada, Tomohiro Tsuchiya, Masayuki IshikawaAbstract:Arabidopsis TOM1 (AtTOM1) and TOM2A (AtTOM2A) are integral membrane proteins genetically identified to be necessary for efficient intracellular multiplication of Tobamoviruses. AtTOM1 interacts with the helicase domain polypeptide of Tobamovirus-encoded replication proteins and with AtTOM2A, suggesting that both AtTOM1 and AtTOM2A are integral components of the Tobamovirus replication complex. We show here that AtTOM1 and AtTOM2A proteins tagged with green fluorescent protein (GFP) are targeted to the vacuolar membrane (tonoplast)-like structures in plant cells. In subcellular fractionation analyses, GFP–AtTOM2A, AtTOM2A and its tobacco homolog NtTOM2A were predominantly fractionated to low-density tonoplast-rich fractions, whereas AtTOM1–GFP, AtTOM1 and its tobacco homolog NtTOM1 were distributed mainly into the tonoplast-rich fractions and partially into higher-buoyant-density fractions containing membranes from several other organelles. The Tobamovirus-encoded replication proteins were co-fractionated with both NtTOM1 and viral RNA-dependent RNA polymerase activity. The replication proteins were also found in the fractions containing non-membrane-bound proteins, but neither NtTOM1 nor the polymerase activity was detected there. These observations suggest that the formation of tobamoviral RNA replication complex occurs on TOM1-containing membranes and is facilitated by TOM2A.
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Complete inhibition of Tobamovirus multiplication by simultaneous mutations in two homologous host genes.
Journal of virology, 2002Co-Authors: Takuya Yamanaka, Satoshi Naito, Takahiro Imai, Rena Satoh, Arata Kawashima, Miki Takahashi, Kayo Tomita, Kenji Kubota, Tetsuo Meshi, Masayuki IshikawaAbstract:The TOM1 gene of Arabidopsis thaliana encodes a putative multipass transmembrane protein which is necessary for the efficient multiplication of Tobamoviruses. We have previously shown that mutations severely destructive to the TOM1 gene reduce Tobamovirus multiplication to low levels but do not impair it completely. In this report, we subjected one of the tom1 mutants (tom1-1) to another round of mutagenesis and isolated a new mutant which did not permit a detectable level of Tobamovirus multiplication. In addition to tom1-1, this mutant carried a mutation referred to as tom3-1. Positional cloning showed that TOM3 was one of two TOM1-like genes in Arabidopsis. Based on the similarity between the amino acid sequences of TOM1 and TOM3, together with the results of a Sos recruitment assay suggesting that both TOM1 and TOM3 bind Tobamovirus-encoded replication proteins, we propose that TOM1 and TOM3 play parallel and essential roles in the replication of Tobamoviruses.
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TOM1, an Arabidopsis gene required for efficient multiplication of a Tobamovirus, encodes a putative transmembrane protein
Proceedings of the National Academy of Sciences of the United States of America, 2000Co-Authors: Takuya Yamanaka, Satoshi Naito, Miki Takahashi, Tetsuo Meshi, Takehiro Ohta, Renate Schmidt, Caroline Dean, Masayuki IshikawaAbstract:Host-encoded factors play an important role in virus multiplication, acting in concert with virus-encoded factors. However, information regarding the host factors involved in this process is limited. Here we report the map-based cloning of an Arabidopsis thaliana gene, TOM1, which is necessary for the efficient multiplication of Tobamoviruses, positive-strand RNA viruses infecting a wide variety of plants. The TOM1 mRNA is suggested to encode a 291-aa polypeptide that is predicted to be a multipass transmembrane protein. The Sos recruitment assay supported the hypothesis that TOM1 is associated with membranes, and in addition, that TOM1 interacts with the helicase domain of Tobamovirus-encoded replication proteins. Taken into account that the Tobamovirus replication complex is associated with membranes, we propose that TOM1 participates in the in vivo formation of the replication complex by serving as a membrane anchor.
Yule Liu - One of the best experts on this subject based on the ideXlab platform.
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the rubisco small subunit is involved in Tobamovirus movement and tm 2 mediated extreme resistance
Plant Physiology, 2013Co-Authors: Jinping Zhao, Qi Liu, Haili Zhang, Qi Jia, Yiguo Hong, Yule LiuAbstract:The multifunctional movement protein (MP) of Tomato mosaic Tobamovirus (ToMV) is involved in viral cell-to-cell movement, symptom development, and resistance gene recognition. However, it remains to be elucidated how ToMVMP plays such diverse roles in plants. Here, we show that ToMVMP interacts with the Rubisco small subunit (RbCS) of Nicotiana benthamiana in vitro and in vivo. In susceptible N. benthamiana plants, silencing of NbRbCS enabled ToMV to induce necrosis in inoculated leaves, thus enhancing virus local infectivity. However, the development of systemic viral symptoms was delayed. In transgenic N. benthamiana plants harboring Tobacco mosaic virus resistance-2 2 (Tm-2 2 ) , which mediates extreme resistance to ToMV, silencing of NbRbCS compromised Tm-2 2 -dependent resistance. ToMV was able to establish efficient local infection but was not able to move systemically. These findings suggest that NbRbCS plays a vital role in Tobamovirus movement and plant antiviral defenses.
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The rubisco small subunit is involved in Tobamovirus movement and Tm-2²-mediated extreme resistance.
Plant physiology, 2012Co-Authors: Jinping Zhao, Qi Liu, Haili Zhang, Qi Jia, Yiguo Hong, Yule LiuAbstract:The multifunctional movement protein (MP) of Tomato mosaic Tobamovirus (ToMV) is involved in viral cell-to-cell movement, symptom development, and resistance gene recognition. However, it remains to be elucidated how ToMVMP plays such diverse roles in plants. Here, we show that ToMVMP interacts with the Rubisco small subunit (RbCS) of Nicotiana benthamiana in vitro and in vivo. In susceptible N. benthamiana plants, silencing of NbRbCS enabled ToMV to induce necrosis in inoculated leaves, thus enhancing virus local infectivity. However, the development of systemic viral symptoms was delayed. In transgenic N. benthamiana plants harboring Tobacco mosaic virus resistance-2 2 (Tm-2 2 ) , which mediates extreme resistance to ToMV, silencing of NbRbCS compromised Tm-2 2 -dependent resistance. ToMV was able to establish efficient local infection but was not able to move systemically. These findings suggest that NbRbCS plays a vital role in Tobamovirus movement and plant antiviral defenses.
