1
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Crawshaw S, Watt LG, Murphy AM, Carr JP. Strain-specific differences in the interactions of the cucumber mosaic virus 2b protein with the viral 1a and host Argonaute 1 proteins. J Virol 2024; 98:e0099324. [PMID: 39162432 PMCID: PMC11406993 DOI: 10.1128/jvi.00993-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2024] [Accepted: 07/08/2024] [Indexed: 08/21/2024] Open
Abstract
The cucumber mosaic virus (CMV) 2b protein is a potent counter-defense factor and symptom determinant that inhibits antiviral silencing by titrating short double-stranded RNAs. Expression of the CMV subgroup IA strain Fny-CMV 2b protein in transgenic Arabidopsis thaliana plants disrupts microRNA-mediated cleavage of host mRNAs by binding Argonaute 1 (AGO1), leading to symptom-like phenotypes. This also triggers AGO2-mediated antiviral resistance and resistance to CMV's aphid vectors. However, in authentic viral infections, the Fny-CMV 1a protein modulates 2b-AGO1 interactions, inhibiting induction of AGO2-mediated virus resistance and aphid resistance. Contrastingly, 2b proteins encoded by the subgroup II strain LS-CMV and the recently discovered subgroup IA strain Ho-CMV induce no symptoms. Confocal laser scanning microscopy, bimolecular fluorescence complementation, and co-immunoprecipitation showed that Fny-CMV and Ho-CMV 2b proteins interact with Fny-CMV and LS-CMV 1a proteins, while the CMV-LS 2b protein cannot. However, Fny-CMV, Ho-CMV, and LS-CMV 2b proteins, all interacted with AGO1, but while AGO1-Fny2b complexes occurred in the nucleus and cytoplasm, corresponding AGO1-2b complexes for LS-CMV and Ho-CMV accumulated almost exclusively in nuclei. AGO2 transcript accumulation was used to assess the inhibition of AGO1-mediated mRNA degradation. Fny-CMV 2b induced a fivefold increase in AGO2 accumulation, but LS-CMV and Ho-CMV 2b proteins induced only twofold increases. Thus, these 2b proteins bind AGO1 but are less effective at inhibiting AGO1 activity. We conclude that the intracellular localization of 2b-AGO1 complexes influences the degree to which a 2b protein inhibits microRNA-mediated host mRNA degradation and that cytoplasmic AGO1 has the strongest influence on miRNA-mediated cellular mRNA turnover. IMPORTANCE The cucumber mosaic virus (CMV) 2b protein was among the first discovered viral suppressors of RNA silencing. It has additional pro-viral functions through effects on plant defensive signaling pathways mediated by salicylic acid and jasmonic acid, the abscisic acid pathway and virus-induced drought resistance, and on host plant interactions with insect vectors. Many of these effects occur due to interaction with the important host RNA silencing component Argonaute 1 (AGO1). It was thought that only 2b proteins of "severe" CMV strains interacted with AGO1 and inhibited its microRNA-mediated "slicing" of cellular mRNAs and that the lack of interaction with AGO1 explained the moderate symptoms typically seen in plants infected with mild CMV strains. Our work overthrows this paradigm by showing that mild strain CMV 2b proteins can interact with AGO1, but their in vivo localization prevents them from interacting with AGO1 molecules present in the infected cell cytoplasm.
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Affiliation(s)
- Sam Crawshaw
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Lewis G Watt
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Alex M Murphy
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
| | - John P Carr
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
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2
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Kwon MJ, Kwon SJ, Kim MH, Choi B, Byun HS, Kwak HR, Seo JK. Visual tracking of viral infection dynamics reveals the synergistic interactions between cucumber mosaic virus and broad bean wilt virus 2. Sci Rep 2023; 13:7261. [PMID: 37142679 PMCID: PMC10160061 DOI: 10.1038/s41598-023-34553-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Accepted: 05/03/2023] [Indexed: 05/06/2023] Open
Abstract
Cucumber mosaic virus (CMV) is one of the most prevalent plant viruses in the world, and causes severe damage to various crops. CMV has been studied as a model RNA virus to better understand viral replication, gene functions, evolution, virion structure, and pathogenicity. However, CMV infection and movement dynamics remain unexplored due to the lack of a stable recombinant virus tagged with a reporter gene. In this study, we generated a CMV infectious cDNA construct tagged with a variant of the flavin-binding LOV photoreceptor (iLOV). The iLOV gene was stably maintained in the CMV genome after more than four weeks of three serial passages between plants. Using the iLOV-tagged recombinant CMV, we visualized CMV infection and movement dynamics in living plants in a time course manner. We also examined whether CMV infection dynamics is influenced by co-infection with broad bean wilt virus 2 (BBWV2). Our results revealed that no spatial interference occurred between CMV and BBWV2. Specifically, BBWV2 facilitated the cell-to-cell movement of CMV in the upper young leaves. In addition, the BBWV2 accumulation level increased after co-infection with CMV.
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Affiliation(s)
- Min-Jun Kwon
- Department of International Agricultural Technology, Seoul National University, Pyeongchang, 25354, Republic of Korea
| | - Sun-Jung Kwon
- Institutes of Green Bio Science and Technology, Seoul National University, Pyeongchang, 25354, Republic of Korea
| | - Myung-Hwi Kim
- Department of Agricultural Biotechnology, Seoul National University, Seoul, 08826, Republic of Korea
| | - Boram Choi
- Institutes of Green Bio Science and Technology, Seoul National University, Pyeongchang, 25354, Republic of Korea
| | - Hee-Seong Byun
- Crop Protection Division, National Institute of Agricultural Sciences, Rural Development Administration, Wanju, 55365, Republic of Korea
| | - Hae-Ryun Kwak
- Crop Protection Division, National Institute of Agricultural Sciences, Rural Development Administration, Wanju, 55365, Republic of Korea
| | - Jang-Kyun Seo
- Department of International Agricultural Technology, Seoul National University, Pyeongchang, 25354, Republic of Korea.
- Institutes of Green Bio Science and Technology, Seoul National University, Pyeongchang, 25354, Republic of Korea.
- Department of Agricultural Biotechnology, Seoul National University, Seoul, 08826, Republic of Korea.
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3
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Yang T, Peng Q, Lin H, Xi D. Alpha-momorcharin preserves catalase activity to inhibit viral infection by disrupting the 2b-CAT interaction in Solanum lycopersicum. MOLECULAR PLANT PATHOLOGY 2023; 24:107-122. [PMID: 36377585 PMCID: PMC9831283 DOI: 10.1111/mpp.13279] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Revised: 10/20/2022] [Accepted: 10/26/2022] [Indexed: 06/16/2023]
Abstract
Many host factors of plants are used by viruses to facilitate viral infection. However, little is known about how alpha-momorcharin (αMMC) counters virus-mediated attack strategies in tomato. Our present research revealed that the 2b protein of cucumber mosaic virus (CMV) directly interacted with catalases (CATs) and inhibited their activities. Further analysis revealed that transcription levels of catalase were induced by CMV infection and that virus accumulation increased in CAT-silenced or 2b-overexpressing tomato plants compared with that in control plants, suggesting that the interaction between 2b and catalase facilitated the accumulation of CMV in hosts. However, both CMV accumulation and viral symptoms were reduced in αMMC transgenic tomato plants, indicating that αMMC engaged in an antiviral role in the plant response to CMV infection. Molecular experimental analysis demonstrated that αMMC interfered with the interactions between catalases and 2b in a competitive manner, with the expression of αMMC inhibited by CMV infection. We further demonstrated that the inhibition of catalase activity by 2b was weakened by αMMC. Accordingly, αMMC transgenic plants exhibited a greater ability to maintain redox homeostasis than wild-type plants when infected with CMV. Altogether, these results reveal that αMMC retains catalase activity to inhibit CMV infection by subverting the interaction between 2b and catalase in tomato.
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Affiliation(s)
- Ting Yang
- Key Laboratory of Bio‐Resource and Eco‐Environment of Ministry of Education, College of Life SciencesSichuan UniversityChengduChina
- Hubei Engineering Research Center for Protection and Utilization of Special Biological Resources in the Hanjiang River Basin, College of Life SciencesJianghan UniversityWuhanChina
| | - Qiding Peng
- Key Laboratory of Bio‐Resource and Eco‐Environment of Ministry of Education, College of Life SciencesSichuan UniversityChengduChina
| | - Honghui Lin
- Key Laboratory of Bio‐Resource and Eco‐Environment of Ministry of Education, College of Life SciencesSichuan UniversityChengduChina
| | - Dehui Xi
- Key Laboratory of Bio‐Resource and Eco‐Environment of Ministry of Education, College of Life SciencesSichuan UniversityChengduChina
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4
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Nishiguchi M, Ali ME, Kaya T, Kobayashi K. Plant virus disease control by vaccination and transgenic approaches: Current status and perspective. PLANT RNA VIRUSES 2023:373-424. [DOI: 10.1016/b978-0-323-95339-9.00028-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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5
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Liu D, Zhao Q, Cheng Y, Li D, Jiang C, Cheng L, Wang Y, Yang A. Transcriptome analysis of two cultivars of tobacco in response to Cucumber mosaic virus infection. Sci Rep 2019; 9:3124. [PMID: 30816259 PMCID: PMC6395745 DOI: 10.1038/s41598-019-39734-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 01/31/2019] [Indexed: 01/23/2023] Open
Abstract
Cucumber mosaic virus (CMV) is among the most important plant virus infections, inducing a variety of disease symptoms. However, the molecular mechanisms underlying plant responses to CMV infection remain poorly understood. In this study, we performed RNA sequencing analysis of tolerant (Taiyan8) and susceptible (NC82) tobacco cultivars on CMV-infected plants, using mock-inoculated plants as a control. The propagation of CMV in inoculated leaves did not show obvious difference between two cultivars, whereas virus accumulation in systemic leaves of Taiyan8 was smaller than those of NC82 at the same time point. We observed 765 and 1,011 differentially expressed genes (DEGs) in Taiyan8 and NC82, respectively, in CMV-inoculated leaves. DEGs related to reactive oxygen species, salicylic acid signal transduction, and plant-pathogen interaction were upregulated or downregulated in Taiyan8, which indicates that defense response pathways to CMV were activated in the tolerant cultivar. In addition, we identified several DEGs related to disease defense and stress resistance showing opposing expression patterns in the two cultivars. Our comparative transcriptome analysis will improve our understanding of the mechanisms of CMV tolerance in plants, and will be of great importance in the molecular breeding of CMV- tolerant genotypes.
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Affiliation(s)
- Dan Liu
- Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao, 266101, China
| | - Qiang Zhao
- Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao, 266101, China
| | - Yazeng Cheng
- Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao, 266101, China
| | - Dandan Li
- Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao, 266101, China
| | - Caihong Jiang
- Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao, 266101, China
| | - Lirui Cheng
- Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao, 266101, China
| | - Yuanying Wang
- Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao, 266101, China
| | - Aiguo Yang
- Tobacco Research Institute, Chinese Academy of Agricultural Sciences, Qingdao, 266101, China.
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6
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Willemsen A, Zwart MP, Ambrós S, Carrasco JL, Elena SF. 2b or Not 2b: Experimental Evolution of Functional Exogenous Sequences in a Plant RNA Virus. Genome Biol Evol 2017; 9:297-310. [PMID: 28137747 PMCID: PMC5381683 DOI: 10.1093/gbe/evw300] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/19/2016] [Indexed: 02/05/2023] Open
Abstract
Horizontal gene transfer (HGT) is pervasive in viruses and thought to be a key mechanism in their evolution. On the other hand, strong selective constraints against increasing genome size are an impediment for HGT, rapidly purging horizontally transferred sequences and thereby potentially hindering evolutionary innovation. Here, we explore experimentally the evolutionary fate of viruses with simulated HGT events, using the plant RNA virus Tobacco etch virus (TEV), by separately introducing two functional, exogenous sequences to its genome. One of the events simulates the acquisition of a new function though HGT of a conserved AlkB domain, responsible for the repair of alkylation or methylation damage in many organisms. The other event simulates the acquisition of a sequence that duplicates an existing function, through HGT of the 2b RNA silencing suppressor from Cucumber mosaic virus. We then evolved these two viruses, tracked the maintenance of the horizontally transferred sequences over time, and for the final virus populations, sequenced their genome and measured viral fitness. We found that the AlkB domain was rapidly purged from the TEV genome, restoring fitness to wild-type levels. Conversely, the 2b gene was stably maintained and did not have a major impact on viral fitness. Moreover, we found that 2b is functional in TEV, as it provides a replicative advantage when the RNA silencing suppression domain of HC-Pro is mutated. These observations suggest a potentially interesting role for HGT of short functional sequences in ameliorating evolutionary constraints on viruses, through the duplication of functions.
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Affiliation(s)
- Anouk Willemsen
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia, València, Spain
- Present address: MIVEGEC (UMR CNRS 5290, IRD 224, UM), National Center for Scientific Research (CNRS), Montpellier, Cedex, France
| | - Mark P. Zwart
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia, València, Spain
- Present address: Institute of Theoretical Physics, University of Cologne, Cologne, Germany
| | - Silvia Ambrós
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia, València, Spain
| | - José L. Carrasco
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia, València, Spain
| | - Santiago F. Elena
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia, València, Spain
- The Santa Fe Institute, Santa Fe, NM
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7
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Lipid flippases promote antiviral silencing and the biogenesis of viral and host siRNAs in Arabidopsis. Proc Natl Acad Sci U S A 2017; 114:1377-1382. [PMID: 28123063 DOI: 10.1073/pnas.1614204114] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Dicer-mediated processing of virus-specific dsRNA into short interfering RNAs (siRNAs) in plants and animals initiates a specific antiviral defense by RNA interference (RNAi). In this study, we developed a forward genetic screen for the identification of host factors required for antiviral RNAi in Arabidopsis thaliana Using whole-genome sequencing and a computational pipeline, we identified aminophospholipid transporting ATPase 2 (ALA2) and the related ALA1 in the type IV subfamily of P-type ATPases as key components of antiviral RNAi. ALA1 and ALA2 are flippases, which are transmembrane lipid transporter proteins that transport phospholipids across cellular membranes. We found that the ala1/ala2 single- and double-mutant plants exhibited enhanced disease susceptibility to cucumber mosaic virus when the virus-encoded function to suppress RNAi was disrupted. Notably, the antiviral activity of both ALA1 and ALA2 was abolished by a single amino acid substitution known to inactivate the flippase activity. Genetic analysis revealed that ALA1 and ALA2 acted to enhance the amplification of the viral siRNAs by RNA-dependent RNA polymerase (RdRP) 1 (RDR1) and RDR6 and of the endogenous virus-activated siRNAs by RDR1. RNA virus replication by plant viral RdRPs occurs inside vesicle-like membrane invaginations induced by the recruitment of the viral RdRP and host factors to subcellular membrane microdomains enriched with specific phospholipids. Our results suggest that the phospholipid transporter activity of ALA1/ALA2 may be necessary for the formation of similar invaginations for the synthesis of dsRNA precursors of highly abundant viral and host siRNAs by the cellular RdRPs.
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8
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Murota K, Shimura H, Takeshita M, Masuta C. Interaction between Cucumber mosaic virus 2b protein and plant catalase induces a specific necrosis in association with proteasome activity. PLANT CELL REPORTS 2017; 36:37-47. [PMID: 27659495 PMCID: PMC5206265 DOI: 10.1007/s00299-016-2055-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 09/06/2016] [Indexed: 05/20/2023]
Abstract
Cucumber mosaic virus (CMV) can induce a specific necrosis on Arabidopsis through the interaction between the CMV 2b protein and host catalase, in which the ubiquitin-proteasome pathway may be involved. We previously reported that the CMV 2b protein, the viral RNA silencing suppressor, interacted with the H2O2 scavenger catalase (CAT3), leading to necrosis on CMV-inoculated Arabidopsis leaves. We here confirmed that CMV could more abundantly accumulate in the CAT3-knockout mutant (cat3), and that CAT3 makes host plants a little more tolerant to CMV. We also found that the necrosis severity is not simply explained by a high level of H2O2 given by the lack of CAT3, because the recombinant CMV, CMV-N, induced much milder necrosis in cat3 than in the wild type, suggesting some specific mechanism for the necrosis induction. To further characterize the 2b-inducing necrosis in relation to its binding to CAT3, we conducted the agroinfiltration experiments to overexpress CAT3 and 2b in N. benthamiana leaves. The accumulation levels of CAT3 were higher when co-expressed with the CMV-N 2b (N2b) than with CMV-Y 2b (Y2b). We infer that N2b made a more stable complex with CAT3 than Y2b did, and the longevity of the 2b-CAT3 complex seemed to be important to induce necrosis. By immunoprecipitation (IP) with an anti-ubiquitin antibody followed by the detection with anti-CAT3 antibodies, we detected a higher molecular-weight smear and several breakdown products of CAT3 among the IP-proteins. In addition, the proteasome inhibitor MG132 treatment could actually increase the accumulation levels of CAT3. This study suggests that the host proteasome pathway is, at least partially, responsible for the degradation of CAT3, which is manifested in CMV-infected tissues.
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Affiliation(s)
- Katsunori Murota
- Research Faculty of Agriculture, Hokkaido University, Kita-ku kita 9, Nishi 9, Sapporo, 060-8589, Japan
| | - Hanako Shimura
- Research Faculty of Agriculture, Hokkaido University, Kita-ku kita 9, Nishi 9, Sapporo, 060-8589, Japan.
| | - Minoru Takeshita
- Laboratory of Plant Pathology, Faculty of Agriculture, University of Miyazaki, Miyazaki, 889-2192, Japan
| | - Chikara Masuta
- Research Faculty of Agriculture, Hokkaido University, Kita-ku kita 9, Nishi 9, Sapporo, 060-8589, Japan.
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9
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Nemes K, Gellért Á, Balázs E, Salánki K. Alanine scanning of cucumber mosaic virus (CMV) 2b protein identifies different positions for cell-to-cell movement and gene silencing suppressor activity. PLoS One 2014; 9:e112095. [PMID: 25380036 PMCID: PMC4224413 DOI: 10.1371/journal.pone.0112095] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2014] [Accepted: 10/06/2014] [Indexed: 12/29/2022] Open
Abstract
The multifunctional 2b protein of CMV has a role in the long distance and local movement of the virus, in symptom formation, in evasion of defense mediated by salicylic acid as well as in suppression of RNA silencing. The role of conserved amino acid sequence domains were analyzed previously in the protein function, but comprehensive analysis of this protein was not carried out until recently. We have analyzed all over the 2b protein by alanine scanning mutagenesis changing three consecutive amino acids (aa) to alanine. We have identified eight aa triplets as key determinants of the 2b protein function in virus infection. Four of them (KKQ/22-24/AAA, QNR/31-33/AAA, RER/34-36/AAA, SPS/40-42/AAA) overlap with previously determined regions indispensable in gene silencing suppressor function. We have identified two additional triplets necessary for the suppressor function of the 2b protein (LPF/55-57/AAA, NVE/10-12/AAA), and two other positions were required for cell-to-cell movement of the virus (MEL/1-3/AAA, RHV/70-72/AAA), which are not essential for suppressor activity.
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Affiliation(s)
- Katalin Nemes
- Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary
- Department of Plant Pathology, Corvinus University of Budapest, Budapest, Hungary
| | - Ákos Gellért
- Agricultural Institute, Centre for Agricultural Research, Hungarian Academy of Sciences Department of Applied Genomics, Martonvásár, Hungary
| | - Ervin Balázs
- Agricultural Institute, Centre for Agricultural Research, Hungarian Academy of Sciences Department of Applied Genomics, Martonvásár, Hungary
| | - Katalin Salánki
- Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary
- Agricultural Biotechnology Center, Gödöllő, Hungary
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10
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Kim MK, Jeong RD, Kwak HR, Lee SH, Kim JS, Kim KH, Cha B, Choi HS. First Report of Cucumber mosaic virus Isolated from Wild Vigna angularis var. nipponensis in Korea. THE PLANT PATHOLOGY JOURNAL 2014; 30:200-7. [PMID: 25289004 PMCID: PMC4174850 DOI: 10.5423/ppj.nt.01.2013.0012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 03/25/2014] [Accepted: 04/02/2014] [Indexed: 06/03/2023]
Abstract
A viral disease causing severe mosaic, necrotic, and yellow symptoms on Vigna angularis var. nipponensis was prevalent around Suwon area in Korea. The causal virus was characterized as Cucumber mosaic virus (CMV) on the basis of biological and nucleotide sequence properties of RNAs 1, 2 and 3 and named as CMV-wVa. CMV-wVa isolate caused mosaic symptoms on indicator plants, Nicotiana tabacum cv. Xanthi-nc, Petunia hybrida, and Cucumis sativus. Strikingly, CMV-wVa induced severe mosaic and malformation on Cucurbita pepo, and Solanum lycopersicum. Moreover, it caused necrotic or mosaic symptoms on V. angularis and V. radiate of Fabaceae. Symptoms of necrotic local or pin point were observed on inoculated leaves of V. unguiculata, Vicia fava, Pisum sativum and Phaseolus vulgaris. However, CMV-wVa isolate failed to infect in Glycine max cvs. 'Sorok', 'Sodam' and 'Somyeong'. To assess genetic variation between CMV-wVa and the other known CMV isolates, phylogenetic analysis using 16 complete nucleotide sequences of CMV RNA1, RNA2, and RNA3 including CMV-wVa was performed. CMV-wVa was more closely related to CMV isolates belonging to CMV subgroup I showing about 85.1-100% nucleotide sequences identity to those of subgroup I isolates. This is the first report of CMV as the causal virus infecting wild Vigna angularis var. nipponensis in Korea.
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Affiliation(s)
- Mi-Kyeong Kim
- Crop Protection Division, National Academy of Agricultural Science, Suwon 441-707, Korea
- Department of Plant Medicine, Chungbuk National University, Cheongju 361-763, Korea
| | - Rae-Dong Jeong
- Animal, Plant and Fishieries Quarantine and Inspection Agency, Pyeongtaek 451-821, Korea
| | - Hae-Ryun Kwak
- Crop Protection Division, National Academy of Agricultural Science, Suwon 441-707, Korea
- Department of Plant Medicine, Chungbuk National University, Cheongju 361-763, Korea
| | - Su-Heon Lee
- Department of Applied Biology, Kyungpook National University, Daegu 702-701, Korea
| | - Jeong-Soo Kim
- Department of Plant Medicine, Andong National University, Andong 760-749, Korea
| | - Kook-Hyung Kim
- Department of Agricultural Biotechnology, Seoul National University, Seoul 151-921, Korea
| | - Byeongjin Cha
- Department of Plant Medicine, Chungbuk National University, Cheongju 361-763, Korea
| | - Hong-Soo Choi
- Crop Protection Division, National Academy of Agricultural Science, Suwon 441-707, Korea
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11
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Takagi K, Nishizawa K, Hirose A, Kurauchi T, Senda M, Masuta C, Ishimoto M. Seed coat pigmentation in transgenic soybean expressing the silencing suppressor 2b gene of Cucumber mosaic virus. PLANT CELL REPORTS 2013; 32:1903-12. [PMID: 24022064 DOI: 10.1007/s00299-013-1502-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Revised: 08/21/2013] [Accepted: 08/26/2013] [Indexed: 06/02/2023]
Abstract
KEY MESSAGE Soybean expressing the Cucumber mosaic virus 2b gene manifests seed coat pigmentation due to suppression of endogenous RNA silencing but no other morphological abnormality. This gene may help prevent transgene silencing. RNA silencing is an important mechanism for gene regulation and antiviral defense in plants. It is also responsible for transgene silencing, however, and thus hinders the establishment of transgenic plants. The 2b protein of Cucumber mosaic virus (CMV) functions as a suppressor of RNA silencing and therefore might prove beneficial for stabilization of transgene expression. We have now generated transgenic soybean that harbors the 2b gene of a CMV-soybean strain under the control of a constitutive promoter to investigate the effects of 2b expression. No growth abnormality was apparent in 2b transgenic plants, although the seed coat was pigmented in several of the transgenic lines. Genes for chalcone synthase (CHS), a key enzyme of the flavonoid pathway, are posttranscriptionally silenced by the inhibitor (I) locus in nonpigmented (yellow) soybean seeds. The levels of CHS mRNA and CHS small interfering RNA in strongly pigmented 2b transgenic seed coats were higher and lower, respectively, than those in the seed coat of a control transgenic line. The expression level of 2b also correlated with the extent of seed coat pigmentation. On the other hand, introduction of the 2b gene together with the DsRed2 gene into somatic embryos prevented the time-dependent decrease in transient DsRed2 expression. Our results indicate that the 2b gene alone is able to suppress RNA silencing of endogenous CHS genes regulated by the I locus, and that 2b is of potential utility for stabilization of transgene expression in soybean without detrimental effects other than seed coat pigmentation.
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12
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Pita JS, Roossinck MJ. Fixation of emerging interviral recombinants in cucumber mosaic virus populations. J Virol 2013; 87:1264-9. [PMID: 23115282 PMCID: PMC3554057 DOI: 10.1128/jvi.01892-12] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Accepted: 10/23/2012] [Indexed: 11/20/2022] Open
Abstract
Interstrain recombinants were observed in the progenies of the Cucumber mosaic virus (CMV) reassortant L(1)L(2)F(3) containing RNAs 1 and 2 from LS-CMV and RNA 3 from Fny-CMV. We characterized these recombinants, and we found that their fixation was controlled by the nature of the replicating RNAs 1 and 2. We demonstrate that the 2b gene partially affects this fixation process, but only in the context of homologous RNAs 1 and 2.
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Affiliation(s)
- Justin S Pita
- Department of Plant Pathology and Environmental Biology, and The Huck Institutes of The Life Sciences, Center for Infectious Disease Dynamics, Pennsylvania State University, University Park, PA, USA
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13
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Abstract
Cucumber mosaic virus (CMV) comprises numerous isolates with various levels of in-host diversity. Subgroup-distinctive features of the Fny and LS strains provided us with a platform to genetically map the viral control elements for genetic variation in planta. We found that both RNAs 1 and 2 controlled levels of genetic diversity, and further fine mapping revealed that the control elements of mutation frequency reside within the first 596 amino acids (aa) of RNA 1. The 2a/2b overlapping region of the 2a protein also contributed to control of viral genetic variation. Furthermore, the 3' nontranslated region (NTR) of RNA 3 constituted a hot spot of polymorphism, where the majority of fixed mutations found in the population were clustered. The 2b gene of CMV, a viral suppressor of gene silencing, controls the abundance of the fixed mutants in the viral population via a host-dependent mechanism.
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14
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Takeshita M, Koizumi E, Noguchi M, Sueda K, Shimura H, Ishikawa N, Matsuura H, Ohshima K, Natsuaki T, Kuwata S, Furuya N, Tsuchiya K, Masuta C. Infection dynamics in viral spread and interference under the synergism between Cucumber mosaic virus and Turnip mosaic virus. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2012; 25:18-27. [PMID: 21916556 DOI: 10.1094/mpmi-06-11-0170] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Mixed infection of Cucumber mosaic virus (CMV) and Turnip mosaic virus (TuMV) induced more severe symptoms on Nicotiana benthamiana than single infection. To dissect the relationships between spatial infection patterns and the 2b protein (2b) of CMV in single or mixed infections, the CMV vectors expressing enhanced green fluorescent or Discosoma sp. red fluorescent proteins (EGFP [EG] or DsRed2 [Ds], respectively were constructed from the same wild-type CMV-Y and used for inoculation onto N. benthamiana. CMV2-A1 vector (C2-A1 [A1]) has a functional 2b while CMV-H1 vector (C2-H1 [H1]) is 2b deficient. As we expected from the 2b function as an RNA silencing suppressor (RSS), in a single infection, A1Ds retained a high level of accumulation at initial infection sites and showed extensive fluorescence in upper, noninoculated leaves, whereas H1Ds disappeared rapidly at initial infection sites and could not spread efficiently in upper, noninoculated leaf tissues. In various mixed infections, we found two phenomena providing novel insights into the relationships among RSS, viral synergism, and interference. First, H1Ds could not spread efficiently from vasculature into nonvascular tissues with or without TuMV, suggesting that RNA silencing was not involved in CMV unloading from vasculature. These results indicated that 2b could promote CMV to unload from vasculature into nonvascular tissues, and that this 2b function might be independent of its RSS activity. Second, we detected spatial interference (local interference) between A1Ds and A1EG in mixed infection with TuMV, between A1Ds (or H1Ds) and TuMV, and between H1Ds and H1EG. This observation suggested that local interference between two viruses was established even in the synergism between CMV and TuMV and, again, RNA silencing did not seem to contribute greatly to this phenomenon.
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15
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Abstract
Cucumber mosaic virus (CMV) is an important virus because of its agricultural impact in the Mediterranean Basin and worldwide, and also as a model for understanding plant-virus interactions. This review focuses on those areas where most progress has been made over the past decade in our understanding of CMV. Clearly, a deep understanding of the role of the recently described CMV 2b gene in suppression of host RNA silencing and viral virulence is the most important discovery. These findings have had an impact well beyond the virus itself, as the 2b gene is an important tool in the studies of eukaryotic gene regulation. Protein 2b was shown to be involved in most of the steps of the virus cycle and to interfere with several basal host defenses. Progress has also been made concerning the mechanisms of virus replication and movement. However, only a few host proteins that interact with viral proteins have been identified, making this an area of research where major efforts are still needed. Another area where major advances have been made is CMV population genetics, where contrasting results were obtained. On the one hand, CMV was shown to be prone to recombination and to show high genetic diversity based on sequence data of different isolates. On the other hand, populations did not exhibit high genetic variability either within plants, or even in a field and the nearby wild plants. The situation was partially clarified with the finding that severe bottlenecks occur during both virus movement within a plant and transmission between plants. Finally, novel studies were undertaken to elucidate mechanisms leading to selection in virus population, according to the host or its environment, opening a new research area in plant-virus coevolution.
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16
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Shi BJ, Palukaitis P. The N-terminal 12 amino acids of tomato aspermy virus 2b protein function in infection and recombination. J Gen Virol 2011; 92:2706-2710. [PMID: 21880843 DOI: 10.1099/vir.0.035071-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023] Open
Abstract
The roles for various regions of the 2b protein in infection, hypervirulence and recombination were examined by introducing stop codons in a chimeric virus containing RNA 1 from the cucumber mosaic virus (CMV strain Q), RNA 3 from the tomato aspermy virus (TAV) and RNA 2 of CMV with a 2b gene from TAV. Chimeric virus expressing the intact 2b protein induced severe symptoms in inoculated Nicotiana clevelandii and Nicotiana glutinosa and facilitated CMV-TAV recombination, while chimeric viruses not expressing 2b protein did not infect plants systemically. Chimeric viruses expressing either the N-terminal 43 or 12 aa of the 2b protein infected both plant species systemically and facilitated CMV-TAV recombination, but induced mild symptoms and no symptoms in the infected plants, respectively. These data suggest that oligopeptides can have important functions in the biology of viruses and prompt a re-examination of existing small ORFs in sequenced virus genomes.
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Affiliation(s)
- Bu-Jun Shi
- Australian Centre for Plant Functional Genomics, and School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA 5064, Australia
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17
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Inaba JI, Kim BM, Shimura H, Masuta C. Virus-induced necrosis is a consequence of direct protein-protein interaction between a viral RNA-silencing suppressor and a host catalase. PLANT PHYSIOLOGY 2011; 156:2026-36. [PMID: 21622812 PMCID: PMC3149961 DOI: 10.1104/pp.111.180042] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2011] [Accepted: 05/26/2011] [Indexed: 05/19/2023]
Abstract
Many plant host factors are known to interact with viral proteins during pathogenesis, but how a plant virus induces a specific disease symptom still needs further research. A lily strain of Cucumber mosaic virus (CMV-HL) can induce discrete necrotic spots on infected Arabidopsis (Arabidopsis thaliana) plants; other CMV strains can induce similar spots, but they are not as distinct as those induced by CMV-HL. The CMV 2b protein (2b), a known RNA-silencing suppressor, is involved in viral movement and symptom induction. Using in situ proximity ligation assay immunostaining and the protoplast assays, we report here that CMV 2b interacts directly with Catalase3 (CAT3) in infected tissues, a key enzyme in the breakdown of toxic hydrogen peroxide. Interestingly, CAT3, normally localized in the cytoplasm (glyoxysome), was recruited to the nucleus by an interaction between 2b and CAT3. Although overexpression of CAT3 in transgenic plants decreased the accumulation of CMV and delayed viral symptom development to some extent, 2b seems to neutralize the cellular catalase contributing to the host defense response, thus favoring viral infection. Our results thus provide evidence that, in addition to altering the type of symptom by disturbing microRNA pathways, 2b can directly bind to a host factor that is important in scavenging cellular hydrogen peroxide and thus interfere specifically with that host factor, leading to the induction of a specific necrosis.
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18
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Fukuzawa N, Ishihara T, Itchoda N, Tabayashi N, Kataoka C, Masuta C, Matsumura T. Risk-managed production of bioactive recombinant proteins using a novel plant virus vector with a helper plant to complement viral systemic movement. PLANT BIOTECHNOLOGY JOURNAL 2011; 9:38-49. [PMID: 20492549 DOI: 10.1111/j.1467-7652.2010.00529.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
A plant viral vector has the potential to efficiently produce recombinant proteins at a low cost in a short period. Although recombinant proteins can be also produced by transgenic plants, a plant viral vector, if available, may be more convenient when urgent scale-up in production is needed. However, it is difficult to use a viral vector in open fields because of the risk of escape to the environment. In this study, we constructed a novel viral vector system using a movement-defective Cucumber mosaic virus (CMV) vector, which is theoretically localized in the inoculated cells but infects systemically only with the aid of the transgenic helper plant that complements viral movement, diminishing the risk of viral proliferation. Interestingly, the helper plant systemically infected with the vector gave strong cross-protection against challenge inoculation with wild-type CMVs. Using CMV strains belonging to two discrete CMV groups (subgroups I and II), we also improved the system to prevent recombination between the vector and the transgene transcript in the helper plant. We here demonstrate the expression of an anti-dioxin single chain variable fragment (DxscFv) and interleukin-1 receptor antagonist (IL1-Ra) in Nicotiana benthamiana by this viral vector confinement system, which is applicable for many useful high-quality recombinant proteins.
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Affiliation(s)
- Noriho Fukuzawa
- Plant Molecular Technology Research Group, Research Institute of Genome-based Biofactory, National Institute of Advanced Industrial Science and Technology (AIST), Tsukisamuhigashi Toyohira-Ku, Sapporo, Japan
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19
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Asaoka R, Shimura H, Arai M, Masuta C. A progeny virus from a cucumovirus pseudorecombinant evolved to gain the ability to accumulate Its RNA-silencing suppressor leading to systemic infection in tobacco. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2010; 23:332-9. [PMID: 20121454 DOI: 10.1094/mpmi-23-3-0332] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Two isolates of Tomato aspermy virus (TAV), V-TAV and C-TAV, can systemically infect Nicotiana benthamiana but only C-TAV can move systemically in N. tabacum. Any pseudorecombinants between the two strains could not move systemically in tobacco as efficiently as C-TAV. However, a pseudorecombinant consisting of RNAs 1 and 3 of V-TAV and RNA 2 of C-TAV (V1C2V3), which cannot infect tobacco systemically, generated progeny with a mutation in V1 and a recombination in C2 (V1(m)C2(r)V3), enabling the virus to move systemically. To avoid further mutation and recombination in the virus, we used Cucumber mosaic virus RNA3 (Y3) for subsequent experiments. Northern blot analyses showed that RNA4A, which encodes the 2b protein (2b), and RNA5 abundantly accumulated in V1(m)C2(r)Y3-infected tobacco. V1(m)C2(r)Y3 actually caused higher accumulation of 2b than did V1C2Y3 in Western blots, and overexpression of 2b by the PVX vector enabled V1C2Y3 to move systemically in tobacco, suggesting that 2b accumulation promotes viral systemic movement. Because RNA-silencing suppressor (RSS) activity of 2b was thought to be involved in systemic movement, we compared the RSS activity of 2b for the two TAV isolates; C-TAV 2b had stronger activity than did V-TAV 2b in tobacco in a transient protoplast assay. Our data also demonstrated that 2b and RNA5 play an important role in the evolution of members of genus Cucumovirus by generating mutant/recombinant viruses and viral systemic movement over RNA silencing.
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Affiliation(s)
- Ryota Asaoka
- Laboratory Of Cell Biology And Manipulation, Graduate School Of Agriculture, Hokkaido University, Sapporo, Japan
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20
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The C-terminal residues of the 2b protein of Cucumber mosaic virus
are important for efficient expression in Escherichia coli
and DNA-binding. FEBS Lett 2010; 584:945-50. [DOI: 10.1016/j.febslet.2010.01.033] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Revised: 12/29/2009] [Accepted: 01/15/2010] [Indexed: 11/19/2022]
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21
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Cillo F, Mascia T, Pasciuto MM, Gallitelli D. Differential effects of mild and severe Cucumber mosaic virus strains in the perturbation of MicroRNA-regulated gene expression in tomato map to the 3' sequence of RNA 2. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2009; 22:1239-49. [PMID: 19737097 DOI: 10.1094/mpmi-22-10-1239] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Viral infections interfere with the microRNA (miRNA)-mediated regulation of gene expression, determining developmental defects. In tomato leaves, the accumulation levels of six miRNA species and their target transcripts corresponding to transcription factors with roles in plant development and leaf morphogenesis and two genes involved in the short RNA processing, DCL1 and AGO1, were significantly enhanced upon infection with the severe strain Cucumber mosaic virus (CMV)-Fny, while that of AGO4 was reduced. In plants harboring the infection of the mild strain CMV-LS, the effects on miRNA pathway were reduced, although AGO1, DCL1, and NAC1 also were shown to overaccumulate during infections exhibiting a mild phenotype. The use of the recombinant strain CMV-Fny(LS2b), in which the 3'-terminal region of CMV-Fny RNA 2, including the 2b coding sequence, was replaced with the corresponding region of CMV-LS RNA 2, provided evidence that the exchanged region was implicated in the perturbation of miRNA metabolism. In tomato plants infected with CMV-Fny supporting the ameliorative satellite (sat)RNA variant Tfn-satRNA, the symptomless phenotype correlated, with the exception of NAC1 upregulation, with the absence of effects on mitochondrial RNA and miRNA expression. Some of the aspects of miRNA pathway perturbation described were peculiar to CMV-tomato interactions and involved in the etiology of the disease phenotype elicited in this host.
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Affiliation(s)
- Fabrizio Cillo
- Istituto di Virologia Vegetale, CNR, and Dipartimento di Protezione delle Piante e Microbiologia Applicata, Università degli Studi di Bari, Via Amendola 165/A, 70126 Bari, Italy
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22
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Lewsey M, Surette M, Robertson FC, Ziebell H, Choi SH, Ryu KH, Canto T, Palukaitis P, Payne T, Walsh JA, Carr JP. The role of the Cucumber mosaic virus 2b protein in viral movement and symptom induction. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2009; 22:642-54. [PMID: 19445589 DOI: 10.1094/mpmi-22-6-0642] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The Cucumber mosaic virus (CMV) 2b protein is a counter-defense factor and symptom determinant. Conserved domains in the 2b protein sequence were mutated in the 2b gene of strain Fny-CMV. The effects of these mutations were assessed by infection of Nicotiana tabacum, N. benthamiana, and Arabidopsis thaliana (ecotype Col-0) with mutant viruses and by expression of mutant 2b transgenes in A. thaliana. We confirmed that two nuclear localization signals were required for symptom induction and found that the N-terminal domain was essential for symptom induction. The C-terminal domain and two serine residues within a putative phosphorylation domain modulated symptom severity. Further infection studies were conducted using Fny-CMVdelta2b, a mutant that cannot express the 2b protein and that induces no symptoms in N. tabacum, N. benthamiana, or A. thaliana ecotype Col-0. Surprisingly, in plants of A. thaliana ecotype C24, Fny-CMVdelta2b induced severe symptoms similar to those induced by the wild-type virus. However, C24 plants infected with the mutant virus recovered from disease while those infected with the wild-type virus did not. Expression of 2b transgenes from either Fny-CMV or from LS-CMV (a mild strain) in Col-0 plants enhanced systemic movement of Fny-CMVdelta2b and permitted symptom induction by Fny-CMVdelta2b. Taken together, the results indicate that the 2b protein itself is an important symptom determinant in certain hosts. However, they also suggest that the protein may somehow synergize symptom induction by other CMV-encoded factors.
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Affiliation(s)
- Mathew Lewsey
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
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23
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Shi BJ, Symons RH, Palukaitis P. Stability and competitiveness of interviral recombinant RNAs derived from a chimeric cucumovirus. Virus Res 2009; 140:216-21. [PMID: 19063925 DOI: 10.1016/j.virusres.2008.11.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2008] [Revised: 10/01/2008] [Accepted: 11/10/2008] [Indexed: 11/17/2022]
Abstract
We previously described interviral recombinant RNAs derived from a chimeric virus having RNAs 1 and 2 of cucumber mosaic virus (CMV) with RNA 3 from the related tomato aspermy virus (TAV) and the 2b gene from either TAV or another strain of CMV. Here, we show that these interviral recombinant RNAs 3 were stable in the infected plants and could co-exist with their wild-type parental viral RNAs in the same plants, but their de novo generations were inhibited in the presence of the wild-type parental viral RNAs. The recombinant viral genomes did not prevent the replication of other viral RNAs or vice versa, but one of the interviral recombinant viruses induced different symptoms in Physalis floridana from those induced by the parental chimeric virus without the interviral RNA 3 recombinant. Factors such as the nature of the 2b gene and/or the presence or absence of competing wild-type parental RNAs influenced the generation of the recombinant RNAs described. Our data provide additional mechanistic insight into generation, stabilization and competition of recombinant viral RNA in infected host plants.
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Affiliation(s)
- Bu-Jun Shi
- Australian Centre for Plant Functional Genomics, University of Adelaide, Glen Osmond, SA 5064, Australia
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24
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Praveen S, Mangrauthia SK, Singh P, Mishra AK. Behavior of RNAi suppressor protein 2b of Cucumber mosaic virus in planta in presence and absence of virus. Virus Genes 2008; 37:96-102. [PMID: 18438704 DOI: 10.1007/s11262-008-0232-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2008] [Accepted: 04/08/2008] [Indexed: 10/22/2022]
Abstract
The 2b protein encoded by Cucumber mosaic virus (CMV) has been shown as a virus counter defense factor that interferes with the RNAi pathway. The 2b gene from CMV-banana, New Delhi isolate (CMV-NDLS) was amplified from CMV infected cucumber plants to generate the sense and antisense binary vector constructs for 2b expression and repression in planta. Constitutive expression of 2b gene in healthy Nicotiana tabacum caused phenotypic aberrations during somatic embryogenesis, which were not observed when expressed in CMV infected N. tabacum. Further, the established virus population in CMV infected N. tabacum was not affected by constitutive expression and repression of 2b gene. Thus, indicating its role in initiation of gene silencing, at the early stage of viral infection. This is the first demonstration of differential behavior of 2b suppressor protein in host development in the absence and presence of virus.
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Affiliation(s)
- Shelly Praveen
- Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi 12, India.
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25
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Shi BJ, Symons RH, Palukaitis P. The cucumovirus 2b gene drives selection of inter-viral recombinants affecting the crossover site, the acceptor RNA and the rate of selection. Nucleic Acids Res 2007; 36:1057-71. [PMID: 18086712 PMCID: PMC2275080 DOI: 10.1093/nar/gkm1036] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
RNA–RNA recombination is an important pathway in virus evolution and has been described for many viruses. However, the factors driving recombination or promoting the selection of recombinants are still unclear. Here, we show that the small movement protein (2b) was able to promote selection of RNA 1/2–RNA 3 recombinants within a chimeric virus having RNAs 1 and 2 from cucumber mosaic virus, and RNA 3 from the related tomato aspermy virus, along with heterologous 2b genes. The source of the 2b also determined the selection of the acceptor RNA and the crossover site, as well as affecting the rate of selection of the recombinant RNAs. The nature of the RNA 3 also influenced the selection of the recombinant RNAs. A 163-nt tandem repeat in RNA 3 significantly affected the rate of selection of the recombinant RNA, while a single nucleotide within the repeat affected the crossover site. The recombination occurred in a non-random manner, involved no intermediates and probably was generated via a copy-choice mechanism during (+) strand RNA synthesis.
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Affiliation(s)
- Bu-Jun Shi
- Australian Centre for Plant Functional Genomics, University of Adelaide, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, SA 5064, Australia.
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26
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Du ZY, Chen FF, Liao QS, Zhang HR, Chen YF, Chen JS. 2b ORFs encoded by subgroup IB strains of cucumber mosaic virus induce differential virulence on Nicotiana species. J Gen Virol 2007; 88:2596-2604. [PMID: 17698672 DOI: 10.1099/vir.0.82927-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cucumber mosaic virus (CMV)-encoded 2b protein from subgroup IA or subgroup II was shown to be a determinant of virulence in many solanaceous hosts. In this study, the virulence of 2b proteins from subgroup IB strains was analysed using four intraspecies hybrid viruses, which were generated by precise replacement of the 2b open reading frame (ORF) in subgroup IA strain Fny-CMV with the 2b ORFs of four subgroup IB strains, Cb7-CMV, PGs-CMV, Rad35-CMV and Na-CMV, generating FCb7(2b)-CMV, FPGs(2b)-CMV, FRad35(2b)-CMV and FNa(2b)-CMV, respectively. FCb7(2b)-CMV was more virulent than Fny-CMV, and was similar in phenotype to its parental virus Cb7-CMV on the three Nicotiana species tested. FNa(2b)-CMV also was virulent on these host species, equivalent to Fny-CMV or Na-CMV. However, FRad35(2b)-CMV only caused mild mosaic or undetectable symptoms on all the host species tested, and was less virulent than Fny-CMV or Rad35-CMV. FPGs(2b)-CMV infected all the host species systemically, and induced either mosaic or barely visible symptoms, demonstrating that the inability of PGs-CMV to infect these three Nicotiana species was not due to its 2b protein. The diverse virulence was shown to be mediated by the 2b proteins rather than the C-terminal overlapping parts of the 2a proteins, and was associated with the level of viral progeny RNA accumulation in systemically infected leaves, but not with the rate of long-distance viral movement in host plants. Through analysis of encapsidation of viral RNAs, there was an apparent correlation between the virulence and the high level of encapsidated RNA 2 in virions of Fny-CMV, FCb7(2b)-CMV and FNa(2b)-CMV.
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Affiliation(s)
- Zhi-You Du
- Institute of Bioengineering, Zhejiang Sci-Tech University, Hangzhou 310018, PR China
| | - Fei-Fei Chen
- Institute of Bioengineering, Zhejiang Sci-Tech University, Hangzhou 310018, PR China
| | - Qian-Sheng Liao
- College of Life Sciences, Zhejiang University, Hangzhou 310029, PR China
- Institute of Bioengineering, Zhejiang Sci-Tech University, Hangzhou 310018, PR China
| | - Hua-Rong Zhang
- College of Life Sciences, Zhejiang University, Hangzhou 310029, PR China
| | - Yan-Fei Chen
- Institute of Bioengineering, Zhejiang Sci-Tech University, Hangzhou 310018, PR China
| | - Ji-Shuang Chen
- Institute of Bioengineering, Zhejiang Sci-Tech University, Hangzhou 310018, PR China
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27
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Maliogka VI, Dovas CI, Katis NI. Demarcation of ilarviruses based on the phylogeny of RNA2-encoded RdRp and a generic ramped annealing RT-PCR. Arch Virol 2007; 152:1687-98. [PMID: 17541699 DOI: 10.1007/s00705-007-0995-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2006] [Accepted: 04/16/2007] [Indexed: 11/28/2022]
Abstract
In this study, a generic ramped-annealing (RAN) nested RT-PCR was developed, allowing the simultaneous detection and fast characterization of ilarviruses. The method involves a one-step RT-PCR in which a pair of degenerate primers amplifies a 381-bp part of the polymerase gene (RNA2), followed by a nested PCR amplification that increases detection sensitivity. The sensitivity and detection range of the method were further increased by applying a ramped annealing thermocycling step both in the first RT-PCR and in the subsequent nested PCR. The 371-bp nested amplicons can be sequenced directly, without cloning, to obtain initial sequence information on ilarvirus genomes, or can undergo a restriction enzyme analysis for rapid identification of already known virus species. Phylogenetic relationships among different members of the family Bromoviridae were inferred with maximum likelihood and Bayesian analysis, using published homologous partial amino acid sequences corresponding to the nested amplicon and also to a longer residue data set (432-453 aa) comprising all possible positions of homology among the RNA2-encoded polymerases of members of the family Bromoviridae. The implications of these analyses on the taxonomy of ilarviruses are discussed. The specific partial polymerase sequence, corresponding to the polymerase core palm structure (motifs A-D), was verified as phylogenetically informative and can be used to separate ilarviruses from other members of the family Bromoviridae, providing initial information for ilarvirus species characterization. However, the phylogenetic signal of this region is not reliable for inferring relationships among distantly related ilarviruses.
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Affiliation(s)
- V I Maliogka
- Plant Pathology Laboratory, School of Agriculture, Aristotle University of Thessaloniki, Thessaloniki, Greece
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28
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Lewsey M, Robertson FC, Canto T, Palukaitis P, Carr JP. Selective targeting of miRNA-regulated plant development by a viral counter-silencing protein. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2007; 50:240-52. [PMID: 17444907 DOI: 10.1111/j.1365-313x.2007.03042.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The cucumber mosaic virus (CMV) 2b protein suppresses RNA silencing and determines viral symptoms. Among Arabidopsis thaliana lines expressing 2b proteins from mild (LS and Q CMV) or severe (Fny CMV) strains, only Fny 2b-transgenic plants displayed strong symptom-like phenotypes in leaves, stems and flowers, together with stunting of main root growth and increased emergence of lateral roots. However, LS and Fny 2b proteins both enhanced lateral root length. Micro (mi)RNA-mediated cellular mRNA turnover was inhibited in Fny 2b-transgenic plants, but there was no evidence for this in LS 2b-transgenic plants. Both 2b proteins efficiently suppressed small interfering (si)RNA-mediated RNA silencing, suggesting that 2b proteins can target the siRNA pathway without disrupting miRNA-regulated RNA turnover. Thus, symptom induction is not an inevitable consequence of RNA silencing suppression. For CMV, strain-specific differences between the 2b silencing proteins determine whether only one or both small RNA-guided RNA destruction pathways are disrupted.
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Affiliation(s)
- Mathew Lewsey
- Department of Plant Sciences, Downing Street, Cambridge, UK
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29
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Liao Q, Zhu L, Du Z, Zeng R, Peng J, Chen J. Satellite RNA-mediated reduction of cucumber mosaic virus genomic RNAs accumulation in Nicotiana tabacum. Acta Biochim Biophys Sin (Shanghai) 2007; 39:217-23. [PMID: 17342261 DOI: 10.1111/j.1745-7270.2007.00266.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Satellite RNAs (satRNAs) are molecular parasites that interfere with the pathogenesis of the helper viruses. In this study, the relative accumulation of cucumber mosaic virus (CMV)-Fny genomic RNAs with or without satRNAs were quantitatively analyzed by real-time RT-PCR. The results showed that satRs apparently attenuated the symptoms of CMV-Fny on Nicotiana tabacum by depressing the accumulation of CMV-Fny genomic RNAs, tested as open reading frames. The accumulation of CMV-Fny 1a, 2a, 2b, 3a, and CP genes was much higher than that of CMV-Fny with satRs added (CMV-Fsat), at different inoculation times. CMV-FnyDelta2b, in which the complete 2b gene and 41 amino acids at the C-terminal of the 2a gene were deleted, caused only a slight mosaic effect on N. tabacum seedlings, similar to that of CMV-Fsat, but the addition of satRs to CMV-FnyDelta2b showed further decrease in the accumulation of CMV-FnyDelta2b genomic RNAs. Our results indicated that the attenuation of CMV, by adding satRs or deleting the 2b gene, was due to the low accumulation of CMV genomic RNAs, and that satRNA-mediated reduction of CMV genomic RNAs accumulation in N. tabacum was possibly related to the 2b gene.
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Affiliation(s)
- Qiansheng Liao
- College of Life Sciences, Zhejiang University, Hangzhou, China.
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30
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Shi BJ, Palukaitis P, Symons RH. The conserved, 5' termini of RNAs 1 and 2 of Tomato aspermy virus are dispensable for infection but affect virulence. Virus Genes 2005; 30:181-91. [PMID: 15744575 DOI: 10.1007/s11262-004-5626-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2004] [Accepted: 08/30/2004] [Indexed: 11/28/2022]
Abstract
The 5' terminus of each of the three genomic RNAs (RNAs 1, 2 and 3) of Tomato aspermy virus (TAV) begins with the sequence 5'-GUUU, which is also shared by a number of other viruses. Mutagenic analyses showed that the 5'-GUUU sequence of RNAs 1 and 2 of TAV was dispensable for viral infection and did not prevent symptom induction. On the other hand, substitution of U at position 5 for G in RNA 1, but not RNA 2, induced veinal necrosis symptoms in Nicotiana glutinosa. The mutants constructed included insertion of UUU into the 5'-GUUU sequence of TAV RNAs 1 and/or 2. All RNA 2 mutants induced more severe symptoms than viral RNAs containing either mutated RNA 1 or most combinations of mutated RNAs 1 and 2. Some combinations of mutated RNAs 1 and 2 also induced veinal necrosis in N. glutinosa. Virulence was unrelated to the levels of viral RNA accumulation. Sequence analysis of progeny viral RNAs showed that only the mutant viral RNAs with a G to U substitution in RNA 1 and the deletion of the 5'-GUUU in both RNAs 1 and 2 were able to maintain the same sequence as the inoculum. The other mutants either reverted to the wildtype sequence or underwent further deletion or insertion. None of the constructed mutants were able to compete for accumulation with the wildtype virus after co-inoculation to the plant species tested.
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Affiliation(s)
- Bu-Jun Shi
- Department of Plant Science, Waite Campus, University of Adelaide, Glen Osmond, 5064, SA, Australia
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Wang Y, Tzfira T, Gaba V, Citovsky V, Palukaitis P, Gal-On A. Functional analysis of the Cucumber mosaic virus 2b protein: pathogenicity and nuclear localization. J Gen Virol 2004; 85:3135-3147. [PMID: 15448377 DOI: 10.1099/vir.0.80250-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The 2b protein encoded by Cucumber mosaic virus (CMV) has been shown to be a silencing suppressor and pathogenicity determinant in solanaceous hosts, but a movement determinant in cucumber. In addition, synergistic interactions between CMV and Zucchini yellow mosaic virus (ZYMV) have been described in several cucurbit species. Here, it was shown that deletion of the 2b gene from CMV prevented extensive systemic movement of the virus in zucchini squash, which could not be complemented by co-infection with ZYMV. Thus, ZYMV expressing a silencing suppressor with a different target could not complement the CMV 2b-specific movement function. Expression of the 2b protein from an attenuated ZYMV vector resulted in a synergistic response, largely restoring infection symptoms of wild-type ZYMV in several cucurbit species. Deletion or alteration of either of two nuclear localization signals (NLSs) did not affect nuclear localization in two assays, but did affect pathogenicity in several cucurbit species, whilst deletion of both NLSs led to loss of nuclear localization. The 2b protein interacted with an Arabidopsis thaliana karyopherin alpha protein (AtKAPalpha) in the yeast two-hybrid system, as did each of the two single NLS-deletion mutants. However, 2b protein containing a deletion of both NLSs was unable to interact with AtKAPalpha. These data suggest that the 2b protein localizes to the nucleus by using the karyopherin alpha-mediated system, but demonstrate that nuclear localization was insufficient for enhancement of the 2b-mediated pathogenic response in cucurbit hosts. Thus, the sequences corresponding to the two NLSs must have another role leading to pathogenicity enhancement.
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Affiliation(s)
- Yongzeng Wang
- Department of Virology, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel
| | - Tzvi Tzfira
- Department of Biochemistry and Cell Biology, State University of New York at Stony Brook, Stony Brook, NY 11794-5215, USA
| | - Victor Gaba
- Department of Virology, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel
| | - Vitaly Citovsky
- Department of Biochemistry and Cell Biology, State University of New York at Stony Brook, Stony Brook, NY 11794-5215, USA
| | - Peter Palukaitis
- Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
| | - Amit Gal-On
- Department of Virology, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel
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Shi BJ, Palukaitis P, Symons RH. Stable and unstable mutations in the 5' non-translated regions of tomato aspermy virus RNAs 1 and 2 generated de novo from infectious cDNA clones containing a cauliflower mosaic virus 35S promoter. Virus Genes 2004; 28:277-83. [PMID: 15266109 DOI: 10.1023/b:viru.0000025775.20862.50] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Tomato aspermy virus RNAs derived from infectious cDNA clones exhibited a number of sequence alterations in the 5' non-translated region (NTR). These included a deletion of the first four residues in both RNAs 1 and 2, transversion of residue 5 from a G to a U in RNA 1, and transversion of A to C at position of 50 of RNA 1. These alterations were not stable in the infected plants while the insertion of a U residue between nucleotides 1 and 5 of RNA 1 was stable in the infected plants. Generation of these sequence alternations was not dependent upon either the host species or the concentration of the inoculum. The sequence alterations also did not occur on passage of wildtype virus. Rather, the sequence alterations related to transcription from the cauliflower mosaic virus 35S RNA promoter-driving infectious cDNAs. The alternations observed had no impact on symptoms or infectivity, but did affect the accumulation of specific viral RNAs. The data also demonstrated the existence of some plasticity in the sequence of the 5' NTR.
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Affiliation(s)
- Bu-Jun Shi
- Department of Plant Science, Waite Institute, Adelaide University, Glen Osmond, SA 5064, Australia
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Salánki K, Gellért Á, Huppert E, Náray-Szabó G, Balázs E. Compatibility of the movement protein and the coat protein of cucumoviruses is required for cell-to-cell movement. J Gen Virol 2004; 85:1039-1048. [PMID: 15039546 DOI: 10.1099/vir.0.19687-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
For the cell-to-cell movement of cucumoviruses both the movement protein (MP) and the coat protein (CP) are required. These are not reversibly exchangeable between Cucumber mosaic virus (CMV) and Tomato aspermy virus (TAV). The MP of CMV is able to function with the TAV CP (chimera RT), but TAV MP is unable to promote the cell-to-cell movement in the presence of CMV CP (chimera TR). To gain further insight into the non-infectious nature of the TR recombinant, RNA 3 chimeras were constructed with recombinant MPs and CPs. The chimeric MP and one of the CP recombinants were infectious. The other recombinant CP enabled virus movement only after the introduction of two point mutations (Glu-->Lys and Lys-->Arg at aa 62 and 65, respectively). The mutations served to correct the CP surface electrostatic potential that was altered by the recombination. The infectivity of the TR virus on different test plants was restored by replacing the sequence encoding the C-terminal 29 aa of the MP with the corresponding sequence of the CMV MP gene or by exchanging the sequence encoding the C-terminal 15 aa of the CP with the same region of TAV. The analysis of the recombinant clones suggests a requirement for compatibility between the C-terminal 29 aa of the MP and the C-terminal two-thirds of the CP for cell-to-cell movement of cucumoviruses.
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Affiliation(s)
- Katalin Salánki
- Agricultural Biotechnology Center, Szent-Györgyi Albert u. 4, H-2100 Gödöllő, Hungary
| | - Ákos Gellért
- Department of Theoretical Chemistry, Eötvös Loránd University, Pázmány Péter Sétány 1/A, H-1117 Budapest, Hungary
- Agricultural Biotechnology Center, Szent-Györgyi Albert u. 4, H-2100 Gödöllő, Hungary
| | - Emese Huppert
- Agricultural Biotechnology Center, Szent-Györgyi Albert u. 4, H-2100 Gödöllő, Hungary
| | - Gábor Náray-Szabó
- Protein Modelling Group, Hungarian Academy of Sciences - Eötvös Lóránd University, Pázmány Péter Sétány 1/A, H-1117 Budapest, Hungary
| | - Ervin Balázs
- Agricultural Biotechnology Center, Szent-Györgyi Albert u. 4, H-2100 Gödöllő, Hungary
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Abstract
Research on the molecular biology of cucumoviruses and their plant-virus interactions has been very extensive in the last decade. Cucumovirus genome structures have been analyzed, giving new insights into their genetic variability, evolution, and taxonomy. A new viral gene has been discovered, and its role in promoting virus infection has been delineated. The localization and various functions of each viral-encoded gene product have been established. The particle structures of Cucumber mosaic virus (CMV) and Tomato aspermy virus have been determined. Pathogenicity domains have been mapped, and barriers to virus infection have been localized. The movement pathways of the viruses in some hosts have been discerned, and viral mutants affecting the movement processes have been identified. Host responses to viral infection have been characterized, both temporally and spatially. Progress has been made in determining the mechanisms of replication, gene expression, and transmission of CMV. The pathogenicity determinants of various satellite RNAs have been characterized, and the importance of secondary structure in satellite RNA-mediated interactions has been recognized. Novel plant genes specifying resistance to infection by CMV have been identified. In some cases, these genes have been mapped, and one resistance gene to CMV has been isolated and characterized. Pathogen-derived resistance has been demonstrated against CMV using various segments of the CMV genome, and the mechanisms of some of these forms of resistances have been analyzed. Finally, the nature of synergistic interactions between CMV and other viruses has been characterized. This review highlights these various achievements in the context of the previous work on the biology of cucumoviruses and their interactions with plants.
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Affiliation(s)
- Peter Palukaitis
- Gene Expression Programme, Scottish Crop Research Institute, Invergowrie, Dundee, DD2 5DA, United Kingdom
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