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An Evolved 5' Untranslated Region of Alfalfa Mosaic Virus Allows the RNA Transport of Movement-Defective Variants. J Virol 2022; 96:e0098822. [PMID: 36314818 PMCID: PMC9683001 DOI: 10.1128/jvi.00988-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Although the coat protein (CP) has a relevant role in the long-distance movement of alfalfa mosaic virus (AMV) and brome mosaic virus (BMV), its precise function is not fully understood. Previous results showed that a specific interaction between the C termini of the movement protein (MP) and the cognate CP is required for systemic transport. Thus, we have performed a compensatory evolution experiment using an AMV RNA3 derivative defective in long-distance transport that carries a BMV MP lacking the C-terminal 48 residues and unable to interact with the AMV CP. After several passages, five independent evolution lineages were able to move long distance. The analysis of the viral RNA of these lineages showed the presence of three different modifications located exclusively at the 5' untranslated region (5' UTR). The three evolved 5' UTR variants accumulated comparable levels of viral RNA and CP but reduced the accumulation of virus particles and the affinity between the 5' UTR and the AMV CP. In addition, the evolved 5' UTR increased cell-to-cell transport for both the AMV RNA3 carrying the BMV MP and that carrying the AMV MP. Finally, the evolved 5' UTRs allowed the systemic transport of an AMV RNA3 carrying a CP mutant defective in virus particles and increased the systemic transport of several AMV RNA3 derivatives carrying different viral MPs associated with the 30K superfamily. Altogether, our findings indicate that virus particles are not required for the systemic transport of AMV but also that BMV MP is competent for the short- and long-distance transport without the interaction with the CP. IMPORTANCE The results obtained in the present work could challenge the view of the role of the virus particle in the systemic transport of plant viruses. In this sense, we show that two different MPs are competent to systemically transport the AMV genome without the requirement of the virus particles, as reported for viruses lacking a CP (e.g., Umbravirus). The incapability of the viral MP to interact with the CP triggered virus variants that evolved to reduce the formation of virus particles, probably to increase the accessibility of the MP to the viral progeny. Our results point to the idea that virus particles would not be necessary for the viral systemic transport but would be necessary for vector virus transmission. This idea is reinforced by the observation that heterologous MPs also increased the systemic transport of the AMV constructs that have reduced encapsidation capabilities.
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Lezzhov AA, Morozov SY, Solovyev AG. Phloem Exit as a Possible Control Point in Selective Systemic Transport of RNA. FRONTIERS IN PLANT SCIENCE 2021; 12:739369. [PMID: 34899773 PMCID: PMC8660857 DOI: 10.3389/fpls.2021.739369] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Accepted: 10/28/2021] [Indexed: 06/01/2023]
Affiliation(s)
- Alexander A. Lezzhov
- Faculty of Bioengineering and Bioinformatics, Moscow State University, Moscow, Russia
- A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, Russia
| | - Sergey Y. Morozov
- A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, Russia
- Department of Virology, Faculty of Biology, Moscow State University, Moscow, Russia
| | - Andrey G. Solovyev
- A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, Russia
- Department of Virology, Faculty of Biology, Moscow State University, Moscow, Russia
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3
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Anil Sushma A, Zhao B, Tsvetkova IB, Pérez-Segura C, Hadden-Perilla JA, Reilly JP, Dragnea B. Subset of Fluorophores Is Responsible for Radiation Brightening in Viromimetic Particles. J Phys Chem B 2021; 125:10494-10505. [PMID: 34507491 DOI: 10.1021/acs.jpcb.1c06395] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In certain conditions, dye-conjugated icosahedral virus shells exhibit suppression of concentration quenching. The recently observed radiation brightening at high fluorophore densities has been attributed to coherent emission, i.e., to a cooperative process occurring within a subset of the virus-supported fluorophores. Until now, the distribution of fluorophores among potential conjugation sites and the nature of the active subset remained unknown. With the help of mass spectrometry and molecular dynamics simulations, we found which conjugation sites in the brome mosaic virus capsid are accessible to fluorophores. Reactive external surface lysines but also those at the lumenal interface where the coat protein N-termini are located showed virtually unrestricted access to dyes. The third type of labeled lysines was situated at the intercapsomeric interfaces. Through limited proteolysis of flexible N-termini, it was determined that dyes bound to them are unlikely to be involved in the radiation brightening effect. At the same time, specific labeling of genetically inserted cysteines on the exterior capsid surface alone did not lead to radiation brightening. The results suggest that lysines situated within the more rigid structural part of the coat protein provide the chemical environments conducive to radiation brightening, and we discuss some of the characteristics of these environments.
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Affiliation(s)
- Arathi Anil Sushma
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Bingqing Zhao
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Irina B Tsvetkova
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Carolina Pérez-Segura
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Jodi A Hadden-Perilla
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - James P Reilly
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Bogdan Dragnea
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
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4
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Tolstyko EA, Lezzhov AA, Morozov SY, Solovyev AG. Phloem transport of structured RNAs: A widening repertoire of trafficking signals and protein factors. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2020; 299:110602. [PMID: 32900440 DOI: 10.1016/j.plantsci.2020.110602] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 06/20/2020] [Accepted: 07/14/2020] [Indexed: 06/11/2023]
Abstract
The conducting sieve tubes of the phloem consist of sieve elements (SEs), which are enucleate cells incapable of transcription and translation. Nevertheless, SEs contain a large variety of RNAs, and long-distance RNA trafficking via the phloem has been documented. The phloem transport of certain RNAs, as well as the further unloading of these RNAs at target tissues, is essential for plant individual development and responses to environmental cues. The translocation of such RNAs via the phloem is believed to be directed by RNA structural elements serving as phloem transport signals (PTSs), which are recognized by proteins that direct the PTS-containing RNAs into the phloem translocation pathway. The ability of phloem transport has been reported for several classes of structured RNAs including viroids, genuine tRNAs, mRNAs with tRNA sequences embedded into mRNA untranslated regions, tRNA-like structures in the genomic RNAs of plant viruses, and micro-RNA (miRNA) precursors (pri-miRNA). Here, three distinct types of such RNAs are discussed, along with the proteins that may specifically interact with these structures in the phloem. Three-dimensional (3D) motifs, which are characteristic of imperfect RNA duplexes, are discussed as elements of phloem-mobile structured RNAs specifically recognized by proteins involved in phloem transport, thus serving as PTSs.
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Affiliation(s)
- Eugeny A Tolstyko
- Department of Virology, Biological Faculty, Moscow State University, Moscow, 119234, Russia
| | - Alexander A Lezzhov
- Faculty of Bioengineering and Bioinformatics, Moscow State University, Moscow, 119991, Russia
| | - Sergey Y Morozov
- Department of Virology, Biological Faculty, Moscow State University, Moscow, 119234, Russia; Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, 119992, Russia
| | - Andrey G Solovyev
- Department of Virology, Biological Faculty, Moscow State University, Moscow, 119234, Russia; Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, 119992, Russia; Sechenov First Moscow State Medical University, Institute of Molecular Medicine, Moscow, 119991, Russia.
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5
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Bond KM, Lyktey NA, Tsvetkova IB, Dragnea B, Jarrold MF. Disassembly Intermediates of the Brome Mosaic Virus Identified by Charge Detection Mass Spectrometry. J Phys Chem B 2020; 124:2124-2131. [PMID: 32141748 DOI: 10.1021/acs.jpcb.0c00008] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Capsid disassembly and genome release are critical steps in the lifecycle of a virus. However, their mechanisms are poorly understood, both in vivo and in vitro. Here, we have identified two in vitro disassembly pathways of the brome mosaic virus (BMV) by charge detection mass spectrometry and transmission electron microscopy. When subjected to a pH jump to a basic environment at low ionic strength, protein-RNA interactions are disrupted. Under these conditions, BMV appears to disassemble mainly through a global cleavage event into two main fragments: a near complete capsid that has released the RNA and the released RNA complexed to a small number of the capsid proteins. Upon slow buffer exchange to remove divalent cations at neutral pH, capsid protein interactions are disrupted. The BMV virions swell but there is no measurable loss of the RNA. Some of the virions break into small fragments, leading to an increase in the abundance of species with masses less than 1 MDa. The peak attributed to the BMV virion shifts to a higher mass with time. The mass increase is attributed to additional capsid proteins associating with the disrupted capsid protein-RNA complex, where the RNA is presumably partially exposed. It is likely that this pathway is more closely related to how the capsid disassembles in vivo, as it offers the advantage of protecting the RNA with the capsid protein until translation begins.
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Affiliation(s)
- Kevin M Bond
- Chemistry Department, Indiana University, 800 E Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Nicholas A Lyktey
- Chemistry Department, Indiana University, 800 E Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Irina B Tsvetkova
- Chemistry Department, Indiana University, 800 E Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Bogdan Dragnea
- Chemistry Department, Indiana University, 800 E Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Martin F Jarrold
- Chemistry Department, Indiana University, 800 E Kirkwood Avenue, Bloomington, Indiana 47405, United States
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de Wispelaere M, Sivanandam V, Rao ALN. Regulation of Positive-Strand Accumulation by Capsid Protein During Brome mosaic virus Infection In Planta. PHYTOPATHOLOGY 2020; 110:228-236. [PMID: 31411546 DOI: 10.1094/phyto-07-19-0236-fi] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
A hallmark feature of (+)-strand RNA viruses of eukaryotic cells is that progeny (+)-strands are accumulated 100-fold over (-)-strands. Previous experimental evidence suggests that, in Brome mosaic virus (BMV), a plant-infecting member of the alphavirus-like superfamily, the addition of RNA3 and, specifically, translation of the wild-type (WT) coat protein (CP) gene contributes to increased accumulation of (+)-strands. It is unclear whether this stimulation of (+)-strand accumulation by CP is due to direct regulation of viral RNA replication or RNA stabilization via encapsidation. Analysis of BMV progeny RNA in Nicotiana benthamiana plants revealed that expression of RNA3 variants that did not express WT CP led to a severe defect in BMV (+)-strand accumulation. The (+)-strand accumulation could be rescued when CP was complemented in trans. To verify whether stimulation of (+)-strand accumulation is coupled with encapsidation, two independent mutations were engineered into CP open reading frames. An N-terminal deletion that prevented CP binding to the viral RNAs resulted in a severe reduction of BMV (+)-strand accumulation but stimulated (-)-strand accumulation over the WT. On the other hand, a C-terminal mutation affecting CP dimerization caused a significant decrease in (+)-strand accumulation but had no detectable effect on (-)-strand accumulation. Nucleotide sequences in the movement protein-coding region were also found to contribute to (+)-strand accumulation, in part by providing packaging signals for efficient RNA3 encapsidation. Overall, these results show that RNA encapsidation is a significant determinant of BMV RNA intracellular accumulation.
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Affiliation(s)
- Mélissanne de Wispelaere
- Department of Microbiology and Plant Pathology, University of California, Riverside, CA 92521-0122
| | - Venkatesh Sivanandam
- Department of Microbiology and Plant Pathology, University of California, Riverside, CA 92521-0122
| | - A L N Rao
- Department of Microbiology and Plant Pathology, University of California, Riverside, CA 92521-0122
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7
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Tsvetkova IB, Anil Sushma A, Wang JCY, Schaich WL, Dragnea B. Radiation Brightening from Virus-like Particles. ACS NANO 2019; 13:11401-11408. [PMID: 31335115 DOI: 10.1021/acsnano.9b04786] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Concentration quenching is a well-known challenge in many fluorescence imaging applications. Here, we show that the optical emission from hundreds of chromophores confined onto the surface of a 28 nm diameter virus particle can be recovered under pulsed irradiation. We have found that as one increases the number of chromophores tightly bound to the virus surface, fluorescence quenching ensues at first, but when the number of chromophores per particle is nearing the maximum number of surface sites allowable, a sudden brightening of the emitted light and a shortening of the excited-state lifetime are observed. This radiation brightening occurs only under short pulse excitation; steady-state excitation is characterized by conventional concentration quenching for any number of chromophores per particle. The observed suppression of fluorescence quenching is consistent with efficient, collective relaxation at room temperature. Interestingly, radiation brightening disappears when the emitters' spatial and/or dynamic heterogeneity is increased, suggesting that the template structural properties may play a role that could be instrumental in developing virus-enabled imaging vectors that have optical properties qualitatively different than those of state-of-the-art biophotonic agents.
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Calderón-Pérez B, Piedra-Ibarra E, de la Torre-Almaráz R, Xoconostle-Cázares B, Ruiz-Medrano R. Host-specific loss of sequences of an alfalfa mosaic virus isolate during systemic infection. Virus Res 2019; 272:197703. [PMID: 31412275 DOI: 10.1016/j.virusres.2019.197703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 08/06/2019] [Accepted: 08/09/2019] [Indexed: 10/26/2022]
Abstract
Infectivity of an alfalfa mosaic virus (AMV) isolate from Leonotis nepetaefolia in different tomato cultivars was analyzed. Symptoms typical of AMV infection were observed in indicator plants, but not in Flora Dade and Rio Grande tomato cultivars; however, mild symptoms were observed in cv. Rutgers. Furthermore, at least 1 kb of the 3´ segment of RNA 2 and the coat protein gene were missing in systemic leaves of inoculated Rio Grande and Flora Dade plants, while in cv. Rutgers infected with this AMV strain all genomic components were detected. Northern blot analysis of plants infected with the aforementioned AMV isolate confirmed the absence of the CP gene, but suggested rearrangements in both RNA 2 and 3. Factors that may affect differential movement or systemic accumulation of genomic components in multipartite viruses in plants are discussed.
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Affiliation(s)
- Berenice Calderón-Pérez
- Departamento de Biotecnología y Bioingeniería, CINVESTAV-IPN, Avenida IPN 2508, Col. San Pedro Zacatenco, Ciudad de México, C.P. 07360, Mexico; Servicio Nacional de Sanidad, Inocuidad y Calidad Agroalimentaria, Centro Nacional de Referencia Fitosanitaria, Unidad Integral de Servicios, Diagnóstico y Constatación, Km 37.5, Carretera Federal México-Pachuca, Tecámac, Estado de México, C.P. 55740, Mexico
| | - Elías Piedra-Ibarra
- Facultad de Estudios Profesionales Iztacala UNAM, Avenida de los Barrios 1, Los Reyes Iztacala, Tlalnepantla, Estado de México, C.P. 54090, Mexico
| | - Rodolfo de la Torre-Almaráz
- Facultad de Estudios Profesionales Iztacala UNAM, Avenida de los Barrios 1, Los Reyes Iztacala, Tlalnepantla, Estado de México, C.P. 54090, Mexico
| | - Beatriz Xoconostle-Cázares
- Departamento de Biotecnología y Bioingeniería, CINVESTAV-IPN, Avenida IPN 2508, Col. San Pedro Zacatenco, Ciudad de México, C.P. 07360, Mexico
| | - Roberto Ruiz-Medrano
- Departamento de Biotecnología y Bioingeniería, CINVESTAV-IPN, Avenida IPN 2508, Col. San Pedro Zacatenco, Ciudad de México, C.P. 07360, Mexico.
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9
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Lezzhov AA, Atabekova AK, Tolstyko EA, Lazareva EA, Solovyev AG. RNA phloem transport mediated by pre-miRNA and viral tRNA-like structures. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2019; 284:99-107. [PMID: 31084885 DOI: 10.1016/j.plantsci.2019.04.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 04/03/2019] [Accepted: 04/05/2019] [Indexed: 06/09/2023]
Abstract
Phloem-mobile mRNAs are assumed to contain sequence elements directing RNA to the phloem translocation pathway. One of such elements is represented by tRNA sequences embedded in untranslated regions of many mRNAs, including those proved to be mobile. Genomic RNAs of a number of plant viruses possess a 3'-terminal tRNA-like structures (TLSs) only distantly related to genuine tRNAs, but nevertheless aminoacylated and capable of interaction with some tRNA-binding proteins. Here, we elaborated an experimental system for analysis of RNA phloem transport based on an engineered RNA of Potato virus X capable of replication, but not encapsidation and movement in plants. The TLSs of Brome mosaic virus, Tobacco mosaic virus and Turnip yellow mosaic virus were demonstrated to enable the phloem transport of foreign RNA. A miRNA precursor, pre-miR390b, was also found to render RNA competent for the phloem transport. In line with this, sequences of miRNA precursors were identified in a Cucurbita maxima phloem transcriptome, supporting the hypothesis that, at least in some cases, miRNA phloem signaling can involve miRNA precursors. Collectively, the data presented here suggest that RNA molecules can be directed into the phloem translocation pathway by structured RNA elements such as those of viral TLSs and miRNA precursors.
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Affiliation(s)
- Alexander A Lezzhov
- Faculty of Bioengineering and Bioinformatics, Moscow State University, Moscow 119991, Russia
| | - Anastasia K Atabekova
- Department of Virology, Biological Faculty, Moscow State University, Moscow 119234, Russia
| | - Eugeny A Tolstyko
- Department of Virology, Biological Faculty, Moscow State University, Moscow 119234, Russia
| | - Ekaterina A Lazareva
- Department of Virology, Biological Faculty, Moscow State University, Moscow 119234, Russia
| | - Andrey G Solovyev
- Department of Virology, Biological Faculty, Moscow State University, Moscow 119234, Russia; Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russia; Sechenov First Moscow State Medical University, Institute of Molecular Medicine, Moscow 119991, Russia.
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10
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Small RNA Functions as a Trafficking Effector in Plant Immunity. Int J Mol Sci 2019; 20:ijms20112816. [PMID: 31181829 PMCID: PMC6600683 DOI: 10.3390/ijms20112816] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 06/01/2019] [Accepted: 06/06/2019] [Indexed: 01/04/2023] Open
Abstract
Small RNAs represent a class of small but powerful agents that regulate development and abiotic and biotic stress responses during plant adaptation to a constantly challenging environment. Previous findings have revealed the important roles of small RNAs in diverse cellular processes. The recent discovery of bidirectional trafficking of small RNAs between different kingdoms has raised many interesting questions. The subsequent demonstration of exosome-mediated small RNA export provided a possible tool for further investigating how plants use small RNAs as a weapon during the arms race between plant hosts and pathogens. This review will focus on discussing the roles of small RNAs in plant immunity in terms of three aspects: the biogenesis of extracellular small RNAs and the transportation and trafficking small RNA-mediated gene silencing in pathogens.
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Lucía-Sanz A, Aguirre J, Manrubia S. Theoretical approaches to disclosing the emergence and adaptive advantages of multipartite viruses. Curr Opin Virol 2018; 33:89-95. [PMID: 30121469 DOI: 10.1016/j.coviro.2018.07.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Revised: 07/19/2018] [Accepted: 07/31/2018] [Indexed: 01/02/2023]
Abstract
Multipartite viruses have a segmented genome encapsidated in different viral particles that, in principle, propagate independently. Current empirical knowledge on the molecular, ecological and evolutionary features underlying the very existence of multipartitism is fragmented and puzzling. Although it is generally assumed that multipartitism is viable only when propagation occurs at high multiplicity of infection, evidence indicates that severe population bottlenecks are common. Mathematical models aimed at describing the dynamics of multipartite viruses typically assign an advantage to the multipartite form to compensate for the cost of high multiplicity of infection. Since progress in the theoretical understanding of the evolutionary ecology of multipartitism is strongly conditioned by empirical advances, both aspects are jointly revised in this contribution.
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Affiliation(s)
- Adriana Lucía-Sanz
- Spanish National Centre for Biotechnology (CSIC), Madrid, Spain; Grupo Interdisciplinar de Sistemas Complejos (GISC), Madrid, Spain
| | - Jacobo Aguirre
- Spanish National Centre for Biotechnology (CSIC), Madrid, Spain; Grupo Interdisciplinar de Sistemas Complejos (GISC), Madrid, Spain
| | - Susanna Manrubia
- Spanish National Centre for Biotechnology (CSIC), Madrid, Spain; Grupo Interdisciplinar de Sistemas Complejos (GISC), Madrid, Spain.
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12
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Sanjuán R. Collective properties of viral infectivity. Curr Opin Virol 2018; 33:1-6. [PMID: 30015082 DOI: 10.1016/j.coviro.2018.06.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 06/14/2018] [Accepted: 06/19/2018] [Indexed: 12/22/2022]
Abstract
Individual virions typically fail to infect cells. Such decoupling between virions and infectious units is most evident in multicomponent and other segmented viruses, but is also frequent in non-segmented viruses. Despite being a well-known observation, the causes and implications of low single-virion infectivity often remain unclear. In principle, this can originate from intrinsic genetic and/or structural virion defects, but also from host infection barriers that limit early viral proliferation. Hence, viruses may have evolved strategies to increase the per-virion likelihood of establishing successful infections. This can be achieved by adopting spread modes that elevate the multiplicity of infection at the cellular level, including direct cell-to-cell viral transfer, encapsulation of multiple virions in microvesicles or other intercellular vehicles, virion aggregation, and virion binding to microbiota. In turn, increasing the multiplicity of infection could favor the evolution of defective viruses, hence modifying the fitness value of these spread modes.
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Affiliation(s)
- Rafael Sanjuán
- Institute for Integrative Systems Biology (I2SysBio), Universitat de València, València 46980, Spain.
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13
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Folimonova SY, Tilsner J. Hitchhikers, highway tolls and roadworks: the interactions of plant viruses with the phloem. CURRENT OPINION IN PLANT BIOLOGY 2018; 43:82-88. [PMID: 29476981 DOI: 10.1016/j.pbi.2018.02.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Revised: 02/07/2018] [Accepted: 02/08/2018] [Indexed: 05/24/2023]
Abstract
The phloem is of central importance to plant viruses, providing the route by which they spread throughout their host. Compared with virus movement in non-vascular tissue, phloem entry, exit, and long-distance translocation usually involve additional viral factors and complex virus-host interactions, probably, because the phloem has evolved additional protection against these molecular 'hitchhikers'. Recent progress in understanding phloem trafficking of endogenous mRNAs along with observations of membranous viral replication 'factories' in sieve elements challenge existing conceptions of virus long-distance transport. At the same time, the central role of the phloem in plant defences against viruses and the sophisticated viral manipulation of this host tissue are beginning to emerge.
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Affiliation(s)
| | - Jens Tilsner
- Biomedical Sciences Research Complex, University of St Andrews, BMS Building, North Haugh, St Andrews, Fife KY16 9ST, United Kingdom; Cell and Molecular Sciences, The James Hutton Institute, Invergowrie, Dundee DD2 5DA, United Kingdom.
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14
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Jiang D, Wang M, Li S. Functional analysis of a viroid RNA motif mediating cell-to-cell movement in Nicotiana benthamiana. J Gen Virol 2017; 98:121-125. [PMID: 27902342 DOI: 10.1099/jgv.0.000630] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cell-to-cell trafficking through different cellular layers is a key process for various RNAs including those of plant viruses and viroids, but the regulatory mechanisms involved are still not fully elucidated and good model systems are important. Here, we analyse the function of a simple RNA motif (termed 'loop19') in potato spindle tuber viroid (PSTVd) which is required for trafficking in Nicotiana benthamiana leaves. Northern blotting, reverse transcriptase PCR (RT-PCR) and in situ hybridization analyses demonstrated that unlike wild-type PSTVd, which was present in the nuclei in all cell types, the trafficking-defective loop19 mutants were visible only in the nuclei of upper epidermal and palisade mesophyll cells, which shows that PSTVd loop19 plays a role in mediating RNA trafficking from palisade to spongy mesophyll cells in N.benthamiana leaves. Our findings and approaches have broad implications for studying the RNA motifs mediating trafficking of RNAs across specific cellular boundaries in other biological systems.
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Affiliation(s)
- Dongmei Jiang
- Center for Applied Plant Sciences, Ohio State University, Columbus, OH 43210, USA
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China
- Beijing Research Center for Agricultural Standards and Testing, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, PR China
| | - Meng Wang
- Beijing Research Center for Agricultural Standards and Testing, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, PR China
| | - Shifang Li
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China
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15
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Abstract
Multipartite viruses have one of the most puzzling genetic organizations found in living organisms. These viruses have several genome segments, each containing only a part of the genetic information, and each individually encapsidated into a separate virus particle. While countless studies on molecular and cellular mechanisms of the infection cycle of multipartite viruses are available, just as for other virus types, very seldom is their lifestyle questioned at the viral system level. Moreover, the rare available “system” studies are purely theoretical, and their predictions on the putative benefit/cost balance of this peculiar genetic organization have not received experimental support. In light of ongoing progresses in general virology, we here challenge the current hypotheses explaining the evolutionary success of multipartite viruses and emphasize their shortcomings. We also discuss alternative ideas and research avenues to be explored in the future in order to solve the long-standing mystery of how viral systems composed of interdependent but physically separated information units can actually be functional.
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16
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Chang CH, Hsu FC, Lee SC, Lo YS, Wang JD, Shaw J, Taliansky M, Chang BY, Hsu YH, Lin NS. The Nucleolar Fibrillarin Protein Is Required for Helper Virus-Independent Long-Distance Trafficking of a Subviral Satellite RNA in Plants. THE PLANT CELL 2016; 28:2586-2602. [PMID: 27702772 PMCID: PMC5134973 DOI: 10.1105/tpc.16.00071] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 08/30/2016] [Accepted: 09/30/2016] [Indexed: 05/03/2023]
Abstract
RNA trafficking plays pivotal roles in regulating plant development, gene silencing, and adaptation to environmental stress. Satellite RNAs (satRNAs), parasites of viruses, depend on their helper viruses (HVs) for replication, encapsidation, and efficient spread. However, it remains largely unknown how satRNAs interact with viruses and the cellular machinery to undergo trafficking. Here, we show that the P20 protein of Bamboo mosaic potexvirus satRNA (satBaMV) can functionally complement in trans the systemic trafficking of P20-defective satBaMV in infected Nicotiana benthamiana The transgene-derived satBaMV, uncoupled from HV replication, was able to move autonomously across a graft union identified by RT-qPCR, RNA gel blot, and in situ RT-PCR analyses. Coimmunoprecipitation experiments revealed that the major nucleolar protein fibrillarin is coprecipitated in the P20 protein complex. Notably, silencing fibrillarin suppressed satBaMV-, but not HV-, phloem-based movement following grafting or coinoculation with HV Confocal microscopy revealed that the P20 protein colocalized with fibrillarin in the nucleoli and formed punctate structures associated with plasmodesmata. The mobile satBaMV RNA appears to exist as ribonucleoprotein (RNP) complex composed of P20 and fibrillarin, whereas BaMV movement proteins, capsid protein, and BaMV RNA are recruited with HV coinfection. Taken together, our findings provide insight into movement of satBaMV via the fibrillarin-satBaMV-P20 RNP complex in phloem-mediated systemic trafficking.
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Affiliation(s)
- Chih-Hao Chang
- Institute of Plant Biology, National Taiwan University, Taipei 11106, Taiwan
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Fu-Chen Hsu
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Shu-Chuan Lee
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Yih-Shan Lo
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Jiun-Da Wang
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Jane Shaw
- The James Hutton Institute, Invergowrie, Dundee DD2 5DA, United Kingdom
| | - Michael Taliansky
- The James Hutton Institute, Invergowrie, Dundee DD2 5DA, United Kingdom
| | - Ban-Yang Chang
- Department of Biochemistry, National Chung Hsing University, Taichung 40227, Taiwan
| | - Yau-Heiu Hsu
- Graduate Institute of Biotechnology, National Chung Hsing University, Taichung 40227, Taiwan
| | - Na-Sheng Lin
- Institute of Plant Biology, National Taiwan University, Taipei 11106, Taiwan
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
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17
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Dall'Ara M, Ratti C, Bouzoubaa SE, Gilmer D. Ins and Outs of Multipartite Positive-Strand RNA Plant Viruses: Packaging versus Systemic Spread. Viruses 2016; 8:E228. [PMID: 27548199 PMCID: PMC4997590 DOI: 10.3390/v8080228] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 07/29/2016] [Accepted: 08/09/2016] [Indexed: 11/16/2022] Open
Abstract
Viruses possessing a non-segmented genome require a specific recognition of their nucleic acid to ensure its protection in a capsid. A similar feature exists for viruses having a segmented genome, usually consisting of viral genomic segments joined together into one viral entity. While this appears as a rule for animal viruses, the majority of segmented plant viruses package their genomic segments individually. To ensure a productive infection, all viral particles and thereby all segments have to be present in the same cell. Progression of the virus within the plant requires as well a concerted genome preservation to avoid loss of function. In this review, we will discuss the "life aspects" of chosen phytoviruses and argue for the existence of RNA-RNA interactions that drive the preservation of viral genome integrity while the virus progresses in the plant.
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Affiliation(s)
- Mattia Dall'Ara
- Institut de Biologie Moléculaire des Plantes, Integrative Virology, CNRS UPR2367, Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France.
- Dipartimento di Scienze Agrarie, Area Patologia Vegetale, Università di Bologna, Viale Fanin 40, 40127 Bologna, Italy.
| | - Claudio Ratti
- Dipartimento di Scienze Agrarie, Area Patologia Vegetale, Università di Bologna, Viale Fanin 40, 40127 Bologna, Italy.
| | - Salah E Bouzoubaa
- Institut de Biologie Moléculaire des Plantes, Integrative Virology, CNRS UPR2367, Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France.
| | - David Gilmer
- Institut de Biologie Moléculaire des Plantes, Integrative Virology, CNRS UPR2367, Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France.
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18
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Zhang W, Thieme CJ, Kollwig G, Apelt F, Yang L, Winter N, Andresen N, Walther D, Kragler F. tRNA-Related Sequences Trigger Systemic mRNA Transport in Plants. THE PLANT CELL 2016; 28:1237-49. [PMID: 27268430 PMCID: PMC4944404 DOI: 10.1105/tpc.15.01056] [Citation(s) in RCA: 120] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 05/25/2016] [Accepted: 06/07/2016] [Indexed: 05/18/2023]
Abstract
In plants, protein-coding mRNAs can move via the phloem vasculature to distant tissues, where they may act as non-cell-autonomous signals. Emerging work has identified many phloem-mobile mRNAs, but little is known regarding RNA motifs triggering mobility, the extent of mRNA transport, and the potential of transported mRNAs to be translated into functional proteins after transport. To address these aspects, we produced reporter transcripts harboring tRNA-like structures (TLSs) that were found to be enriched in the phloem stream and in mRNAs moving over chimeric graft junctions. Phenotypic and enzymatic assays on grafted plants indicated that mRNAs harboring a distinctive TLS can move from transgenic roots into wild-type leaves and from transgenic leaves into wild-type flowers or roots; these mRNAs can also be translated into proteins after transport. In addition, we provide evidence that dicistronic mRNA:tRNA transcripts are frequently produced in Arabidopsis thaliana and are enriched in the population of graft-mobile mRNAs. Our results suggest that tRNA-derived sequences with predicted stem-bulge-stem-loop structures are sufficient to mediate mRNA transport and seem to be necessary for the mobility of a large number of endogenous transcripts that can move through graft junctions.
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MESH Headings
- Arabidopsis/genetics
- Arabidopsis/metabolism
- Flowers/genetics
- Flowers/metabolism
- Gene Expression Regulation, Plant/genetics
- Gene Expression Regulation, Plant/physiology
- Nucleic Acid Conformation
- Phloem/metabolism
- Plant Leaves/genetics
- Plant Leaves/metabolism
- Plant Roots/genetics
- Plant Roots/metabolism
- Plant Stems/genetics
- Plant Stems/metabolism
- RNA Transport/genetics
- RNA Transport/physiology
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Plant/chemistry
- RNA, Plant/genetics
- RNA, Plant/metabolism
- RNA, Transfer/chemistry
- RNA, Transfer/genetics
- RNA, Transfer/metabolism
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Affiliation(s)
- Wenna Zhang
- Max Planck Institut für Molekulare Pflanzenphysiologie, Wissenschaftspark Golm, Golm, Germany
| | - Christoph J Thieme
- Max Planck Institut für Molekulare Pflanzenphysiologie, Wissenschaftspark Golm, Golm, Germany
| | - Gregor Kollwig
- Department of Biochemistry, Centre of Molecular Biology, Max F. Perutz Laboratories, University of Vienna, A1030 Vienna, Austria
| | - Federico Apelt
- Max Planck Institut für Molekulare Pflanzenphysiologie, Wissenschaftspark Golm, Golm, Germany
| | - Lei Yang
- Max Planck Institut für Molekulare Pflanzenphysiologie, Wissenschaftspark Golm, Golm, Germany
| | - Nikola Winter
- Max Planck Institut für Molekulare Pflanzenphysiologie, Wissenschaftspark Golm, Golm, Germany
| | - Nadine Andresen
- Institut für Biochemie, CCM, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany
| | - Dirk Walther
- Max Planck Institut für Molekulare Pflanzenphysiologie, Wissenschaftspark Golm, Golm, Germany
| | - Friedrich Kragler
- Max Planck Institut für Molekulare Pflanzenphysiologie, Wissenschaftspark Golm, Golm, Germany Department of Biochemistry, Centre of Molecular Biology, Max F. Perutz Laboratories, University of Vienna, A1030 Vienna, Austria
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19
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Saplaoura E, Kragler F. Mobile Transcripts and Intercellular Communication in Plants. DEVELOPMENTAL SIGNALING IN PLANTS 2016; 40:1-29. [DOI: 10.1016/bs.enz.2016.07.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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20
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Singh P, Savithri HS. GBNV encoded movement protein (NSm) remodels ER network via C-terminal coiled coil domain. Virology 2015; 482:133-46. [PMID: 25863878 DOI: 10.1016/j.virol.2015.01.030] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 01/24/2015] [Accepted: 01/31/2015] [Indexed: 02/03/2023]
Abstract
Plant viruses exploit the host machinery for targeting the viral genome-movement protein complex to plasmodesmata (PD). The mechanism by which the non-structural protein m (NSm) of Groundnut bud necrosis virus (GBNV) is targeted to PD was investigated using Agrobacterium mediated transient expression of NSm and its fusion proteins in Nicotiana benthamiana. GFP:NSm formed punctuate structures that colocalized with mCherry:plasmodesmata localized protein 1a (PDLP 1a) confirming that GBNV NSm localizes to PD. Unlike in other movement proteins, the C-terminal coiled coil domain of GBNV NSm was shown to be involved in the localization of NSm to PD, as deletion of this domain resulted in the cytoplasmic localization of NSm. Treatment with Brefeldin A demonstrated the role of ER in targeting GFP NSm to PD. Furthermore, mCherry:NSm co-localized with ER-GFP (endoplasmic reticulum targeting peptide (HDEL peptide fused with GFP). Co-expression of NSm with ER-GFP showed that the ER-network was transformed into vesicles indicating that NSm interacts with ER and remodels it. Mutations in the conserved hydrophobic region of NSm (residues 130-138) did not abolish the formation of vesicles. Additionally, the conserved prolines at positions 140 and 142 were found to be essential for targeting the vesicles to the cell membrane. Further, systematic deletion of amino acid residues from N- and C-terminus demonstrated that N-terminal 203 amino acids are dispensable for the vesicle formation. On the other hand, the C-terminal coiled coil domain when expressed alone could also form vesicles. These results suggest that GBNV NSm remodels the ER network by forming vesicles via its interaction through the C-terminal coiled coil domain. Interestingly, NSm interacts with NP in vitro and coexpression of these two proteins in planta resulted in the relocalization of NP to PD and this relocalization was abolished when the N-terminal unfolded region of NSm was deleted. Thus, the NSm interacts with NP via its N-terminal unfolded region and the NSm-NP complex could in turn interact with the ER membrane via the C-terminal coiled coil domain of NSm to form vesicles that are targeted to PD and there by assist the cell to cell movement of the viral genome complex.
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Affiliation(s)
- Pratibha Singh
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
| | - H S Savithri
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India.
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21
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Wan J, Cabanillas DG, Zheng H, Laliberté JF. Turnip mosaic virus moves systemically through both phloem and xylem as membrane-associated complexes. PLANT PHYSIOLOGY 2015; 167:1374-88. [PMID: 25717035 PMCID: PMC4378181 DOI: 10.1104/pp.15.00097] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 02/23/2015] [Indexed: 05/08/2023]
Abstract
Plant viruses move systemically in plants through the phloem. They move as virions or as ribonucleic protein complexes, although it is not clear what these complexes are made of. The approximately 10-kb RNA genome of Turnip mosaic virus (TuMV) encodes a membrane protein, known as 6K2, that induces endomembrane rearrangements for the formation of viral replication factories. These factories take the form of vesicles that contain viral RNA (vRNA) and viral replication proteins. In this study, we report the presence of 6K2-tagged vesicles containing vRNA and the vRNA-dependent RNA polymerase in phloem sieve elements and in xylem vessels. Transmission electron microscopy observations showed the presence in the xylem vessels of vRNA-containing vesicles that were associated with viral particles. Stem-girdling experiments, which leave xylem vessels intact but destroy the surrounding tissues, confirmed that TuMV could establish a systemic infection of the plant by going through xylem vessels. Phloem sieve elements and xylem vessels from Potato virus X-infected plants also contained lipid-associated nonencapsidated vRNA, indicating that the presence of membrane-associated ribonucleic protein complexes in the phloem and xylem may not be limited to TuMV. Collectively, these studies indicate that viral replication factories could end up in the phloem and the xylem.
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Affiliation(s)
- Juan Wan
- Institut National de la Recherche Scientifique-Institut Armand-Frappier, Laval, Quebec, Canada H7V 1B7 (J.W., D.G.C., J.-F.L.); andDepartment of Biology, McGill University, Montreal, Quebec, Canada H3A 1B1 (H.Z.)
| | - Daniel Garcia Cabanillas
- Institut National de la Recherche Scientifique-Institut Armand-Frappier, Laval, Quebec, Canada H7V 1B7 (J.W., D.G.C., J.-F.L.); andDepartment of Biology, McGill University, Montreal, Quebec, Canada H3A 1B1 (H.Z.)
| | - Huanquan Zheng
- Institut National de la Recherche Scientifique-Institut Armand-Frappier, Laval, Quebec, Canada H7V 1B7 (J.W., D.G.C., J.-F.L.); andDepartment of Biology, McGill University, Montreal, Quebec, Canada H3A 1B1 (H.Z.)
| | - Jean-François Laliberté
- Institut National de la Recherche Scientifique-Institut Armand-Frappier, Laval, Quebec, Canada H7V 1B7 (J.W., D.G.C., J.-F.L.); andDepartment of Biology, McGill University, Montreal, Quebec, Canada H3A 1B1 (H.Z.)
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22
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Abstract
The self-assembly of virus-like particles may lead to materials which combine the unique characteristics of viruses, such as precise size control and responsivity to environmental cues, with the properties of abiotic cargo. For a few different viruses, shell proteins are amenable to the in vitro encapsulation of non-genomic cargo in a regular protein cage. In this chapter we describe protocols of high-efficiency in vitro self-assembly around functionalized gold nanoparticles for three examples of icosahedral and non-icosahedral viral protein cages derived from a plant virus, an animal virus, and a human retrovirus. These protocols can be readily adapted with small modifications to work for a broad variety of inorganic and organic nanoparticles.
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Affiliation(s)
- Irina B Tsvetkova
- Department of Chemistry, Indiana University, 800 E. Kirkwood Avenue, Bloomington, IN, 47405, USA
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23
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Wan J, Laliberté JF. Membrane-associated virus replication complexes locate to plant conducting tubes. PLANT SIGNALING & BEHAVIOR 2015; 10:e1042639. [PMID: 25955489 PMCID: PMC4622829 DOI: 10.1080/15592324.2015.1042639] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Revised: 04/06/2015] [Accepted: 04/14/2015] [Indexed: 05/18/2023]
Abstract
It is generally accepted that in order to establish a systemic infection in a plant, viruses move from the initially infected cell to the vascular tissues by cell-to-cell movement through plasmodesmata (PD), and load into the vascular conducting tubes (i.e. phloem sieve elements and xylem vessel elements) for long-distance movement. The viral unit in these movements can be a virion or a yet-to-be-defined ribonucleic protein (RNP) complex. Using live-cell imaging, our laboratory has previously demonstrated that membrane-bound replication complexes move cell-to-cell during turnip mosaic virus (TuMV) infection. Our recent study shows that these membrane-bound replication complexes end up in the vascular conducting tubes, which is likely the case for potato virus X (PVX) also. The presence of TuMV-induced membrane complexes in xylem vessels suggests that viral components could also be found in other apoplastic regions of the plant, such as the intercellular space. This possibility may have implications regarding how we approach the study of plant innate immune responses against viruses.
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Affiliation(s)
- Juan Wan
- INRS-Institut Armand-Frappier; Laval; Québec, Canada
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24
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Kwon SJ, Chaturvedi S, Rao ALN. Repair of the 3' proximal and internal deletions of a satellite RNA associated with Cucumber mosaic virus is directed toward restoring structural integrity. Virology 2014; 450-451:222-32. [PMID: 24503085 DOI: 10.1016/j.virol.2013.12.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 11/29/2013] [Accepted: 12/08/2013] [Indexed: 11/27/2022]
Abstract
The phenomenon of rapid turnover of 3' proximal nucleotides (nt) lost by the action of nuclease in RNA viruses is integral to replication. Here, a set of six deletions encompassing the 3' 23 nt region of a satellite RNA (satRNA) of Cucumber mosaic virus (CMV) strain Q (Q-sat), were engineered. Repair of the 3' end was not observed in the absence of CMV. However, co-expression with CMV in planta revealed that Q-sat mutants lacking the 3' 18 nt but not the 3' 23 nt are repaired and the progeny accumulation was inversely proportional to the extent of the deletion. Progeny of the 3'Δ3 mutant were repaired to wild type (wt) while those from the remaining four mutants were heterogeneous, exhibiting a wt secondary structure. Analysis of additional 3' internal deletions mutants revealed that progeny with a repaired sequence reminiscent of wt secondary structure were competent for replication and systemic spread.
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Affiliation(s)
- Sun-Jung Kwon
- Department of Plant Pathology & Microbiology, University of California, Riverside, CA 92521-0122, United States
| | - Sonali Chaturvedi
- Department of Plant Pathology & Microbiology, University of California, Riverside, CA 92521-0122, United States
| | - A L N Rao
- Department of Plant Pathology & Microbiology, University of California, Riverside, CA 92521-0122, United States.
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25
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Hipper C, Brault V, Ziegler-Graff V, Revers F. Viral and cellular factors involved in Phloem transport of plant viruses. FRONTIERS IN PLANT SCIENCE 2013; 4:154. [PMID: 23745125 PMCID: PMC3662875 DOI: 10.3389/fpls.2013.00154] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Accepted: 05/05/2013] [Indexed: 05/03/2023]
Abstract
Phloem transport of plant viruses is an essential step in the setting-up of a complete infection of a host plant. After an initial replication step in the first cells, viruses spread from cell-to-cell through mesophyll cells, until they reach the vasculature where they rapidly move to distant sites in order to establish the infection of the whole plant. This last step is referred to as systemic transport, or long-distance movement, and involves virus crossings through several cellular barriers: bundle sheath, vascular parenchyma, and companion cells for virus loading into sieve elements (SE). Viruses are then passively transported within the source-to-sink flow of photoassimilates and are unloaded from SE into sink tissues. However, the molecular mechanisms governing virus long-distance movement are far from being understood. While most viruses seem to move systemically as virus particles, some viruses are transported in SE as viral ribonucleoprotein complexes (RNP). The nature of the cellular and viral factors constituting these RNPs is still poorly known. The topic of this review will mainly focus on the host and viral factors that facilitate or restrict virus long-distance movement.
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Affiliation(s)
| | | | - Véronique Ziegler-Graff
- Laboratoire Propre du CNRS (UPR 2357), Virologie Végétale, Institut de Biologie Moléculaire des Plantes, Université de StrasbourgStrasbourg, France
| | - Frédéric Revers
- UMR 1332 de Biologie du Fruit et Pathologie, INRA, Université de BordeauxVillenave d’Ornon, France
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26
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Seo JK, Kwon SJ, Rao ALN. A physical interaction between viral replicase and capsid protein is required for genome-packaging specificity in an RNA virus. J Virol 2012; 86:6210-21. [PMID: 22438552 PMCID: PMC3372179 DOI: 10.1128/jvi.07184-11] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 03/09/2012] [Indexed: 01/03/2023] Open
Abstract
Genome packaging is functionally coupled to replication in RNA viruses pathogenic to humans (Poliovirus), insects (Flock house virus [FHV]), and plants (Brome mosaic virus [BMV]). However, the underlying mechanism is not fully understood. We have observed previously that in FHV and BMV, unlike ectopically expressed capsid protein (CP), packaging specificity results from RNA encapsidation by CP that has been translated from mRNA produced from replicating genomic RNA. Consequently, we hypothesize that a physical interaction with replicase increases the CP specificity for packaging viral RNAs. We tested this hypothesis by evaluating the molecular interaction between replicase protein and CP using a FHV-Nicotiana benthamiana system. Bimolecular fluorescence complementation in conjunction with fluorescent cellular protein markers and coimmunoprecipitation assays demonstrated that FHV replicase (protein A) and CP physically interact at the mitochondrial site of replication and that this interaction requires the N-proximal region from either amino acids 1 to 31 or amino acids 32 to 50 of the CP. In contrast to the mitochondrial localization of CP derived from FHV replication, ectopic expression displayed a characteristic punctate pattern on the endoplasmic reticulum (ER). This pattern was altered to relocalize the CP throughout the cytoplasm when the C-proximal hydrophobic domain was deleted. Analysis of the packaging phenotypes of the CP mutants defective either in protein A-CP interactions or ER localization suggested that synchronization between protein A-CP interaction and its subcellular localization is imperative to confer packaging specificity.
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Affiliation(s)
- Jang-Kyun Seo
- Department of Plant Pathology and Microbiology, University of California, Riverside, California, USA
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27
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Guelette BS, Benning UF, Hoffmann-Benning S. Identification of lipids and lipid-binding proteins in phloem exudates from Arabidopsis thaliana. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:3603-16. [PMID: 22442409 PMCID: PMC3388829 DOI: 10.1093/jxb/ers028] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 01/12/2012] [Accepted: 01/18/2012] [Indexed: 05/19/2023]
Abstract
The phloem plays a crucial role in assimilate and nutrient transport, pathogen response, and plant growth and development. Yet, few species have yielded pure phloem exudate and, if proteins need to be analysed, those species may not have sequenced genomes, making identification difficult. The enrichment of Arabidopsis thaliana phloem exudate in amounts large enough to allow for metabolite and protein analysis is described. Using this method, it was possible to identify 65 proteins present in the Arabidopsis phloem exudate. The majority of these proteins could be grouped by response to pathogens, stress, or hormones, carbon metabolism, protein interaction, modification, and turnover, and transcription factors. It was also possible to detect 11 proteins that play a role in lipid/fatty acid metabolism (aspartic protease, putative 3-β-hydroxysteroid dehydrogenase, UDP-sulphoquinovose synthase/SQD1, lipase, PIG-P-like protein: phosphatidylinositol-N-acetylglucosaminyltransferase), storage (glycine-rich protein), binding (annexin, lipid-associated family protein, GRP17/oleosin), and/or signalling (annexin, putative lipase, PIG-P-like protein). Along with putative lipid-binding proteins, several lipids and fatty acids could be identified. Only a few examples exist of lipids (jasmonic acid, oxylipins) or lipid-binding proteins (DIR1, acyl-CoA-binding protein) in the phloem. Finding hydrophobic compounds in an aqueous environment is not without precedence in biological systems: human blood contains a variety of lipids, many of which play a significant role in human health. In blood, lipids are transported while bound to proteins. The present findings of lipids and lipid-binding proteins in phloem exudates suggest that a similar long-distance lipid signalling exists in plants and may play an important role in plant growth and development.
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28
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Kwon SJ, Rao ALN. Emergence of distinct brome mosaic virus recombinants is determined by the polarity of the inoculum RNA. J Virol 2012; 86:5204-20. [PMID: 22357282 PMCID: PMC3347362 DOI: 10.1128/jvi.00351-12] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Accepted: 02/14/2012] [Indexed: 12/22/2022] Open
Abstract
Despite overwhelming interest in the impact exerted by recombination during evolution of RNA viruses, the relative contribution of the polarity of inoculum templates remains poorly understood. Here, by agroinfiltrating Nicotiana benthamiana leaves, we show that brome mosaic virus (BMV) replicase is competent to initiate positive-strand [(+)-strand] synthesis on an ectopically expressed RNA3 negative strand [(-) strand] and faithfully complete the replication cycle. Consequently, we sought to examine the role of RNA polarity in BMV recombination by expressing a series of replication-defective mutants of BMV RNA3 in (+) or (-) polarity. Temporal analysis of progeny sequences revealed that the genetic makeup of the primary recombinant pool is determined by the polarity of the inoculum template. When the polarity of the inoculum template was (+), the recombinant pool that accumulated during early phases of replication was a mixture of nonhomologous recombinants. These are longer than the inoculum template length, and a nascent 3' untranslated region (UTR) of wild-type (WT) RNA1 or RNA2 was added to the input mutant RNA3 3' UTR due to end-to-end template switching by BMV replicase during (-)-strand synthesis. In contrast, when the polarity of the inoculum was (-), the progeny contained a pool of native-length homologous recombinants generated by template switching of BMV replicase with a nascent UTR from WT RNA1 or RNA2 during (+)-strand synthesis. Repair of a point mutation caused by polymerase error occurred only when the polarity of the inoculum template was (+). These results contribute to the explanation of the functional role of RNA polarity in recombination mediated by copy choice mechanisms.
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Affiliation(s)
- Sun-Jung Kwon
- Department of Plant Pathology & Microbiology, University of California, Riverside, California, USA
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29
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Kao CC, Ni P, Hema M, Huang X, Dragnea B. The coat protein leads the way: an update on basic and applied studies with the Brome mosaic virus coat protein. MOLECULAR PLANT PATHOLOGY 2011; 12:403-12. [PMID: 21453435 PMCID: PMC6640235 DOI: 10.1111/j.1364-3703.2010.00678.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The Brome mosaic virus (BMV) coat protein (CP) accompanies the three BMV genomic RNAs and the subgenomic RNA into and out of cells in an infection cycle. In addition to serving as a protective shell for all of the BMV RNAs, CP plays regulatory roles during the infection process that are mediated through specific binding of RNA elements in the BMV genome. One regulatory RNA element is the B box present in the 5' untranslated region (UTR) of BMV RNA1 and RNA2 that play important roles in the formation of the BMV replication factory, as well as the regulation of translation. A second element is within the tRNA-like 3' UTR of all BMV RNAs that is required for efficient RNA replication. The BMV CP can also encapsidate ligand-coated metal nanoparticles to form virus-like particles (VLPs). This update summarizes the interaction between the BMV CP and RNAs that can regulate RNA synthesis, translation and RNA encapsidation, as well as the formation of VLPs.
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Affiliation(s)
- C Cheng Kao
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405, USA.
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30
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Cellular factors in plant virus movement: at the leading edge of macromolecular trafficking in plants. Virology 2011; 411:237-43. [PMID: 21239029 DOI: 10.1016/j.virol.2010.12.021] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Accepted: 12/14/2010] [Indexed: 11/22/2022]
Abstract
To establish systemic infection, plant viruses must be localized to the correct subcellular sites to accomplish replication and then traffic from initially infected cells into neighboring cells and even distant organs. Viruses have evolved various strategies to interact with pre-existing cellular factors to achieve these functions. In this review we discuss plant virus intracellular, intercellular and long-distance movement, focusing on the host cellular factors involved. We emphasize that elucidating viral movement mechanisms will not only shed light on the molecular mechanisms of infection, but will also contribute valuable insights into the regulation of endogenous macromolecular trafficking.
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31
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Takeda R, Petrov AI, Leontis NB, Ding B. A three-dimensional RNA motif in Potato spindle tuber viroid mediates trafficking from palisade mesophyll to spongy mesophyll in Nicotiana benthamiana. THE PLANT CELL 2011; 23:258-72. [PMID: 21258006 PMCID: PMC3051236 DOI: 10.1105/tpc.110.081414] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 12/13/2010] [Accepted: 12/25/2010] [Indexed: 05/04/2023]
Abstract
Cell-to-cell trafficking of RNA is an emerging biological principle that integrates systemic gene regulation, viral infection, antiviral response, and cell-to-cell communication. A key mechanistic question is how an RNA is specifically selected for trafficking from one type of cell into another type. Here, we report the identification of an RNA motif in Potato spindle tuber viroid (PSTVd) required for trafficking from palisade mesophyll to spongy mesophyll in Nicotiana benthamiana leaves. This motif, called loop 6, has the sequence 5'-CGA-3'...5'-GAC-3' flanked on both sides by cis Watson-Crick G/C and G/U wobble base pairs. We present a three-dimensional (3D) structural model of loop 6 that specifies all non-Watson-Crick base pair interactions, derived by isostericity-based sequence comparisons with 3D RNA motifs from the RNA x-ray crystal structure database. The model is supported by available chemical modification patterns, natural sequence conservation/variations in PSTVd isolates and related species, and functional characterization of all possible mutants for each of the loop 6 base pairs. Our findings and approaches have broad implications for studying the 3D RNA structural motifs mediating trafficking of diverse RNA species across specific cellular boundaries and for studying the structure-function relationships of RNA motifs in other biological processes.
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Affiliation(s)
- Ryuta Takeda
- Molecular, Cellular, and Developmental Biology Program, Ohio State University, Columbus, Ohio 43210
| | - Anton I. Petrov
- Department of Biological Sciences, Bowling Green State University, Bowling Green, Ohio 43403
| | - Neocles B. Leontis
- Department of Chemistry and Center for Biomolecular Sciences, Bowling Green State University, Bowling Green, Ohio 43403
| | - Biao Ding
- Molecular, Cellular, and Developmental Biology Program, Ohio State University, Columbus, Ohio 43210
- Department of Plant Cellular and Molecular Biology and Plant Biotechnology Center, Ohio State University, Columbus, Ohio 43210
- The Center for RNA Biology, Ohio State University, Columbus, Ohio 43210
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32
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Hema M, Murali A, Ni P, Vaughan RC, Fujisaki K, Tsvetkova I, Dragnea B, Kao CC. Effects of amino-acid substitutions in the Brome mosaic virus capsid protein on RNA encapsidation. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2010; 23:1433-1447. [PMID: 20923351 DOI: 10.1094/mpmi-05-10-0118] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Brome mosaic virus (BMV) packages its genomic RNAs (RNA1, RNA2, and RNA3) and subgenomic RNA4 into three different particles. However, since the RNAs in the virions have distinct lengths and electrostatic charges, we hypothesize that subsets of the virions should have distinct properties. A glutamine to cysteine substitution at position 120 of the capsid protein (CP) was found to result in a mutant virus named QC that exhibited a dramatically altered ratio of the RNAs in virions. RNA2 was far more abundant than the other RNAs, although the ratios could be affected by the host plant species. RNAs with the QC mutation were competent for replication early in the infection, suggesting that they were either selectively packaged or degraded after packaging. In support of the latter idea, low concentrations of truncated RNA1 that co-migrated with RNA2 were found in the QC virions. Spectroscopic analysis and peptide fingerprinting experiments showed that the QC virus capsid interacted with the encapsidated RNAs differently than did the wild type. Furthermore, wild-type BMV RNA1 was found to be more susceptible to nuclease digestion relative to RNA2 as a function of the buffer pH. Other BMV capsid mutants also had altered ratios of packaged RNAs.
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Affiliation(s)
- Masarapu Hema
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405, USA
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33
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Wang Y, Ding B. Viroids: small probes for exploring the vast universe of RNA trafficking in plants. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2010; 52:28-39. [PMID: 20074138 DOI: 10.1111/j.1744-7909.2010.00900.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Cell-to-cell and long-distance trafficking of RNA is a rapidly evolving frontier of integrative plant biology that broadly impacts studies on plant growth and development, spread of infectious agents and plant defense responses. The fundamental questions being pursued at the forefronts revolve around function, mechanism and evolution. In the present review, we will first use specific examples to illustrate the biological importance of cell-to-cell and long-distance trafficking of RNA. We then focus our discussion on research findings obtained using viroids that have advanced our understanding of the underlying mechanisms involved in RNA trafficking. We further use viroid examples to illustrate the great diversity of trafficking machinery evolved by plants, as well as the promise for new insights in the years ahead. Finally, we discuss the prospect of integrating findings from different experimental systems to achieve a systems-based understanding of RNA trafficking function, mechanism and evolution.
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Affiliation(s)
- Ying Wang
- Department of Plant Cellular and Molecular Biology and Plant Biotechnology Center, The Ohio State University, Columbus, OH 43210, USA
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Takeda R, Ding B. Viroid intercellular trafficking: RNA motifs, cellular factors and broad impacts. Viruses 2009; 1:210-21. [PMID: 21994546 PMCID: PMC3185492 DOI: 10.3390/v1020210] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 08/31/2009] [Accepted: 09/01/2009] [Indexed: 12/30/2022] Open
Abstract
Viroids are noncoding RNAs that infect plants. In order to establish systemic infection, these RNAs must traffic from an initially infected host cell into neighboring cells and ultimately throughout a whole plant. Recent studies have identified structural motifs in a viroid that are required for trafficking, enabling further studies on the mechanisms of their function. Some cellular proteins interact with viroids in vivo and may play a role in viroid trafficking, which can now be directly tested by using a virus-induced gene silencing system that functions efficiently in plant species from which these factors were identified. This review discusses these recent advances, unanswered questions and the use of viroid infection as an highly productive model to elucidate mechanisms of RNA trafficking that is of broad biological significance.
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Affiliation(s)
- Ryuta Takeda
- Department of Plant Cellular and Molecular Biology and Molecular, Cellular and Developmental Biology Program, Ohio State University, 207 Rightmire Hall, 1060 Carmack Road, Columbus, 43210 USA; E-Mail:
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Torrance L, Lukhovitskaya NI, Schepetilnikov MV, Cowan GH, Ziegler A, Savenkov EI. Unusual long-distance movement strategies of Potato mop-top virus RNAs in Nicotiana benthamiana. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2009; 22:381-90. [PMID: 19271953 DOI: 10.1094/mpmi-22-4-0381] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The Potato mop-top virus (PMTV) genome encodes replicase, movement, and capsid proteins on three different RNA species that are encapsidated within tubular rod-shaped particles. Previously, we showed that the protein produced on translational readthrough (RT) of the coat protein (CP) gene, CP-RT, is associated with one extremity of the virus particles, and that the two RNAs encoding replicase and movement proteins can move long distance in the absence of the third RNA (RNA-CP) that encodes the capsid proteins, CP and CP-RT. Here, we examined the roles of the CP and CP-RT proteins on RNA movement using infectious clones carrying mutations in the CP and CP-RT coding domains. The results showed that, in infections established with mutant RNA-CP expressing CP together with truncated CP-RT, systemic movement of the mutant RNA-CP was inhibited but not the movement of the other two RNAs. Furthermore, RNA-CP long-distance movement was inhibited in a mutant clone expressing only CP in the absence of the CP-RT polypeptide. CP-RT was not necessary for particle assembly because virions were observed in leaf extracts infected with the CP-RT deletion mutants. RNA-CP moved long distance when protein expression was suppressed completely or when CP expression was suppressed so that only CP-RT or truncated CP-RT was expressed. CP-RT but not CP interacted with the movement protein TGB1 in the yeast two-hybrid system. CP-RT and TGB1 were detected by enzyme-linked immunosorbent assay in virus particles and the long-distance movement of RNA-CP was correlated with expression of CP-RT that interacted with TGB1; mutant RNA-CP expressing truncated CP-RT proteins that did not interact with TGB1 formed virions but did not move to upper noninoculated leaves. The results indicate that PMTV RNA-CP can move long distance in two distinct forms: either as a viral ribonucleoprotein complex or as particles that are most likely associated with CP-RT and TGB1.
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Affiliation(s)
- Lesley Torrance
- Department of Plant Biology and Forest Genetics, Uppsala BioCenter SLU, Sweden
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36
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Li C, Zhang K, Zeng X, Jackson S, Zhou Y, Hong Y. A cis element within flowering locus T mRNA determines its mobility and facilitates trafficking of heterologous viral RNA. J Virol 2009; 83:3540-8. [PMID: 19193810 PMCID: PMC2663265 DOI: 10.1128/jvi.02346-08] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Accepted: 01/22/2009] [Indexed: 01/18/2023] Open
Abstract
The Arabidopsis flowering locus T (FT) gene encodes the mobile florigen essential for floral induction. While movement of the FT protein has been shown to occur within plants, systemic spread of FT mRNA remains to be unequivocally demonstrated. Utilizing novel RNA mobility assay vectors based on two distinct movement-defective viruses, Potato virus X and Turnip crinkle virus, and an agroinfiltration assay, we demonstrate that nontranslatable FT mRNA, independent of the FT protein, moves throughout Nicotiana benthamiana and mutant Arabidopsis plants and promotes systemic trafficking of viral and green fluorescence protein RNAs. Viral ectopic expression of FT induced flowering in the short-day N. tabacum Maryland Mammoth tobacco under long-day conditions. Recombinant Potato virus X bearing FT RNA spread and established systemic infection more quickly than the parental virus. The cis-acting element essential for RNA movement was mapped to the nucleotides 1 to 102 of the FT mRNA coding sequence. These data demonstrate that a plant self-mobile RNA molecule can mediate long-distance trafficking of heterologous RNAs and raise the possibility that FT RNA, along with the FT protein, may be involved in the spread of the floral stimulus throughout the plant.
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Affiliation(s)
- Chunyang Li
- Warwick HRI, University of Warwick, Wellesbourne, Warwick CV35 9EF, United Kingdom.
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Ding B, Wang Y. Viroids: Uniquely Simple and Tractable Models to Elucidate Regulation of Cell-to-Cell Trafficking of RNA. DNA Cell Biol 2009; 28:51-6. [DOI: 10.1089/dna.2008.0811] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Affiliation(s)
- Biao Ding
- Department of Plant Cellular and Molecular Biology and Plant Biotechnology Center, The Ohio State University, Columbus, Ohio
| | - Ying Wang
- Department of Plant Cellular and Molecular Biology and Plant Biotechnology Center, The Ohio State University, Columbus, Ohio
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38
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Seo JK, Kwon SJ, Choi HS, Kim KH. Evidence for alternate states of Cucumber mosaic virus replicase assembly in positive- and negative-strand RNA synthesis. Virology 2009; 383:248-60. [PMID: 19022467 DOI: 10.1016/j.virol.2008.10.033] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2008] [Revised: 08/30/2008] [Accepted: 10/21/2008] [Indexed: 01/22/2023]
Abstract
Cucumber mosaic virus (CMV) encodes two viral replication proteins, 1a and 2a. Accumulating evidence implies that different aspects of 1a-2a interaction in replication complex assembly are involved in the regulation of virus replication. To further investigate CMV replicase assembly and to dissect the involvement of replicase activities in negative- and positive-strand synthesis, we transiently expressed CMV RNAs and/or proteins in Nicotiana benthamiana leaves using a DNA or RNA-mediated expression system. Surprisingly, we found that, even in the absence of 1a, 2a is capable of synthesizing positive-strand RNAs, while 1a and 2a are both required for negative-strand synthesis. We also report evidence that 1a capping activities function independently of 2a. Moreover, using 1a mutants, we show that capping activities of 1a are crucial for viral translation but not for RNA transcription. These results support the concept that two or more alternate states of replicase assembly are involved in CMV replication.
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Affiliation(s)
- Jang-Kyun Seo
- Department of Agricultural Biotechnology, College of Agriculture and Life Sciences, Seoul National University, Seoul, South Korea
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39
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Abstract
Viroids are single-stranded, circular, and noncoding RNAs that infect plants. They replicate in the nucleus or chloroplast and then traffic cell-to-cell through plasmodesmata and long distance through the phloem to establish systemic infection. They also cause diseases in certain hosts. All functions are mediated directly by the viroid RNA genome or genome-derived RNAs. I summarize recent advances in the understanding of viroid structures and cellular factors enabling these functions, emphasizing conceptual developments, major knowledge gaps, and future directions. Newly emerging experimental systems and research tools are discussed that are expected to enable significant progress in a number of key areas. I highlight examples of groundbreaking contributions of viroid research to the development of new biological principles and offer perspectives on using viroid models to continue advancing some frontiers of life science.
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Affiliation(s)
- Biao Ding
- Department of Plant Cellular and Molecular Biology and Plant Biotechnology Center, The Ohio State University, Columbus, Ohio 43210, USA.
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Zhong X, Archual AJ, Amin AA, Ding B. A genomic map of viroid RNA motifs critical for replication and systemic trafficking. THE PLANT CELL 2008; 20:35-47. [PMID: 18178767 PMCID: PMC2254921 DOI: 10.1105/tpc.107.056606] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Revised: 12/12/2007] [Accepted: 12/13/2007] [Indexed: 05/19/2023]
Abstract
RNA replication and systemic trafficking play significant roles in developmental regulation and host-pathogen interactions. Viroids are the simplest noncoding eukaryotic RNA pathogens and genetic units that are capable of autonomous replication and systemic trafficking and offer excellent models to investigate the role of RNA structures in these processes. Like other RNAs, the predicted secondary structure of a viroid RNA contains many loops and bulges flanked by double-stranded helices, the biological functions of which are mostly unknown. Using Potato spindle tuber viroid infection of Nicotiana benthamiana as the experimental system, we tested the hypothesis that these loops/bulges are functional motifs that regulate replication in single cells or trafficking in a plant. Through a genome-wide mutational analysis, we identified multiple loops/bulges essential or important for each of these biological processes. Our results led to a genomic map of viroid RNA motifs that mediate single-cell replication and systemic trafficking, respectively. This map provides a framework to enable high-throughput studies on the tertiary structures and functional mechanisms of RNA motifs that regulate viroid replication and trafficking. Our model and approach should also be valuable for comprehensive investigations of the replication and trafficking motifs in other RNAs.
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Affiliation(s)
- Xuehua Zhong
- Department of Plant Cellular and Molecular Biology, Plant Biotechnology Center, Ohio State University, Columbus, Ohio 43210, USA
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Zhong X, Ding B. Distinct RNA motifs mediate systemic RNA trafficking. PLANT SIGNALING & BEHAVIOR 2008; 3:58-9. [PMID: 19704772 PMCID: PMC2633962 DOI: 10.4161/psb.3.1.4890] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2007] [Accepted: 08/16/2007] [Indexed: 05/02/2023]
Abstract
Systemic RNA trafficking is emerging as a new paradigm in gene regulation at the whole plant level. The mechanisms that ensure delivery of all sorts of RNAs to their respective cellular destinations remain poorly understood. Several lines of research suggest that specific sequence/structural motif(s) within an RNA directs its trafficking. The first motif was identified in Potato spindle tuber viroid (PSTVd), which mediates trafficking from bundle sheath to mesophyll in young tobacco leaves. Our recent work identified a tertiary structural motif in PSTVd that is required for trafficking from bundle sheath to phloem in Nicotiana benthamiana to initiate long-distance trafficking. This motif consists of a U/C cis Watson-Crick/Watson-Crick base pair with water insertion to widen the minor groove. Similar motifs that are structurally conserved in rRNAs serve as protein-binding sites. These data suggest that distinct RNA motifs interact with specific cellular factors for trafficking across various cellular boundaries to achieve systemic trafficking.
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Affiliation(s)
- Xuehua Zhong
- Department of Plant Cellular and Molecular Biology and Plant Biotechnology Center; Ohio State University; Columbus, Ohio USA
| | - Biao Ding
- Department of Plant Cellular and Molecular Biology and Plant Biotechnology Center; Ohio State University; Columbus, Ohio USA
- The RNA Group; Ohio State University; Columbus, Ohio USA
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