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Karen Beth G. Scholthof - One of the best experts on this subject based on the ideXlab platform.
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de novo generation of helper Virus Satellite chimera rnas results in disease attenuation and Satellite sequence acquisition in a host dependent manner
Virology, 2018Co-Authors: Jesse D. Pyle, Karen Beth G. ScholthofAbstract:Abstract Panicum mosaic Virus (PMV) is a helper RNA Virus for Satellite RNAs (satRNAs) and a Satellite Virus (SPMV). Here, we describe modifications that occur at the 3′-end of a satRNA of PMV, satS. Co-infections of PMV+satS result in attenuation of the disease symptoms induced by PMV alone in Brachypodium distachyon and proso millet. The 375 nt satS acquires ~100–200 nts from the 3′-end of PMV during infection and is associated with decreased abundance of the PMV RNA and capsid protein in millet. PMV-satS chimera RNAs were isolated from native infections of St. Augustinegrass and switchgrass. Phylogenetic analyses revealed that the chimeric RNAs clustered according to the host species from which they were isolated. Additionally, the chimera satRNAs acquired non-viral "linker" sequences in a host-specific manner. These results highlight the dynamic regulation of viral pathogenicity by Satellites, and the selective host-dependent, sequence-based pressures for driving satRNA generation and genome compositions.
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Multi-Year Pathogen Survey of Biofuel Switchgrass Breeding Plots Reveals High Prevalence of Infections by Panicum mosaic Virus and Its Satellite Virus.
Phytopathology, 2015Co-Authors: Catherine L. Stewart, Jesse D. Pyle, Charlene C. Jochum, Kenneth P. Vogel, Gary Y. Yuen, Karen Beth G. ScholthofAbstract:Switchgrass (Panicum virgatum) cultivars are currently under development as lignocellulosic feedstock. Here we present a survey of three established switchgrass experimental nurseries in Nebraska in which we identified Panicum mosaic Virus (PMV) as the most prevalent Virus. In 2012, 72% of 139 symptomatic plants tested positive for PMV. Of the PMV-positive samples, 19% were coinfected with its Satellite Virus (SPMV). Less than 14% of all sampled plants in 2012 were positive for four additional Viruses known to infect switchgrass. In 2013, randomized sampling of switchgrass individuals from the same 2012 breeding plots revealed that infection by PMV or PMV+SPMV was both more prevalent and associated with more severe symptoms in the cultivar Summer, and experimental lines with Summer parentage, than populations derived from the cultivar Kanlow. A 3-year analysis, from 2012 to 2014, showed that previously uninfected switchgrass plants acquire PMV or PMV+SPMV between harvest cycles. In contrast, some plants a...
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comparative analysis of antiviral responses in brachypodium distachyon and setaria viridis reveals conserved and unique outcomes among c3 and c4 plant defenses
Molecular Plant-microbe Interactions, 2014Co-Authors: Kranthi K. Mandadi, Jesse D. Pyle, Karen Beth G. ScholthofAbstract:Viral diseases cause significant losses in global agricultural production, yet little is known about grass antiviral defense mechanisms. We previously reported on host immune responses triggered by Panicum mosaic Virus (PMV) and its Satellite Virus (SPMV) in the model C3 grass Brachypodium distachyon. To aid comparative analyses of C3 and C4 grass antiviral defenses, here, we establish B. distachyon and Setaria viridis (a C4 grass) as compatible hosts for seven grass-infecting Viruses, including PMV and SPMV, Brome mosaic Virus, Barley stripe mosaic Virus, Maize mild mottle Virus, Sorghum yellow banding Virus, Wheat streak mosaic Virus (WSMV), and Foxtail mosaic Virus (FoMV). Etiological and molecular characterization of the fourteen grass-Virus pathosystems showed evidence for conserved crosstalk among salicylic acid (SA), jasmonic acid, and ethylene pathways in B. distachyon and S. viridis. Strikingly, expression of PHYTOALEXIN DEFICIENT4, an upstream modulator of SA signaling, was consistently suppress...
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Host responses elicited by a Satellite Virus-associated synergism in multiple Brachypodium distachyon accessions
2012Co-Authors: Jesse D. Pyle, Kranthi K. Mandadi, Christopher W. P. Lyons, Karen Beth G. ScholthofAbstract:inbred accessions of Brachypodium by co-infecting with PMV+SPMV. Plants were scored for disease symptoms at 7, 14, and 21 days post inoculation (dpi) and subsequently analyzed for accumulation of the 26-kDa PMV capsid protein and SPCP, as markers for mixed Virus infections, by immunoblot analyses. At 21 dpi, analysis of Virus accumulation on upper-non-inoculated leaves of the 189 accessions revealed that only 24 accessions consistently supported SPMV, characterized by the typical severe disease symptoms of PMV+SPMV-infected plants, while the others did not. Plants that did not support SPMV had milder symptoms. The future goal of this study is to identify genetic factors that contribute to the PMV and SPMV-synergism, thus facilitating the engineering of new strategies for host plant resistance.
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the complex subcellular distribution of Satellite panicum mosaic Virus capsid protein reflects its multifunctional role during infection
Virology, 2008Co-Authors: Rustem T Omarov, Karen Beth G. ScholthofAbstract:Satellite panicum mosaic Virus (SPMV) depends on its helper Panicum mosaic Virus for replication and movement in host plants. The positive-sense single-stranded genomic RNA of SPMV encodes a 17-kDa capsid protein (CP) to form 16-nm virions. We determined that SPMV CP accumulates in both cytosolic and non-cytosolic fractions, but cytosolic accumulation of SPMV CP is exclusively associated with virions. An N-terminal arginine-rich motif (N-ARM) on SPMV CP is used to bind its cognate RNA and to form Virus particles. Intriguingly, virion formation is dispensable for successful systemic SPMV RNA accumulation, yet this process still depends on an intact N-ARM. In addition, a C-terminal domain on the SPMV CP is necessary for self-interaction. Biochemical fractionation and fluorescent microscopy of green fluorescent protein-tagged SPMV CP demonstrated that the non-cytosolic SPMV CP is associated with the cell wall, the nucleus and other membranous organelles. To our knowledge, this is the first report that a Satellite Virus CP not only accumulates exclusively as virions in the cytosol but also is directed to the nucleolus and membranes. That SPMV CP is found both in the nucleus and the cell wall suggests its involvement in viral nuclear import and cell-to-cell transport.
Michael Metzlaff - One of the best experts on this subject based on the ideXlab platform.
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Current Protocols in Microbiology - Using Satellite tobacco mosaic Virus vectors for gene silencing.
Current protocols in microbiology, 2005Co-Authors: Veronique Gossele, Michael MetzlaffAbstract:This unit describes the use of Satellite tobacco mosaic Virus (STMV) vectors in combination with native TMV particles for inducing transient gene silencing in tobacco plants. Target gene fragment selection and insertion, Virus delivery procedures, and phenotype screening of silenced plants are described in detail. All critical parameters for tobacco plant cultivation, Virus infection, and RNA silencing efficiency are discussed. Keywords: RNA silencing; viral vectors; Satellite Virus–induced silencing system; Nicotiana tabacum; tobacco mosaic Virus; plant gene function discovery
Bernard La Scola - One of the best experts on this subject based on the ideXlab platform.
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eLS - Virophage Concept, The
eLS, 2013Co-Authors: Morgan Gaia, Christelle Desnues, Philippe Colson, Bernard La ScolaAbstract:The existence of small Viruses that depend on the coinfection of their host cells by another Virus has been known for a long time. These Viruses are considered to be Satellites of their helper Viruses. The discovery of Sputnik, MaVirus and the Organic Lake virophage shook this vision of subviral agents. Indeed, these new Viruses are not only dependent on coinfection but are also noxious for their so-called host Viruses, leading to sick particles. This surprising capability established the concept of a virophage, which is a Virus infecting a Virus. Studies on the morphology, life cycle and genomes of virophages have enriched this concept by highlighting unexpected features. Thus, the question of the classification of the virophages among the Satellite Viruses within the virosphere has been brought to light. Key Concepts: Virophages are small Viruses discovered to be associated with the largest Viruses of the virosphere. As Satellite Viruses, virophages are dependent on coinfection of their host cells with their host Viruses. This coinfection results in the lysis of the cell, diminution of the production and infectivity of the host Virus and an increase in the production of abnormal particles of the giant Virus. The virophages may hijack the replication mechanisms of their host Viruses within their host cells. Virophage replication occurs in the viral factory, a dense cytoplasmic region that appears a few hours after infection by the host Virus with or without its virophage. Keywords: virophage; Satellite Virus; Mimiviridae; nucleocytoplasmic large DNA Viruses; virosphere
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Structural Studies of the Sputnik Virophage
Journal of Virology, 2009Co-Authors: Bernard La Scola, Valorie D Bowman, Christopher M. Ryan, Julian P Whitelegge, Didier Raoult, Michael G. RossmannAbstract:The virophage Sputnik is a Satellite Virus of the giant mimiVirus and is the only Satellite Virus reported to date whose propagation adversely affects its host Virus' production. Genome sequence analysis showed that Sputnik has genes related to Viruses infecting all three domains of life. Here, we report structural studies of Sputnik, which show that it is about 740 A in diameter, has a T=27 icosahedral capsid, and has a lipid membrane inside the protein shell. Structural analyses suggest that the major capsid protein of Sputnik is likely to have a double jelly-roll fold, although sequence alignments do not show any detectable similarity with other viral double jelly-roll capsid proteins. Hence, the origin of Sputnik's capsid might have been derived from other Viruses prior to its association with mimiVirus.
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the virophage as a unique parasite of the giant mimiVirus
Nature, 2008Co-Authors: Bernard La Scola, Christelle Desnues, Isabelle Pagnier, Catherine Robert, Lina Barrassi, Ghislain Fournous, Michele Merchat, Marie Suzanmonti, Patrick ForterreAbstract:The first 'giant Virus' isolate came from a cooling tower in Bradford, UK. Initially mistaken for a bacterium because of its size — three times larger than that of the biggest known Viruses and bigger than many bacteria — it was found in the protozoon Acanthamoeba polyphaga. It was termed a mimiVirus (for mimicking microbe) and became known as APMV (Acanthamoeba polyphaga mimiVirus). Now an even larger APMV strain, a 'mamaVirus', has been isolated from a water cooling tower in Paris. Remarkably it is not alone, but is itself parasitized by a 'Satellite Virus'. Called Sputnik, it replicates in the Virus factory built in amoebae co-infected with APMV. By analogy with bacteriophage, Sputnik is seen as the first virophage to be discovered. It may be the tip of a virophage iceberg, since metagenomic studies of ocean waters reveal an abundance of genetic sequences closely related to giant Viruses, leading to a suspicion that they are a common parasite of plankton. The Satellite Virus Sputnik is a parasite that infects the giant MamaVirus and replicates in the Virus factory built by MamaVirus, interfering with MamaVirus reproduction. Viruses are obligate parasites of Eukarya, Archaea and Bacteria. Acanthamoeba polyphaga mimiVirus (APMV) is the largest known Virus; it grows only in amoeba and is visible under the optical microscope. MimiVirus possesses a 1,185-kilobase double-stranded linear chromosome whose coding capacity is greater than that of numerous bacteria and archaea1,2,3. Here we describe an icosahedral small Virus, Sputnik, 50 nm in size, found associated with a new strain of APMV. Sputnik cannot multiply in Acanthamoeba castellanii but grows rapidly, after an eclipse phase, in the giant Virus factory found in amoebae co-infected with APMV4. Sputnik growth is deleterious to APMV and results in the production of abortive forms and abnormal capsid assembly of the host Virus. The Sputnik genome is an 18.343-kilobase circular double-stranded DNA and contains genes that are linked to Viruses infecting each of the three domains of life Eukarya, Archaea and Bacteria. Of the 21 predicted protein-coding genes, eight encode proteins with detectable homologues, including three proteins apparently derived from APMV, a homologue of an archaeal Virus integrase, a predicted primase–helicase, a packaging ATPase with homologues in bacteriophages and eukaryotic Viruses, a distant homologue of bacterial insertion sequence transposase DNA-binding subunit, and a Zn-ribbon protein. The closest homologues of the last four of these proteins were detected in the Global Ocean Survey environmental data set5, suggesting that Sputnik represents a currently unknown family of Viruses. Considering its functional analogy with bacteriophages, we classify this Virus as a virophage. The virophage could be a vehicle mediating lateral gene transfer between giant Viruses.
Manuel A.f.v. Gonçalves - One of the best experts on this subject based on the ideXlab platform.
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Adeno-associated Virus: from defective Virus to effective vector.
Virology journal, 2005Co-Authors: Manuel A.f.v. GonçalvesAbstract:The initial discovery of adeno-associated Virus (AAV) mixed with adenoVirus particles was not a fortuitous one but rather an expression of AAV biology. Indeed, as it came to be known, in addition to the unavoidable host cell, AAV typically needs a so-called helper Virus such as adenoVirus to replicate. Since the AAV life cycle revolves around another unrelated Virus it was dubbed a Satellite Virus. However, the structural simplicity plus the defective and non-pathogenic character of this Satellite Virus caused recombinant forms to acquire centre-stage prominence in the current constellation of vectors for human gene therapy. In the present review, issues related to the development of recombinant AAV (rAAV) vectors, from the general principle to production methods, tropism modifications and other emerging technologies are discussed. In addition, the accumulating knowledge regarding the mechanisms of rAAV genome transduction and persistence is reviewed. The topics on rAAV vectorology are supplemented with information on the parental Virus biology with an emphasis on aspects that directly impact on vector design and performance such as genome replication, genetic structure, and host cell entry.
Reed B Wickner - One of the best experts on this subject based on the ideXlab platform.
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His-154 is involved in the linkage of the Saccharomyces cerevisiae L-A double-stranded RNA Virus Gag protein to the cap structure of mRNAs and is essential for M1 Satellite Virus expression.
Molecular and Cellular Biology, 1994Co-Authors: A. Blanc, Jessyca C. R. Ribas, Reed B Wickner, Nahum SonenbergAbstract:Abstract The coat protein (Gag) of the double-stranded RNA Virus L-A was previously shown to form a covalent bond with the cap structure of eukaryotic mRNAs. Here, we identify the linkage as a phosphoroimidazole bond between the alpha phosphate of the cap structure and a nitrogen in the Gag protein His-154 imidazole side chain. Mutations of His-154 abrogate the ability of Gag to bind to the cap structure, without affecting cap recognition, in vivo Virus particle formation from an L-A cDNA clone, or in vitro specific binding and replication of plus-stranded single-stranded RNA. However, genetic analyses demonstrate that His-154 is essential for M1 Satellite Virus expression.
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Expression of yeast L-A double-stranded RNA Virus proteins produces derepressed replication: a ski- phenocopy.
Journal of virology, 1991Co-Authors: Reed B Wickner, T Icho, T Fujimura, W R WidnerAbstract:The plus strand of the L-A double-stranded RNA Virus of Saccharomyces cerevisiae has two large open reading frames, ORF1, which encodes the major coat protein, and ORF2, which encodes a single-stranded RNA-binding protein having a sequence diagnostic of viral RNA-dependent RNA polymerases. ORF2 is expressed only as a Gag-Pol-type fusion protein with ORF1. We have constructed a plasmid which expresses these proteins from the yeast PGK1 promoter. We show that this plasmid can support the replication of the killer toxin-encoding M1 Satellite Virus in the absence of an L-A double-stranded RNA helper Virus itself. This requires ORF2 expression, providing a potential in vivo assay for the RNA polymerase and single-stranded RNA-binding activities of the fusion protein determined by ORF2. ORF1 expression, like a host ski- mutation, can suppress the usual requirement of M1 for the MAK11, MAK18, and MAK27 genes and allow a defective L-A (L-A-E) to support M1 replication. These results suggest that expression of ORF1 from the vector makes the cell a ski- phenocopy. Indeed, expression of ORF1 in a wild-type killer makes it a superkiller, suggesting that a target of the SKI antiviral system may be the major coat protein.
