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Im JSH, Newburn LR, Kent G, White KA. Trans-Activator Binding Site Context in RCNMV Modulates Subgenomic mRNA Transcription. Viruses 2021; 13:v13112252. [PMID: 34835058 PMCID: PMC8622197 DOI: 10.3390/v13112252] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 10/29/2021] [Accepted: 11/08/2021] [Indexed: 11/16/2022] Open
Abstract
Many positive-sense RNA viruses transcribe subgenomic (sg) mRNAs during infections that template the translation of a subset of viral proteins. Red clover necrotic mosaic virus (RCNMV) expresses its capsid protein through the transcription of a sg mRNA from RNA1 genome segment. This transcription event is activated by an RNA structure formed by base pairing between a trans-activator (TA) in RNA2 and a trans-activator binding site (TABS) in RNA1. In this study, the impact of the structural context of the TABS in RNA1 on the TA–TABS interaction and sg mRNA transcription was investigated using in vitro and in vivo approaches. The results (i) generated RNA secondary structure models for the TA and TABS, (ii) revealed that the TABS is partially base paired with proximal upstream sequences, which limits TA access, (iii) demonstrated that the aforementioned intra-RNA1 base pairing involving the TABS modulates the TA–TABS interaction in vitro and sg mRNA levels during infections, and (iv) revealed that the TABS in RNA1 can be modified to mediate sg mRNA transcription in a TA-independent manner. These findings advance our understanding of transcriptional regulation in RCNMV and provide novel insights into the origin of the TA–TABS interaction.
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2
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Porter AF, Cobbin J, Li CX, Eden JS, Holmes EC. Metagenomic Identification of Viral Sequences in Laboratory Reagents. Viruses 2021; 13:v13112122. [PMID: 34834931 PMCID: PMC8625350 DOI: 10.3390/v13112122] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Revised: 10/13/2021] [Accepted: 10/19/2021] [Indexed: 12/16/2022] Open
Abstract
Metagenomic next-generation sequencing has transformed the discovery and diagnosis of infectious disease, with the power to characterise the complete 'infectome' (bacteria, viruses, fungi, parasites) of an individual host organism. However, the identification of novel pathogens has been complicated by widespread microbial contamination in commonly used laboratory reagents. Using total RNA sequencing ("metatranscriptomics") we documented the presence of contaminant viral sequences in multiple 'blank' negative control sequencing libraries that comprise a sterile water and reagent mix. Accordingly, we identified 14 viral sequences in 7 negative control sequencing libraries. As in previous studies, several circular replication-associated protein encoding (CRESS) DNA virus-like sequences were recovered in the blank control libraries, as well as contaminating sequences from the Totiviridae, Tombusviridae and Lentiviridae families of RNA virus. These data suggest that viral contamination of common laboratory reagents is likely commonplace and can comprise a wide variety of viruses.
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Affiliation(s)
- Ashleigh F. Porter
- The Peter Doherty Institute of Immunity and Infection, Department of Microbiology and Immunity, University of Melbourne, Melbourne, VIC 3000, Australia;
| | - Joanna Cobbin
- Sydney Institute for Infectious Diseases, School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia; (J.C.); (J.-S.E.)
- Sydney Institute for Infectious Diseases, School of Medical Sciences, The University of Sydney, Sydney, NSW 2006, Australia
| | - Ci-Xiu Li
- Key Laboratory of Etiology and Epidemiology of Emerging Infectious Diseases in Universities of Shandong, Shandong First Medical University & Shandong Academy of Medical Sciences, Taian 271000, China;
| | - John-Sebastian Eden
- Sydney Institute for Infectious Diseases, School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia; (J.C.); (J.-S.E.)
- Sydney Institute for Infectious Diseases, School of Medical Sciences, The University of Sydney, Sydney, NSW 2006, Australia
- Centre for Virus Research, Westmead Institute for Medical Research, Westmead, NSW 2145, Australia
| | - Edward C. Holmes
- Sydney Institute for Infectious Diseases, School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW 2006, Australia; (J.C.); (J.-S.E.)
- Sydney Institute for Infectious Diseases, School of Medical Sciences, The University of Sydney, Sydney, NSW 2006, Australia
- Correspondence:
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3
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Kwon SJ, Bodaghi S, Dang T, Gadhave KR, Ho T, Osman F, Al Rwahnih M, Tzanetakis IE, Simon AE, Vidalakis G. Complete Nucleotide Sequence, Genome Organization, and Comparative Genomic Analyses of Citrus Yellow-Vein Associated Virus (CYVaV). Front Microbiol 2021; 12:683130. [PMID: 34168635 PMCID: PMC8218546 DOI: 10.3389/fmicb.2021.683130] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 05/05/2021] [Indexed: 12/22/2022] Open
Abstract
Citrus yellow-vein disease (CYVD) was first reported in California in 1957. We now report that CYVD is associated with a virus-like agent, provisionally named citrus yellow-vein associated virus (CYVaV). The CYVaV RNA genome has 2,692 nucleotides and codes for two discernable open reading frames (ORFs). ORF1 encodes a protein of 190 amino acid (aa) whereas ORF2 is presumably generated by a −1 ribosomal frameshifting event just upstream of the ORF1 termination signal. The frameshift product (717 aa) encodes the RNA-dependent RNA polymerase (RdRp). Phylogenetic analyses suggest that CYVaV is closely related to unclassified virus-like RNAs in the family Tombusviridae. Bio-indexing and RNA-seq experiments indicate that CYVaV can induce yellow vein symptoms independently of known citrus viruses or viroids.
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Affiliation(s)
- Sun-Jung Kwon
- Department of Microbiology and Plant Pathology, University of California, Riverside, Riverside, CA, United States.,Institutes of Green Bio Science and Technology, Seoul National University, Pyeongchang, South Korea
| | - Sohrab Bodaghi
- Department of Microbiology and Plant Pathology, University of California, Riverside, Riverside, CA, United States
| | - Tyler Dang
- Department of Microbiology and Plant Pathology, University of California, Riverside, Riverside, CA, United States
| | - Kiran R Gadhave
- Department of Microbiology and Plant Pathology, University of California, Riverside, Riverside, CA, United States
| | - Thien Ho
- Department of Entomology and Plant Pathology, University of Arkansas, Fayetteville, AR, United States
| | - Fatima Osman
- Department of Plant Pathology, University of California, Davis, Davis, CA, United States
| | - Maher Al Rwahnih
- Department of Plant Pathology, University of California, Davis, Davis, CA, United States
| | - Ioannis E Tzanetakis
- Department of Entomology and Plant Pathology, University of Arkansas, Fayetteville, AR, United States
| | - Anne E Simon
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, United States
| | - Georgios Vidalakis
- Department of Microbiology and Plant Pathology, University of California, Riverside, Riverside, CA, United States
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4
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Alam SB, Reade R, Maghodia AB, Ghoshal B, Theilmann J, Rochon D. Targeting of cucumber necrosis virus coat protein to the chloroplast stroma attenuates host defense response. Virology 2021; 554:106-119. [PMID: 33418272 DOI: 10.1016/j.virol.2020.10.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 10/27/2020] [Accepted: 10/27/2020] [Indexed: 01/17/2023]
Abstract
Cucumber necrosis virus (CNV) is a (+)ssRNA virus that elicits spreading local and systemic necrosis in Nicotiana benthamiana. We previously showed that the CNV coat protein (CP) arm functions as a chloroplast transit peptide that targets a CP fragment containing the S and P domains to chloroplasts during infection. Here we show that several CP arm mutants that inefficiently target chloroplasts, along with a mutant that lacks the S and P domains, show an early onset of more localized necrosis along with protracted induction of pathogenesis related protein (PR1a). Agroinfiltrated CNV CP is shown to interfere with CNV p33 and Tomato bushy stunt virus p19 induced necrosis. Additionally, we provide evidence that a CP mutant that does not detectably enter the chloroplast stroma induces relatively higher levels of several plant defense-related genes compared to WT CNV. Together, our data suggest that targeting of CNV CP to the chloroplast stroma interferes with chloroplast-mediated plant defense.
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Affiliation(s)
- Syed Benazir Alam
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, V6T 1B4, Canada; Summerland Research and Development Centre, Agriculture and Agri-Food Canada, Summerland, BC, V0H 1Z0, Canada.
| | - Ron Reade
- Summerland Research and Development Centre, Agriculture and Agri-Food Canada, Summerland, BC, V0H 1Z0, Canada
| | - Ajay B Maghodia
- Summerland Research and Development Centre, Agriculture and Agri-Food Canada, Summerland, BC, V0H 1Z0, Canada
| | - Basudev Ghoshal
- Summerland Research and Development Centre, Agriculture and Agri-Food Canada, Summerland, BC, V0H 1Z0, Canada
| | - Jane Theilmann
- Summerland Research and Development Centre, Agriculture and Agri-Food Canada, Summerland, BC, V0H 1Z0, Canada
| | - D'Ann Rochon
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, V6T 1B4, Canada; Summerland Research and Development Centre, Agriculture and Agri-Food Canada, Summerland, BC, V0H 1Z0, Canada
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5
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Kanodia P, Prasanth KR, Roa-Linares VC, Bradrick SS, Garcia-Blanco MA, Miller WA. A rapid and simple quantitative method for specific detection of smaller coterminal RNA by PCR (DeSCo-PCR): application to the detection of viral subgenomic RNAs. RNA 2020; 26:888-901. [PMID: 32238481 PMCID: PMC7297113 DOI: 10.1261/rna.074963.120] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 03/26/2020] [Indexed: 05/10/2023]
Abstract
RNAs that are 5'-truncated versions of a longer RNA but share the same 3' terminus can be generated by alternative promoters in transcription of cellular mRNAs or by replicating RNA viruses. These truncated RNAs cannot be distinguished from the longer RNA by a simple two-primer RT-PCR because primers that anneal to the cDNA from the smaller RNA also anneal to-and amplify-the longer RNA-derived cDNA. Thus, laborious methods, such as northern blot hybridization, are used to distinguish shorter from longer RNAs. For rapid, low-cost, and specific detection of these truncated RNAs, we report detection of smaller coterminal RNA by PCR (DeSCo-PCR). DeSCo-PCR uses a nonextendable blocking primer (BP), which outcompetes a forward primer (FP) for annealing to longer RNA-derived cDNA, while FP outcompetes BP for annealing to shorter RNA-derived cDNA. In the presence of BP, FP, and the reverse primer, only cDNA from the shorter RNA is amplified in a single-tube reaction containing both RNAs. Many positive strand RNA viruses generate 5'-truncated forms of the genomic RNA (gRNA) called subgenomic RNAs (sgRNA), which play key roles in viral gene expression and pathogenicity. We demonstrate that DeSCo-PCR is easily optimized to selectively detect relative quantities of sgRNAs of red clover necrotic mosaic virus from plants and Zika virus from human cells, each infected with viral strains that generate different amounts of sgRNA. This technique should be readily adaptable to other sgRNA-producing viruses, and for quantitative detection of any truncated or alternatively spliced RNA.
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Affiliation(s)
- Pulkit Kanodia
- Interdepartmental Genetics and Genomics, Iowa State University, Ames, Iowa 50011, USA
- Plant Pathology and Microbiology Department, Iowa State University, Ames, Iowa 50011, USA
| | - K Reddisiva Prasanth
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas 77555, USA
| | - Vicky C Roa-Linares
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas 77555, USA
- Molecular and Translational Medicine Group, Institute of Medical Research, Faculty of Medicine University of Antioquia, Medellin 050010, Colombia
| | - Shelton S Bradrick
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas 77555, USA
| | - Mariano A Garcia-Blanco
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas 77555, USA
- Programme of Emerging Infectious Diseases, Duke-NUS Medical School, Singapore 169857, Singapore
- Institute of Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas 77555, USA
| | - W Allen Miller
- Interdepartmental Genetics and Genomics, Iowa State University, Ames, Iowa 50011, USA
- Plant Pathology and Microbiology Department, Iowa State University, Ames, Iowa 50011, USA
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6
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Naveen KP, Bhat AI. Development of reverse transcription loop-mediated isothermal amplification (RT-LAMP) and reverse transcription recombinase polymerase amplification (RT-RPA) assays for the detection of two novel viruses infecting ginger. J Virol Methods 2020; 282:113884. [PMID: 32442456 DOI: 10.1016/j.jviromet.2020.113884] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 05/14/2020] [Accepted: 05/14/2020] [Indexed: 12/25/2022]
Abstract
Our recent studies have shown the association of two novel viruses namely, ginger chlorotic fleck-associated virus 1 (GCFaV-1) and ginger chlorotic fleck-associated virus 2 (GCFaV-2) with chlorotic fleck disease of ginger. As ginger is propagated through vegetative means, the development of diagnostics would aid in the identification of virus-free plants. In the present study, reverse transcription loop-mediated isothermal amplification (RT-LAMP) and reverse transcription recombinase polymerase amplification (RT-RPA) assays were developed and validated for the quick detection of GCFaV-1 and GCFaV-2. The detection limits of viruses by these assays, when compared with conventional and real-time RT-PCR, showed that RT-LAMP was up to 1000 times more sensitive than conventional RT-PCR and one-hundredth that of real-time RT-PCR for both the viruses. The detection limit of RT-RPA for GCFaV-1 was up to 100 times more than that of RT-PCR and one-thousandth that of real-time RT-PCR. On the other hand, for detecting GCFaV-2, RT-RPA was found up to 1000 times more sensitive than conventional RT-PCR and one hundredth that of real-time RT-PCR. Based on the cost-effectiveness and duration, RT-LAMP and RT-RPA assays can be suggested for the rapid detection of both viruses.
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Affiliation(s)
- K P Naveen
- Division of Crop Protection, ICAR-Indian Institute of Spices Research, Marikunnu, Kozhikode 673012, India
| | - A I Bhat
- Division of Crop Protection, ICAR-Indian Institute of Spices Research, Marikunnu, Kozhikode 673012, India.
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7
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Pérez-Cañamás M, Hevia E, Hernández C. Epigenetic Changes in Host Ribosomal DNA Promoter Induced by an Asymptomatic Plant Virus Infection. Biology (Basel) 2020; 9:biology9050091. [PMID: 32353984 PMCID: PMC7285159 DOI: 10.3390/biology9050091] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 04/25/2020] [Accepted: 04/26/2020] [Indexed: 11/16/2022]
Abstract
DNA cytosine methylation is one of the main epigenetic mechanisms in higher eukaryotes and is considered to play a key role in transcriptional gene silencing. In plants, cytosine methylation can occur in all sequence contexts (CG, CHG, and CHH), and its levels are controlled by multiple pathways, including de novo methylation, maintenance methylation, and demethylation. Modulation of DNA methylation represents a potentially robust mechanism to adjust gene expression following exposure to different stresses. However, the potential involvement of epigenetics in plant-virus interactions has been scarcely explored, especially with regard to RNA viruses. Here, we studied the impact of a symptomless viral infection on the epigenetic status of the host genome. We focused our attention on the interaction between Nicotiana benthamiana and Pelargonium line pattern virus (PLPV, family Tombusviridae), and analyzed cytosine methylation in the repetitive genomic element corresponding to ribosomal DNA (rDNA). Through a combination of bisulfite sequencing and RT-qPCR, we obtained data showing that PLPV infection gives rise to a reduction in methylation at CG sites of the rDNA promoter. Such a reduction correlated with an increase and decrease, respectively, in the expression levels of some key demethylases and of MET1, the DNA methyltransferase responsible for the maintenance of CG methylation. Hypomethylation of rDNA promoter was associated with a five-fold augmentation of rRNA precursor levels. The PLPV protein p37, reported as a suppressor of post-transcriptional gene silencing, did not lead to the same effects when expressed alone and, thus, it is unlikely to act as suppressor of transcriptional gene silencing. Collectively, the results suggest that PLPV infection as a whole is able to modulate host transcriptional activity through changes in the cytosine methylation pattern arising from misregulation of methyltransferases/demethylases balance.
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8
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Sherman MB, Guenther R, Reade R, Rochon D, Sit T, Smith TJ. Near-Atomic-Resolution Cryo-Electron Microscopy Structures of Cucumber Leaf Spot Virus and Red Clover Necrotic Mosaic Virus: Evolutionary Divergence at the Icosahedral Three-Fold Axes. J Virol 2020; 94:e01439-19. [PMID: 31694952 PMCID: PMC6955255 DOI: 10.1128/jvi.01439-19] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 10/28/2019] [Indexed: 12/11/2022] Open
Abstract
Members of the Tombusviridae family have highly similar structures, and yet there are important differences among them in host, transmission, and capsid stabilities. Viruses in the Tombusviridae family have single-stranded RNA (ssRNA) genomes with T=3 icosahedral protein shells with a maximum diameter of ∼340 Å. Each capsid protein is comprised of three domains: R (RNA binding), S (shell), and P (protruding). Between the R domain and S domain is the "arm" region that studies have shown to play a critical role in assembly. To better understand how the details of structural differences and similarities influence the Tombusviridae viral life cycles, the structures of cucumber leaf spot virus (CLSV; genus Aureusvirus) and red clover necrotic mosaic virus (RCNMV; genus Dianthovirus) were determined to resolutions of 3.2 Å and 2.9 Å, respectively, with cryo-electron microscopy and image reconstruction methods. While the shell domains had homologous structures, the stabilizing interactions at the icosahedral 3-fold axes and the R domains differed greatly. The heterogeneity in the R domains among the members of the Tombusviridae family is likely correlated with differences in the sizes and characteristics of the corresponding genomes. We propose that the changes in the R domain/RNA interactions evolved different arm domain interactions at the β-annuli. For example, RCNMV has the largest genome and it appears to have created the necessary space in the capsid by evolving the shortest R domain. The resulting loss in RNA/R domain interactions may have been compensated for by increased intersubunit β-strand interactions at the icosahedral 3-fold axes. Therefore, the R and arm domains may have coevolved to package different genomes within the conserved and rigid shell.IMPORTANCE Members of the Tombusviridae family have nearly identical shells, and yet they package genomes that range from 4.6 kb (monopartite) to 5.3 kb (bipartite) in size. To understand how this genome flexibility occurs within a rigidly conserved shell, we determined the high-resolution cryo-electron microscopy (cryo-EM) structures of cucumber leaf spot virus and red clover necrotic mosaic virus. In response to genomic size differences, it appears that the ssRNA binding (R) domain of the capsid diverged evolutionarily in order to recognize the different genomes. The next region, the "arm," seems to have also coevolved with the R domain to allow particle assembly via interactions at the icosahedral 3-fold axes. In addition, there are differences at the icosahedral 3-fold axes with regard to metal binding that are likely important for transmission and the viral life cycle.
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Affiliation(s)
- Michael B Sherman
- University of Texas Medical Branch at Galveston, Department of Biochemistry and Molecular Biology, Galveston, Texas, USA
| | - Richard Guenther
- North Carolina State University, Department of Entomology and Plant Pathology, Raleigh, North Carolina, USA
| | - Ron Reade
- Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, Summerland, British Columbia, Canada
| | - D'Ann Rochon
- Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, Summerland, British Columbia, Canada
| | - Tim Sit
- North Carolina State University, Department of Entomology and Plant Pathology, Raleigh, North Carolina, USA
| | - Thomas J Smith
- University of Texas Medical Branch at Galveston, Department of Biochemistry and Molecular Biology, Galveston, Texas, USA
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Campbell AJ, Erickson A, Pellerin E, Salem N, Mo X, Falk BW, Ferriol I. Phylogenetic classification of a group of self-replicating RNAs that are common in co-infections with poleroviruses. Virus Res 2020; 276:197831. [PMID: 31790776 DOI: 10.1016/j.virusres.2019.197831] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 11/25/2019] [Accepted: 11/29/2019] [Indexed: 11/22/2022]
Abstract
Tombusvirus-like associated RNAs (tlaRNAs) are positive-sense single-stranded RNAs found in plants co-infected with viruses of the genus Polerovirus. TlaRNAs depend upon capsid proteins supplied in trans by the co-infecting polerovirus vector for transmission and intra-host systemic movement. Here, the full-length genomes of five tlaRNAs were determined using a combination of RT-PCR and next-generation sequencing, and evidence is provided for an additional tlaRNA associated with potato leafroll virus. Phylogenetic analyses based on conserved domains of the RdRp placed tlaRNAs as a monophyletic clade clustering with members of the family Tombusviridae and comprising three different subclades. Full-length clones of tlaRNAs from two of three subclades were confirmed to replicate autonomously, and each produces a subgenomic RNA during infection.
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10
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Kraft JJ, Peterson MS, Cho SK, Wang Z, Hui A, Rakotondrafara AM, Treder K, Miller CL, Miller WA. The 3' Untranslated Region of a Plant Viral RNA Directs Efficient Cap-Independent Translation in Plant and Mammalian Systems. Pathogens 2019; 8:E28. [PMID: 30823456 DOI: 10.3390/pathogens8010028] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 02/03/2019] [Accepted: 02/23/2019] [Indexed: 11/29/2022] Open
Abstract
Many plant viral RNA genomes lack a 5′ cap, and instead are translated via a cap-independent translation element (CITE) in the 3′ untranslated region (UTR). The panicum mosaic virus-like CITE (PTE), found in many plant viral RNAs, binds and requires the cap-binding translation initiation factor eIF4E to facilitate translation. eIF4E is structurally conserved between plants and animals, so we tested cap-independent translation efficiency of PTEs of nine plant viruses in plant and mammalian systems. The PTE from thin paspalum asymptomatic virus (TPAV) facilitated efficient cap-independent translation in wheat germ extract, rabbit reticulocyte lysate, HeLa cell lysate, and in oat and mammalian (BHK) cells. Human eIF4E bound the TPAV PTE but not a PTE that did not stimulate cap-independent translation in mammalian extracts or cells. Selective 2′-hydroxyl acylation analyzed by primer extension (SHAPE) footprinting revealed that both human and wheat eIF4E protected the conserved guanosine (G)-rich domain in the TPAV PTE pseudoknot. The central G plays a key role, as it was found to be required for translation and protection from SHAPE modification by eIF4E. These results provide insight on how plant viruses gain access to the host’s translational machinery, an essential step in infection, and raise the possibility that similar PTE-like mechanisms may exist in mRNAs of mammals or their viruses.
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11
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Miras M, Truniger V, Querol‐Audi J, Aranda MA. Analysis of the interacting partners eIF4F and 3'-CITE required for Melon necrotic spot virus cap-independent translation. Mol Plant Pathol 2017; 18:635-648. [PMID: 27145354 PMCID: PMC6638222 DOI: 10.1111/mpp.12422] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Revised: 04/26/2016] [Accepted: 04/28/2016] [Indexed: 05/17/2023]
Abstract
We have shown previously that the translation of Melon necrotic spot virus (MNSV, family Tombusviridae, genus Carmovirus) RNAs is controlled by a 3'-cap-independent translation enhancer (CITE), which is genetically and functionally dependent on the eukaryotic translation initiation factor (eIF) 4E. Here, we describe structural and functional analyses of the MNSV-Mα5 3'-CITE and its translation initiation factor partner. We first mapped the minimal 3'-CITE (Ma5TE) to a 45-nucleotide sequence, which consists of a stem-loop structure with two internal loops, similar to other I-shaped 3'-CITEs. UV crosslinking, followed by gel retardation assays, indicated that Ma5TE interacts in vitro with the complex formed by eIF4E + eIF4G980-1159 (eIF4Fp20 ), but not with each subunit alone or with eIF4E + eIF4G1003-1092 , suggesting binding either through interaction with eIF4E following a conformational change induced by its binding to eIF4G980-1159 , or through a double interaction with eIF4E and eIF4G980-1159 . Critical residues for this interaction reside in an internal bulge of Ma5TE, so that their mutation abolished binding to eIF4E + eIF4G1003-1092 and cap-independent translation. We also developed an in vivo system to test the effect of mutations in eIF4E in Ma5TE-driven cap-independent translation, showing that conserved amino acids in a positively charged RNA-binding motif around amino acid position 228, implicated in eIF4E-eIF4G binding or belonging to the cap-recognition pocket, are essential for cap-independent translation controlled by Ma5TE, and thus for the multiplication of MNSV.
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Affiliation(s)
- Manuel Miras
- Centro de Edafología y Biología Aplicada del Segura (CEBAS) ‐ CSICApdo. correos 164, 30100 EspinardoMurciaSpain
| | - Verónica Truniger
- Centro de Edafología y Biología Aplicada del Segura (CEBAS) ‐ CSICApdo. correos 164, 30100 EspinardoMurciaSpain
| | - Jordi Querol‐Audi
- Molecular Biology Institute of Barcelona (IBMB‐CSIC)Parc Científic de Barcelona, Baldiri i Reixac 10Barcelona08028Spain
| | - Miguel A. Aranda
- Centro de Edafología y Biología Aplicada del Segura (CEBAS) ‐ CSICApdo. correos 164, 30100 EspinardoMurciaSpain
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12
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Newburn LR, White KA. Atypical RNA Elements Modulate Translational Readthrough in Tobacco Necrosis Virus D. J Virol 2017; 91:e02443-16. [PMID: 28148800 DOI: 10.1128/JVI.02443-16] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 01/27/2017] [Indexed: 12/13/2022] Open
Abstract
Tobacco necrosis virus, strain D (TNV-D), is a positive-strand RNA virus in the genus Betanecrovirus and family Tombusviridae The production of its RNA-dependent RNA polymerase, p82, is achieved by translational readthrough. This process is stimulated by an RNA structure that is positioned immediately downstream of the recoding site, termed the readthrough stem-loop (RTSL), and a sequence in the 3' untranslated region of the TNV-D genome, called the distal readthrough element (DRTE). Notably, a base pairing interaction between the RTSL and the DRTE, spanning ∼3,000 nucleotides, is required for enhancement of readthrough. Here, some of the structural features of the RTSL, as well as RNA sequences and structures that flank either the RTSL or DRTE, were investigated for their involvement in translational readthrough and virus infectivity. The results revealed that (i) the RTSL-DRTE interaction cannot be functionally replaced by stabilizing the RTSL structure, (ii) a novel tertiary RNA structure positioned just 3' to the RTSL is required for optimal translational readthrough and virus infectivity, and (iii) these same activities also rely on an RNA stem-loop located immediately upstream of the DRTE. Functional counterparts for the RTSL-proximal structure may also be present in other tombusvirids. The identification of additional distinct RNA structures that modulate readthrough suggests that regulation of this process by genomic features may be more complex than previously appreciated. Possible roles for these novel RNA elements are discussed.IMPORTANCE The analysis of factors that affect recoding events in viruses is leading to an ever more complex picture of this important process. In this study, two new atypical RNA elements were shown to contribute to efficient translational readthrough of the TNV-D polymerase and to mediate robust viral genome accumulation in infections. One of the structures, located close to the recoding site, could have functional equivalents in related genera, while the other structure, positioned 3' proximally in the viral genome, is likely limited to betanecroviruses. Irrespective of their prevalence, the identification of these novel RNA elements adds to the current repertoire of viral genome-based modulators of translational readthrough and provides a notable example of the complexity of regulation of this process.
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Sandra N, Jailani AAK, Jain RK, Mandal B. Genome characterization, infectivity assays of in vitro and in vivo infectious transcripts of soybean yellow mottle mosaic virus from India reveals a novel short mild genotype. Virus Res 2017; 232:96-105. [PMID: 28215614 DOI: 10.1016/j.virusres.2017.02.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 02/11/2017] [Accepted: 02/14/2017] [Indexed: 01/16/2023]
Abstract
Nucleotide sequence of a distinct soybean yellow mottle mosaic virusisolate from Vignaradiata (mungbean isolate, SYMMV-Mb) from India was determined and compared with othermembers of the family Tombusviridae. The complete monopartite single-stranded RNA genome of SYMMV-Mb consisted of 3974nt with six putative open reading frames and includes 5' and 3' untranslated regions of 35 and 254nt, respectively. SYMMV-Mb genome shared 75% nt sequence identity at complete genome level and 67-92% identity at all ORFs level with SYMMV Korean and USA isolates (soybean isolates) followed by CPMoV, whereas it shared very low identity with other tombusviridae members (5-41%). A full-length infectious cDNA clone of the SYMMV-Mb placed under the control of the T7 RNA polymerase and the CaMV35S promoters was generated and French bean plants on mechanical inoculation with in vitro RNA transcripts, p35SSYMMV-O4 plasmid and agroinoculation with p35SSYMMV-O4 showed symptoms typical of SYMMV-Mb infection. The infection was confirmed by DAC-ELISA, ISEM, RT-PCR and mechanical transmission to new plant species. Further testing of different plant species with agroinoculation of p35SSYMMV-O4 showed delay in symptoms but indistinguishable from mechanical sap inoculation and the infection was confirmed by DAC-ELISA, RT-PCR and mechanical transmission to new plants. The system developed here will be useful for further studies on pathogenecity, viral gene functions, plant-virus-vector interactions of SYMMV-Mb and to utilize it as a gene expression and silencing vector.
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Affiliation(s)
- Nagamani Sandra
- Advanced Centre for Plant Virology, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi 110012, India.
| | - A Abdul Kader Jailani
- Advanced Centre for Plant Virology, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi 110012, India
| | - Rakesh Kumar Jain
- Advanced Centre for Plant Virology, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi 110012, India
| | - Bikash Mandal
- Advanced Centre for Plant Virology, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi 110012, India
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Janowski AB, Krishnamurthy SR, Lim ES, Zhao G, Brenchley JM, Barouch DH, Thakwalakwa C, Manary MJ, Holtz LR, Wang D. Statoviruses, A novel taxon of RNA viruses present in the gastrointestinal tracts of diverse mammals. Virology 2017; 504:36-44. [PMID: 28152382 PMCID: PMC5515247 DOI: 10.1016/j.virol.2017.01.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 01/13/2017] [Accepted: 01/17/2017] [Indexed: 01/21/2023]
Abstract
Next-generation sequencing has expanded our understanding of the viral populations that constitute the mammalian virome. We describe a novel taxon of viruses named Statoviruses, for Stool associated Tombus-like viruses, present in multiple metagenomic datasets. These viruses define a novel clade that is phylogenetically related to the RNA virus families Tombusviridae and Flaviviridae. Five distinct statovirus types were identified in human, macaque, mouse, and cow gastrointestinal tract samples. The prototype genome, statovirus A, was frequently identified in macaque stool samples from multiple geographically distinct cohorts. Another genome, statovirus C1, was discovered in a stool sample from a human child with fever, cough, and rash. Further experimental data will clarify whether these viruses are infectious to mammals or if they originate from another source present in the mammalian gastrointestinal tract.
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Affiliation(s)
- Andrew B Janowski
- Department of Pediatrics, Washington University School of Medicine, St Louis, MO, USA
| | - Siddharth R Krishnamurthy
- Department of Molecular Microbiology and Pathology and Immunology, Washington University School of Medicine, St Louis, MO, USA
| | - Efrem S Lim
- Department of Molecular Microbiology and Pathology and Immunology, Washington University School of Medicine, St Louis, MO, USA
| | - Guoyan Zhao
- Department of Molecular Microbiology and Pathology and Immunology, Washington University School of Medicine, St Louis, MO, USA
| | - Jason M Brenchley
- Lab of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Dan H Barouch
- Center for Virology and Vaccine Research Beth Israel Deaconess Medical Center, Boston, MA, USA; Ragon Institute of MGH, MIT, and Harvard, Boston, MA, USA
| | - Chrissie Thakwalakwa
- Department of Community Health, College of Medicine, University of Malawi, Blantyre 3, Malawi
| | - Mark J Manary
- Department of Pediatrics, Washington University School of Medicine, St Louis, MO, USA
| | - Lori R Holtz
- Department of Pediatrics, Washington University School of Medicine, St Louis, MO, USA
| | - David Wang
- Department of Molecular Microbiology and Pathology and Immunology, Washington University School of Medicine, St Louis, MO, USA.
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Pérez-Cañamás M, Blanco-Pérez M, Forment J, Hernández C. Nicotiana benthamiana plants asymptomatically infected by Pelargonium line pattern virus show unusually high accumulation of viral small RNAs that is neither associated with DCL induction nor RDR6 activity. Virology 2017; 501:136-146. [PMID: 27915129 DOI: 10.1016/j.virol.2016.11.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 11/25/2016] [Accepted: 11/26/2016] [Indexed: 01/25/2023]
Abstract
Pelargonium line pattern virus (PLPV, Tombusviridae) normally establishes systemic, low-titered and asymptomatic infections in its hosts. This type of interaction may be largely determined by events related to RNA silencing, a major antiviral mechanism in plants. This mechanism is triggered by double or quasi double-stranded (ds) viral RNAs which are cut by DCL ribonucleases into virus small RNAs (vsRNAs). Such vsRNAs are at the core of the silencing process as they guide sequence-specific RNA degradation Host RNA dependent-RNA polymerases (RDRs), and particularly RDR6, strengthen antiviral silencing by promoting biosynthesis of secondary vsRNAs. To approach PLPV-host relationship, here we have characterized the vsRNAs that accumulate in PLPV-infected Nicotiana benthamiana. Such accumulation was found unprecedented high despite DCLs were not induced in infected tissue and neither vsRNA generation nor PLPV infection was apparently affected by RDR6 impairment. From the obtained data, triggers and host factors likely involved in anti-PLPV silencing are proposed.
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Affiliation(s)
- Miryam Pérez-Cañamás
- Instituto de Biología Molecular y Celular de Plantas (IBMCP, Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia), Ciudad Politécnica de la Innovación, Ed. 8E. Camino de Vera s/n, 46022 Valencia, Spain
| | - Marta Blanco-Pérez
- Instituto de Biología Molecular y Celular de Plantas (IBMCP, Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia), Ciudad Politécnica de la Innovación, Ed. 8E. Camino de Vera s/n, 46022 Valencia, Spain
| | - Javier Forment
- Instituto de Biología Molecular y Celular de Plantas (IBMCP, Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia), Ciudad Politécnica de la Innovación, Ed. 8E. Camino de Vera s/n, 46022 Valencia, Spain
| | - Carmen Hernández
- Instituto de Biología Molecular y Celular de Plantas (IBMCP, Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia), Ciudad Politécnica de la Innovación, Ed. 8E. Camino de Vera s/n, 46022 Valencia, Spain.
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Alam SB, Rochon D. Evidence that Hsc70 Is Associated with Cucumber Necrosis Virus Particles and Plays a Role in Particle Disassembly. J Virol 2017; 91:e01555-16. [PMID: 27807229 DOI: 10.1128/JVI.01555-16] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 10/25/2016] [Indexed: 11/20/2022] Open
Abstract
Uncoating of a virus particle to expose its nucleic acid is a critical aspect of the viral multiplication cycle, as it is essential for the establishment of infection. In the present study, we investigated the role of plant HSP70 homologs in the uncoating process of Cucumber necrosis virus (CNV), a nonenveloped positive-sense single-stranded RNA [(+)ssRNA] virus having a T=3 icosahedral capsid. We have found through Western blot analysis and mass spectrometry that the HSP70 homolog Hsc70-2 copurifies with CNV particles. Virus overlay and immunogold labeling assays suggest that Hsc70-2 is physically bound to virions. Furthermore, trypsin digestion profiles suggest that the bound Hsc70-2 is partially protected by the virus, indicating an intimate association with particles. In investigating a possible role of Hsc70-2 in particle disassembly, we showed that particles incubated with Hsp70/Hsc70 antibody produce fewer local lesions than those incubated with prebleed control antibody on Chenopodium quinoa In conjunction, CNV virions purified using CsCl and having undetectable amounts of Hsc70-2 produce fewer local lesions. We also have found that plants with elevated levels of HSP70/Hsc70 produce higher numbers of local lesions following CNV inoculation. Finally, incubation of recombinant Nicotiana benthamiana Hsc70-2 with virus particles in vitro leads to conformational changes or partial disassembly of capsids as determined by transmission electron microscopy, and particles are more sensitive to chymotrypsin digestion. This is the first report suggesting that a cellular Hsc70 chaperone is involved in disassembly of a plant virus. IMPORTANCE Virus particles must disassemble and release their nucleic acid in order to establish infection in a cell. Despite the importance of disassembly in the ability of a virus to infect its host, little is known about this process, especially in the case of nonenveloped spherical RNA viruses. Previous work has shown that host HSP70 homologs play multiple roles in the CNV infection cycle. We therefore examined the potential role of these cellular components in the CNV disassembly process. We show that the HSP70 family member Hsc70-2 is physically associated with CNV virions and that HSP70 antibody reduces the ability of CNV to establish infection. Statistically significantly fewer lesions are produced when virions having undetectable HSc70-2 are used as an inoculum. Finally incubation of Hsc70-2 with CNV particles results in conformational changes in particles. Taken together, our data point to an important role of the host factor Hsc70-2 in CNV disassembly.
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Abstract
Gene functions of strains of Maize chlorotic mottle virus, which comprises the monotypic genus Machlomovirus, have not been previously identified. In this study mutagenesis of the seven genes encoded in maize chlorotic mottle virus (MCMV) showed that the genes with positional and sequence similarity to their homologs in viruses of related tombusvirid genera had similar functions. p50 and its readthrough protein p111 are the only proteins required for replication in maize protoplasts, and they function at a low level in trans. Two movement proteins, p7a and p7b, and coat protein, encoded on subgenomic RNA1, are required for cell-to-cell movement in maize, and p7a and p7b function in trans. A unique protein, p31, expressed as a readthrough extension of p7a, is required for efficient systemic infection. The 5' proximal MCMV gene encodes a unique 32kDa protein that is not required for replication or movement. Transcripts lacking p32 expression accumulate to about 1/3 the level of wild type transcripts in protoplasts and produce delayed, mild infections in maize plants. Additional studies on p32, p31 and the unique amino-terminal region of p50 are needed to further characterize the life cycle of this unique tombusvirid.
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Affiliation(s)
- Kay Scheets
- Department of Plant Biology, Ecology, and Evolution, 301 Physical Sciences, Oklahoma State University, Stillwater, OK, 74078-3013, USA.
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Chkuaseli T, Newburn LR, Bakhshinyan D, White KA. Protein expression strategies in Tobacco necrosis virus-D. Virology 2015; 486:54-62. [PMID: 26402375 DOI: 10.1016/j.virol.2015.08.032] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 08/25/2015] [Accepted: 08/29/2015] [Indexed: 02/04/2023]
Abstract
Tobacco necrosis virus (TNV-D) has a plus-strand RNA genome that is neither 5' capped nor 3' poly-adenylated. Instead, it utilizes a 3' cap-independent translational enhancer (3'CITE) located in its 3' untranslated region (UTR) for translation of its proteins. We have examined the protein expression strategies used by TNV-D and our results indicate that: (i) a base pairing interaction between conserved ACCA and UGGU motifs in the genomic 5'UTR and 3'CITE, respectively, is not required for efficient plant cell infection, (ii) similar potential 5'UTR-3'CITE interactions in the two viral subgenomic mRNAs are not needed for efficient translation of viral proteins in vitro, (iii) a small amount of capsid protein is translated from the viral genome by a largely 3'CITE-independent mechanism, (iv) the larger of two possible forms of capsid protein is efficiently translated, and (v) p7b is translated from subgenomic mRNA1 by a leaky scanning mechanism.
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Affiliation(s)
- Tamari Chkuaseli
- Department of Biology, York University, Toronto, Ontario, Canada M3J 1P3
| | - Laura R Newburn
- Department of Biology, York University, Toronto, Ontario, Canada M3J 1P3
| | - David Bakhshinyan
- Department of Biology, York University, Toronto, Ontario, Canada M3J 1P3
| | - K Andrew White
- Department of Biology, York University, Toronto, Ontario, Canada M3J 1P3.
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Ghoshal K, Theilmann J, Reade R, Sanfacon H, Rochon D. The Cucumber leaf spot virus p25 auxiliary replicase protein binds and modifies the endoplasmic reticulum via N-terminal transmembrane domains. Virology 2014; 468-470:36-46. [PMID: 25129437 PMCID: PMC7112066 DOI: 10.1016/j.virol.2014.07.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 06/28/2014] [Accepted: 07/13/2014] [Indexed: 11/23/2022]
Abstract
Cucumber leaf spot virus (CLSV) is a member of the Aureusvirus genus, family Tombusviridae. The auxiliary replicase of Tombusvirids has been found to localize to endoplasmic reticulum (ER), peroxisomes or mitochondria; however, localization of the auxiliary replicase of aureusviruses has not been determined. We have found that the auxiliary replicase of CLSV (p25) fused to GFP colocalizes with ER and that three predicted transmembrane domains (TMDs) at the N-terminus of p25 are sufficient for targeting, although the second and third TMDs play the most prominent roles. Confocal analysis of CLSV infected 16C plants shows that the ER becomes modified including the formation of punctae at connections between ER tubules and in association with the nucleus. Ultrastructural analysis shows that the cytoplasm contains numerous vesicles which are also found between the perinuclear ER and nuclear membrane. It is proposed that these vesicles correspond to modified ER used as sites for CLSV replication.
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Affiliation(s)
- Kankana Ghoshal
- University of British Columbia, Faculty of Land and Food Systems, Vancouver, British Columbia, Canada V6T 1Z4
| | - Jane Theilmann
- Agriculture and Agri-Food Canada Pacific Agri-Food Research Centre, 4200 Hwy 97, Summerland, British Columbia, Canada V0H 1Z0
| | - Ron Reade
- Agriculture and Agri-Food Canada Pacific Agri-Food Research Centre, 4200 Hwy 97, Summerland, British Columbia, Canada V0H 1Z0
| | - Helene Sanfacon
- Agriculture and Agri-Food Canada Pacific Agri-Food Research Centre, 4200 Hwy 97, Summerland, British Columbia, Canada V0H 1Z0
| | - D'Ann Rochon
- University of British Columbia, Faculty of Land and Food Systems, Vancouver, British Columbia, Canada V6T 1Z4; Agriculture and Agri-Food Canada Pacific Agri-Food Research Centre, 4200 Hwy 97, Summerland, British Columbia, Canada V0H 1Z0.
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Newburn LR, Nicholson BL, Yosefi M, Cimino PA, White KA. Translational readthrough in Tobacco necrosis virus-D. Virology 2014; 450-451:258-65. [PMID: 24503089 DOI: 10.1016/j.virol.2013.12.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 11/23/2013] [Accepted: 12/08/2013] [Indexed: 12/16/2022]
Abstract
The plus-strand RNA genome of Tobacco necrosis virus-D (TNV-D) expresses its polymerase via translational readthrough. The RNA signals involved in this readthrough process were characterized in vitro using a wheat germ extract translation system and in vivo via protoplast infections. The results indicate that (i) TNV-D requires a long-range RNA-RNA interaction between an extended stem-loop (SL) structure proximal to the readthrough site and a sequence in the 3'-untranslated region of its genome; (ii) stability of the extended SL structure is important for its function; (iii) TNV-D readthrough elements are compatible with UAG and UGA, but not UAA; (iv) a readthrough defect can be rescued by a heterologous readthrough element in vitro, but not in vivo; and (v) readthrough elements can also mediate translational frameshifting. These results provide new information on determinants of readthrough in TNV-D and further support the concept of a common general mechanism for readthrough in Tombusviridae.
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Affiliation(s)
- Laura R Newburn
- Department of Biology, York University, Toronto, ON, Canada M3J 1P3
| | - Beth L Nicholson
- Department of Biology, York University, Toronto, ON, Canada M3J 1P3
| | - Michael Yosefi
- Department of Biology, York University, Toronto, ON, Canada M3J 1P3
| | - Peter A Cimino
- Department of Biology, York University, Toronto, ON, Canada M3J 1P3
| | - K Andrew White
- Department of Biology, York University, Toronto, ON, Canada M3J 1P3.
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Lee PKK, White KA. Construction and characterization of an aureusvirus defective RNA. Virology 2014; 452-453:67-74. [PMID: 24606684 DOI: 10.1016/j.virol.2013.12.033] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Revised: 12/08/2013] [Accepted: 12/23/2013] [Indexed: 01/30/2023]
Abstract
Defective RNAs (D RNAs) are small RNA replicons derived from viral RNA genomes. No D RNAs have been found associated with members of the plus-strand RNA virus genus Aureusvirus (family Tombusviridae). Accordingly, we sought to construct a D RNA for the aureusvirus Cucumber leaf spot virus (CLSV) using the known structure of tombusvirus defective interfering RNAs as a guide. An efficiently accumulating CLSV D RNA was generated that contained four non-contiguous regions of the viral genome and this replicon was used as a tool to studying viral cis-acting RNA elements. The results of structural and functional analyses indicated that CLSV contains counterparts for several of the major RNA elements found in tombusviruses. However, although similar, the CLSV D RNA and its components are distinct and provide insights into RNA-based specificity and mechanisms of function.
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Affiliation(s)
- Pui Kei K Lee
- Department of Biology, York University, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3
| | - K Andrew White
- Department of Biology, York University, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3.
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Boulila M. Positive selection, molecular recombination structure and phylogenetic reconstruction of members of the family Tombusviridae: Implication in virus taxonomy. Genet Mol Biol 2011; 34:647-60. [PMID: 22215970 PMCID: PMC3229121 DOI: 10.1590/s1415-47572011005000046] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2010] [Accepted: 05/13/2011] [Indexed: 11/22/2022] Open
Abstract
A detailed study of putative recombination events and their evolution frequency in the whole genome of the currently known members of the family Tombusviridae, comprising 79 accessions retrieved from the international databases, was carried out by using the RECCO and RDP version 3.31β algorithms. The first program allowed the detection of potential recombination sites in seven out of eight virus genera (Aureusvirus, Avenavirus, Carmovirus, Dianthovirus, Necrovirus, Panicovirus, and Tombusvirus), the second program provided the same results except for genus Dianthovirus. On the other hand, both methods failed to detect recombination breakpoints in the genome of members of genus Machlomovirus. Furthermore, based on Fisher's Exact Test of Neutrality, positive selection exerted on protein-coding genes was detected in 17 accession pairs involving 15 different lineages. Except genera Machlomovirus, and Panicovirus along with unclassified Tombusviridae, all the other taxonomical genera and the unassigned Tombusviridae encompassed representatives under positive selection. The evolutionary history of all members of the Tombusviridae family showed that they segregated into eight distinct groups corresponding to the eight genera which constitute this family. The inferred phylogeny reshuffled the classification currently adopted by the International Committee on Taxonomy of Viruses. A reclassification was proposed.
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