Ratification vote on taxonomic proposals to the International Committee on Taxonomy of Viruses (2013)

In contrast to begomoviruses, mastreviruses have not previously been shown to interact with satellites. This study reports the first identification of the association of satellites with a mastrevirus in field-grown plants. Two alphasatellite species were detected in different field samples of wheat infected with Wheat dwarf India virus (WDIV), a Cotton leaf curl Multan alphasatellite (CLCuMA) and a Guar leaf curl alphasatellite (GLCuA). In addition to the alphasatellites, a betasatellite, Ageratum yellow leaf curl betasatellite (AYLCB), was also identified in the wheat samples. No begomovirus was detected in the wheat samples, thus establishing association of the above-named satellites with WDIV. Agrobacterium-mediated inoculation of WDIV in wheat, in the presence of either of the alphasatellites or the betasatellite, resulted in infections inducing more severe symptoms. WDIV efficiently maintained each of the alphasatellites and the betasatellite in wheat. The satellites enhanced the level of WDIV DNA in wheat. Inoculation of the satellites isolated from wheat with various begomoviruses into Nicotiana tabacum demonstrated that these remain capable of interacting with the viruses with which they were first identified. Virus-specific small RNAs accumulated in wheat upon infection with WDIV but were lower in abundance in plants coinfected with the satellites, suggesting that both the alphasatellites and the betasatellite suppress RNA silencing. These results suggest that the selective advantage for the maintenance of the alphasatellites and the betasatellite by WDIV in the field is in overcoming RNA silencing-mediated host defense. IMPORTANCE Wheat is the most widely cultivated cereal crop in the world. A number of viruses are important pathogens of wheat, including the viruses of the genus

mentioning

confidence: 99%

Association of Satellites with a Mastrevirus in Natural Infection: Complexity of Wheat Dwarf India Virus Disease

Kumar

Singh

et al. 2014

“…P icornaviruses (family Picornaviridae), with small, nonenveloped viruses with single-stranded, positive-sense genomic RNA, are one of at least five virus families forming the order Picornavirales (1; http://ictvonline.org/Virustaxonomy.asp). The picornaviruses are currently classified into 17 official genera (Aphthovirus, Aquamavirus, Avihepatovirus, Cardiovirus, Cosavirus, Dicipivirus, Enterovirus, Erbovirus, Hepatovirus, Kobuvirus, Megrivirus, Parechovirus, Salivirus, Sapelovirus, Senecavirus, Teschovirus, and Tremovirus) (1,2). Nine new genera ("Avisivirus," "Gallivirus," "Hunnivirus," "Mischivirus," "Mosavirus," "Oscivirus," "Pasivirus," "Passerivirus," and "Rosavirus") are awaiting approval by the International Committee on Taxonomy of Viruses (http://talk.ictvonline.org/), and approximately 18 candidate species await classification (http://www.picornaviridae.com/).…”

Section: Importancementioning

confidence: 99%

Comparative Complete Genome Analysis of Chicken and Turkey Megriviruses (Family Picornaviridae): Long 3′ Untranslated Regions with a Potential Second Open Reading Frame and Evidence for Possible Recombination

Boros

Pankovics

Knowles

et al. 2014

Members of the family IMPORTANCEThe comparative genome analysis of turkey and novel chicken megriviruses revealed numerous unique genome features, e.g., up to four potential 2A peptides, unusually long 3= genome parts with various lengths containing a potential second open reading frame, multiple repeating sequence motifs, and heterogeneous sequence relationships (possibly due to a recombination event) between the structural and nonstructural genome regions. Our results could help us to better understand the evolution and diversity (in terms of sequence and genome layout) of picornaviruses. P icornaviruses (family Picornaviridae), with small, nonenveloped viruses with single-stranded, positive-sense genomic RNA, are one of at least five virus families forming the order Picornavirales (1; http://ictvonline.org/Virustaxonomy.asp). The picornaviruses are currently classified into 17 official genera

“…Geminiviruses are classified into seven genera (Begomovirus, Mastrevirus, Curtovirus, Becurtovirus, Eragrovirus, Topocuvirus and Turncurtovirus) on the basis of their genome organization, host range, and insect vector (1)(2)(3)(4). After transmission by the insect vector, the ssDNA genome is released from the capsid and converted to double-stranded DNA (dsDNA) through complementary strand replication (CSR) assisted by host enzymes (5).…”

mentioning

confidence: 99%

Two Populations of Viral Minichromosomes Are Present in a Geminivirus-Infected Plant Showing Symptom Remission (Recovery)

Ceniceros-Ojeda

Rodríguez-Negrete

Rivera-Bustamante

2016

Geminiviruses are important plant pathogens characterized by circular, single-stranded DNA (ssDNA) genomes. However, in the nuclei of infected cells, viral double-stranded DNA (dsDNA) associates with host histones to form a minichromosome. In phloem-limited geminiviruses, the characterization of viral minichromosomes is hindered by the low concentration of recovered complexes due to the small number of infected cells. Nevertheless, geminiviruses are both inducers and targets of the host posttranscriptional gene silencing (PTGS) and transcriptional gene silencing (TGS) machinery. We have previously characterized a "recovery" phenomenon observed in pepper plants infected with pepper golden mosaic virus (PepGMV) that is associated with a reduction of viral DNA and RNA levels, the presence of virus-related siRNAs, and an increase in the levels of viral DNA methylation. Initial micrococcal nuclease-based assays pinpointed the presence of different viral chromatin complexes in symptomatic and recovered tissues. Using the pepper-PepGMV system, we developed a methodology to obtain a viral minichromosome-enriched fraction that does not disturb the basic chromatin structural integrity, as evaluated by the detection of core histones. Using this procedure, we have further characterized two populations of viral minichromosomes in PepGMV-infected plants. After further purification using sucrose gradient sedimentation, we also observed that minichromosomes isolated from symptomatic tissue showed a relaxed conformation (based on their sedimentation rate), are associated with a chromatin activation marker (H3K4me3), and present a low level of DNA methylation. The minichromosome population obtained from recovered tissue, on the other hand, sedimented as a compact structure, is associated with a chromatin-repressive marker (H3K9me2), and presents a high level of DNA methylation. IMPORTANCEViral minichromosomes have been reported in several animal and plant models. However, in the case of geminiviruses, there has been some recent discussion about the importance of this structure and the significance of the epigenetic modifications that it can undergo during the infective cycle. Major problems in this type of studies are the low concentration of these complexes in an infected plant and the asynchronicity of infected cells along the process; therefore, the complexes isolated in a given moment usually represent a mixture of cells at different infection stages. The recovery process observed in PepGMV-infected plants and the isolation procedure described here provide two distinct populations of minichromosomes that will allow a more precise characterization of the modifications of viral DNA and its host proteins associated along the infective cycle. This structure could be also an interesting model to study several processes involving plant chromatin. G eminiviruses are important plant pathogens consisting of circular, single-stranded DNA (ssDNA) genomes ranging from 2.7 to 5.2 kb packed into 1 or 2 icosahedral twine-shaped part...