The Totiviridae are a family of viruses. They are non enveloped, icosahedral viruses. The viron is composed of a single capsid protein and are ~40 nanometers in diameter. The capsid has a T=2 symmetry.
The genome is composed of a linear double stranded RNA molecule of 4.6-6.7 kilobases. It contains 2 overlapping open reading frames (ORF) - gag and pol - which respectively encode the capid protein and the RNA dependent RNA polymerase. Some totiviruses contain a third small potential ORF.
The family Totiviridae comprises viruses with nonsegmented dsRNA genomes and isometric virions. A new genus, Victorivirus, has been approved for this family, named from the specific epithet of Helminthosporium victoriae, host of the type species, Helminthosporium victoriae virus 190S. Distinguishing characteristics of the 11 viruses so far assigned to this genus include infection of filamentous fungi, an apparently coupled termination-reinitiation mechanism for translating the RNA-dependent RNA polymerase as a separate product from the upstream capsid protein, and sequence-based phylogenetic grouping in a distinct clade from other family members.
A dsRNA virus with a genome of 3.5 kb was isolated from field and greenhouse-grown tomato plants of different cultivars and geographic locations in North America. Cloning and sequencing of the viral genome showed the presence of two partially overlapping open reading frames (ORFs), and a genomic organization resembling members of the family Totiviridae that comprises fungal and protozoan viruses, but not plant viruses. The 5'-proximal ORF codes for a 377 amino acid-long protein of unknown function, whereas the product of ORF2 contains typical motifs of an RNA-dependant RNA-polymerase and is likely expressed by a +1 ribosomal frame shift. Despite the similarity in the genome organization with members of the family Totiviridae, this virus shared very limited sequence homology with known totiviruses or with other viruses. Repeated attempts to detect the presence of an endophytic fungus as the possible host of the virus failed, supporting its phytoviral nature. The virus was efficiently transmitted by seed but not mechanically and/or by grafting. Phylogenetic analyses revealed that this virus, for which the name Southern tomato virus (STV) is proposed, belongs to a partitivirus-like lineage and represents a species of a new taxon of plant viruses.
The genome is composed of a linear double stranded RNA molecule of 4.6-6.7 kilobases. It contains 2 overlapping open reading frames (ORF) - gag and pol - which respectively encode the capid protein and the RNA dependent RNA polymerase. Some totiviruses contain a third small potential ORF.
The family Totiviridae comprises viruses with nonsegmented dsRNA genomes and isometric virions. A new genus, Victorivirus, has been approved for this family, named from the specific epithet of Helminthosporium victoriae, host of the type species, Helminthosporium victoriae virus 190S. Distinguishing characteristics of the 11 viruses so far assigned to this genus include infection of filamentous fungi, an apparently coupled termination-reinitiation mechanism for translating the RNA-dependent RNA polymerase as a separate product from the upstream capsid protein, and sequence-based phylogenetic grouping in a distinct clade from other family members.
A dsRNA virus with a genome of 3.5 kb was isolated from field and greenhouse-grown tomato plants of different cultivars and geographic locations in North America. Cloning and sequencing of the viral genome showed the presence of two partially overlapping open reading frames (ORFs), and a genomic organization resembling members of the family Totiviridae that comprises fungal and protozoan viruses, but not plant viruses. The 5'-proximal ORF codes for a 377 amino acid-long protein of unknown function, whereas the product of ORF2 contains typical motifs of an RNA-dependant RNA-polymerase and is likely expressed by a +1 ribosomal frame shift. Despite the similarity in the genome organization with members of the family Totiviridae, this virus shared very limited sequence homology with known totiviruses or with other viruses. Repeated attempts to detect the presence of an endophytic fungus as the possible host of the virus failed, supporting its phytoviral nature. The virus was efficiently transmitted by seed but not mechanically and/or by grafting. Phylogenetic analyses revealed that this virus, for which the name Southern tomato virus (STV) is proposed, belongs to a partitivirus-like lineage and represents a species of a new taxon of plant viruses.
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