-terminus is capped. The 3-end does not possess a poly(A) tail. It is not known if sgRNA(s) are formed in infected tissues.
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Type Species |
(OCSV) |
This monotypic genus is distinguished from other genera in the family Tombusviridae because the CP is significantly larger than other members with a protruding domain. The genome organization is intermediate between those of the genera Carmovirus and Tombusvirus. Oat chlorotic stunt virus (OCSV) has a movement protein related to the movement proteins of the genera Carmovirus, Machlomovirus and Necrovirus, but it lacks the second movement protein ORF associated with these viruses.
Particles are isometric and approximately 35 nm in diameter. Based on sequence similarity with the CPs of members of the family Tombusviridae that contain a protruding domain, it is assumed that the particle has T = 3 icosahedral symmetry and are composed of 180 protein subunits.
Physicochemical and Physical Properties
No information exists on physicochemical and physical properties.
The genome is composed of a single positive-sense ssRNA molecule of 4114 nts. It is not known if the 5-terminus is capped. The 3-end does not possess a poly(A) tail. It is not known if sgRNA(s) are formed in infected tissues.
The virion is probably composed of 180 copies of the single Mr 48,231 CP.
None reported.
None reported.
Genome Organization and Replication
The genomic RNA contains 3 ORFs (Fig. 4). The genome organization is intermediate between those of the genera Carmovirus and Tombusvirus. ORF1 encodes a Mr 23 
103 protein. Readthrough of the ORF1 amber termination codon allows the expression of a Mr 84 103 protein. ORF2 encodes the Mr 48 103 CP. ORF3 is within ORF2, in a different reading frame. This ORF encodes a Mr 8 103 polypeptide. It is not known if a sgRNA is synthesized in infected cells. However, based on the conservation of sequence and genome organization with members of the family Tombusviridae, it is speculated that the one sgRNA is formed to allow the expression of the 3-proximal CP ORF as well as ORF3. The ORF1 product and its amber terminator readthrough product are thought to form the viral polymerase. ORF2 encodes the virus CP. The ORF3 gene product is believed to encode the movement protein. Probably a sgRNA is formed in infected plants to serve as the translational template for ORFs 2 and 3.
The virus is a moderate immunogen. Antibodies do not cross-react with other unrelated icosahedral viruses of oats or with representative members of the genera Carmovirus and Machlomovirus.
The virus has only been identified and studied in oats (Avena sativa).
The virus is easily mechanically transmitted from oat plant to oat plant. Infection patterns in winter oat fields are consistent with the virus being soil-borne, and possibly transmitted by zoosporic fungi.
This virus has only been reported in the United Kingdom.
None reported.
List of Species Demarcation Criteria in the Genus
Not applicable.
Official virus species names are in italics. Tentative virus species names, alternative names ( ), strains or serotypes are not italicized. Virus names, genome sequence accession numbers [ ], and assigned abbreviations ( ) are:
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Oat chlorotic stunt virus |
[X89864] |
(OCSV) |
Tentative Species in the Genus
None reported.
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