Notes on Genus: Dianthovirus
icosahedra
Type member: Carnation ringspot virus
Contents
General Description
The genus
Dianthovirus derives its name from the scientific name (
Dianthus) of the host of the type member, carnation ringspot virus. It is one of 11 genera in the family
Tombusviridae. All the genera are morphologically similar, with icosahedral particles and ss RNA genomes which are monopartite in the other genera but bipartite in the dianthoviruses. In its bipartite genome, it resembles members of the family
Comoviridae. However, the virions (at 31-34 nm) are slightly larger and the genome is translated from several open reading frames and a subgenomic RNA rather than from polyproteins.
Morphology
Virions isometric (polyhedral), not enveloped, 31-34 nm in diameter. Nucleocapsids have an obvious apparently angular surface structure.
Genome
Bipartite, linear, single stranded, positive sense RNA. The genome segments are encapsidated separately into different types of particle. The sizes of the RNAs are 3700-4000 (RNA1) and 1380-1450 (RNA2) nucleotides. The 3' terminus has no poly(A) tract. The 5' terminus has a methylated nucleotide cap, with the sequence m
7GpppA. There is strong sequence homology in the 3' untranslated region of the two RNAs, which can give rise to a stable stem-loop structure believed to be involved in polymerase recognition.
Genus Genomic Organization
The genome strategy of sequenced members is:
RNA1 has three or four open reading frames |
1. | 27 kDa | Polymerase |
2. | 57 kDa | Polymerase, expressed as an 88 kDa fusion protein with the product of ORF1 by ribosomal frameshift |
3. | 37-38 kDa | Coat protein possibly expressed from a subgenomic RNA |
X. | 10 kDa | possible ORF in carnation ringspot virus |
RNA2 has one open reading frame: |
4. | 34-35 kDa | Movement protein (cell-to-cell movement) |
Type Member Genomic Organization
RNA1 (3756 nts) has (probably) four open reading frames |
1. | 27 kDa | Polymerase |
2. | 57 kDa | Polymerase, expressed as an 88 kDa fusion protein with the product of ORF1 by ribosomal frameshift |
3. | 38 kDa | Coat protein possibly expressed from a subgenomic RNA |
X. | 10 kDa | possible ORF of unknown function |
RNA2 (1394 nts) has one open reading frame: |
4. | 33.8 kDa | Movement protein (cell-to-cell movement) |