Notes on Genus: Dianthovirus

icosahedra

Type member: Carnation ringspot virus

Contents

Members of this Genus
General Description
Morphology
Electron Micrograph
Genome
Genus Genomic Organization
Genome Map
Type Member Genomic Organization
All Known Sequences
Curated Sequences

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 m7GpppA. 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 kDaPolymerase, 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 kDapossible ORF in carnation ringspot virus
RNA2 has one open reading frame:
4. 34-35 kDaMovement protein (cell-to-cell movement)

Type Member Genomic Organization

RNA1 (3756 nts) has (probably) four open reading frames
1. 27 kDaPolymerase
2. 57 kDaPolymerase, expressed as an 88 kDa fusion protein with the product of ORF1 by ribosomal frameshift
3. 38 kDaCoat protein possibly expressed from a subgenomic RNA
X. 10 kDapossible ORF of unknown function
RNA2 (1394 nts) has one open reading frame:
4. 33.8 kDaMovement protein (cell-to-cell movement)