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 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)