Notes on Genus: Cheravirus

icosahedra

Type member: Cherry rasp leaf 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 Cheravirus (from the type member Cherry rasp leaf virus) contains viruses that were previously classified as tentative members of the genus Nepovirus. In common with nepoviruses, its members are characterised by their bipartite genome encapsidated in icosahedral particles with each genome segment producing a polyprotein. However, there are three distinct coat protein subunits of fairly similar size (20-25 kDa) and phylogenetic analyses suggest the viruses should be classified in a distinct genus within the plant picornavirus family Secoviridae. Vectors are believed to be nematodes.

Morphology

Virions isometric (icosahedral), not enveloped, about 30 nm in diameter.

Genome

Bipartite, linear, single stranded, positive sense RNA. The 3'- terminus of each RNA has a poly(A) tract and the 5'- terminus has a genome-linked protein (VPg).

Genus Genomic Organization

Each RNA is translated into a polyprotein, which is then processed by a series of steps into functional proteins: RNA1 encodes proteins necessary for replication while the cell-to-cell movement protein and coat proteins are encoded on RNA2. The complete genome sequence for the type member is not available, but the products of Apple latent spherical virus are as follows:
RNA1 (6.5 kb) produces a polyprotein of 235 kDa processed into 5 peptides:
1. Processing regulator
2. Nucleotide binding protein
3. VPg: genome-linked protein
4. Protease
5. Polymerase
RNA2 (3.4 kb) produces a polyprotein of 108 kDa processed into 4 functional peptides:
1. Movement protein
2. Coat protein 1
3. Coat protein 2
4. Coat protein 3

Type Member Genomic Organization

Only partial sequence data is available for the this virus:
RNA2 (3.3 kb) produces a polyprotein of 106 kDa processed into 4 functional peptides:
1. 42 kDa Movement protein
2. 24 kDa Coat protein 1
3. 19 kDa Coat protein 2
4. 22 kDa Coat protein 3