Notes on Genus: Umbravirus
enveloped bacilliform (?)
Type member: Carrot mottle virus
Contents
General Description
The genus
Umbravirus contains viruses that, in nature, depend upon a specific helper virus (commonly a
luteovirus) for their (persistent aphid) transmission. The name umbra (Latin for a shadow) reflects this property. Structures seen in infected cells (enveloped and bullet shaped) may or may not be virions.
Morphology
Virions may be enveloped and bullet shaped but the structures found in plant cells are not clearly understood and may be cytopathological structures involved in virus replication. No structural protein has been identified from sequence data.
Genome
Single stranded, positive sense RNA, about 4500 nucleotides long. The 3' terminus has no poly(A) tract.
Genus Genomic Organization
In the members sequenced there are four open reading frames:
1. | 31-37 kDa | Replication protein |
2. | 64 kDa | Polymerase, probably expressed as a 90-100 kDa translational frameshift fusion with the product of ORF1 |
3. | 27-29 kDa | Putative long distance movement protein, probably expressed from a subgenomic RNA |
4. | 28-31 kDa | Cell-to-cell movement protein, probably expressed from a subgenomic RNA |
Type Member Genomic Organization
There are four open reading frames:
1. | 37 kDa | Replication protein |
2. | 64 kDa | Polymerase, probably expressed as a 96 kDa translational frameshift fusion with the product of ORF1 |
3. | 29 kDa | Putative long distance movement protein, probably expressed from a subgenomic RNA |
4. | 31 kDa | Cell-to-celll movement protein, probably expressed from a subgenomic RNA |