Ipomovirus
| Ipomovirus | |
|---|---|
| Virus classification | |
| Group: | Group IV ((+)ssRNA) |
| Family: | Potyviridae |
| Genus: | Ipomovirus |
| Type species | |
| Sweet potato mild mottle virus | |
| Species | |
|
Cassava brown streak virus | |
Ipomovirus is a genus of positive sense single stranded RNA viruses belonging to the family Potyviridae. They infect plants and are transmitted by whiteflies (Bemisia tabaci). The name of the genus is derived from Ipomoea - the generic name of sweet potato.
Virology
The virons are non enveloped, flexuous, filamentous and may have a variety of lengths depending on the species (200-300 nanometers (nm): 500-600 nm: 650-900 nm). They are 12-15 nm in diameter. The capsid has helical symmetry with a pitch of 3.4 nm. They induce characteristic inclusion bodies (pinwheels) within infected plant cells.
Genome
The genome is a monpartite linear, single stranded RNA genome of positive polarity about 10-11 kilobases in length. The 3’ terminus has a poly (A) tract and the 5’ terminus has a genome linked protein (VPg).
It encodes a single polypeptide with a predicted molecular weight of 390 kiloDaltons (kDa) which is cleaved into ~10 proteins. In 5'-3' order these proteins are
- P1 (a serine protease): 83 kDa
- HC (a protease): 51 kDa
- P3: 34 kDa
- 6K1: 5 kDa
- Cl (helicase): 71 kDa
- 6K2: 6 kDa
- VPg (the 5' binding protein): 20 kDa
- NIa-Pro (a protease): 27 kDa
- NIb (RNA dependent RNA polymerase): 57 kDa
- Capsid protein: 34 kDa
There may be some variation in the number of the proteins depending on the species.