Tombusviridae

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Tombusviridae

Virus classification

Group:	Group IV ((+)ssRNA)
Family:	Tombusviridae

Genera

Tombusvirus
Carmovirus
Necrovirus
Dianthovirus
Machlomovirus
Avenavirus
Aureusvirus
Panicovirus

[edit] Tombusviridae

Tombusviruses have a small positive sense RNA genome that uses negative strand templates to replicate. The replication process leaves a surplus of positive sense RNA stands and it is thought that not only does the viral RNA act as a template for replication, but is also able to manipulate and regulate RNA synthesis. The level of RNA synthesis has been shown to be affected by the cis-acting properties of certain elements on the RNA which include core promoter sequences which regulates the site of initiation for the complementary RNA strand, synthesis. This mechanism is thought to be recognised by RNA-dependent RNA polymerase, found encoded within the genome. Tomato bushy stunt virus (TBSV) and cucumber necrosis virus (CNV) both belong to the family Tombusviridae and have a genome size of roughly 4.8 kilo bases. The virions have a diameter of around 30nm and are not enclosed within an envelope. They have an isometric capsid around their genome and it has been shown that T=3 and therefore has 180 subunits. They are type IV viruses on the baltimore classification. Research has shown that Infection of plants from tombusviruses contain defective interfering RNAs that are born directly from the viruses RNA genome, and no host genome. Viral DI RNAs with their Small size and cis acting elements are good templates both in vivo and in Vitro on which to study RNA replication.

The Tombusviridae are a family of viruses, including the following genera: