Double-stranded RNA viruses
| Double-stranded RNA viruses | |
|---|---|
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| Electron micrograph of rotaviruses. The bar = 100 nm | |
| Virus classification | |
| Group: | Group III (dsRNA) |
| Families | |
Double-stranded (ds) RNA viruses are a diverse group of viruses that vary widely in host range (humans, animals, plants, fungi, and bacteria), genome segment number (one to twelve) and virion organization (T-number, capsid layers or turrets). Members of this group include the rotaviruses, known globally as a common cause of gastroenteritis in young children, and bluetongue virus, an economically important pathogen of cattle and sheep.
Of these families, the Reoviridae is the largest and most diverse in terms of host range.
In recent years the increasing knowledge of virus particle assembly, virus-cell interactions, and viral pathogenesis allow approaches for the development of novel antiviral strategies or agents.
Viruses with dsRNA genomes are currently grouped into a number of families, unassigned genera and species.
Three families infect fungi: Totiviridae, Partitiviridae and Chrysoviridae. These families have monopartite, bipartite and quadripartite genomes respectively. They are typically isometric particles 25–50 nanometers in diameter. Based on sequence similarity of the RNA dependent RNA polymerase, the partitiviruses are probably derived from a totivirus ancestor. A fourth family — Alternaviridae — has recently been described also with quadripartite genome.
Hypoviruses are mycoviruses (fungal viruses) with unencapsidated dsRNA genomes. They may have common ancestry with plant positive strand RNA viruses in supergroup 1 with potyvirus lineages, respectively
A new clade (as yet unnamed) of six viruses infecting filamentous fungi has been reported.
Families
Unassigned species
Reoviridae are currently classified into nine genera. The genomes of these viruses consist of 10 to 12 segments of dsRNA, each generally encoding one protein. The mature virions are non-enveloped. Their capsids, formed by multiple proteins, have icosahedral symmetry and are arranged generally in concentric layers. A distinguishing feature of the dsRNA viruses, irrespective of their family association, is their ability to carry out transcription of the dsRNA segments, under appropriate conditions, within the capsid. In all these viruses, the enzymes required for endogenous transcription are thus part of the virion structure.
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