| Potexvirus | |
|---|---|
| Virus classification | |
| Group: | Group IV ((+)ssRNA) |
| Order: | Tymovirales |
| Family: | Alphaflexiviridae |
| Genus: | Potexvirus |
| Species | |
|
Allium virus X |
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Potexvirus (from POTato Virus X) is a genus of plant pathogenic viruses, belonging to the family Alphaflexiviridae and the order Tymovirales. Transmission occurs mechanically, with viruses in this genus causing mosaic and ringspot symptoms.
There are at least 25 viruses in this genus. A number of candidates for inclusion are also known (~20) but a decision to include these in the genus or not is still pending.
Contents |
The virion length may vary considerably (between 470-1000 nanometers or more) and is 12-13 nm in diameter. The pitch of the helix is of the basic helix 3.3-3.7 nm (8-9 copies of the coat protein per turn). It is non-enveloped, flexuous and filamentous. The coat itself is composed of 1000-1500 copies of the coat protein.
The genome is linear, 5.9-7 kilobases in length with a capped 5' end and a polyadenylated 3' end. The genome encodes 5 proteins. From left to right these proteins are: the viral replication protein that consists of a capping enzyme domain, a helicase-like domain, the RNA dependent RNA polymerase, three proteins - the triple gene block (TGB) 1, 2 and 3 - and the coat protein.
The RNA is translated giving rise to the viral RNA polymerase. This in turn produces a negative stranded template from which a series of subgenomic RNAs are generated. These subgenomic RNAs are then translated into the viral proteins.
The 5' end is ~80 nucleotides in length and typically begins with the sequence GAAAA.
In addition to its RNA polymerase activity, the viral RNA polymerase (molecular weight ~150 kiloDaltons) also has methyltransferase and RNA helicase activities.
The TGB proteins are conserved among the Allexivirus, Carlavirus, Foveavirus, Furovirus, Hordeivirus, Pecluvirus, Pomovirus and Potexvirus genera. Their functions are a matter of active research.
TGB 1 (molecular weight 23 kDa) is a multifunctional protein. It has RNA helicase activity and seems to be involved in cell to cell movement.
The TGB 2 (molecular weight 11 kDa) and TGB 3 (molecular weight 10 kDa) proteins associate with the endoplasmic reticulum.
The coat protein has a molecular weight of ~25kDa.
The 3' untranslated region is ~100 nucleotides in length.
Known hosts are from the Liliopsida or Magnoliopsida.
These viruses appear to occur world wide.