Potexvirus
| Potexvirus | |
|---|---|
| Virus classification | |
| Group: | Group IV ((+)ssRNA) |
| Order: | Tymovirales |
| Family: | Alphaflexiviridae |
| Genus: | Potexvirus |
| Type species | |
| Potato virus X | |
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.
Taxonomy
There are currently 37 virus species included in this genus. Other candidates exist, but these requests are still pending. The type species for which the genus is named after is the Potato virus X.
Species:
- Allium virus X
- Alstroemeria virus X
- Alternanthera mosaic virus
- Asparagus virus 3
- Bamboo mosaic virus
- Cactus virus X
- Cassava common mosaic virus
- Cassava virus X
- Clover yellow mosaic virus
- Commelina virus X
- Cymbidium mosaic virus
- Daphne virus X
- Foxtail mosaic virus
- Hosta virus X
- Hydrangea ringspot virus
- Lagenaria mild mosaic virus
- Lettuce virus X
- Lily virus X
- Malva mosaic virus
- Mint virus X
- Narcissus mosaic virus
- Nerine virus X
- Opuntia virus X
- Papaya mosaic virus
- Pepino mosaic virus
- Phaius virus X
- Plantago asiatica mosaic virus
- Plantago severe mottle virus
- Plantain virus X
- Potato aucuba mosaic virus
- Potato virus X
- Schlumbergera virus X
- Strawberry mild yellow edge virus
- Tamus red mosaic virus
- Tulip virus X
- White clover mosaic virus
- Zygocactus virus X
Virology
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 about 80 nucleotides in length and typically begins with the sequence GAAAA.[1]
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.
Hosts
Known hosts are from the Liliopsida or Magnoliopsida.
Viral distribution
These viruses appear to occur world wide.
References
- ↑ Côté, F.; Paré, C.; Majeau, N.; Bolduc, M. N.; Leblanc, É.; Bergeron, M. G.; Bernardy, M. G.; Leclerc, D. (2008). "Nucleotide sequence and phylogenetic analysis of a new potexvirus: Malva Mosaic Virus". Infection, Genetics and Evolution 8 (1): 83–93. doi:10.1016/j.meegid.2007.10.006. PMID 18054524.