Potexvirus


Potexvirus is a genus of pathogenic viruses in the order Tymovirales, in the family Alphaflexiviridae. Plants serve as natural hosts. There are 52 species in this genus, three of which are assigned to a subgenus. Diseases associated with this genus include: mosaic and ringspot symptoms. The genus name comes from POTato virus X).

Taxonomy

Potexvirus contains one subgenus that has three species and 49 additional species unassigned to a subgenus. The following 52 species are assigned to the genus, listed by scientific name and followed by their common names:
The following species are unassigned to a subgenus:Potexvirus alternantherae, Alternanthera mosaic virusPotexvirus babaci, Babaco mosaic virusPotexvirus bambusae, Bamboo mosaic virusPotexvirus chaenostomae, Chaenostoma potexvirusPotexvirus colombiense, Cassava Colombian symptomless virusPotexvirus cymbidii, Cymbidium mosaic virusPotexvirus ecsadenii, Adenium obesum virus XPotexvirus ecsallii, Allium virus XPotexvirus ecsalstroemeriae, Alstroemeria virus XPotexvirus ecscacti, Cactus virus XPotexvirus ecscaricae, Papaya virus XPotexvirus ecschlumbergerae, Schlumbergera virus XPotexvirus ecscnidii, Cnidium virus XPotexvirus ecsdioscoreae, Yam virus XPotexvirus ecshibisci, Hibiscus virus XPotexvirus ecshostae, Hosta virus XPotexvirus ecslactucae, Lettuce virus XPotexvirus ecslilii, Lily virus XPotexvirus ecsmanihotis, Cassava virus XPotexvirus ecsmenthae, Mint virus XPotexvirus ecsnerinis, Nerine virus XPotexvirus ecsopuntiae, Opuntia virus XPotexvirus ecsphaii, Phaius virus XPotexvirus ecspitayae, Pitaya virus XPotexvirus ecsplantagonis, Plantain virus XPotexvirus ecspotati, Potato virus XPotexvirus ecsthalassiae, Turtle grass virus XPotexvirus ecstulipae, Tulip virus XPotexvirus ecsvanillae, Vanilla virus XPotexvirus eczygocacti, Zygocactus virus XPotexvirus flavimaculae, Euonymus yellow mottle associated virusPotexvirus flavitrifolii, Clover yellow mosaic virusPotexvirus flavivenae, Euonymus yellow vein virusPotexvirus fragariae, Strawberry mild yellow edge virusPotexvirus hydrangeae, Hydrangea ringspot virusPotexvirus lagenariae, Lagenaria mild mosaic virusPotexvirus malvae, Malva mosaic virusPotexvirus marmoraucuba, Potato aucuba mosaic virusPotexvirus marmordioscoreae, Tamus red mosaic virusPotexvirus marmormanihotis, Cassava common mosaic virusPotexvirus marmorplantagonis, Plantago asiatica mosaic virusPotexvirus marmorsennae, Senna mosaic virusPotexvirus narcissi, Narcissus mosaic virusPotexvirus nesignambrosiae, Ambrosia asymptomatic virus 1Potexvirus papayae, Papaya mosaic virusPotexvirus pepini, Pepino mosaic virusPotexvirus setariae, Foxtail mosaic virusPotexvirus triasparagi, Asparagus virus 3Potexvirus trifolii, White clover mosaic virus

Virology

The virion length may vary considerably and is 12–13 nm in diameter. The pitch of the helix is of the basic helix 3.3–3.7 nm. 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 1, 2 and 3—and the coat protein.
GenusStructureSymmetryCapsidGenomic arrangementGenomic segmentation
PotexvirusFilamentousNon-envelopedLinearMonopartite

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.
In addition to its RNA polymerase activity, the viral RNA polymerase 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 is a multifunctional protein. It has RNA helicase activity and seems to be involved in cell to cell movement.
The TGB 2 and TGB 3 proteins associate with the endoplasmic reticulum.
The coat protein has a molecular weight of ~25 kDa.
The 3' untranslated region is ~100 nucleotides in length.

Life cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by penetration into the host cell. Replication follows the positive stranded RNA virus replication model. Positive stranded RNA virus transcription is the method of transcription. Translation takes place by leaky scanning. The virus exits the host cell by tripartite non-tubule guided viral movement. The virus is transmitted via a vector. Transmission routes are vector and mechanical.
GenusHost detailsTissue tropismEntry detailsRelease detailsReplication siteAssembly siteTransmission
PotexvirusPlants-Viral movement; mechanical inoculationViral movementCytoplasmCytoplasmInsects

Hosts

Known hosts are various flowering plants.

Distribution

These viruses appear to occur worldwide.