Potyvirus

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Potyvirus
PPV genome.svg
Genome of typical potyvirus PPV with proteolytic cleavage sites
Virus classification
Group: Group IV ((+)ssRNA)
Family: Potyviridae
Genus: Potyvirus
Species

See text; 176 total

Potyviruses infect plants and belong to the family Potyviridae. The genus is named after the type virus - Potato virus Y.

Potyviruses, like begomoviruses, account for ~30% of the currently known plant viruses and have at least 180 definitive and possible members. Members of this genus may cause significant losses in agricultural, pastoral, horticultural and ornamental crops.

There are 73 described genera of plant viruses.

More than 200 species of aphids spread potyviruses and most are from the subfamily Aphidinae (genera Macrosiphum and Myzus).

Evolution[edit]

The potyviruses evolved between 6,600 to 7,250 years ago.[1][2] They appear to have evolved in southwest Eurasia or north Africa. The estimated mutation rate is about 1.15×10−4 nucleotide substitutions/site/year.

Virology[edit]

The virion is non-enveloped with a filamentous nucleocapsid, 680 to 900 nanometers (nm) long and is 11-20 nm in diameter. The nucleocapsid contains ~2000 copies of the capsid protein. The symmetry of the nucleocapsid is helical with a pitch of 3.4 nm.

The genome is a linear positive sense ssRNA ranging in size from 9000-12000bp. A number of species have a bipartate genome.The base composition is: 21-23.51-26% G; 23-30.15-44% A; 14.9-22.41-28% C; 15.6-24.41-30.9% U.

In the species with a single genome, at the 5' end a protein is covalently linked (the Vg protein). It encodes a single open reading frame (ORF) expressed as a 350kDa polyprotein precursor. This is processed into seven smaller proteins: P1, helper component (HC), P3, cylindrical inclusion (CI), nuclear inclusion A (NIa), nuclear inclusion B (NIb), capsid protein (CP) and two small putative proteins known as 6K1 and 6K2. The P3 protein also encodes a second protein - P3N-PIPO - which is generated by a +2 frameshift.[3]

Molecular biology[edit]

Protein P1 (~33 kiloDaltons (kDa) in molecular weight) is a serine protease.

HC (~52 KDa) is a protease that is also involved in aphid transmission. As a protease it cleaves a glycine-glycine dipeptide at its own C terminus. It also interacts with eukaryotic initiation factor 4 (eIF4). It acts as a viral RNA silencing suppressor.

The function of P3 (~41 kDa) is not known. It interacts with large subunit of the ribulose-1,5-bisphosphate carboxylase/oxygenase.

CI (~71 kDa) is an RNA helicase with ATPase activity. It is also involved in membrane attachment.

NIa (~50 kDa) is cleaved into a protease (~27 kDa) and the VPg (~22 kDa) protein.

NIb (~59 kDa) is an RNA-dependent RNA polymerase.

The functions of the 6K1 (~6 kDa) is not known. 6K2 (~6 kDa) protein, having a single trans membrane domain, is accumulating in the host cellular membranes and is thought to play a role in forming the replication vesicles of the virus.

The function of the P3N-PIPO (~25 kDa) is not known but it appears to be essential. It interacts with both the large and small subunits of the ribulose-1,5-bisphosphate carboxylase/oxygenase.

The capsid protein ranges between 30 and 35 kDa in weight.

The VPg protein interacts with eukaryotic initiation factor 4E (eIF4E).[4] This interaction appears to be essential to viral infectivity.

Two proteinases, P1 and the helper component proteinase (HC) catalyse only autoproteolytic reactions at their respective C termini. The remaining cleavage reactions are catalysed by either trans-proteolytic or autoproteolytic mechanisms by the small nuclear inclusion protein (NIa-Pro). This latter protein is an evolutionary homology of the picornavirus 3C proteinase.

Life cycle[edit]

Replication may occur in the cytoplasm, nuclei, chloroplasts, Golgi apparatus, cell vacuoles or more rarely in unusual sites.

Potyviruses make proteinacous inclusions in infected plant cells. These may be crystals in either the cytoplasm or in the nucleus, as amorphous X-bodies, membranous bodies, viroplasms or pinwheels. The inclusions may or may not (depending on the species) contain virions. These inclusions can be seen in the light microscope in leaf strips of infected plant tissue stained with Orange-Green (protein stain) but not Azure A (nucleic acid stain).[5][6] [7] There are four different kinds of Potyvirus inclusions.[8]

Species[edit]

Alstroemeria mosaic potyvirus
Amaranthus leaf mottle potyvirus
Apium virus Y
Araujia mosaic potyvirus
Arracacha Y potyvirus
Artichoke latent potyvirus
Asparagus 1 potyvirus
Banana bract mosaic potyvirus
Bean common mosaic necrosis potyvirus
Bean common mosaic potyvirus
Bean yellow mosaic potyvirus
Beet mosaic potyvirus
Bidens mosaic potyvirus
Bidens mottle virus
Brugmansia mosaic virus
Caladenia virus A
Canna yellow streak virus
Cardamom mosaic potyvirus
Carnation vein mottle potyvirus
Carrot thin leaf potyvirus
Cassava brown streak potyvirus
Cassia yellow spot potyvirus
Celery mosaic virus
Chickpea bushy dwarf potyvirus
Chickpea distortion mosaic potyvirus
Chilli ringspot virus[9]
Chilli veinal mottle virus
Clitoria chlorosis virus
Clover yellow vein virus
Cocksfoot streak virus
Commelina diffusa potyvirus
Commelina mosaic virus
Cowpea green vein-banding potyvirus
Cowpea Moroccan aphid-borne mosaic potyvirus
Cowpea rugose mosaic potyvirus
Crinum mosaic potyvirus
Daphne Y potyvirus
Dasheen mosaic potyvirus
Datura Colombian potyvirus
Datura distortion mosaic potyvirus
Datura necrosis potyvirus
Datura shoestring potyvirus
Dendrobium mosaic potyvirus
Desmodium mosaic potyvirus
Dioscorea alata potyvirus
Dioscorea green banding mosaic potyvirus
Eggplant green mosaic potyvirus
Euphorbia ringspot potyvirus
Freesia mosaic potyvirus
Groundnut eyespot potyvirus
Guar symptomless potyvirus
Guinea grass mosaic potyvirus
Hardenbergia mosaic virus
Helenium Y potyvirus
Henbane mosaic potyvirus
Hippeastrum mosaic potyvirus
Hyacinth mosaic potyvirus
Iris fulva mosaic potyvirus
Iris mild mosaic potyvirus
Iris severe mosaic potyvirus
Japanese hornwort mosaic virus
Johnsongrass mosaic virus
Kennedya Y potyvirus
Leek yellow stripe potyvirus
Lettuce mosaic potyvirus
Lily mottle potyvirus
Lupine potyvirus
Maize dwarf mosaic potyvirus
Malva vein clearing potyvirus
Marigold mottle potyvirus
Narcissus yellow stripe potyvirus
Nerine potyvirus
Onion yellow dwarf potyvirus
Ornithogalum mosaic potyvirus
Papaya ringspot potyvirus
Parsnip mosaic potyvirus
Passiflora ringspot potyvirus
Passiflora South African potyvirus
Passiflora virus Y
Passionfruit woodiness virus
Patchouli mosaic potyvirus
Pea mosaic potyvirus
Pea seed-borne mosaic potyvirus
Peanut green mosaic potyvirus
Peanut mottle virus
Pepper Indian mottle potyvirus
Pepper mottle virus
Pepper severe mosaic potyvirus
Pepper vein banding virus
Pepper veinal mottle potyvirus
Plum pox potyvirus
Pokeweed mosaic potyvirus
Potato A potyvirus
Potato V potyvirus
Potato virus Y (type species)
Primula mosaic potyvirus
Ranunculus mottle potyvirus
Shallot yellow stripe potyvirus
Sorghum mosaic potyvirus
Soybean mosaic virus
Statice Y potyvirus
Sugarcane mosaic virus
Sweet potato feathery mottle potyvirus
Sweet potato G potyvirus
Sweet potato latent virus
Swordbean distortion mosaic potyvirus
Sunflower chlorotic mottle virus
Tamarillo mosaic potyvirus
Telfairia mosaic potyvirus
Tobacco etch virus
Tobacco vein-banding mosaic potyvirus
Tobacco vein mottling potyvirus
Tobacco wilt potyvirus
Tomato Peru potyvirus
Tradescantia mosaic virus
Triteleia mosaic virus
Tropaeolum 1 potyvirus
Tropaeolum 2 potyvirus
Tuberose potyvirus
Tulip band-breaking potyvirus
Tobacco vein banding mosaic virus
Tulip breaking potyvirus
Tulip chlorotic blotch potyvirus
Turnip mosaic potyvirus
Tradescantia mosaic virus
Ullucus mosaic potyvirus
Vallota mosaic potyvirus
Vanilla mosaic potyvirus
Vanilla necrosis potyvirus
Voandzeia distortion mosaic potyvirus
Watermelon mosaic virus
Wild potato mosaic potyvirus
Wisteria vein mosaic potyvirus
Yam mosaic potyvirus
Zucchini yellow fleck potyvirus
Zucchini yellow mosaic virus

Possible additional viruses[edit]

A number of viruses that have not been fully characterised may also belong in this genus:

Asystasia gangetica mottle potyvirus
Celery latent potyvirus
Datura mosaic potyvirus
Endive necrotic mosaic potyvirus
Kalanchoe mosaic potyvirus
Konjak mosaic potyvirus
Nasturtium mosaic potyvirus
Patchouli mottle potyvirus
Shallot yellow stripe potyvirus
Sweet potato vein mosaic potyvirus
Welsh onion yellow stripe potyvirus

Geographical spread[edit]

Agriculture was introduced into Australia in the 18th century. This introduction also included plant pathogens. Thirty eight potyvirus species have been isolated in Australia. Eighteen potyviruses have been found only in Australia and are presumed to be endemic there. The remaining twenty appear to have been introduced with agriculture.

References[edit]

  1. ^ Gibbs AJ, Ohshima K, Phillips MJ, Gibbs MJ, 2008 The Prehistory of potyviruses: Their initial radiation was during the dawn of agriculture. PLoS ONE 3(6): e2523. doi:10.1371/journal.pone.0002523
  2. ^ Gibbs A, Ohshima K (2010) Potyviruses and the digital revolution. Annu Rev Phytopathol 48:205-223.
  3. ^ Chung BY, Miller WA, Atkins JF, Firth AE (2008) An overlapping essential gene in the Potyviridae. Proc Natl Acad Sci U S A 105: 5897–5902
  4. ^ Léonard S, Plante D, Wittmann S, Daigneault N, Fortin MG, Laliberté JF (2000) Complex formation between potyvirus VPg and translation eukaryotic initiation factor 4E correlates with virus infectivity. J Virol 74(17):7730-7737
  5. ^ Materials and Methods for the Detection of Viral Inclusions
  6. ^ Christie, R.G. and Edwardson, J.R. (1977). Fla Agric. Exp. Stn Monog. No. 9, 150 pp.
  7. ^ How do you diagnose a virus infection in a plant?
  8. ^ Florida Department of Agriculture and Consumer Services: Florida plant viruses and their inclusions - Potyvirus
  9. ^ Gong D, Wang JH, Lin ZS, Zhang SY, Zhang YL, Yu NT, Xiong Z, Liu ZX (2011) Genomic sequencing and analysis of Chilli ringspot virus, a novel potyvirus. Virus Genes

Bibliography[edit]

External links[edit]