Potyvirus
| Potyvirus | |
|---|---|
 |
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| Genome of typical potyvirus PPV with proteolytic cleavage sites | |
| Virus classification | |
| Group: | Group IV ((+)ssRNA) |
| Family: | Potyviridae |
| Genus: | Potyvirus |
| Type species | |
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Potato virus Y |
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Potyvirus is a genus of viruses, in the family Potyviridae. Plants serve as natural hosts. There are currently 158 species in this genus including the type species Potato virus Y. The genus is named after the type virus (Potato virus Y). Potyviruses account for ~30% of the currently known plant viruses. Like Begomoviruses, members of this genus may cause significant losses in agricultural, pastoral, horticultural and ornamental crops. More than 200 species of aphids spread potyviruses and most are from the subfamily Aphidinae (genera Macrosiphum and Myzus).
Group: ssRNA(+)
The potyviruses evolved between 6,600 to 7,250 years ago. 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.
The virion is non-enveloped with a flexuous and 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 9000–12000 bases/nucleotides. Most potyviruses have non-segmented genomes, though a number of species are bipartite. 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 cistron also encodes a second protein—P3N-PIPO—which is generated by a +2 frameshift.
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.
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