Notes on Genus: Potyvirus
Type member: Potato virus Y
This is the largest and best-studied genus in the family Potyviridae
. Like the other genera, it is characterised by its flexuous filamentous particles, inclusion bodies in infected plant cells and by having a polyprotein genome strategy. It differs from most of the other genera in having insect transmission, and from the genus Macluravirus
in having particles that are 700 nm or more in length. Like all the genera except the genus Bymovirus
, it has a monopartite genome. It is named after its type member, pot
ato virus Y
Virions filamentous, not enveloped, usually flexuous, 720-850 nm long and 12-15 nm in diameter. Symmetry helical with a pitch of 3.4 nm
Virions composed of 5 % nucleic acid and 95 % protein.
Monopartite, linear, single-stranded positive sense RNA up to about 10,000 nucleotides long. The 3' terminus has a poly(A) tract and the 5' terminus has a genome-linked protein (VPg).
Genus Genomic Organization
Genome organisation appears to be uniform throughout this genus and is similar to other members of the family Potyviridae
. The genome is translated into a single polyprotein, which is subsequently processed into ten, products with the coat protein at the C-terminus. An additional small ORF (PIPO) is generated by frameshifting within the third (P3) cistron.
Type Member Genomic Organization
The genome of about 9,700 nucleotides is translated into a single polyprotein, which is subsequently processed into at least eight, and probably ten, products:
|P1 protein||32.4 kDa|| unknown function|
|HC-Pro ||51.9 kDa||helper component (insect transmission) |
|P3 protein||41.5 kDa|| unknown function|
|6K1 || 6.0 kDa||unknown function|
|CI ||71.4 kDa||Cylindrical inclusion protein possibly involved in cell to cell movement|
|6K2 ||5.5 kDa||unknown function|
|VPg ||21.7 kDa ||Genome-linked protein |
|NIa-pro ||27.7 kDa||Nuclear Inclusion proteinase|
|NIb ||59.8 kDa||Nuclear Inclusion polymerase|
|CP ||29.8 kDa||coat protein|
An additional small ORF (PIPO) is generated by frameshifting within the third (P3) cistron.