Notes on Genus: Tritimovirus
Type member: Wheat streak mosaic virus
This is one of the genera 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 others in having mite transmission and from the genus Bymovirus
in having a monopartite genome. The viruses in this genus were previously regarded as members of the genus Rymovirus
, but have been separated into a new genus because of substantial differences in nucleotide homology and because the vector is a different species (Aceria tulipae
). The genus name is derived from Triti
cum, the genus name of the host of the type member, wheat streak mosaic virus.
Virions filamentous, not enveloped, usually flexuous, 680-750 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, 9000-10000 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 monopartite 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 is translated into a single polyprotein of 344 kDa, from which an estimated ten functional products are produced by proteolytic processing:
|P1 protein|| ||putative protease|| ||40 kDa |
|HC-Pro || || putative helper component protease|| ||44 kDa|
|P3 protein|| ||unknown function|| || 32 kDa|
|6K1|| ||unknown function|| ||6 kDa |
|CI || || Cylindrical inclusion putative helicase|| ||73 kDa|
|6K2|| ||unknown function|| || 6 kDa|
|VPg|| ||Genome-linked protein|| || 23 kDa|
|NIa|| ||Nuclear Inclusion putative protease|| ||26 kDa|
|NIb|| ||Nuclear Inclusion putative polymerase|| ||57 kDa|
|CP|| ||coat protein || ||37 kDa|
An additional small ORF (PIPO) is generated by frameshifting within the third (P3) cistron.