Notes on Genus: Rymovirus
Type member: Ryegrass 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 (Abacarus hystrix
) and from the genus Bymovirus
in having a monopartite genome. Some viruses previously placed in this genus have now been moved to the new genus Tritimovirus
on the basis of substantial differences in nucleotide homology and because they have a different vector species (Aceria tulipae
). Recent sequence analyses have also shown that the species now remaining in the genus cluster with the genus Potyvirus
and, unlike other genera in the family, do not form a distinct cluster of their own. There are therefore proposals to abolish the genus. It is named after its type member, ry
Virions filamentous, usually flexuous, not enveloped, 690-720 nm long and 12-15 nm in diameter. Symmetry helical with pitch of 3.4 nm.
Virions composed of 5 % nucleic acid and 95 % protein.
Monopartite, linear, single stranded, positive sense RNA, 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 resembles 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 348 kDa, from which an estimated ten functional products are produced by proteolytic processing:
|P1 protein|| ||putative protease|| ||29 kDa |
|HC-Pro || || putative helper component protease|| ||52 kDa|
|P3 protein|| ||unknown function|| || 40 kDa|
|6K1|| ||unknown function|| ||6 kDa |
|CI || || Cylindrical inclusion putative helicase|| ||71 kDa|
|6K2|| ||unknown function|| || 6 kDa|
|VPg|| ||Genome-linked protein|| || 22 kDa|
|NIa|| ||Nuclear Inclusion putative protease|| ||27 kDa|
|NIb|| ||Nuclear Inclusion putative polymerase|| ||50 kDa|
|CP|| ||coat protein || ||44 kDa|
An additional small ORF (PIPO) is generated by frameshifting within the third (P3) cistron.