Notes on Genus: Varicosavirus
Type member: Lettuce big-vein associated virus
Members of this genus have rather labile rod shaped particles and are transmitted internally in spores of the chytrid fungus Olpidium brassicae
. The name arises from the apparently swollen (varicose) veins that were thought to be caused in lettuce by the type member. Unfortunately, recent data suggest that these symptoms are actually caused by Mirafiori lettuce big-vein virus, a member of the genus Ophiovirus
, with which LBVaV is often associated.
Virions rod-shaped, not enveloped, straight or slightly flexuous, with distinct central canal. They are 320-360 nm long and c.
18 nm wide, with a pitch of 5nm.
Although orginally believed to be dsRNA and possibly bipartite, it is now known to be bipartite single stranded negative sense RNA.
Genus Genomic Organization
Only the type member has been sequenced. RNA1 is about 6.8kb and encodes a single polymerase gene while the coat protein and other products of unknown function are encoded on RNA2 (6.1 kb).
Type Member Genomic Organization
RNA1 (6.8 kb) encodes a 232 kDa polymerase (L) gene in the negative sense.
RNA2 (6.1 kb) also codes in the negative sense. The genes identified are listed here in their order on the template strand (i.e. from 3' to 5' with respenct to the virion strand):
- Coat protein (44kDa)
- Protein 2 (36 kDa) unknown function
- Protein 3 (32 kDa) unknown function
- Protein 4 (19 kDa) unknown function
- Protein 5 (41 kDa) unknown function
The coding strategy and the sequences of the polymerase and coat protein show similarity to rhabdoviruses.