Notes on Genus: Idaeovirus
Type member: Raspberry bushy dwarf virus
The genus Idaeovirus
currently consists of one virus, raspberry bushy dwarf, and the name is derived from the scientific name for raspberry, Rubus idaeus
. It was originally placed with the genus Ilarvirus
in the family Bromoviridae
because of its isometric particles, pollen-associated transmission and multi-partite genome. Now that sequence data is available, it is clear that the genome strategy is quite distinct, justifying a genus separate from that family.
Virions isometric (icosahedral) but slightly flattened, not enveloped, of three types but similar in size (33 nm). The nucleocapsids appear to be angular.
Virions composed of 24 % nucleic acid and 76 % protein.
Three components (2 genomic and 1 subgenomic), linear, single stranded, positive sense RNA distributed among the particles which can therefore be separated on their densities. The three RNAs have c.
5400 (RNA1), 2200 (RNA2) and 1000 (subgenomic RNA3) nucleotides. The 3'-terminal regions of the RNAs may form a stem loop structure.
Genus Genomic Organization
RNA1 has a single open reading frame, RNA2 has two open reading frames and RNA3 is the encapsidated subgenomic of RNA2 expressing the coat protein
Type Member Genomic OrganizationRNA1 has a single open reading frame:
1. 191.1 kDa Polymerase: multi-function replication protein containing methyl transferase, helicase and RNA polymerase domains
RNA2 has two open reading frames:
2. Movement protein, 38.9 kDa with some homology to the alfalfa mosaic virus 32 kDa protein (3a)
3. Coat protein, 30.5 kDa
RNA3 is an encapsidated subgenomic expressing the coat protein