Notes on Genus: Densovirus
Type member: Junonia coenia densovirus
This is one of the genera in the subfamily Densovirinae
, the insect pathogens in the family Parvoviridae
. Members are distinguished from those of the other genera by genome size (about 6kb), genomic organisation (particularly the ambisense strategy) and phylogenetic analysis.
Virions isometric (icosahedral), not enveloped, 18-26 nm in diameter, made of 60 units of the capsid protein.
Linear, single-stranded monopartite DNA, about 6 kb long. Both ends have palindromic sequences that can fold to form T-shaped structures. Both plus and minus strand DNAs are encapsidated, in approximately equal amounts.
Genus Genomic Organization
There is an ambisense coding strategy. Three non-structural proteins are encoded in different ORFs in one sense (using a single mRNA promoter and leaky scanning). On the complementary strand, a single structural ORF is translated by a leaky scanning strategy to produce virion proteins of different sizes.
Type Member Genomic Organization
There are 3 non-structural ORFs in one orientation:
- NS1, 22.5 kDa
- NS2, 31.19 kDa
- NS3, 63.4 kDa
The single capsid protein ORF (87.9 kDa) is in the opposite orientation. It is translated by leaky scanning to produce (probably 4) products of differing length (with the same C-terminus).