Group Group II (ssDNA) Rank Family | Order Unassigned | |
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Bidnaviridae is a family of single stranded DNA viruses. Members of this family infect invertebrates. These viruses were once considered members of the family Parvoviridae (subfamily Densovirinae) their genomes differ greatly from those viruses in size and coding strategy. Because of this they have been classified into a family of their own.
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Virology
This family uniquely among ssDNA viruses in having a bipartite linear genome.
The virons are icosahedral, not enveloped and ~25 nanometers in diameter. There are two structural proteins in the viron.
The genome consists of two linear ssDNA segments of ~6 and 6.5 kilobases (kb) that are packaged separately. The complementary strands are also packaged giving rise to 4 distinct types of full particles. The total genome length is ~13 kb while that the parvoviruses is 4–6 kb.
Evolution
Comprehensive analysis of the bidnavirus genes has shown that these viruses have evolved from a parvovirus ancestor from which they inherit a jelly-roll capsid protein and a superfamily 3 helicase. It has been further suggested that the key event that led to the secession of the bidnaviruses from parvoviruses was the acquisition of the PolB gene. A likely scenario has been proposed under which the ancestral parvovirus genome was integrated into a large virus-derived DNA transposon of the Polinton/Maverick (polintovirus) family resulting in the acquisition of the polintovirus PolB gene along with terminal inverted repeats. Bidnavirus genes for a minor structural protein (putative receptor-binding protein) and a potential novel antiviral defense modulator were derived from dsRNA viruses (Reoviridae) and dsDNA viruses (Baculoviridae), respectively.
Taxonomy
Only one genus in this family is currently recognised - Bidensovirus.