''Bidensovirus'' is a genus of single stranded DNA viruses that infect invertebrates. The species in this genus were originally classified in the family ''

Parvoviridae Parvoviruses are a family of animal viruses that constitute the family ''Parvoviridae''. They have linear, single-stranded DNA (ssDNA) genomes that typically contain two genes encoding for a replication initiator protein, called NS1, and the pr ...

'' (subfamily '' Densovirinae'') but were moved to a new genus because of significant differences in the genomes.Virus Taxonomy: Ninth Report of the International Committee on Taxonomy of Viruses (2011)

Taxonomy

There is one species in this genus currently recognised: ''Bombyx mori bidensovirus''.

Host

As the name suggests this virus infects ''

Bombyx mori The domestic silk moth (''Bombyx mori''), is an insect from the moth family Bombycidae. It is the closest relative of ''Bombyx mandarina'', the wild silk moth. The silkworm is the larva or caterpillar of a silk moth. It is an economically imp ...

'', the silkworm.

Virology

The virions are

icosahedral In geometry, an icosahedron ( or ) is a polyhedron with 20 faces. The name comes and . The plural can be either "icosahedra" () or "icosahedrons". There are infinitely many non- similar shapes of icosahedra, some of them being more symmetrica ...

, non enveloped and ~25

nanometer 330px, Different lengths as in respect to the molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American and British English spelling differences#-re ...

s in diameter. They contain two structural

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

The genome is bipartite, unique among ssDNA viruses, with two linear segments of ~6 and 6.5 kilobases (kb). These segments and the complementary strands are that are packaged separately giving rise to 4 different types of full particles. Both segments have an ambisense organization, coding for a structural protein in one sense and the non-structural proteins on the complementary strand. * DNA1 (aka VD1) — the larger segment of 6.5 kb — encodes the capsid protein VP1 (128 kDa — kiloDaltons) on one strand and three non-structural proteins — NS1 of 14 kDa, NS2 of 37 kDa and NS3 of 55 kDa — on the complementary strand. * DNA2 (aka VD2) — the smaller segment of 6 kb — encodes the capsid protein VP2 (133 kDa) on one strand and the non-structural protein NS4 (27 kDa) on the complementary strand. The

open reading frame In molecular biology, open reading frames (ORFs) are defined as spans of DNA sequence between the start and stop codons. Usually, this is considered within a studied region of a prokaryotic DNA sequence, where only one of the six possible readin ...

4 (VD1-ORF4) is 3318 nucleotides (bases) in length and encodes a predicted () 1105 amino acid protein which has a conserved DNA polymerase motif. It appears to encode at least 2 other proteins including one of ~53 kDa that forms part of the virion.

Evolution

Comprehensive analysis of bidnavirus genes has shown that these viruses have evolved from a

parvovirus Parvoviruses are a family of animal viruses that constitute the family ''Parvoviridae''. They have linear, single-stranded DNA (ssDNA) genomes that typically contain two genes encoding for a replication initiator protein, called NS1, and the p ...

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 separation 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 A transposable element (TE, transposon, or jumping gene) is a nucleic acid sequence in DNA that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genetic identity and genome size. Transpo ...

of the

Polinton Polintons (also called Mavericks) are large DNA transposons which contain genes with homology to viral proteins and which are often found in eukaryotic genomes. They were first discovered in the mid-2000s and are the largest and most complex kno ...

/Maverick family (polintoviruses) 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 ''Reoviridae'' is a family of double-stranded RNA viruses. Member viruses have a wide host range, including vertebrates, invertebrates, plants, protists and fungi. They lack lipid envelopes and package their segmented genome within multi-layere ...

'') and dsDNA viruses (''

Baculoviridae ''Baculoviridae'' is a family of viruses. Arthropods, among the most studied being Lepidoptera, Hymenoptera and Diptera, serve as natural hosts. Currently, 85 species are placed in this family, assigned to four genera. Baculoviruses are known ...

''), respectively.

References

External links

Bidensovirus ~ ViralZone page
The top image erraneously shows a monopartite genome, text and genome map are right (March 30, 2021). {{Taxonbar, from=Q4904115 Single-stranded DNA viruses Virus genera