Bidensovirus

Bidensovirus is a genus of single stranded DNA viruses that infect invertebrates. The species in this genus were originally classified in the family Parvoviridae (subfamily Densovirinae) but were moved to a new genus because of significant differences in the genomes.[1]

Bidensovirus
Virus classification Edit this classification
(unranked): Virus
Realm: Monodnaviria
Kingdom: Shotokuvirae
Phylum: Cossaviricota
Class: Mouviricetes
Order: Polivirales
Family: Bidnaviridae
Genus: Bidensovirus
Species

Bombyx mori bidensovirus

Taxonomy

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

Host

As the name suggests this virus infects Bombyx mori, the silkworm.[2]

Virology

The virions are icosahedral, non enveloped and ~25 nanometers in diameter. They contain two structural proteins.

Genome map of genus Bidensovirus

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 4 (VD1-ORF4) is 3318 nucleotides (bases) in length and encodes a predicted (3318/3 - 1 =) 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.[3]

Evolution

Comprehensive analysis of 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.[4] 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 of the Polinton/Maverick family (polintoviruses) [5] 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.[4]

References
  1. Virus Taxonomy: Ninth Report of the International Committee on Taxonomy of Viruses (2011) ISBN 978-0123846846
  2. "Bidensovirus ~ ViralZone page".
  3. "Li G, Hu Z, Guo X, Li G, Tang Q, Wang P, Chen K, Yao Q Identification of Bombyx mori Bidensovirus VD1-ORF4 Reveals a Novel Protein Associated with Viral Structural Component. Curr Microbiol 66, 527–534 (2013)". doi:10.1007/s00284-013-0306-9.
  4. Krupovic M, Koonin EV (2014). "Evolution of eukaryotic single-stranded DNA viruses of the Bidnaviridae family from genes of four other groups of widely different viruses". Sci Rep. 4: 5347. doi:10.1038/srep05347. PMC 4061559. PMID 24939392.
  5. Krupovic M, Bamford DH, Koonin EV (2014). "Conservation of major and minor jelly-roll capsid proteins in Polinton (Maverick) transposons suggests that they are bona fide viruses". Biol Direct. 9 (1): 6. doi:10.1186/1745-6150-9-6. PMC 4028283. PMID 24773695.
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