Densovirinae Explained

Densovirinae[1] is a subfamily of single-stranded DNA viruses in the family Parvoviridae.[2] [3] The subfamily has 11 recognized genera and 21 species.[4] Densoviruses are known to infect members of insect orders Blattodea, Diptera, Hemiptera, Hymenoptera, Lepidoptera, and Orthoptera, while some viruses infect and multiply in crustaceans such as shrimp or crayfish, or sea stars from phylum Echinodermata.[3]

Virology

Densoviruses are small (18–26 nanometers in diameter) and non enveloped. Virions are icosahedral in shape with triangulation number (T) = 1. There are 60 copies of the coat protein in the virion. Each copy has a shape described as a "quadrilateral 'kite-shaped' wedge", and the appearance of the surface is rough with many small projections. Virions do not appear to contain lipids.[5] [6]

Genomes are non-segmented, about 4–6 kilobases in length and usually contain two or three open reading frames. The 5' open reading frame encodes two nonstructural proteins (NS-1 and NS-2) and the 3' open reading frame encodes two or three capsid proteins (VP1, VP2, VP3). Both the 5' and 3' termini have hairpin loops. If a third open reading frame is present (depends on the genus) it encodes a second non structural protein. The genome is ambisense, encoding proteins on both the positive sense and negative sense directions. Transcriptional regulation and post-transcriptional modification are used to produce different nonstructural proteins and structural proteins.[7] [8] [9]

Virions enter the host cell is achieved by attachment to host receptors, which may be mediated by clathrin-mediated endocytosis or clathrin-independent dynamin-dependent endocytosis.[10] The NS-1 protein has a superfamily 3 DNA helicase and an HuH endonuclease motif. These motifs are common in small DNA viruses. The proteins that contain these motifs bind to the viral origins of replication and unwind and nick these origins, allowing access by the host's proteins to the viral genome for replication and transcription. The genome is replicated by a unique rolling hairpin mechanism. DNA-templated transcription, with some alternative splicing mechanism is the manner of transcription.[3] [11]

Taxonomy

Eleven genera are currently recognized, containing a combined 21 species:

Ambidensovirus was previously recognized as a genus, but in 2019 it was split into the six genera prefixed with Aqu-, Blatt-, Hemi-, Pefu-, Proto-, and Scindo-.[12]

Notes and References

  1. Web site: Subfamily: Densovirinae . 13 May 2020 . ICTV . ICTV Report on Virus Taxonomy (10th Report) .
  2. Cotmore . SF . Agbandje-McKenna . M . Canuti . M . Chiorini . JA . Eis-Hubinger . A . Hughes . J . Mietzsch . M . Modha . S . Ogliastro . M . Pénzes . JJ . Pintel . DJ . Qiu . J . Soderlund-Venermo . M . Tattersall . P . Tijssen . P . and the ICTV Report Consortium . 2019 . ICTV Virus Taxonomy Profile: Parvoviridae . Journal of General Virology . 100 . 3 . 367–368 . 10.1099/jgv.0.001212. 30672729. 6537627 .
  3. Web site: ICTV 10th Report (2018) Parvoviridae.
  4. Web site: Virus Taxonomy: 2020 Release . International Committee on Taxonomy of Viruses (ICTV) . March 2021 . 10 May 2021.
  5. Web site: Densovirinae . ICTVdB—The Universal Virus Database, version 4 . 12 May 2020.
  6. Simpson AA, Chipman PR, Baker TS, Tijssen P, Rossmann MG . The structure of an insect parvovirus (Galleria mellonella densovirus) at 3.7 A resolution . Structure . 6 . 11 . 1355–67 . November 1998 . 9817847 . 4167665 . 10.1016/S0969-2126(98)00136-1.
  7. Pham HT, Huynh OT, Jousset FX, Bergoin M, Tijssen P . Junonia coenia Densovirus (JcDNV) Genome Structure . Genome Announcements . 1 . 4 . August 2013 . 23929483 . 3738899 . 10.1128/genomeA.00591-13.
  8. Dumas B, Jourdan M, Pascaud AM, Bergoin M . Complete nucleotide sequence of the cloned infectious genome of Junonia coenia densovirus reveals an organization unique among parvoviruses . Virology . 191 . 1 . 202–22 . November 1992 . 1413502 . 10.1016/0042-6822(92)90182-O.
  9. Bruemmer A, Scholari F, Lopez-Ferber M, Conway JF, Hewat EA . Structure of an insect parvovirus (Junonia coenia Densovirus) determined by cryo-electron microscopy . Journal of Molecular Biology . 347 . 4 . 791–801 . April 2005 . 15769470 . 10.1016/j.jmb.2005.02.009.
  10. Wang Y, Gosselin Grenet AS, Castelli I, Cermenati G, Ravallec M, Fiandra L, Debaisieux S, Multeau C, Lautredou N, Dupressoir T, Li Y, Casartelli M, Ogliastro M . Densovirus crosses the insect midgut by transcytosis and disturbs the epithelial barrier function . Journal of Virology . 87 . 22 . 12380–91 . November 2013 . 24027326 . 3807927 . 10.1128/JVI.01396-13.
  11. Web site: Viral Zone. ExPASy. 12 May 2020.
  12. Web site: ICTV Taxonomy history: Ambidensovirus. talk.ictvonline.org. International Committee on Taxonomy of Viruses. 12 May 2020.

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