Ascoviridae

Ascoviridae is a family of double strand DNA viruses that infect primarily invertebrates, mainly noctuids and spodoptera species; it contains two genera, Ascovirus, which contains three species, and Toursvirus with a single species Diadromus pulchellus toursvirus.[1][2][3][4] The type species of Ascovirus is Spodoptera frugiperda ascovirus 1a, which infects the army worm (Spodoptera frugiperda).[5]

Ascoviridae
Virus classification
(unranked): Virus
Realm: Varidnaviria
Kingdom: Bamfordvirae
Phylum: Nucleocytoviricota
Class: Megaviricetes
Order: Pimascovirales
Family: Ascoviridae
Type species
Spodoptera frugiperda ascovirus 1a
Genera

Genome
Genome

The genome is not segmented and contains a single molecule of circular double-stranded DNA. The genome has a guanine + cytosine content of 42-60%.

The genome of Spodoptera frugiperda ascovirus 1a has been sequenced.[6] It is 156,922 bases in length and encodes 123 putative open reading frames. The G+C ratio is 49.2%. Among the encoded proteins are a caspase, a cathepsin B, several kinases, E3 ubiquitin ligases, a fatty acid elongase, a sphingomyelinase, a phosphate acyltransferase and a patatin-like phospholipase.[6]

Virology

The virions consist of an envelope, a core, and an internal lipid membrane associated with the inner particle. The virus capsid is enveloped and measures 130 nm in diameter, and 200-240 nm in length. Virions are bacilliform, ovoid, and allantoid.

GenusStructureSymmetryCapsidGenomic arrangementGenomic segmentation
AscovirusBacilliform, ovoidal or allantoidEnvelopedCircularMonopartite

[1][2][3]

These viruses infect immature stages of the order Lepidoptera, in which they cause a chronic, fatal disease.[7] They are transmissed by endoparasitic wasps and the host develops a unique cytopathology that resembles apoptosis. Cell infection induces apoptosis and in some species is associated with synthesis of a virus-encoded executioner caspase and several lipid-metabolizing enzymes. After infection the host cell DNA is degraded, the nucleus fragments and the cell then cleaves into large virion-containing vesicles. Synthesis of viral proteins results in the rescue of developing apoptotic bodies that are converted into large vesicles in which virions accumulate and continue to assemble. In infected larvae, millions of these virion-containing vesicles begin to disperse from infected tissues 48–72 hours after infection into the haemolymph, making it milky white, a characteristic of this disease. The circulation of virions and vesicles in the blood facilitates mechanical transmission by parasitic wasps.[7]

GenusHost detailsTissue tropismEntry detailsRelease detailsReplication siteAssembly siteTransmission
AscovirusInsects: NoctuidsMostCell receptor endocytosisCleavageNucleusCytoplasmMechanical

[1][2][3]

Evolution

Ascoviruses evolved from iridoviruses (family Iridoviridae) that also attack lepidopteran larvae and are likely the evolutionary source of ichnoviruses (family Polydnaviridae).[7]

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References
  1. Asgari, S; Bideshi, DK; Bigot, Y; Federici, BA; Cheng, XW; ICTV Report Consortium (January 2017). "ICTV Virus Taxonomy Profile: Ascoviridae". The Journal of General Virology. 98 (1): 4–5. doi:10.1099/jgv.0.000677. PMC 5370392. PMID 28218573.
  2. "Ascoviridae". ICTV Online (10th) Report.
  3. "Viral Zone". ExPASy. Retrieved 12 June 2015.
  4. ICTVdB Management (2006). 00.082.0.01. Ascovirus. In: ICTVdB - The Universal Virus Database, version 4. Büchen-Osmond, C. (Ed), Columbia University, New York, USA
  5. Xue, J. -L.; Cheng, X. -W. (2011). "Comparative analysis of a highly variable region within the genomes of Spodoptera frugiperda ascovirus 1d (SfAV-1d) and SfAV-1a". Journal of General Virology. 92 (12): 2797–802. doi:10.1099/vir.0.035733-0. PMID 21832004.
  6. Bideshi, D. K.; Demattei, M. -V.; Rouleux-Bonnin, F.; Stasiak, K.; Tan, Y.; Bigot, S.; Bigot, Y.; Federici, B. A. (2006). "Genomic Sequence of Spodoptera frugiperda Ascovirus 1a, an Enveloped, Double-Stranded DNA Insect Virus That Manipulates Apoptosis for Viral Reproduction". Journal of Virology. 80 (23): 11791–805. CiteSeerX 10.1.1.332.7512. doi:10.1128/JVI.01639-06. PMC 1642580. PMID 16987980.
  7. Federici, B. A.; Bideshi, D. K.; Tan, Y.; Spears, T.; Bigot, Y. (2009). "Ascoviruses: Superb Manipulators of Apoptosis for Viral Replication and Transmission". Lesser Known Large dsDNA Viruses. Current Topics in Microbiology and Immunology. 328. pp. 171–96. doi:10.1007/978-3-540-68618-7_5. ISBN 978-3-540-68617-0. PMID 19216438.
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