Ascovirus

Ascovirus
Systematics
Classification : Viruses Area : Varidnaviria Empire : Bamfordvirae Phylum : Nucleocytoviricota Class : Megaviricetes Order : Pimascovirales Family : Ascoviridae Genre : Ascovirus
Taxonomic characteristics
Genome : dsDNA circular Baltimore : Group 1 Symmetry : ovoid , allantoid Cover : available
Scientific name
Ascovirus
Left
NCBI  Taxonomy: 43680 ViralZone ( ExPASy , SIB): 276 ICTV Taxon History: 201852611 (type)

Ascovirus is a genus of viruses from the family Ascoviridae with double-stranded DNA (dsDNA). As of February 2019, this genus has three species. The type of ascovirus is Spodoptera frugiperda ascovirus 1a (SfAV-1a), whichinfectsthe owl butterfly Spodoptera frugiperda ( English fall armyworm ).

construction

The virus particles (virions) have a shell and a core. There is an inner lipid membrane connected to the inner part. The capsid is encased and has a diameter of 130  nm and a length of 200 to 240 nm. Virions are bacilli-shaped , egg-shaped ( ovoid ) and sausage-shaped ( allantoid ).

Genome

Genome of Spodoptera frugiperda ascovirus 1a , here abbreviated as SvAV-1a

Larva of Spodoptera frugiperda

The genome is unsegmented and contains a single molecule of circular double-stranded DNA . The genome has a GC content of 42–60% .

• The genome of the type species Spodoptera frugiperda ascovirus 1a (SfAV-1a) was sequenced . It has a length of 156 922 bp and encodes putative 123 open reading frames ( English open reading frames , ORFs). The GC content here is 49.2%. To the encoded proteins include a caspase , a cathepsin B , several kinases , E3 ubiquitin ligases , a fatty acid elongase , a sphingomyelinase , a phosphate acyltransferase and a patatinähnliche phospholipase ( English patatin-like phospholipase ).
• The genome of Diadromus pulchellus ascovirus 4a is 119,343 bp in length and is expected to encode 119 proteins.

Transmission and cycle of reproduction

The viruses of the genus Ascovirus infect immature stages of butterflies (insect order Lepidoptera ), in which they cause a chronic, fatal disease. They are transmitted by endoparasitic wasps and the host develops a unique cytopathology similar to apoptosis . The infection of the cell causes apoptosis and, in some species with the synthesis of a virus-encoded "executioner caspase" ( English executioner caspase ) and several lipid-metabolizing enzymes, respectively. After infection, the host cell's DNA is broken down, and the nuclear fragments and the cell then split into large vesicles containing the virions. The synthesis of the virus proteins leads to apoptosis bodies being converted into large vesicles in which the virions accumulate more and more. In infected larvae, 48 to 72 hours after infection, millions of these virion-containing vesicles begin to distribute from the infected tissue into the hemolymph , making it milky white, which is a characteristic of this disease.

Systematics

Ascoviruses possibly evolved from iridoviruses (family Iridoviridae ), which also infect butterfly larvae and are likely the evolutionary source of ichnoviruses (genus Ichnovirus of the apparently polyphyletic family Polydnaviridae ).

The internal systematics of the genus Ascovirus as of February 2019 according to ICTV is as follows:

• Family: Ascoviridae

• Genus Ascovirus

• Species Heliothis virescens ascovirus 3a (alias Heliothis virescens ascovirus , HvV, HVAV or HvAV-3a)

• Subtype: HvAV-3a
• Subtype: HvAV-3b
• Subtype: HvAV-3c
• Subtype: HvAV-3e (ICTV: Asgari et al. , 2007, sequencing)
• Subtype: HvAV-3g (ICTV: Huang et al. , 2012, sequencing)
• Subtype: HvAV-3f (ICTV: Wei et al. , 2014, sequencing)

• Species Spodoptera frugiperda ascovirus 1a (SfV or SfAV-1a, type species) (ICTV: Bideshi et al. , 2006, sequencing)
• Species Trichoplusia ni ascovirus 2a (alias Trichoplusia ni ascovirus , TnV, TNAV or TnAV-2a)

Other candidates are:

• Helicoverpa armigera ascovirus 7a (HaAV-7a)
• Helicoverpa punctigera ascovirus 8a (HpAV-8a)
• Spodoptera exigua ascovirus 5a (SeAV-5a)
• Spodoptera exigua ascovirus 6a (SeAV-6a)
• Trichoplusia ni ascovirus 6a (outdated 2c, ICTV: Wang et al. , 2006, sequencing)

The species Diadromus pulchellus ascovirus 4a (DpV or DpAV-4a) (ICTV: Bigot et al. , 2009, sequencing) with a genome length of 186,262 bp and probably encoded 180 proteins has meanwhile been identified by the ICTV as Diadromus pulchellus toursvirus 4a (DpTV-4a ) placed in a newly established genus Toursvirus , which is thus a sister genus of Ascovirus - other of the candidates listed above may also have to be placed in this new genus.

For the exact relationships within the genus Ascovirus , the ICTV suggests the following cladogram:

Ascovirus	HvAV-3g     SfAV-1a     TnAV-6a

Individual evidence

1. ↑ ^{a b c d e} ICTV: ICTV Taxonomy history: Spodoptera frugiperda ascovirus 1a , EC 51, Berlin, Germany, July 2019; Email ratification March 2020 (MSL # 35)
2. ↑ ^{a b} S Asgari, DK Bideshi, Y Bigot, BA Federici, XW Cheng, ICTV Report Consortium: ICTV Virus Taxonomy Profile: Ascoviridae. . In: The Journal of General Virology . 98, No. 1, January 2017, pp. 4–5. doi : 10.1099 / jgv.0.000677 . PMID 28218573 . PMC 5370392 (free full text).
3. ↑ ^{a b c d e f g h i} ICTV : dsDNA Viruses> Ascoviridae ( en ), December 2016
4. ↑ ^{a b c} ViralZone: Ascovirus . ExPASy. Retrieved July 23, 2019.
5. ↑ J.-L. Xue, X.-W. Cheng: Comparative analysis of a highly variable region within the genomes of Spodoptera frugiperda ascovirus 1d (SfAV-1d) and SfAV-1a . In: Journal of General Virology . 92, No. 12, 2011, p. 2797. doi : 10.1099 / vir.0.035733-0 .
6. ↑ ^{a b} D. K. Bideshi, M.-V. Demattei, F. Rouleux-Bonnin, K. Stasiak, Y. Tan, S. Bigot, Y. Bigot, BA Federici: Genomic Sequence of Spodoptera frugiperda Ascovirus 1a , an Enveloped, Double-Stranded DNA Insect Virus That Manipulates Apoptosis for Viral Reproduction . In: Journal of Virology . 80, No. 23, 2006, p. 11791. doi : 10.1128 / JVI.01639-06 . PMID 16987980 .
7. ↑ ^{a b c} Disa Bäckström, Natalya Yutin, Steffen L. Jørgensen, Jennah Dharamshi, Felix Homa, Katarzyna Zaremba-Niedwiedzka, Anja Spang, Yuri I. Wolf, Eugene V. Koonin, Thijs JG Ettema; Richard P. Novick (Ed.): Virus Genomes from Deep Sea Sediments Expand the Ocean Megavirome and Support Independent Origins of Viral Gigantism , in: mBio Vol. 10, No. 2, March – April 2019, pp. E02497-18, PDF , doi: 10.1128 / mBio.02497-18 , PMC 6401483 (free full text), PMID 30837339 , ResearchGate
8. ↑ ^{a b c} B. A. Federici, DK Bideshi, Y. Tan, T. Spears, Y. Bigot: Lesser Known Large dsDNA Viruses (=  Current Topics in Microbiology and Immunology . Vol. 328). 2009, ISBN 978-3-540-68617-0 , Ascoviruses: Superb Manipulators of Apoptosis for Viral Replication and Transmission, pp. 171-196 , doi : 10.1007 / 978-3-540-68618-7_5 , PMID 19216438 .
9. ↑ ^{a b c} William H Wilson,. * Ilana C Gilg, Mohammad Moniruzzaman, Erin K Field, Sergey Koren, Gary R LeCleir, Joaquín Martínez Martínez, Nicole J Poulton, Brandon K Swan, Ramunas Stepanauskas, Steven W Wilhelm: Genomic exploration of individual giant ocean viruses , in: ISME Journal 11 (8), August 2017, pp. 1736–1745, doi: 10.1038 / ismej.2017.61 , PMC 5520044 (free full text), PMID 28498373
10. ↑ ^{a b c d} Padhoe: Famili (e) Ascoviridae , October 15, 2011

Web links

• ICTV Online (10th) Report: Ascoviridae