Ascoviridae

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Ascoviridae
Systematics
Classification : Viruses
Area : Varidnaviria
Empire : Bamfordvirae
Phylum : Nucleocytoviricota
Class : Megaviricetes
Order : Pimascovirales
Family : Ascoviridae
Taxonomic characteristics
Genome : dsDNA circular
Baltimore : Group 1
Symmetry : complex , ovoid
Cover : available
Scientific name
Ascoviridae
Left
NCBI  Taxonomy: 43680
ViralZone ( ExPASy , SIB): 139
ICTVdB Virus Code : 00.082.0.01

The Ascoviridae (ascoviruses) are a family of viruses with the type genus Ascovirus , which belonged to the phylum of the Nucleocytoviricota (outdated Nucleocytoplasmic large DNA viruses , NCLDV; earlier proposals had been called " Nucleocytoplasmaviricota " or - in the rank of an order - " Megavirales ") becomes. These are enveloped viruses with a double-stranded, circular DNA as genome , which so far have only been found in insects of the order butterflies ( Lepidoptera ). The name of the family is derived from the Greek ασκός 'tube, sachet' , which indicates the constriction of virus-containing membrane vesicles in infected cells, which is typical for ascoviruses. The family's first virus species was discovered in 1983.

Several studies since 2000 support the assumption that the Ascoviridae evolved from the Iridoviridae .

morphology

The enveloped virions of the Ascoviridae have an irregular, elongated, oval shape with a diameter of about 130 nm and a length of 200-400 nm. They consist of a virus envelope with a net-like surface and an internal particle structure. This inner particle is formed by a capsid with complex symmetry and an inner lipid membrane wrapped around it . This second inner membrane is reminiscent of the structure of the Poxviridae , with which the ascoviruses do not otherwise share any sequence similarities .

Genome and reproduction

The circular genome of the ascoviruses sequenced so far is between 120 and 180 kBp in size; This makes them one of the largest viruses, along with the Herpesvirales and Poxviridae . At least 15 polyproteins can be derived from the not yet fully understood open reading frames of the genome . The reproduction of the genome and the assembly of the capsid takes place in the nucleus of the insect cell , which swells up and tears the nuclear membrane . Typical membrane folds and multiple constrictions form inside the cell. The capsids formed first are covered with a de novo formed lipid membrane and this inner particle is covered with the virus envelope by budding on the cell membrane .

Biological properties

Larva of Spodoptera frugiperda
The parasitic wasp Aleiodes indiscretus laying eggs in a moth larva

Ascoviruses infect the larvae of butterflies and moths, mainly from the family Noctuidae (owl butterflies). The larvae die in a chronic ascovirus infection and their development has previously been considerably slowed down; The virus multiplies mainly in the fatty tissue of the caterpillars. The ascoviruses are likely to be found worldwide wherever species of owl butterfly can be found.

So far, different virus species have been isolated from species of the Noctuidae family, namely from Spodoptera frugiperda , Trichoplusia ni , Heliothis virescens , Helicoverpa spp. and Autographa precationis . An infection has also been described in the leek moth Acrolepiopsis assectella (family Yponomeutidae ). The virus species TnAV-2a and HvAV-3a can be found in several butterfly species and can reproduce experimentally in insect cells from a large number of species of the Noctuidae family. The reproduction of SfAV-1a is strictly limited to the species Spodoptera frugiperda .

The virus is transmitted by parasitic parasitic wasps (families Brachonidae and Ichneumonidae ), whose oviposition apparatus ( ovipositor ) is contaminated when the eggs are laid in infected caterpillars. If the eggs are laid again in other caterpillars, the virus can spread further. In a wasp species ( Diadromus pulchellus ), the genome of the ascovirus DpTV-4a is present in the cell nuclei in a non-integrated form, so that the virus is already transmitted to the wasp eggs within the transmitting (but not diseased) wasp population.

Systematics

Internal system

The classification of the Ascoviridae according to the International Committee on Taxonomy of Viruses (ICTV), as of June 2019 (ICTV Master Species List 2018b of February 2019, MSL # 34) is:

  • Family Ascoviridae
  • Species Spodoptera frugiperda ascovirus 1a (SfV or SfAv-1a)
  • Species Heliothis virescens ascovirus 3a (HvV or HvAV-3a, three subtypes 3a, 3b, 3c)
  • Species Trichoplusia-ni-Ascovirus 2a (TnV or TnAV-2a)
  • Species Diadromus pulchellus toursvirus 4a (DpTV) -4a, formerly Diadromus pulchellus ascovirus 4a (DpAV-4a)

In addition, provisionally classified species of the Ascoviridae family :

  • Species Helicoverpa armigera ascovirus 7a (HaAV-7a)
  • Species Helicoverpa punctigera ascovirus 8a (HpAV-8a)
  • Species Spodoptera exigua ascovirus 5a (SeAV-5a)
  • Species Spodoptera exigua ascovirus 6a (SeAV-6a)

The ICTV suggests the following cladogram for the exact relationships within the Ascoviridae family :

 Ascoviridae  
 Ascovirus 


HvAV-3g


   

SfAV-1a



   

TnAV-6a



 Tours virus 

DpTV



Template: Klade / Maintenance / Style

External system

Based on sequence studies, it can be assumed that the Ascoviridae and the morphologically very different Iridoviridae share a common ancestor.

A cladogram of the Asco and Iridiviridae can be found at ICTV, and in Fenner's Veterinary Virology (Fifth Edition) 2017 According to this, the Iridoviridae are a sister group of the genus Toursvirus (with DpTV alias DpAV), while the genus Ascovirus occupies a basal position in the common clade . According to Andreani et al. (2018), conversely, the Ascoviridae are a sister group of the Alphairidovirinae , while here the Betairidovirinae are in the basal clade. This view is also supported by Rolland et al. (2019) supported. In addition to the subfamilies of the Iridoviridae , the Ascoviridae appear as a subfamily within a common family " Irido-Ascoviridae ".

It is also assumed that the genus Ichnovirus (family Polydnaviridae ) developed from the Ascoviridae .

Individual evidence

  1. ↑ a b c d e f ICTV: ICTV Taxonomy history: Spodoptera frugiperda ascovirus 1a , EC 51, Berlin, Germany, July 2019; Email ratification March 2020 (MSL # 35)
  2. ↑ Eugene V. Koonin, Natalya Yutin: Evolution of the Large Nucleocytoplasmatic DNA Viruses of Eukaryotes and Convergent Origins of Viral Gigantism , in: Advances in Virus Research, Volume 103, AP January 21, 2019, doi: 10.1016 / bs.aivir.2018.09 .002 , pp. 167-202. Egg-shaped three-dimensional bodies are referred to as ovoid.
  3. ↑ BA Federici: Enveloped double-stranded DNA insect virus with novel structure and cytopathology. In: PNAS. 80, 24, 1983, pp. 7664-7668. PMID 16593397
  4. ↑ K. Stasiak, MV Demattei, BA Federici, Y. Bigot: Phylogenetic position of the Diadromus pulchellus ascovirus DNA polymerase among viruses with large double-stranded DNA genomes . In: The Journal of General Virology . tape 81 , Pt 12, December 2000, p. 3059-3072 , doi : 10.1099 / 0022-1317-81-12-3059 , PMID 11086137 .
  5. ↑ K. Stasiak, S. Renault, MV Demattei, Y. Bigot, BA Federici: Evidence for the evolution of ascoviruses from iridoviruses . In: The Journal of General Virology . tape 84 , Pt 11, November 2003, p. 2999-3009 , doi : 10.1099 / vir.0.19290-0 , PMID 14573805 .
  6. ↑ a b B. A. Federici, DK Bideshi, Y. Tan, T. Spears, Y. Bigot: Ascoviruses: superb manipulators of apoptosis for viral replication and transmission . In: Current Topics in Microbiology and Immunology . tape 328 , 2009, ISBN 978-3-540-68617-0 , pp. 171-196 , doi : 10.1007 / 978-3-540-68618-7_5 , PMID 19216438 .
  7. ↑ B. Piégu, S. Asgari, D. Bideshi, BA Federici, Y. Bigot: Evolutionary relationships of iridoviruses and divergence of ascoviruses from invertebrate iridoviruses in the superfamily Megavirales . In: Molecular Phylogenetics and Evolution . tape 84 , March 2015, p. 44-52 , doi : 10.1016 / j.ympev.2014.12.013 , PMID 25562178 .
  8. ↑ R. Govindarajan, BA Federici: Ascovirus infectivity and effects of infection on the growth and development of noctuid larvae. In: J. Invertebr. Pathology. 56, 3, 1990, pp. 291-299. PMID 2250099
  9. ↑ Y. Bigot, A. Rabouille et al. : Biological and molecular features of the relationships between Diadromus pulchellus ascovirus, a parasitoid hymenopteran wasp (Diadromus pulchellus) and its lepidopteran host, Acrolepiopsis assectella. In: J. Gen. Virol. 78, 5, 1997, pp. 1149-1163. PMID 9152436
  10. ↑ a b dsDNA Viruses> Ascoviridae , on: ICTV online, December 2016 (here: Fig. 2)
  11. ↑ Fenner's Veterinary Virology (Fifth Edition): Chapter 8 - Asfarviridae and Iridoviridae , online November 4, 2016, pp. 175–188, doi: 10.1016 / B978-0-12-800946-8.00008-8 (here: Fig. 1 )
  12. ↑ Julien Andreani, Jacques YB Khalil, Emeline Baptiste, Issam Hasni, Caroline Michelle, Didier Raoult, Anthony Levasseur, Bernard La Scola: Orpheovirus IHUMI-LCC2: A New Virus among the Giant Viruses , in: Front. Microbiol., January 22, 2018, doi: 10.3389 / fmicb.2017.02643
  13. ↑ Clara Rolland, Julien Andreani, Amina Cherif Louazani, Sarah Aherfi, Rania Francis, Rodrigo Rodrigues, Ludmila Santos Silva, Dehia Sahmi, Said Mougari, Nisrine Chelkha, Meriem Bekliz, Lorena Silva, Felipe Assis, Fábio Dornas, Jacques Yaacoub Bou Khalil, Isabelle Pagnier, Christelle Desnues, Anthony Levasseur, Philippe Colson, Jônatas Abrahão, Bernard La Scola: Discovery and Further Studies on Giant Viruses at the IHU Mediterranee Infection That Modified the Perception of the Virosphere , in: Viruses 11 (4), March / April 2019, pii: E312, doi: 10.3390 / v11040312 , PMC 6520786 (free full text), PMID 30935049 , Fig. 2

literature

  • BA Federici et al. : Family Ascoviridae, Genus Ascovirus. In: CM Fauquet, MA Mayo et al : Eighth Report of the International Committee on Taxonomy of Viruses. London / San Diego 2004, 2,269-274
  • David M. Knipe, Peter M. Howley, et al. (Ed.): Fields' Virology ,. 4th edition. Philadelphia 2001.

Web links