Ascovirus

The Ascoviridae family with the single genus Ascovirus comprises enveloped viruses with a double-stranded, circular DNA genome as that can only be found in insects of the order butterflies ( Lepidoptera). The name of the family is derived from the Greek ασκός for " hose bag " from, indicating the typical for the Ascoviren pinch of virus-containing membrane vesicles in infected cells. The first virus species of the family was discovered in 1983.

Morphology

The enveloped virions of Ascoviridae have an irregular, elongated, oval shape having a diameter of about 130 nm and a length of 200-400 nm, and they are made of a viral envelope with a grid -shaped surface and an internal particle structure. This particle is formed by an inner capsid and a complex symmetry thereabout defined inner lipid membrane. This second inner membrane is reminiscent of the structure of the Poxviridae, but otherwise share with those who Ascoviren no sequence similarities.

Genome and propagation

The circular genome of the previously sequenced Ascoviren is between 120 and 180 kbp; that they belong together with the Herpesviridae and Poxviridae the largest viruses. From the not yet fully enlightened open reading frame of the genome at least 15 polyproteins derived. The replication of the genome and of the assembly of the capsid occurs in the nucleus of insect cell, said swell, and the nuclear membrane breaks. Results in the formation of typical membrane wrinkles and multiple constrictions inside the cell. The capsids formed first be clothed with a de novo formed lipid membrane and this inner particle is cased by budding at the cell membrane with the viral envelope.

Biological Properties

Ascoviren infect the larvae of butterflies and moths mostly from the family Noctuidae ( cutworms ). The larvae die in a chronic Ascovirus infection, and previously slowed considerably in their development; multiplication of the virus occurs mainly in adipose tissue of the caterpillars. The Ascoviren are likely to spread throughout the world wherever cutworm species are to be found.

So far, different virus species from species of the Noctuidae family were isolated, namely in Spodoptera frugiperda, Trichoplusia ni, Heliothis virescens, Helicoverpa spp. and Autographa precationis. Infection is also 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 be experimentally reproduce in insect cells from many species of the family Noctuidae. The proliferation of SFAV -1a is strictly limited to the species Spodoptera frugiperda.

Transmission of the virus occurs through parasitic ichneumon wasps ( Family Brachonidae and Ichneumonidae ), the egg-laying apparatus ( ovipositor ) is contaminated laying eggs in infected caterpillars. On re oviposition in other tracked the virus can be circulated. When a wasp ( Diadromus pulchellus ) the genome of the Ascovirus DPAV -4a in non- integrated form in the nuclei is available, so that even within the transferor (but not sick ) wasp population, the virus is already transferred to the wasp eggs.

System

• Family Ascoviridae

• Genus Ascovirus

• Species Spodoptera frugiperda Ascovirus 1a ( SFAV -1a)
• Species Diadromus - pulchellus - Ascovirus 4a ( DPAV -4a )
• Species Heliothis virescens Ascovirus 3a ( HvAV -3a, three subtypes 3a, 3b, 3c)
• Species Trichoplusia ni Ascovirus 2a ( TNAV 2a)

• 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 )

Similarities to other viruses

Based on sequence studies is to assume that the Ascoviridae and morphologically but very different Iridoviridae share a common ancestor and evolved from the Ascoviridae probably the genus Ichnovirus (Family Polydnaviridae ).