Totiviridae

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Totiviridae
Systematics
Classification : Viruses
Area : Riboviria
Empire : Orthornavirae
Phylum : Duplornaviricota
Class : Chrymotiviricetes
Order : Ghabrivirales
Family : Totiviridae
Taxonomic characteristics
Genome : dsRNA
Baltimore : Group 3
Symmetry : icosahedral
Cover : uncovered
Scientific name
Totiviridae
Left
NCBI  Taxonomy: 11006
ViralZone ( ExPASy , SIB): 161

Totiviridae is a family of RNA viruses with double-stranded RNA - genome .

properties

The virus particles (virions) of the Totiviridae have an icosahedral capsid without a virus envelope of about 36 to 40 nm diameter with a triangulation number of one on the inner capsid layer and thirteen on the outer one. The genomes of the totiviruses can be divided into two types, with overlapping genes and without overlap. The genome consists of a linear double-stranded RNA of 4.6 to 6.7 kilobases with two open reading frames ( gag and pol ), which are produced under the control of an RNA pseudoknot. In the first type, the proteins are produced as a fusion protein from both genes that overlap by about 210 base pairs via a + 1 or - 1 reading frame shift, while in the second type the genes do not overlap and are individually translated . The Gag protein is the capsid protein and the Pol protein is an RNA polymerase of around 190 kilodaltons. The capsid consists of the Gag protein of around 100 kilodaltons , which initially forms asymmetric dimers after acetylation of the N-terminus . The aggregated capsid proteins bind the RNA-dependent RNA polymerase Pol , which in turn binds the RNA, whereby a newly formed virion assembles. Some totiviruses have a third open reading frame. Totiviruses presumably arose independently of other RNA viruses with a double-stranded genome from RNA viruses with a single-stranded genome of positive polarity (see below).

Systematics

Internal system

The following breakdown into 5 genera and 28 species of the Totiviridae follows the requirements of the International Committee on Taxonomy of Viruses (ICTV) as of November 2018, the type species is given as an example :

  • Family Totiviridae

External system

In 2015, Koonin et al assigned the Totiviridae taxonomically (due to their relationship) to one of their postulated supergroups, “Picornavirus-like superfamily”. The members of this proposed supergroup belong to different groups of the Baltimore classification , usually single-stranded RNA viruses of positive polarity ((+) ssRNA, Baltimore group 4), but they are also - like the Birnaviridae - double-stranded representatives (marked with dsRNA, Baltimore Group 3). This suggestion has now been replaced by the ICTV Master Species List # 35 of March 2020. A comparison of the cladograms can be found in Picornavirales §ICTV Master Species List # 35 .

Web links

Individual evidence

  1. ↑ ICTV Master Species List 2018b v1 MSL # 34, Feb. 2019
  2. ↑ a b c d ICTV: ICTV Taxonomy history: Saccharomyces cerevisiae virus LA , EC 51, Berlin, Germany, July 2019; Email ratification March 2020 (MSL # 35)
  3. ↑ a b c d D. M. Knipe, Peter M. Howley , DE Griffin, (Ed.): Fields Virology. 5th edition, Lippincott Williams & Wilkins, Philadelphia 2007, ISBN 978-0-7817-6060-7 .
  4. ↑ a b c d e M. A. Hartley, C. Ronet, H. Zangger, SM Beverley, N. Fasel: Leishmania RNA virus: when the host pays the toll. In: Frontiers in cellular and infection microbiology. Volume 2, 2012, p. 99, ISSN  2235-2988 . doi : 10.3389 / fcimb.2012.00099 . PMID 22919688 . PMC 3417650 (free full text).
  5. ↑ ICTV : Master Species List 2018a v1 , MSL (# 33) including all taxa updates since the 2017 release. Fall 2018
  6. ^ Eugene V. Koonin, Valerian V. Dolja, Mart Krupovic: Origins and evolution of viruses of eukaryotes: The ultimate modularity , in: Virology from May 2015; 479-480. 2-25, Epub March 12, 2015, PMC 5898234 (free full text), PMID 25771806
  7. ↑ ICTV: ICTV Master Species List 2019.v1 , New MSL including all taxa updates since the 2018b release, March 2020 (MSL # 35)