Ortervirales

Ortervirales is an order that contains all accepted species of single-stranded RNA viruses that replicate through a DNA intermediate (Group VI) and all accepted species of double-stranded DNA viruses (except Hepadnaviridae) that replicate through an RNA intermediate (Group VII). [1][2] The name is derived from the reverse of retro.[3]

Ortervirales
HI-virión
Virus classification
(unranked): Virus
Realm: Riboviria
Kingdom: Pararnavirae
Phylum: Artverviricota
Class: Revtraviricetes
Order: Ortervirales
Families
  • Belpaoviridae
  • Caulimoviridae
  • Metaviridae
  • Pseudoviridae
  • Retroviridae

All reverse-transcribing viruses possess significant similarities to each other. Their reverse transcriptase proteins share a common origin. Moreover, belpaoviruses, metaviruses, pseudoviruses, and retroviruses have other features in common. Their polymerase proteins are similar in structure and include aspartic protease (retroviral aspartyl protease) and an integrase belonging to the DDE recombinase superfamily (see Recombination-activating gene [structure]). They also share similar capsid and nucleocapsid proteins/domains.[4] Caulimoviruses also share some features with belpaoviruses, metaviruses, pseudoviruses, and retroviruses such as a homologous aspartate protease. On the other hand, Hepadnaviridae family appears to be more distantly related to the above-mentioned families.[1]

Taxonomy

There are five families in this order:

  • Family Belpaoviridae – LTR retrotransposon, Bel/Pao family
  • Family Metaviridae – LTR retrotransposon, Ty3/gypsy family
  • Family Pseudoviridae – LTR retrotransposon, Ty1/copia family
  • Family Retroviridae – Retroviruses, e.g. HIV
  • Family Caulimoviridae – dsDNA-RT viruses infecting plants

References
  1. Krupovic, M; Blomberg, J; Coffin, JM; Dasgupta, I; Fan, H; Geering, AD; Gifford, R; Harrach, B; Hull, R; Johnson, W; Kreuze, JF; Lindemann, D; Llorens, C; Lockhart, B; Mayer, J; Muller, E; Olszewski, N; Pappu, HR; Pooggin, M; Richert-Pöggeler, KR; Sabanadzovic, S; Sanfaçon, H; Schoelz, JE; Seal, S; Stavolone, L; Stoye, JP; Teycheney, PY; Tristem, M; Koonin, EV; Kuhn, JH (4 April 2018). "Ortervirales: New virus order unifying five families of reverse-transcribing viruses". Journal of Virology. 92 (12): e00515–18. doi:10.1128/JVI.00515-18. PMC 5974489. PMID 29618642.
  2. "Taxonomy". International Committee on Taxonomy of Viruses (ICTV). Retrieved 2018-05-23.
  3. Jens H. Kuhn, Mart Krupovic, et al.: Creation of new order, Ortervirales, for 5 families of reverse-transcribing viruses, ICTV Proposal (Taxoprop) 2017.013D, DOI:10.1340/RG.2.2.24914.04804
  4. Krupovic, M; Koonin, EV (2017). "Homologous Capsid Proteins Testify to the Common Ancestry of Retroviruses, Caulimoviruses, Pseudoviruses, and Metaviruses". Journal of Virology. 91 (12): e00210–17. doi:10.1128/JVI.00210-17. PMC 5446648. PMID 28356531.
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