Ortervirales
Ortervirales is an order that contains all accepted species of single-stranded RNA viruses that replicate through a DNA intermediate and all accepted species of double-stranded DNA viruses that replicate through an RNA intermediate.
The name is derived from the reverse of retro.
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 and an integrase belonging to the DDE recombinase superfamily. They also share similar capsid and nucleocapsid proteins/domains. Caulimoviruses also share some features with belpaoviruses, metaviruses, pseudoviruses, and retroviruses such a homologous aspartate protease. On the other hand, Hepadnaviridae family appears to be more distantly related to the above-mentioned families.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 virus infecting plants
