''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).
The name is derived from the reverse of retro.
All reverse-transcribing viruses possess significant similarities to each other. Their
reverse transcriptase
A reverse transcriptase (RT) is an enzyme used to generate complementary DNA (cDNA) from an RNA template, a process termed reverse transcription. Reverse transcriptases are used by viruses such as HIV and hepatitis B to replicate their genom ...
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 tructure. They also share similar
capsid and nucleocapsid proteins/domains.
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.
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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
{{Taxonbar, from=Q51526792
Virus orders