Totiviridae

Totiviridae is a family of viruses. Giardia lamblia, leishmania, trichomonas vaginalis, and fungi serve as natural hosts. There are currently 28 species in this family, divided among 5 genera.[1][2]

Totiviridae
Capsid structure of Helminthosporium victoriae virus 190S (HvV190S)
Cryo-EM of HvV190S virions.
Virus classification
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Duplornaviricota
Class: Chrymotiviricetes
Order: Ghabrivirales
Family: Totiviridae
Genera

Taxonomy

Group: dsRNA

[2]

Structure

Viruses in Totiviridae are non-enveloped, double-stranded RNA viruses with icosahedral geometries, and T=2 symmetry. The virion consists of a single capsid protein and is about 40 nanometers in diameter.

The genome is composed of a linear double-stranded RNA molecule of 4.6–6.7 kilobases. It contains 2 overlapping open reading frames (ORF)[1]—gag and pol—which respectively encode the capsid protein and the RNA-dependent RNA polymerase. Some totiviruses contain a third small potential ORF.

GenusStructureSymmetryCapsidGenomic arrangementGenomic segmentation
GiardiavirusIcosahedralT=2Non-envelopedLinearMonopartite
LeishmaniavirusIcosahedralT=2Non-envelopedLinearMonopartite
TotivirusIcosahedralT=2Non-envelopedLinearMonopartite
VictorivirusIcosahedralT=2Non-envelopedLinear
TrichomonasvirusIcosahedralT=2Non-envelopedLinear

Life cycle

Viral replication is cytoplasmic. Replication follows the double-stranded RNA virus replication model. Double-stranded RNA virus transcription is the method of transcription. Translation takes place by -1 ribosomal frameshifting, +1 ribosomal frameshifting, viral initiation, and RNA termination-reinitiation. The virus exits the host cell by cell-to-cell movement. Giardia lamblia protozoa, leishmania protozoa, protozoan trichomonas vaginalis, and fungi serve as the natural host.[1]

GenusHost detailsTissue tropismEntry detailsRelease detailsReplication siteAssembly siteTransmission
GiardiavirusProtozoaNoneCell receptor endocytosisExocytosisCytoplasmCytoplasmPassive diffusion
LeishmaniavirusProtozoa: leishmaniaNoneCell receptor endocytosisCell divisionCytoplasmCytoplasmCell division
TotivirusFungi: saccharomyces cerevisiae; fungi: smut fungiNoneCytoplasmic exchange, sporogenesis; hyphal anastomosisCytoplasmic exchange, sporogenesis; hyphal anastomosisCytoplasmCytoplasmCell division; sporogenesis; cell fusion
VictorivirusFungiNoneUnknownUnknownCytoplasmCytoplasmUnknown
TrichomonasvirusProtozoaEndocytosisUnknownUnknownCytoplasmCytoplasmUnknown

Examples

An example of fungal totivirus is the L-A helper virus, a cytoplasmic virus found primarily in Saccharomyces cerevisiae.[3]

References
  1. "Viral Zone". ExPASy. Retrieved 15 June 2015.
  2. ICTV. "Virus Taxonomy: 2014 Release". Retrieved 15 June 2015.
  3. https://aem.asm.org/content/aem/early/2016/12/05/AEM.02991-16.full.pdf
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