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.

Taxonomy

Group: dsRNA

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 —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.
GenusHost detailsTissue tropismEntry detailsRelease detailsReplication siteAssembly siteTransmission
GiardiavirusProtozoa-Cell receptor endocytosisExocytosisCytoplasmCytoplasmPassive diffusion
LeishmaniavirusProtozoa: leishmania-Cell receptor endocytosisCell divisionCytoplasmCytoplasmCell division
TotivirusFungi: saccharomyces cerevisiae; fungi: smut fungi-Cytoplasmic exchange, sporogenesis; hyphal anastomosisCytoplasmic exchange, sporogenesis; hyphal anastomosisCytoplasmCytoplasmCell division; sporogenesis; cell fusion
VictorivirusFungi-UnknownUnknownCytoplasmCytoplasmUnknown
TrichomonasvirusProtozoaEndocytosisUnknownUnknownCytoplasmCytoplasmUnknown

Examples

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