Totiviridae Explained

Totiviridae is a family of double-stranded RNA viruses. Giardia lamblia, leishmania, trichomonas vaginalis, and fungi serve as natural hosts. The name of the group derives from Latin toti which means undivided or whole. There are 28 species in this family, assigned to 5 genera.^{[1] [2]}

Structure

Viruses in the family 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.

Genome

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

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.

Genus	Host details	Tissue tropism	Entry details	Release details	Replication site	Assembly site	Transmission
Giardiavirus	Protozoa	None	Cell receptor endocytosis	Exocytosis	Cytoplasm	Cytoplasm	Passive diffusion
Leishmaniavirus	Protozoa: leishmania	None	Cell receptor endocytosis	Cell division	Cytoplasm	Cytoplasm	Cell division
Totivirus	Fungi: saccharomyces cerevisiae; fungi: smut fungi	None	Cytoplasmic exchange, sporogenesis; hyphal anastomosis	Cytoplasmic exchange, sporogenesis; hyphal anastomosis	Cytoplasm	Cytoplasm	Cell division; sporogenesis; cell fusion
Victorivirus	Fungi	None	Unknown	Unknown	Cytoplasm	Cytoplasm	Unknown
Trichomonasvirus	Protozoa	Endocytosis	Unknown	Unknown	Cytoplasm	Cytoplasm	Unknown

Taxonomy

The family Totiviridae has five genera:

• Giardiavirus
• Leishmaniavirus
• Totivirus
• Trichomonasvirus
• Victorivirus

Examples

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

External links

• Viralzone: Totiviridae
• ICTV

Notes and References

1. Web site: Viral Zone. ExPASy. 15 June 2015.
2. Web site: Virus Taxonomy: 2020 Release . International Committee on Taxonomy of Viruses (ICTV) . March 2021 . 13 May 2021.
3. Rodríguez-Cousiño. Nieves. Esteban. Rosa. 9 December 2016. Analysis of L-A-2, the helper virus of K2 killer toxin-encoding M2 dsRNA, and of L-BC variants from wine yeast strain populations provides new insights into the relationship and evolution of dsRNA viruses of yeast. Appl. Environ. Microbiol.. 83. 4. 10.1128/AEM.02991-16. 27940540. 5288835. aem.asm.org.