Family: Orthototiviridae (Interim Report)
This is a summary page created by the ICTV Report Editors using information from associated Taxonomic Proposals and the Master Species List.
Edited by: Holly Hughes, Luisa Rubino, Sead Sabanadzovic
Posted: November 2024, updated December 2024
Summary
The family Orthototiviridae includes dsRNA viruses of protists, fungi, plants and invertebrates (Table 1 Orthototiviridae). The family Orthototiviridae was established in 2023 (Master Species List #39) and includes viruses previously assigned to the now defunct family Totiviridae.
Table 1 Orthototiviridae. Characteristics of members of the family Orthototiviridae.
| Characteristic | Description |
| Example | Saccharomyces cerevisiae virus L-A (J04692), species Totivirus ichi, genus Totivirus |
| Virion | Non-enveloped, icosahedral, 40–49 nm diameter (Figure 1 Orthototiviridae) |
| Genome | Single dsRNA of 3.9–5.6 kb, uncapped (Figure 2 Orthototiviridae) |
| Replication | Cytoplasmic, positive and negative strand transcription from dsRNA associated with virion; satellite dsRNAs may be associated with some virus isolates |
| Translation | From mRNA, involves ribosomal slippage and cap snatching |
| Host range | Protists, fungi, plants, invertebrates |
| Taxonomy | Realm Riboviria, kingdom Orthornavirae, phylum Duplornaviricota, class Chrymotiviricetes, order Ghabrivirales, suborder Alphatotivirineae: 1 genus, 32 species (Figure 3 Orthototiviridae) |
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| Figure 1 Orthototiviridae. (Left) Transmission electron micrograph of Saccharomyces cerevisiae virus L-BC (La) Gag VLPs. Scale: 200 nm. Image from Celitan et al., (2024) "Highly stable Saccharomyces cerevisiae L-BC capsids with versatile packing potential." Front Bioeng Biotechnol. 12:1456453 under a Creative Commons Attribution 4.0 International License. (Right) Schematics of virion. Image from ViralZone, under a Creative Commons Attribution 4.0 International License, credit: SwissBioPics. |
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| Figure 2 Orthototiviridae. Genome organisation of Saccharomyces cerevisiae virus L-A, a member of the family Orthototiviridae. Boxes indicate open reading frames as annotated on GenBank accession J04692. * indicates a ribosome slippage site. |
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| Figure 3 Orthototiviridae. Relationships of the taxa connected to the family Orthototiviridae. Labels in the column to the right are species names. Coloured circles indicate the host or source of viruses of a given species: light brown - fungi, grey - invertebrate, green - plant, black – protist. |
Derivation of name
Orthototiviridae: from the Ancient Greek ὀρθός (orthos), meaning “correct” or “straight” and the Latin toti, meaning "undivided" or "whole", referring to the mono-segmented dsRNA genome of viruses in the family; the suffix -viridae for family taxa