Quadriviridae

Quadriviridae is a family of double-stranded RNA viruses with a single genus Quadrivirus.[1] The fungi Rosellinia necatrix serves as a natural host. The name of the group derives from the quadripartite genome of its members where in Latin quad means four. There is only one species in this family: Rosellinia necatrix quadrivirus 1.[2][3]

Quadrivirus
(Left) Electron micrographs of the Rosellinia necatrix quadrivirus 1, bar = 50 nm. (Right) Three-dimensional cryo-electron microscopy reconstruction of RnQV1 virions at 8Å resolution.
Virus classification
(unranked): Virus
Realm: Riboviria
Kingdom: Orthornavirae
Phylum: Duplornaviricota
Class: Chrymotiviricetes
Order: Ghabrivirales
Family: Quadriviridae
Genus: Quadrivirus

Structure
Schematic diagram of Quadriviridae virions. The four genomic segments may be separately encapsulated.[3]

Mycoviruses in the family Quadriviridae have a non-enveloped isometric capsid which consists of 60 copies of heterodimers of the structural proteins P2 and P4. The diameter of the capsid is around 48 nm.[2][3]

Genome
Genome of Rosellinia necatrix quadrivirus 1

Family member genomes are composed of double-stranded RNA. They are divided in to four segments which each code for a protein. The length of the different segments are between 3.5 to 5.0 kbp. The total genome is around 16.8 kbp. Inside the capsid with the genome there is also the RNA-dependent RNA polymerase.[2][3]

Life cycle

Quadriviruses are transmitted internally. They are propagated during cell division and hyphal anastomosis. Viral replication occurs in the cytoplasm. It follows the double-stranded RNA virus replication model. Double-stranded RNA virus transcription is the method of transcription. The fungi Rosellinia necatrix serves as a natural host.[2][3]

Taxonomy
Phylogenetic tree of quadriviruses, chrysoviruses and some totiviruses

The family Quadrivirdae has one genus Quadrivirus which contains the species:[4]

  • Rosellinia necatrix quadrivirus 1

References
  1. Chiba, S; Castón, JR; Ghabrial, SA; Suzuki, N; Ictv Report, Consortium (November 2018). "ICTV Virus Taxonomy Profile: Quadriviridae". The Journal of General Virology. 99 (11): 1480–1481. doi:10.1099/jgv.0.001152. PMID 30265238.
  2. "ICTV Report Quadriviridae".
  3. "Viral Zone". ExPASy. Retrieved 13 August 2015.
  4. "Virus Taxonomy: 2020 Release". International Committee on Taxonomy of Viruses (ICTV). March 2021. Retrieved 13 May 2021.
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