(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.
Quadriviridae is a family of double-stranded RNA viruses with a single genus Quadrivirus.[1] The fungiRosellinia necatrix serves as a natural host. The name of the group derives from the quadripartite genome of its members where in Latinquad means four. There is only one species in this family: Rosellinia necatrix quadrivirus 1.[2][3]
Structure
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
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 and 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 hyphalanastomosis. 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
The family Quadrivirdae has one genus Quadrivirus which contains the species:[4]