Partitiviridae is a family of multipartite double-stranded RNA viruses. Plants, fungi, and protozoa serve as natural hosts. It has been suggested that they can also infect bacteria. The name comes from the Latin partitius, which means divided, and refers to the segmented genome of partitiviruses. The family contains five genera.
Structure
Viruses in the family Partitiviridae are non-enveloped with icosahedral geometries and T=1 symmetry. The diameter of partitiviruses is around 25–43 nm.
Genome
Partitiviruses have double-stranded RNA genomes divided into two genomic segments, and there may be additional subgenomic segments. The two genome segments are packaged in separate virus particles. They code for two separate proteins. The first segment codes for the RNA-dependent RNA polymerase (RdRp), and the second segment codes for the coat protein. The segments are around 1.4–3.0 kbp in length, while the total genome length is around 3.0–4.8 kbp.
Life cycle Viral replication is cytoplasmic. Entry into the host cell is achieved by penetration into the host cell. Replication follows the double-stranded RNA virus replication model. Double-stranded RNA virus transcription is the method of transcription. The virus exits the host cell by cell-to-cell movement. Fungi and plants serve as the natural host. Cryspoviruses infect apicomplexan protozoa of the genus Cryptosporidium,Nibert ML, Woods KM, Upton SJ, Ghabrial SA (2009) Cryspovirus: a new genus of protozoan viruses in the family Partitiviridae. Arch Virol 154(12):1959–1965 while viruses of the other genera infect plants and fungi. It has been suggested that they can also infect bacteria.
Genus Host details Tissue tropism Entry details Release details Replication site Assembly site TransmissionCryspovirusProtistsNoneCell division; sporogenesis; hyphal anastomosisCell division; sporogenesis; hyphal anastomosisCytoplasmCytoplasmCell division; sporogenesis; hyphal anastomosisAlphapartitivirusNoneCytoplasmCytoplasmCell divisionDeltapartitivirusPlantsNoneViral movement; mechanical inoculationCell divisionCytoplasmCytoplasmCell divisionBetapartitivirusNoneCytoplasmCytoplasmCell divisionGammapartitivirusFungiNoneCytoplasmic exchange; hyphal anastomosisCytoplasmic exchange; hyphal anastomosisCytoplasmCytoplasmCytoplasmic exchange; hyphal anastomosis
Phylogenetics Based on the RNA polymerase gene this group can be divided into four clades (I-IV). Four isolates from animals and protozoans form a fifth clade. Clades I–IV consist of mixtures of partitivirus-like sequences from plants and fungi.Liu H, Fu Y, Xie J, Cheng J, Ghabrial SA, Li G, Yi X, Jiang D (2012) Discovery of Novel dsRNA Viral Sequences by In Silico Cloning and Implications for Viral Diversity, Host Range and Evolution. PLoS One. 2012;7(7):e42147.
Taxonomy
The family contains the following genera: Alphapartitivirus Betapartitivirus Cryspovirus Deltapartitivirus Gammapartitivirus
References
External links ICTV Online Report: Partitivirdae Viralzone: Partitiviridae