Partitiviridae


Partitiviridae is a family of viruses. Fungi and plants serve as natural hosts. There are currently 60 species in this family, divided among 5 genera or unassigned to a genus. The family name comes from the Latin partitius which means divided and they are called this as they have segmented genomes.

Genome and structure

Viruses in the family Partitiviridae are non-enveloped, with icosahedral geometries, and T=1 symmetry. The diameter is around 35–40 nm. Partitiviruses have double stranded RNA genomes divided into two genomic segments and there may be additional subgenomic segments. The genome segments are packaged in the same virus particle, the larger segment codes for the RNA-dependent RNA polymerase and the smaller codes for the coat protein. Genomes are linear and around 1.4–3.0kb in length. The genome codes for 2 proteins.
GenusStructureSymmetryCapsidGenomic arrangementGenomic segmentation
AlphapartitivirusIcosahedralT=1Non-envelopedLinearSegmented
BetapartitivirusIcosahedralT=1Non-envelopedLinearSegmented
GammapartitivirusIcosahedralT=1Non-envelopedLinearSegmented
DeltapartitivirusIcosahedralT=1Non-envelopedLinearSegmented
CryspovirusIcosahedralT=1Non-envelopedLinearSegmented

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.
GenusHost detailsTissue tropismEntry detailsRelease detailsReplication siteAssembly siteTransmission
CryspovirusProtists-Cell division; sporogenesis; hyphal anastomosisCell division; sporogenesis; hyphal anastomosisCytoplasmCytoplasmCell division; sporogenesis; hyphal anastomosis
Alphapartitivirus-CytoplasmCytoplasmCell division
DeltapartitivirusPlants-Viral movement; mechanical inoculationCell divisionCytoplasmCytoplasmCell division
Betapartitivirus-CytoplasmCytoplasmCell division
GammapartitivirusFungi-Cytoplasmic exchange; hyphal anastomosisCytoplasmic exchange; hyphal anastomosisCytoplasmCytoplasmCytoplasmic exchange; hyphal anastomosis

Taxonomy

There are currently five recognized genera within the Partitiviridae family:
Group: dsRNA
Cryspoviruses infect apicomplexian protozoa of the genus Cryptosporidium, while viruses of the other genera infect plants and fungi. There are an additional fifteen species in the family unassigned to a genus.

Phylogenetics

Based on the RNA polymerase gene this group can be divided into four clades. Four isolates from animals and protozoans form a fifth clade. Clades I-IV consist of mixtures of partitivirus-like sequences from plants and fungi.