Taxonomic Structure of the Family
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Family |
Partitiviridae |
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Genus |
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Genus |
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Genus |
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Genus |
Virions are isometric, nonenveloped, 30-40 nm in diameter. Symmetry of particles has not been determined.
Physicochemical and Physical Properties
Virion buoyant density in CsCl is in the range of 1.34-1.39 g/cm3. Virions are stable in butanol and chloroform.
Virions contain two unrelated linear dsRNA segments (1.4-3.0 kbp in size). The two segments of the individual viruses are usually of similar size.
Single major capsid protein (CP). Virion-associated RNA polymerase activity is present.
None reported.
None reported.
Genome Organization and Replication
The genome is comprised of two linear dsRNA segments, the smaller usually codes for the CP and the larger usually codes for the virion-associated RNA polymerase. Each dsRNA is probably monocistronic. In vitro transcription/replication occurs by a semi-conservative mechanism. Virions accumulate in the cytoplasm.
Virions are efficient immunogens. A single precipitin line is formed in gel diffusion tests. Members that are serologically related may be strains of a single virus. No serological relationships between the fungal viruses and the plant viruses in the family Partitiviridae have been detected.
The viruses are associated with latent infections of their fungal and plant hosts. There are no known natural vectors. The fungal viruses are transmitted intracellularly during cell division and sporogenesis. In some ascomycetes, e.g. Gaeumannomyces graminis, virus is usually eliminated during ascospore formation. Experimental transmission of purified fungal partitiviruses has been reported by fusing virions with fungal protoplasts. The plant cryptoviruses are transmitted by ovule and by pollen to the seed embryo. There is no graft transmission and apparently no cell-to-cell transport, except at cell division; seed transmission is the only known mode for the transmission of cryptoviruses.
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