ABSTRACT
Double-stranded RNA (dsRNA) mycoviruses have been demonstrated in at least 16 species of fungi. Although most of these viruses are propagated from cell to cell only by mating, meiosis, and mitosis, their properties are sufficiently similar to those of infectious dsRNA viruses of plant and animal cells that they are nevertheless considered viruses. In some cases, it has been possible to demonstrate infectivity of viral particles to protoplasts. In most cases, the fungal virus RNA polymerases have been shown to synthesize single-stranded RNA which is extruded from the virion. The virion RNA polymerase of Aspergillus foetidus virus S is typical in some respects of the fungal virus RNA polymerases. In Penicillium stoliniferum virus S particles, the major RNA polymerase activity is not synthesis of single-stranded RNA as in Saccharomyces cerevisiae virus, but rather synthesis of dsRNA. S. cerevisiae is the only fungus whose dsRNA viruses have been studied extensively for which genetic analysis is routine.
