Totivirus

The genus Totivirus belongs to the Totiviridae family. It infects the fungus Saccharomyces cerevisiae and the Helminthosporium victoriae 190S virus (Hv190SV) belongs to the genus totivirus infects the phytopathogenic fungus Helminthosporium victoriae. Totivirus have a genome of 4700-6700 nucleotides in length and only a single copy of the genome is present in the particle. The nucleic acid content of totivirus is usually of one molecule but can also contain three or four segments of linear double stranded RNA. The genome contains two large overlapping open reading frames (ORFs). These open reading frames (ORFs) code for a capsid protein (CP) and an RNA-dependent RNA polymerase (RDRP). The 5' end of the positive strand of the dsRNA genome has no cap and is very structured.Totivirus contains a long 5' untranslated region (5' UTR) which functions as an internal ribosome entry site (IRES). Totiviruses can have satellite RNAs that encoding a toxin. They are nonenveloped and can be present in one type of particle only or more than one type of particle and are icosahedral in structure. The double-stranded RNA (dsRNA) genomes are packaged in isometric particles 40 to 50 nm in diameter which is true for members of the Totiviridae family.