Complete nucleotide sequence and genome organization of a dsRNA partitivirus infecting Pleurotus ostreatus.

The nucleotide sequences of the genomic dsRNA mycovirus infecting Pleurotus ostreatus (P. ostreatus virus 1; PoV1) were determined and compared to the sequences of the other mycoviruses belonging to partitiviruses and totivirues. PoV1 dsRNA-1 and dsRNA-2 had genomes of 2296 and 2223 nucleotides, respectively. The purified virus preparations contained isometric particles of 28-30 nm in diameter, and also the same two dsRNAs were isolated from purified virus preparations. The sequences of PoV1 dsRNA-1 and dsRNA-2 had GC contents of 48.4 and 51.5%, respectively. dsRNA-1 had 78 and 97 nucleotides of 5'- and 3'-untranslated region (UTR) while dsRNA-2 had 114 and 198 nucleotides of 5'- and 3'-UTR, respectively. Computer analysis of putative open reading frame (ORF) shows that dsRNA-1 and dsRNA-2 contain a single ORF encoding proteins of 82.2 and 71.1 kDa that show high sequence identity with RNA-dependent RNA polymerase and capsid protein of partitiviruses, respectively. When compared to other dsRNA mycoviruses in a phylogenetic analysis they were found to form a distinct virus clade with partitiviruses, and were more distantly related to totiviruses.