Complete nucleotide sequences of dsRNA2 and dsRNA7 detected in the phytopathogenic fungus Sclerotium hydrophilum and their close phylogenetic relationship to a group of unclassified viruses.

Ten dsRNA segments were extracted from Sclerotium hydrophilum isolate (HZ11). The isolation of virus-like particles contained 10 dsRNA segments with the same number and migration as those extracted directly from the fungal mycelia. Two of these dsRNA segments, dsRNA2 and dsRNA7, were cloned and sequenced. They were 2121 and 1953 bp, respectively. The dsRNA2 encodes a RNA-dependent RNA polymerase. The dsRNA7 contains two open reading frames that encode putative proteins of unknown functions. Phylogenetic analysis of the putative proteins indicated that they are closely related to protein encoded by unclassified viruses, such as Cryphonectria parasitica bipartite mycovirus 1, Lactarius rufus RNA virus 1, Penicillium aurantiogriseum bipartite virus 1, and Curvularia thermal tolerance virus. The 5'- and 3'-untranslated regions of the two dsRNAs share significant sequence identity and contain conserved sequence stretches. It suggested that dsRNA2 and dsRNA7 have a common origin and a close phylogenetic relationship to a group of unclassified viruses.