A novel double-stranded RNA mycovirus from Fusarium graminearum: nucleic acid sequence and genomic structure.

Ten Fusarium graminearum isolates from China were screened for dsRNA mycoviruses. Five dsRNAs (2.4 to 3.5 kbp) were purified from isolate China 9, cloned, and sequenced. BLAST analysis showed that the proteins encoded by dsRNA1 possess motifs that are conserved in RNA-dependent RNA polymerases, dsRNA2 resembles the hypothetical protein encoded by dsRNA3 of Magnaporthe oryzae chrysovirus 1, dsRNA4 shares no significant similarity to any published protein, and dsRNA5 has a C2H2 zinc finger domain. Tandem mass spectrophotometry, surface protein labeling of virus-like particles, SDS-PAGE, and protein BLAST results supports the notion that three of the virus segments code for structural proteins, of which dsRNA3 possibly codes for the capsid protein. Relative quantitative RT-PCR studies of the 5 dsRNAs suggested that the segments are encapsidated separately in unequal amounts. Genomic structure and phylogenic studies support the possibility that this virus may be a candidate for the type species of a novel genus in the family Chrysoviridae.