Detection of an RNA-dependent RNA polymerase in mitochondria from a mitovirus-infected isolate of the Dutch elm disease fungus, Ophiostoma novo-ulmi

RNA-dependent RNA polymerase (RdRp) activity has been detected in mitochond ria from an isolate of Ophiostoma novo-ulmi infected with O. novo-uimi mito virus 6 (OnuMV6). The reaction products corresponded to the double-stranded and single-stranded forms of OnuMVG6RNA. Western blot analysis using antib odies raised against a conserved RdRp region has detected a protein of ca. 80 kDa in OnuMV6-infected mitochondria, close to the predicted size of the OnuMV6 RdRp. No RdRp activity or protein was detected in mitochondria from an uninfected O. novo-ulmi isolate. This is the first detection of a virus RdRp in fungal mitochondria and the results are consistent with the use of UGA tryptophan codons in its synthesis. (C) 2000 Academic Press.