title: A small mitochondrial double-stranded (ds) RNA element associated with a hypovirulent strain of the chestnut blight fungus and ancestrally related to yeast cytoplasmic T and W dsRNAs.
abstract: A small double-stranded (ds) RNA element was isolated from a moderately hypovirulent strain of the chestnut blight fungus Cryphonectria parasitica (Murr.) Barr. from eastern New Jersey. Virulence was somewhat lower in the dsRNA-containing strain than in a virulent dsRNA-free control strain, but colony morphology and sporulation levels were comparable. A library of cDNA clones was constructed, and overlapping clones representing the entire genome were sequenced. The 2728-bp dsRNA was considerably smaller than previously characterized C. parasitica dsRNAs, which are 12-13 kb and ancestrally related to the Potyviridae family of plant viruses. Sequence analysis revealed one large open reading frame, but only if mitochondrial codon usage (UGA = Trp) was invoked. Nuclease assays of purified mitochondria confirmed that the dsRNA was localized within mitochondria. Assuming mitochondrial translation, the deduced amino acid sequence had landmarks typical of RNA-dependent RNA polymerases. Alignments of the conserved regions indicate that this dsRNA is more closely related to yeast T and W dsRNAs and single-stranded RNA bacteriophages such as Q beta than to other hypovirulence-associated dsRNAs.
authors.affiliation: Department of Plant Pathology, Rutgers University, New Brunswick, NJ 08903.
authors.forename: J J
authors.initials: JJ
authors.lastname: Polashock
authors.forename: B I
authors.initials: BI
authors.lastname: Hillman
mesh_terms: D000595:Amino Acid Sequence; D001203:Ascomycota / Q000235:genetics* / Q000472:pathogenicity; D001483:Base Sequence; D005814:Genes, Viral; D008969:Molecular Sequence Data; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology; D010942:Plant Viruses / Q000235:genetics*; D012313:RNA / Q000235:genetics; D012330:RNA, Double-Stranded / Q000235:genetics*; D012331:RNA, Fungal / Q000235:genetics*; D000077278:RNA, Mitochondrial; D012367:RNA, Viral / Q000235:genetics*; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014197:Trees; D015678:Viral Structural Proteins / Q000235:genetics*
chemical_list: D012330:RNA, Double-Stranded; D012331:RNA, Fungal; D000077278:RNA, Mitochondrial; D012367:RNA, Viral; D015678:Viral Structural Proteins; D012313:RNA; D012324:RNA-Dependent RNA Polymerase