A viral gene confers hypovirulence-associated traits to the chestnut blight fungus.
A viral double-stranded (ds)RNA associated with reduced virulence (hypovirulence) and the accompanying biological control of the chestnut blight fungus, Cryphonectria parasitica, was shown recently to contain two contiguous coding domains designated ORF A and ORF B. We report here that transformation of an isogenic virulent, dsRNA-free C. parasitica strain with a cDNA copy of ORF A conferred traits similar to those exhibited by the dsRNA-containing hypovirulent strain: characteristics included reduced pigmentation, reduced laccase accumulation and suppressed conidiation. However virulence was not reduced, indicating an apparent uncoupling of associated traits from hypovirulence. These results establish a direct cause and effect relationship between a viral dsRNA genetic element present in a hypovirulent C. parasitica strain and specific phenotypic traits. They demonstrate further that these traits are not the result of a general reaction of the fungus to the presence of the replicating viral RNA, but are caused by a specific viral coding domain.
Choi
G H
GH
Department of Molecular Oncology and Virology, Roche Institute of Molecular Biology, Nutley, NJ 07110.
Nuss
D L
DL
D005814:Genes, Viral; D005822:Genetic Vectors; D009693:Nucleic Acid Hybridization; D016366:Open Reading Frames; D010944:Plants; D012330:RNA, Double-Stranded / Q000235:genetics*; D015183:Restriction Mapping; D014170:Transformation, Genetic; D014774:Virulence / Q000235:genetics*; D013098:Xylariales / Q000235:genetics* / Q000472:pathogenicity
D012330:RNA, Double-Stranded