The contribution of defective RNAs to the complexity of viral-encoded double-stranded RNA populations present in hypovirulent strains of the chestnut blight fungus Cryphonectria parasitica.
Hypovirulent strain EP713 of the chestnut blight fungus Cryphonectria (Endothia) parasitica harbors a family of viral encoded double-stranded (ds) RNAs thought to be responsible for the hypovirulence phenotype. These include L-dsRNA, described in the accompanying paper (Shapira et al., 1991); several prominent species in the estimated size range of 8 to 10 kb, referred to here as M-dsRNAs; and several smaller species designated S-dsRNAs which range in size from approximately 0.6 to 1.7 kb. The characterization of the M- and S-dsRNA species is the subject of this report. Results from polymerase chain reaction mapping and molecular hybridization analysis indicate that the M- and S-dsRNA species are internally deleted forms of L-dsRNA. Three different S-dsRNA species were cloned and sequenced. Each species contained a single deletion breakpoint and retained either 149, 155 or 156 bp of the terminus corresponding to the 5'-end of the coding strand and 440, 447 or 449 bp of the other terminus. Two of the S-dsRNA species contained, within the boundaries of the breakpoint, additional sequence information consisting of 42 bp or 95 bp that appeared to be unrelated to the L-dsRNA sequence. These results demonstrate that defective RNAs contribute significantly to the complexity of dsRNA populations found in hypovirulent strains of C. parasitica and provide a first approximation of the location of cis-acting signals involved in their replication.
Shapira
R
R
Department of Molecular Oncology and Virology, Roche Institute of Molecular Biology, Roche Research Center, Nutley, NJ 07110.
Choi
G H
GH
Hillman
B I
BI
Nuss
D L
DL
D001483:Base Sequence; D002872:Chromosome Deletion; D003001:Cloning, Molecular; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D015345:Oligonucleotide Probes; D016366:Open Reading Frames; D010641:Phenotype; D010942:Plant Viruses / Q000235:genetics*; D010944:Plants / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D012330:RNA, Double-Stranded / Q000235:genetics*; D012331:RNA, Fungal / Q000235:genetics*; D012367:RNA, Viral / Q000235:genetics*; D014774:Virulence / Q000235:genetics; D013098:Xylariales / Q000235:genetics* / Q000472:pathogenicity
D015345:Oligonucleotide Probes; D012330:RNA, Double-Stranded; D012331:RNA, Fungal; D012367:RNA, Viral