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

• Published in: The EMBO journal Vol. 10; no. 4; pp. 741 - 746
• Main Authors: Shapira, R, Choi, G.H, Hillman, B.I, Nuss, D.L
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 01.04.1991
• Subjects: Agronomy. Soil science and plant productions; Base Sequence; Biological and medical sciences; biological control; blight; Castanea sativa; Chromosome Deletion; Cloning, Molecular; Cryphonectria parasitica; disease control; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; genetic disorders; Models, Molecular; Molecular Sequence Data; Nucleic Acid Conformation; nucleotide sequences; Oligonucleotide Probes; Open Reading Frames; Phenotype; Phytopathology. Animal pests. Plant and forest protection; plant diseases and disorders; plant viruses; Plant Viruses - genetics; Plants - microbiology; Polymerase Chain Reaction; RNA; RNA, Double-Stranded - genetics; RNA, Fungal - genetics; RNA, Viral - genetics; Variation, races, biotypes, parasitic specialization, genetics; virulence; Virulence - genetics; Xylariales - genetics; Xylariales - pathogenicity; Breakpoint; Double stranded RNA; Mycosis; Nucleotide sequence; Cryphonectria parasitica; Phytopathogen; Fungi; Infection; Northern blotting; Deletion; Replication; Regulatory sequence; Ascomycetes; Molecular cloning; Hypovirulence; Thallophyta
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1002/j.1460-2075.1991.tb08005.x

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.