title: Genome sequence, full-length infectious cDNA clone, and mapping of viral double-stranded RNA accumulation determinant of hypovirus CHV1-EP721.
abstract: Cryphonectria parasitica strain EP721 is infected with a strain of hypovirus CHV1, CHV1-EP721, and exhibits typical hypovirulence-associated traits such as reduced pigmentation and reduced asexual sporulation. However, the accumulation of the viral double-stranded RNA (dsRNA) in this hypovirus-infected C. parasitica strain is atypically low. We now report the complete nucleotide sequence and construction of a full-length infectious cDNA clone for hypovirus CHV1-EP721. The genome sequence of CHV1-EP721 was determined to be 12,724 bp in length and to share extensive homology with two other hypovirus strains, CHV1-Euro7 and CHV1-EP713, with an average of 99% and 90% identities at the nucleotide level and 99% and 92% identities at the amino acid level, respectively. CHV1-EP721 was successfully introduced into virus-free fungal host strain EP721(-v) by transfection with transcripts derived from a full-length viral cDNA. The transfected strain had a phenotype indistinguishable from that of EP721, and the accumulation of CHV1-EP721 dsRNA in the transfectant was lower than those transfected by CHV1-Euro7 and CHV1-EP713 transcripts. Through the construction of chimeric viruses by domain swapping using infectious cDNA clones of CHV1-EP721, CHV1-EP713, and CHV1-Euro7 hypoviruses, the determinant for the low level of viral dsRNA accumulation in CHV1-EP721 was mapped to the second of two CHV1-EP721 open reading frames (ORFs), ORF B. Further refined swapping of domains within ORF B identified a 2.5-kb coding region between p48 and the polymerase domain of CHV1-EP721 as being responsible for the low viral dsRNA accumulation. Evidence is also provided that low rates of hypovirus transmission through conidial spores correlates with low viral dsRNA accumulation.
authors.affiliation: Guangxi Key Laboratory of Subtropical Bioresource Conservation and Utilization, Guangxi University, 100 Daxiu Road, Nanning, Guangxi 530004, People's Republic of China.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Lin
authors.forename: Xiuwan
authors.initials: X
authors.lastname: Lan
authors.forename: Hong
authors.initials: H
authors.lastname: Liao
authors.forename: Todd B
authors.initials: TB
authors.lastname: Parsley
authors.forename: Donald L
authors.initials: DL
authors.lastname: Nuss
authors.forename: Baoshan
authors.initials: B
authors.lastname: Chen
mesh_terms: D001203:Ascomycota / Q000472:pathogenicity / Q000821:virology*; D003001:Cloning, Molecular; D003062:Codon / Q000502:physiology; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D016679:Genome, Viral; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000502:physiology; D010935:Plant Diseases / Q000382:microbiology*; D010944:Plants / Q000235:genetics; D012328:RNA Viruses / Q000235:genetics*; D012330:RNA, Double-Stranded / Q000096:biosynthesis*; D012367:RNA, Viral / Q000096:biosynthesis*; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014162:Transfection; D014774:Virulence
chemical_list: D003062:Codon; D018076:DNA, Complementary; D012330:RNA, Double-Stranded; D012367:RNA, Viral