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Journal of Virology, February 1999, p. 985-992, Vol. 73, No. 2
Center for Agricultural Biotechnology,
University of Maryland Biotechnology Institute, University of
Maryland, College Park, Maryland 20742-4450
Received 19 August 1998/Accepted 21 October 1998
We report the construction of a full-length infectious cDNA clone
for hypovirus CHV1-Euro7, which is associated with reduced virulence
(hypovirulence) of the chestnut blight fungus Cryphonectria parasitica. Field strains infected with CHV1-Euro7 are more
virulent and exhibit less severe phenotypic changes
(hypovirulence-associated traits) than strains infected with the
prototypic hypovirus CHV1-EP713, for which the first infectious cDNA
clone was developed. These differences exist even though the two
hypoviruses show extensive sequence identities: 87 to 93% and 90 to
98% at the nucleotide and amino acid levels, respectively. The
relative contributions of viral and host genomes to phenotypic traits
associated with hypovirus infection were examined by transfecting
synthetic transcripts of the two hypovirus cDNAs independently into two
different virus-free C. parasitica strains, EP155 and
Euro7(
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Infectious cDNA Clone of Hypovirus CHV1-Euro7: a Comparative
Virology Approach To Investigate Virus-Mediated Hypovirulence of
the Chestnut Blight Fungus Cryphonectria
parasitica
v). Although the contribution of the viral genome was clearly
predominant, the final magnitude and constellation of phenotypic
changes were a function of contributions by both genomes. The high
level of sequence identity between the two hypoviruses also allowed
construction of viable chimeras and mapping of the difference in
symptom expression observed for the two viruses to the open reading
frame B coding domain. Implications of these results for engineering
enhanced biological control and elucidating the basis for
hypovirus-mediated attenuation of fungal virulence are discussed.
*
Corresponding author. Mailing address: Center for
Agricultural Biotechnology, University of Maryland Biotechnology
Institute, Plant Sciences Building, Room 5115C, College Park, MD
20742-4450. Phone: (301) 405-0334. Fax: (301) 314-9075. E-mail:
nuss{at}umbi.umd.edu.
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