This Article Full Text Full Text (PDF) Other Versions of this Article: JVI.02638-07v1 82/13/6369    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Google Scholar Articles by Deng, F. Articles by Nuss, D. L. PubMed PubMed Citation Articles by Deng, F. Articles by Nuss, D. L.

 Previous Article  |  Next Article 

Journal of Virology, July 2008, p. 6369-6378, Vol. 82, No. 13
0022-538X/08/$08.00+0     doi:10.1128/JVI.02638-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Hypovirus Papain-Like Protease p48 Is Required for Initiation but Not for Maintenance of Virus RNA Propagation in the Chestnut Blight Fungus Cryphonectria parasitica

Center for Biosystems Research, University of Maryland Biotechnology Institute, Shady Grove Campus, 9600 Gudelsky Drive, Rockville, Maryland 20850

Received 12 December 2007/ Accepted 23 April 2008

The prototypic hypovirus CHV1-EP713, responsible for virulence attenuation (hypovirulence) of the chestnut blight fungus Cryphonectria parasitica, encodes two papain-like proteases, p29 and p48. Protein p29 has been shown to be dispensable for hypovirus RNA replication and to act as a suppressor of RNA silencing. Here we describe a role for p48 in hypovirus RNA propagation. CHV1-EP713 infectious cDNA clones in which the p48 coding region was deleted, p48, were unable to establish infection in C. parasitica when introduced as a DNA form by transformation or as a coding strand transcript by electroporation. However, the p48 mutant virus RNA was rescued when p48 was provided in trans. Surprisingly, the p48 mutant viruses retained replication competence in the apparent absence of p48 following transmission to wild-type C. parasitica and successive subculturing. The replicating p48 mutant virus was reduced in RNA accumulation by 60% both in the absence and presence of p48 provided in trans and was transmitted through asexual spores (conidia) at a rate 3 to 8% of that for full-length CHV1-EP713. Complementary analysis of strains expressing p48 or containing the replicating p48 mutant virus showed that like p29, p48 contributes to virus-mediated suppression of host pigmentation and conidiation, although to a lesser extent, and is dispensable for hypovirus-mediated hypovirulence. The combined results suggest that papain-like protease p48 plays an essential role in the initiation but not the maintenance of virus RNA propagation and also contributes to the regulation of viral RNA accumulation and vertical transmission.

Published ahead of print on 30 April 2008.