Transmissible hypovirulence of the chestnut blight fungus, Cryphonectria parasitica, is associated with cytoplasmic double-stranded-RNA (dsRNA) viruses. The fungal laccase has attracted interest because its activity is reduced in hypovirulent dsRNA-containing strains. A laccase cDNA clone was isolated by screening a cDNA expression library with antibodies against the purified extracellular lacc...

A double-stranded RNA virus of the chestnut blight pathogen, Cryphonectria parasitica, has been shown previously to reduce accumulation of mRNAs of extracellular laccase (laccase A) produced by this fungus. Both extra- and intracellular laccases have been detected after growth of the fungus in liquid culture. In addition to cellular localization, the two laccases are distinguishable by time of ...

Castanea is a hardwood forest genus of considerable agro-economic importance for both timber and nut production. Chestnuts are one of the most significant nut crops in the temperate zone. However, this species is threatened by pollution, social factors, economical changes, and two major fungal diseases: ink disease (Phytophthora spp.), and chestnut blight canker (Cryphonectria parasitica). Simi...

Despite our increasing recognition of the key role that microbes play in ecosystem processes (e.g., Giller et al. 1997; Mills and Bever 1998; van der Heijden et al. 1998), concern over the loss of biodiversity in ecological communities rarely focuses on microbes— particularly pathogenic microbes which are more often targeted for eradication than preservation (but see Windsor 1995). Yet it is be...

Cryparin is a cell-surface-associated hydrophobin of the filamentous ascomycete Cryphonectria parasitica. This protein contains a signal peptide that directs it to the vesicle-mediated secretory pathway. We detected a glycosylated form of cryparin in a secretory vesicle fraction, but secreted forms of this protein are not glycosylated. This glycosylation occurred in the proprotein region, which...

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...

A novel mycovirus termed Rosellinia necatrix partitivirus 2 (RnPV2), isolated from a phytopathogenic fungus, Rosellinina necatrix strain W57, was molecularly and biologically characterized in both natural and experimental host fungi. Three double-stranded RNA (dsRNA) segments, dsRNA1, dsRNA2, and defective interfering dsRNA1 (DI-dsRNA1), whose sizes were approximately 2.0, 1.8, and 1.7 kbp, res...

The prototypic hypovirus CHV1-EP713 attenuates virulence (hypovirulence) and alters several physiological processes of the chestnut blight fungus Cryphonectria parasitica. The papain-like protease, p29, and the highly basic protein, p40, derived, respectively, from the N-terminal and C-terminal portions of the CHV1-EP713-encoded open reading frame (ORF) A polyprotein, p69, both contribute to re...

Chestnut blight, caused by the fungus Cryphonectria parasitica, has been effectively controlled with double-stranded RNA hypoviruses in Europe for over 40 years. The marked reduction in the virulence of C. parasitica by hypoviruses is a phenomenon known as hypovirulence. This virus-fungus pathosystem has become a model system for the study of biological control of fungi with viruses. We studied...

An inducible RNA-silencing pathway, involving a single Dicer protein, DCL2, and a single Argonaute protein, AGL2, was recently shown to serve as an effective antiviral defense response in the chestnut blight fungus Cryphonectria parasitica. Eukaryotic RNA-dependent RNA polymerases (RdRPs) are frequently involved in transcriptional and posttranscriptional gene silencing and antiviral defense. We...