Regulatory pathways governing modulation of fungal gene expression by a virulence-attenuating mycovirus.
A viral double-stranded RNA associated with virulence attenuation (hypovirulence) in the chestnut blight fungus (Cryphonectria parasitica) has been shown by DNA-mediated transformation to be responsible for transmissible hypovirulence. In addition to reduced virulence, the fungal strain harboring this virus exhibits a diverse array of characteristics, termed hypovirulence-associated traits, which distinguish it from an isogenic virus-free strain. We have investigated one of these traits, suppressed lac-1 (laccase) transcript accumulation. Two different and opposing regulatory pathways appear to govern lac-1 transcript levels in the virus-free strain: a stimulatory pathway was found to be dependent on the inositol trisphosphate (IP3) and calcium second messenger systems. A second pathway limiting transcript accumulation was shown to require ongoing protein synthesis. Additionally, changes in the level of lac-1 transcript accumulation were found to be related to modulation of promoter activity and this activity was shown to be suppressed in the virus-containing strain. We conclude that this hypovirulence-associated virus interferes with transduction of an IP3-calcium-dependent signal that is required for stimulation of lac-1 transcription. The perturbation of such signal transduction pathways by hypovirulence-associated viruses may account for the manifold symptoms associated with transmissible hypovirulence.
Larson
T G
TG
Department of Molecular Oncology and Virology, Roche Institute of Molecular Biology, Roche Research Center, Nutley, NJ 07110.
Choi
G H
GH
Nuss
D L
DL
D001203:Ascomycota / Q000235:genetics* / Q000472:pathogenicity; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D016572:Cyclosporine / Q000494:pharmacology; D004277:DNA, Single-Stranded; D004587:Electrophoresis, Agar Gel; D015966:Gene Expression Regulation, Fungal; D015967:Gene Expression Regulation, Viral; D007295:Inositol Phosphates / Q000378:metabolism; D042845:Laccase; D008094:Lithium / Q000494:pharmacology; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012328:RNA Viruses / Q000235:genetics* / Q000472:pathogenicity; D014158:Transcription, Genetic / Q000187:drug effects; D014774:Virulence / Q000235:genetics
D004277:DNA, Single-Stranded; D007295:Inositol Phosphates; D016572:Cyclosporine; D003513:Cycloheximide; D008094:Lithium; D010088:Oxidoreductases; D042845:Laccase; D002118:Calcium