- PhD, Biochemistry, University of New Hampshire
Our laboratory has been studying a family of mycoviruses, the hypoviruses that attenuate virulence of the chestnut blight fungus, Cryphonectria parasitica. The hypovirus/C. parasitica system is one of the very few eucaryotic systems for which both a virus and its host can be genetically manipulated with ease. A very robust DNA transformation system is available for C. parasitica allowing disruption, silencing or over-expression of fungal genes. We have constructed infectious cDNA clones of two hypovirus RNA genomes, CHV1-EP713 and CHV1, Euro7, providing the only viral reverse genetics system for the entire Kingdom Fungi. This development has allowed the construction of "engineered" hypoviruses with enhanced biocontrol potential and the extension of virus host range to include several other pathogenic fungi.
Hypovirus CHV1-EP713 causes very severe phenotypic changes in the infected fungal host while hypovirus CHV1-Euro7 causes mild symptoms. Although these two viruses cause quite different phenotypic changes, they are similar enough in nucleotide sequence to allow the construction of viable chimers that can be used to map symptom determinants and fine-tune the interaction between C. parasitica and its plant host.
Several lines of evidence indicate that hypovirus infection results in alterations of signal transduction pathways involved in normal fungal gene expression. Chimeric and mutant hypoviruses are being used to map viral-encoded modifiers of cellular signaling pathways with the aid of fungal strains stably transformed with novel promoter/reporter gene constructs. These studies are being expanded with the aid of a C. parasitica EST database and microarray analyses to gain deeper insight into virus-host interactions and test the fundamental hypothesis that RNA silencing in fungi evolved as an antiviral defense mechanism. Combined basic and technical advances are providing new opportunities for broadening the potential application of hypoviruses for purposes of understanding and controlling fungal pathogenesis.