VIRUS-MEDIATED OR TRANSGENIC SUPPRESSION OF A G-PROTEIN ALPHA-SUBUNITAND ATTENUATION OF FUNGAL VIRULENCE

Strains of the chestnut blight fungus Cryphonectria parasitica harbori ng RNA viruses of the genus Hypovirus exhibit significantly reduced le vels of virulence (called hypovirulence). The accumulation of a hetero trimeric GTP-binding protein (G protein) alpha subunit of the G(i) cla ss was found to be reduced in hypovirus-containing C. parasitica strai ns. Transgenic cosuppression, a phenomenon frequently observed in tran sgenic plants, reduced the accumulation of this alpha subunit in virus -free fungal strains. Significantly, the resulting transgenic fungal s trains were also hypovirulent. These results indicate a crucial role f or G-protein-linked signal transduction in fungal pathogenesis and sug gest a molecular basis for virus-mediated attenuation of fungal virule nce.