CDNA-DERIVED HYPOVIRUS RNA IN TRANSFORMED CHESTNUT BLIGHT FUNGUS IS SPLICED AND TRIMMED OF VECTOR NUCLEOTIDES

Unencapsidated double-stranded viral RNAs belonging to the genus Hypov irus attenuate virulence of the chestnut blight fungus, Cryphonectria parasitica. A full-length cDNA clone of hypovirus CHV1-713 double-stra nded RNA was recently shown to be infectious when introduced into the C. parasitica genome by DNA-mediated transformation. In this study, we show that the viral RNA derived from the chromosomally integrated cDN A copy is trimmed of extraneous vector nucleotide sequences. The cDNA- derived viral RNA was also found to contain a 73-bp deletion located w ithin the 5'-noncoding leader sequence as a result of a pre-mRNA splic ing event. Implications of these results are discussed in terms of hyp ovirus RNA replication and anticipated field studies involving enginee red hypovirulent C. parasitica strains. (C) 1994 Academic Press, Inc,