THE CONSERVED NONANUCLEOTIDE MOTIF OF THE GEMINIVIRUS STEM-LOOP SEQUENCE PROMOTES REPLICATIONAL RELEASE OF VIRUS MOLECULES FROM REDUNDANT COPIES

Recombinant plasmids containing head-to-tail copies of different coat- protein replacement genomes of wheat dwarf virus (WDV) were used to st udy the mechanism leading to the release of replicating unit-length mo lecules in suspension culture cells of Triticum monococcum. For plasmi ds bearing two complete genomes, the viral unit bracketed by the two l arge intergenic regions (LIR) becomes preferentially released. Additio n of a third copy of the LIR on the inoculum plasmid is necessary for release of both WDV genomes with the same efficiency. Using plasmids c ontaining a single viral genome flanked by two different hybrid LIRs, we show that the sequence TAATATTA, which is part of the conserved gem inivirus nonanucleotide motif of the potential hairpin structure, is t he region of the LIR within which the release of unit-length molecules occurs. Moreover, the data suggest that this release results primaril y from rolling-circle replication, also in situations where intramolec ular homologous recombination is simultaneously possible.