AMPLIFICATION IN-VIVO OF BROME MOSAIC-VIRUS RNAS BEARING 3' NONCODINGREGION FROM CUCUMBER MOSAIC-VIRUS

The 3' noncoding aminoacylatable regions of the three genomic RNAs of brome mosaic (BMV) and cucumber mosaic (CMV) viruses are highly conser ved and exhibit extensive similarities in their primary and secondary structures. To investigate the functional significance of these conser ved features, the 3' 186 nucleotide sequence of Fny-CMV RNA3 was incor porated into the 3' end of full-length genomic BMV RNA2 and RNA3 and t heir replicative competence and infectivity were examined in barley pr otoplasts and Chenopodium quinoa plants, respectively. In barley proto plasts, functional replicase provided by wild-type BMV RNAs 1 and 2 su ccessfully interacted with the CMV 3' end when present on RNA3 and res ulted in the proliferation and accumulation of chimeric progeny RNA3 a nd RNA4. In contrast, when CMV 3' end sequences were present on RNA2 n o amplification of chimeric RNA occurred. Inoculation of chimeric RNAs to C. quinoa revealed that systemic infections were derived from the selection of higher fitness recombinant sequences over lower fitness c himeric RNAs. (C) 1994 Academic Press, Inc.