STRAIN-SPECIFIC MOBILIZATION AND AMPLIFICATION OF A TRANSGENIC DEFECTIVE-INTERFERING DNA OF THE GEMINIVIRUS BEET CURLY TOP VIRUS

Transgenic Nicotiana benthamiana plants have been constructed which be ar integrated, tandemly repeated copies of a beet curly top virus (BCT V) defective-interfering (DI) DNA derived from the Logan strain. Trans genic DI-DNA plant lines challenge-inoculated with BCTV-Logan exhibite d delayed and attenuated symptoms compared to nontransgenic plants. in fection of transgenic plants with the Logan strain resulted in the mob ilization of the integrated DI-DNA sequence, which was subsequently am plified as an episome. The accumulation of Logan helper virus DNA form s was reduced in transgenic plants, relative to nontransgenic plants. In contrast, no delay or attenuation of symptoms was observed for tran sgenic plants challenge-inoculated with the BCTV strains CFH and Worla nd. infection by the CFH and Worland strains did not result in mobiliz ation or amplification of the integrated Logan DI-DNA sequence, and no consistent differences in the accumulation of CFH or Worland genomic viral DNA forms were observed among transgenic and nontransgenic plant s. These results, and a comparison of putative DNA replication origin sequences, suggest that BCTV strains display specificity with respect to recognition of heterologous DNA replication origin cis-elements. (C ) 1994 Academic Press, Inc.