DELETIONS IN THE 3'-UNTRANSLATED REGION OF COWPEA CHLOROTIC MOTTLE VIRUS TRANSGENE REDUCE RECOVERY OF RECOMBINANT VIRUSES IN TRANSGENIC PLANTS

The 3' untranslated region (UTR) adjacent to the capsid gene is freque ntly included with the transgene in the construction of capsid protein mediated virus resistant transgenic plants. Since ribonucleotide sequ ences within the 3' UTR are involved in the initiation of viral replic ation, the presence of this sequence may encourage the participation o f the transgene in RNA recombination. Experiments were designed to exp lore the involvement of the 3' UTR of cowpea chlorotic mottle virus (C CMV) in RNA recombination events between transgenes and challenging vi ruses. Nicotiana benthamiana was transformed with CCMV transgenes cons isting of the 3' two-thirds of the capsid gene and fragments of the as sociated 3' UTR lacking the terminal 69, 83, or 214 nucleotides. Plant s were inoculated with wild-type CCMV transcripts for RNAs 1 and 2 and a movement defective RNA 3 transcript lacking the 3' third of the cap sid gene. While no recombinant virus was detected in plants expressing 3' deletion constructs, 3% of control transformants containing an ide ntical segment of the capsid gene with the complete 3' UTR yielded via ble recombinant virus. These results suggest that RNA recombination be tween transgenic RNA and viral RNA can be reduced significantly by omi tting or disrupting the 3' UTR in the transgene. (C) 1996 Academic Pre ss. Inc.