DNA REARRANGEMENT ASSOCIATED WITH THE INTEGRATION OF T-DNA IN TOBACCO- AN EXAMPLE FOR MULTIPLE DUPLICATIONS OF DNA AROUND THE INTEGRATION TARGET

Transferred DNA (T-DNA) of the tumor-inducing (Ti) plasmid is transfer red from Agrobacterium tumefaciens to plant cells and is stably integr ated into the plant nuclear genome. By the inverse polymerase chain re action DNA fragments were amplified that contained the T-DNA/plant DNA junctions from the total DNA of a transgenic tobacco plant that had a single copy of the T-DNA in a repetitive region of its genome. A DNA fragment containing the target site was amplified from the total DNA o f nontransformed tobacco by the polymerase chain reaction using high-s tringency conditions. Comparison of the nucleotide sequence of the tar get site with those of the T-DNA/plant DNA junctions revealed that var ious duplications of short stretches of nucleotide sequences around th e target and in the incoming T-DNA had accompanied the integration of the T-DNA. A deletion of 16 bp at the target site was also found and t he target site was similar, in terms of nucleotide sequence, to region s around the breakpoints of the T-DNA. This finding provides a clear e xample of the occurrence of complex rearrangements during the integrat ion of T-DNA.