Integration and organization of Ti plasmid sequences in crown gall tumors.

The Ti plasmid sequences (T DNA) maintained in four unorganized crown gall tumor lines were defined by using restriction endonucleases and molecular hybridization techniques. Each tumor line contains a "core" T DNA which is apparently responsible for maintaining the transformed state; the core T DNA is colinear with the Ti plasmid and contains the Ti plasmid sequences referred to as the "common DNA"--sequences found in all Ti plasmids studied to date. A given Ti plasmid does not always give rise to the same T DNA complement. The data suggest that the majority if not all of the T DNA is integrated into plant DNA, that preferred regions of the Ti plasmid serve as the points of attachment to plant DNA and that the T DNA can be linked to more than one site in the plant genome.