The transfer DNA (T-DNA) mobilized into plant cells by Agrobacterium tumefaciens seems to integrate rather randomly into the plant genome. We analyzed a target site in the genome of Nicotiana tabacum before and after integration of a T-DNA. Clones presenting right and left T-DNA/plant DNA junctions were used as probes to identify and isolate a unique 1.8… (More)
FIG. 2. Hae III restriction map of pTT1, cg3, and cg4. Single-lined boxes, T-DNA; double-lined boxes, plant DNA; wavy lines, pBR322. Dashed vertical lines align the corresponding plant sequences in the different clones; cg3 and cg4 are HindIII-EcoRI fragments in pBR322 (12), whereas pTT1 is an EcoRI clone in pBR322. Vertical lines indicate Hae III restriction sites; numbers refer to the sizes of the Hae III fragments. The plant DNAs in the 665-bp (cg4) and 830-bp (pTT1) Hae III fragments are identical (about 650 bp); the sizes of the fragments differ because the inserts were cloned in opposite orientations into pBR322 (the distance from the left EcoRI site to the closest Hae III site in pBR322 is 16 bp in cg4 and 177 bp in pTT1). Some other restriction enzymes used in the analyses are indicated. The direction and length of the horizontal arrows summarize the strategy used to obtain the nucleotide sequences shown in Fig. 3.