ABSTRACT
T-DNA integration into plant chromosomal DNA via Agrobacterium tumefaciens can be achieved by exploiting the double-strand break repair system of the host's DNA. However, the detailed mechanism of T-DNA integration remains unclear. Here, a sequence analysis of the junction sequences of T-DNA and chromosomal DNA was performed to assess the mechanism of T-DNA integration. T-DNA was introduced into Arabidopsis wild-type and NHEJ-deficient ku80 mutant plants using the floral dip method; the junctions of the left border (LB) of T-DNA were subsequently analyzed by adapter PCR. The most frequent junction of the LB of T-DNA with chromosomal DNA was of the filler DNA type in both lines. The lengths of direct or inverted repeat sequences within or around the filler DNA sequence were greater in the ku80 mutant. In addition, the frequency of T-DNA integration near a transcription start site was significantly higher in the ku80 mutant. Our observations suggest that the presence of the Ku80 protein affects the location of the integration of T-DNA and the pattern of formation of repeat sequences within or around the filler DNA during LB integration into chromosomal DNA.