A spontaneous insertion in the agrocin sensitivity region of the Ti-plasmid of Agrobacterium tumefaciens C58.

A spontaneous agrocin-resistant mutant of Agrobacterium tumefaciens strain C58 was shown to have an insertion of 1.2 kb in the agrocin-sensitivity region of pTiC58. The insertion was cloned from the Ti-plasmid, and a subclone containing only DNA internal to the insertion was used to probe the Ti-plasmid and chromosomal DNA of the wild-type strain C58. The probe showed homology to chromosomal sequences but showed no homology to wild-type pTiC58. Homology was also detected with chromosomal sequences of A. tumefaciens strains, B6, K24, and T37. These results suggest that an indigenous insertion sequence of 1.2 kb transposed from the chromosome to the agrocin-sensitivity region of the Ti-plasmid in this spontaneous mutant of C58.