Mapping of promoter-proximal regions by in vitro transcription of two Agrobacterium tumefaciens Ti-plasmids.

Transcription initiation sites were mapped on both the octopine pTi Ach5 and the nopaline pTI C58 plasmids of Agrobacterium tumefaciens. Transcription ternary complexes were subjected to electrophoresis on agarose gels, prior and/or subsequent to restriction endonuclease digestion of the DNA template, evidenced by autoradiography and located on the restriction maps of the two tumor-inducing plasmids. A. tumefaciens RNA polymerase promptly recognizes and starts transcription on a few sequences which include the T-DNA.