Transcription of the Agrobacterium Ti plasmid in the bacterium and in Crown Gall tumors

Abstract

Regions of the Agrobacterium tumefaciens tumor-inducing (Ti) plasmid which are transcribed in the bacterium or in two tobacco Crown Gall tumors were localized. Complementary DNA (cDNA) probes made to bacterial or tumor RNA were hybridized to blots of the Ti-plasmid or cloned “T”-DNA restriction endonuclease fragments digested with various restriction endonucleases. Extensive regions of the Ti plasmid are transcribed in the bacterium grown in minimal or rich medium. An additional region of the plasmid, which has previously been defined genetically as coding for proteins responsible for octopine utilization and conjugative T-plasmid transfer, is transcribed when the bacteria are induced with octopine. This region is transcribed constitutively in a mutant which is constitutive for octopine utilization. Another additional region of the plasmid is transcribed when the bacteria are induced with agropine. All sections of the “T” DNA are weakly transcribed in the bacterium. In contrast to this, specific regions of the “T” DNA are transcribed into both polyadenylated and nonpolyadenylated RNA in the tumors. The selectivity with which regions are transcribed in the tumor may indicate that the “T” DNA has “evolved” for best use in a eucaryotic cell.