The sequence of thetmstranscript 2 locus of theA. tumefaciensplasmid pTiA6 and characterization of the mutation in pTiA66 that is responsible for auxin attenuation

The incorporation of Ti plasmid sequences, the T-DNA, into the genomes of dicotyledenous plants causes the formation of tumors. Here we report the nucleotide sequence of one of the T-DNA "oncogenes", the transcript 2 gene of pTiA6 and we further characterize the 2.7 Kb element that has spontaneously inserted into this gene in plasmid pTiA66. The results indicate that the transcript 2 portion of the T-DNA has an open reading frame that could encode a polypeptide of 49.8 Kd. The open reading frame is surrounded by sequences that typically have roles in eucaryotic gene expression. Nucleotide sequence and Southern blot analysis also indicates that the 2.7 Kb insert in the transcript 2 gene of pTiA66 is located within the coding sequence of the gene and suggests that the element is an insertion sequence. We designate this element, IS66.