Effects of mutations in the TATA box region of the Agrobacterium T-cyt gene on its transcription in plant tissues.

We have generated mutations in the promoter region of the octopine type cytokinin gene of Agrobacterium tumefaciens, and studied their effects on mRNA formation in different plant species. The promoter region of this gene contains several putative TATA boxes. Phenotypic expression and Northern blot hybridization showed that TATA boxes are essential for expression, but that one TATA box leads to wild-type transcript levels. Analysis of the 5' ends of T-cyt transcripts by primer extension using RNA from T-cyt gene transformed tobacco shoots revealed two major cap site clusters and one minor cap site. TATA box consensus sequences can be found approximately 30 bp upstream from each cap site cluster. Deletion of a TATA box results in loss of the corresponding cap sites. An insertion of 7 bp between the right TATA box and corresponding cap sites results in a shift of the position of the cap sites, so that the original distance of TATA box to cap sites is conserved as much as possible.