Nucleotide sequence and expression of a Pseudomonas savastanoi cytokinin biosynthetic gene: homology with Agrobacterium tumefaciens tmr and tzs loci.

The nucleotide sequence of a Pseudomonas trans-zeatin producing gene (ptz) from the pCK1 plasmid of Pseudomonas syringae pv. savastanoi strain 1006 has been determined. This gene confers upon E. coli the ability to synthesize and secrete several cytokinins including trans-zeatin, iso-pentenyladenine and their respective N9-ribosyl derivatives. Sequence analysis indicates an open reading frame encoding a protein of 234 amino acids with a molecular weight of 26,816. Significant sequence homology is found between ptz and both the tzs and tmr genes from Agrobacterium tumefaciens. The results suggest a close relationship between the cytokinin biosynthetic pathways in P. savastanoi and A. tumefaciens.