title: Tumour genes in plants: T-DNA encoded cytokinin biosynthesis.
abstract: Gene 4 from the T-region of Ti plasmids is responsible for cytokinin effects in crown gall cells; we investigated whether it codes for an enzyme of hormone biosynthesis. In a first set of experiments, gene 4 from octopine plasmid pTiAch5 and nopaline plasmid pTiC58 was expressed in Escherichia coli, and the gene products were identified by reaction with antiserum raised against a decapeptide derived from the DNA sequence of the gene. Extracts from cells expressing the gene contained high isopentenyl-transferase activity catalyzing the formation of N6-(delta2-isopentenyl)adenosine from 5'-AMP and delta2-isopentenylpyrophosphate. The cytokinin was identified by sequential h.p.l.c. chromatography and mass spectrometry. In a second set of experiments it was shown that crown gall cells contained isopentenyltransferase activity and a protein of mol. wt. 27 000 which was identified as the product of gene 4 by reaction with the antiserum. Isopentenyltransferase activity was specifically inhibited by the antiserum. No comparable enzyme activity or immunoreactive protein was detected in cytokinin-autotrophic, T-DNA free tobacco cells. The results establish that gene 4 from the T-region of octopine and nopaline Ti plasmids codes for an enzyme of cytokinin biosynthesis.
authors.affiliation: Institut für Biologie II, Universität Freiburg, Schänzlestr. 1, D-7800, Freiburg, FRG.
authors.forename: I
authors.initials: I
authors.lastname: Buchmann
authors.forename: F J
authors.initials: FJ
authors.lastname: Marner
authors.forename: G
authors.initials: G
authors.lastname: Schröder
authors.forename: S
authors.initials: S
authors.lastname: Waffenschmidt
authors.forename: J
authors.initials: J
authors.lastname: Schröder
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics; D002851:Chromatography, High Pressure Liquid; D003583:Cytokinins / Q000096:biosynthesis* / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics*; D004122:Dimethylallyltranstransferase / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D017343:Genes, Plant / Q000235:genetics*; D013058:Mass Spectrometry; D036741:Plant Tumor-Inducing Plasmids / Q000235:genetics; D010941:Plant Tumors / Q000235:genetics*; D014026:Nicotiana / Q000235:genetics
chemical_list: D003583:Cytokinins; D018744:DNA, Plant; D019883:Alkyl and Aryl Transferases; D004122:Dimethylallyltranstransferase; C024274:adenylate isopentenyltransferase