Mass-spectrometric quantitation of cytokinins in tobacco crown-gall tumours induced by mutated octopine Ti plasmids of Agrobacterium tumefaciens.
The levels of the major cytokinins, zeatin, zeatin riboside, zeatin riboside-5'-monophosphate and zeatin-7-glucoside were measured in tobacco (Nicotiana tabacum L.) crown-gall tissues carrying insertion and deletion mutations in the T-DNA. Measurements were made by combined gas chromatography-mass spectrometry using selected ion monitoring with (15)N- and (2)H-labelled internal standards. The results demonstrate that, relative to wild-type tumour tissue, cytokinin levels are considerably elevated in tissues lacking functional T-DNA auxin-biosynthetic genes. From a detailed analysis of the major cytokinin metabolites it is concluded that a reduction in the extent of cytokinin degradation via N(6)-side-chain cleavage is an important factor leading to increased cytokinin levels in these tissues.
The Rowett Research Institute, Greenburn Road, Bucksburn, AB2 9SB, Aberdeen, UK.
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McGaw
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Horgan
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Heald
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GJ
Wullems
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Schilperoort