Metabolism and compartmentation of dihydrozeatin exogenously supplied to photoautotrophic suspension cultures of Chenopodium rubrum

Abstract

[(3)H]Dihydrozeatin supplied to photoautotrophically growing cell suspension cultures of Chenopodium rubrum was rapidly taken up and metabolized by the cells. The predominant metabolites in extracts of the cells were [(3)H]dihydrozeatin-O-glucoside and [(3)H]dihydrozeatin riboside-O-glucoside. Both these compounds could be shown to be compartmented within the vacuole, whereas [(3)H]dihydrozeatin and [(3)H]dihydrozeatin riboside, which were both present to a minor extent in cell extracts, were both present to a minor extent in cell extracts, were localized predominantly outside the vacuole. Analysis of the culture medium at the end of the 36-h incubation period showed that there had been an efflux of [(3)H]dihydrozeatin metabolites out of the cells. Whereas [(3)H]dihydrozeatin riboside was found to be the major extracellular [(3)H]dihydrozeatin metabolite, the O-glucosides of neither this compound nor [(3)H]dihydrozeatin could be detected in the medium. The differential compartmentation of [(3)H]dihydrozeatin metabolites found with the C. rubrum suspension-culture system is discussed with respect to possible mechanisms governing the metabolism of cytokinins in plants cells.