High-performance liquid chromatography of cytokinin ribonucleoside 5′-monophosphates

Study of cytokinin metabolism using HPLC with radioisotope detection

High performance liquid chromatography (HPLC) with an on-line flow-through radioactivity detector was used to monitor the metabolism of cytokinins ([3H]6-benzylaminopurine and [3H]6-benzylaminopurine riboside) after their incorporation into wheat seedlings. The production and conversion of individual metabolites was assayed within a short time interval (0.5-3 h). Extraction recoveries from plant tissue proved to be 85%. The uptake of both cytokinins was very rapid and differences in their metabolism were already perceptible after 30 min. The individual metabolites were identified as adenine (Ade), adenosine (Ado), benzyladenine-9-glucoside (BA-9G), 6-benzyladenine (BA) and benzyladenosine (BAR). The method is very fast, sensitive and very useful for metabolic studies. The detection limit was 40 pg (220 Bq) for BA at the level of 2 ng ml-1.

Mass-spectrometric quantification of cytokinin nucleotides and glycosides in tobacco crown-gall tissue

the cytokinins of tobacco crown-gall tissue have been analysed by quantitative mass spectrometry using (2)H2-labelled cytokinin riboside 5'-monophosphates and (15)N4-labelled cytokinin glycosides as internal standards. The principal endogenous cytokinin of this tissue is zeatin riboside 5'-monophosphate. The biologically inactive 7-glucoside of zeatin is the most abundant basic cytokinin in the tissue. These findings expose the limitations of previously reported analyses of similar tissues, which were restricted to biologically active basic cytokinins. The present study demonstrates that the endogenous cytokinins of tobacco crowngall tissue show a clear correspondence to the range of metabolites formed when exogenous cytokinins are supplied to nontumorous tobacco cells.