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New cytokinin metabolites in IPT transgenic Arabidopsis thaliana plants
Author(s) -
Werner Tomáš,
Hanuš Jan,
Holub Jan,
Schmülling Thomas,
Van Onckelen Harry,
Strnad Miroslav
Publication year - 2003
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.2003.00094.x
Subject(s) - cytokinin , zeatin , glucoside , arabidopsis thaliana , biochemistry , biology , arabidopsis , metabolite , endogeny , auxin , mutant , gene , medicine , alternative medicine , pathology
Two novel cytokinin metabolites were identified in transgenic Arabidopsis thaliana (L.) Heynh. plants containing the bacterial IPT gene under the transcriptional control of a heat‐regulated promoter. After cyclic heat‐shock treatment, the endogenous cytokinin concentrations were elevated up to 100‐fold compared to the wild‐type plants. More then 20 different cytokinin metabolites were found, with zeatin‐type cytokinins being the most abundant. The metabolic inactivation of these compounds occurred predominantly through N ‐glucosylation. No significant accumulation of isopentenyladenine‐type cytokinins, and only a small increase in dihydrozeatin metabolites, was observed. Subsequent studies of the abundant, unidentified conjugates revealed the presence of zeatin and dihydrozeatin diglucoside conjugates. Structural analysis, utilizing electrospray‐liquid tandem mass spectrometry, identified these as a zeatin‐ O ‐glucoside‐9‐glucoside and dihydrozeatin‐ O ‐glucoside‐9‐glucoside, respectively. A third unknown metabolite, was tentatively identified as a phosphorylated form of zeatin‐9‐glucoside. The biological activity of these compounds in three cytokinin bioassays was low. A comparison of the cytokinin pattern in transgenic and wild‐type plants indicates that these specific metabolites accumulate as a consequence of enhanced cytokinin biosynthesis, and are probably involved in the homeostatic mechanisms that control endogenous cytokinin levels.