Topolins and Hydroxylated Thidiazuron Derivatives Are Substrates of Cytokinin O-Glucosyltransferase with Position Specificity Related to Receptor Recognition
- 1 March 2005
- journal article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 137 (3), 1057-1066
- https://doi.org/10.1104/pp.104.057174
Abstract
Glucosides of trans-zeatin occur widely in plant tissues, formed either by O-glucosylation of the hydroxylated side chain or N-glucosylation of the purine ring structure. O-Glucosylation is stereo-specific: the O-glucosyltransferase encoded by the Phaseolus lunatus ZOG1 gene has high affinity for trans-zeatin as the substrate, whereas the enzyme encoded by the maize (Zea mays) cisZOG1 gene prefers cis-zeatin. Here we show that hydroxylated derivatives of benzyladenine (topolins) are also substrates of ZOG1 and cisZOG1. The m-OH and o-OH derivatives are the preferred substrate of ZOG1 and cisZOG1, respectively. Among the hydroxylated derivatives of thidiazuron tested, the only enzyme/substrate combination resulting in conversion was cisZOG1/(o-OH) thidiazuron. The abilities of these cytokinins to serve as substrates to the glucosyltransferases were in a large part correlated with their biological activities in the P. lunatus callus bioassay, indicating that there may be similarities between cytokinin-binding sites on the enzymes and cytokinin receptors. Further support for this interpretation is provided by cytokinin recognition studies involving the Arabidopsis (Arabidopsis thaliana) CRE1/WOL/AHK4 and maize ZmHK1 receptors. The AHK4 receptor responded to trans-zeatin and m-topolin, while the ZmHK1 receptor responded also to cis-zeatin and o-topolin. Three-dimensional molecular models of the substrates were applied to explain the results.Keywords
This publication has 58 references indexed in Scilit:
- Cytokinin Oxidase and the Regulation of Cytokinin DegradationPublished by Taylor & Francis ,2019
- Fast and efficient separation of cytokinins from auxin and abscisic acid and their purification using mixed-mode solid-phase extractionJournal of Chromatography A, 2002
- Molecular and Biochemical Characterization of a Cytokinin Oxidase from MaizePlant Physiology, 2001
- An alternative cytokinin biosynthesis pathwayProceedings of the National Academy of Sciences, 2000
- Influence of White Clover Mosaic Potexvirus Infection on the Endogenous Cytokinin Content of BeanPlant Physiology, 1999
- Cytokinin biosynthesis and interconversionPhysiologia Plantarum, 1997
- Cytokinin conjugation: recent advances and patterns in plant evolutionPlant Growth Regulation, 1997
- Zeatin Glycosylation Enzymes in PhaseolusPlant Physiology, 1989
- Modification of Cytokinins by Cauliflower Microsomal EnzymesPlant Physiology, 1984
- Cytokinin activity of some substituted ureas and thioureasProceedings of the Royal Society of London. B. Biological Sciences, 1966