Cytokinins can be conjugated to N- and O-glucosides. While N-glucosylation generally leads to irretrievable loss of activity, O-glucosides are thought to play an important role in cytokinin storage and homeostasis since they can be hydrolyzed to the corresponding aglycones. The first zeatin O-glycosyltransferase genes isolated were ZOG1 and ZOX1 from...