Abstract
Cytokinin antagonists were discovered in the screening for root growth promoter. Selected compounds from primary hits were suggested to act as cytokinin antagonist by specific inhibition in cytokinin-dependent growth of the recombinant yeast expressing cytokinin receptor gene. The more active compounds designed from the selected compounds were subject to a binding assay comprising H3-labeled cytokinin and recombinant protein of cytokinin receptor to confirm the mechanism of action. Non-competitive inhibition of the specific ligand-binding to the receptor was identified by kinetic studies. Consequently, the compounds have unique mechanism of action different from any anticytokinins that were inactive as antagonist on the recombinant yeast and the binding assay. Furthermore, both cytokinin-specific physiological response in Arabidopsis and cytokinin-dependent signal transduction in the transgenic Arabidopsis expressing cytokinin-inducible reporter gene were suppressed by the compounds. We believe the compounds useful as research tools for functional study of cytokinin and lead compounds for root growth promoter.
