N6-(5-Phenylpentan-1-yl)adenine—A New Non-competitive Receptor-Specific Anti-cytokinin

For the first time, N⁶-(5-phenylpentan-1-yl)adenine, a synthetic adenine derivative with a receptor-specific anticytokinin effect, was obtained. This compound exhibits a pronounced anticytokinin effect, reducing cytokinin-induced expression of the GUS reporter gene when interacting with the cytokinin receptor CRE1/AHK4 of the model plant Arabidopsis thaliana. This effect manifests itself much weaker with the related AHK2 receptor and is not observed at all with the AHK3 receptor. We showed that N⁶-(5-phenylpentan-1-yl)adenine does not bind to the ligand-binding sites of the Arabidopsis cytokinin receptors, which does not allow it to be classified as a true cytokinin antagonist. Despite the currently unknown mechanism of action, this compound may find its use as a component of plant growth regulators. Like true anticytokinins, it enhances root growth of Arabidopsis seedlings, apparently suppressing the action of endogenous cytokinins on the “root” receptor CRE1/AHK4.