Elucidation of cytokinin biosynthesis by ¹⁸O/¹³C-labeling system for isoprenoids in plants

Abstract

Cytokinins induce cell division and differentiation of the plant in the presence of auxin. By using a selective ¹³C-labeling system for isoprenoids from the methylerythritol phosphate (MEP) pathway in plastids or the mevalonate (MVA) pathway in the cytosol, we have previously demonstrated that the prenyl side chain of trans-zeatin (tZ) is mainly derived from dimethylallyl diphosphate in the MEP pathway, but also partially produced through the cis-trans isomerization of cis-zeatin from the MVA pathway in Arabidopsis seedlings. In the present study, we found that Agrobacterium sends its CK biosynthesis enzyme into plastids to create a new tZ biosynthesis pathway using an intermediate of the MEP pathway, hydroxymethylbutenyl diphosphate, in the host plant. We will present new findings from labeling experiments in Arabidopsis seedlings, Catharanthus cell cultures and tomato crown gall using ¹⁸O-labeled precursor.