Abstract
Plants have two routes for isoprenoid biosynthesis; the mevalonate (MVA) pathway in cytosol and the methylerythritol phosphate (MEP) pathway in plastids. We have demonstrated in Arabidopsis seedlings that gibberellins are predominantly produced from the MEP pathway, using a feeding experiment that enabled us to label downstream isoprenoids with stable isotopes from the MVA and MEP pathways, respectively. Here, we further investigate the early steps of other isoprenoids to which the contributions of the MVA and MEP pathways are unclear. The rate-limiting step(s) of the MEP pathway is a critical issue to understand how the pathway is regulated in plants. To address this matter, we produced transgenic Arabidopsis lines, in which each gene encoding enzymes in the MEP pathway was individually overexpressed under the control of the CaMV 35S promoter. Quantitative analysis of isoprenoids and estimation of the rate-limiting step(s) in the MEP pathway were assessed.
