Abstract
Isoprenoids are synthesized from isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) as common precursors. Plants biosynthesize IPP and DMAPP by two pathways; the mevalonate (MVA) pathway in cytosol and the methylerythritol phosphate (MEP) pathway in plastids. In the MVA pathway, DMAPP is converted from IPP by IPP isomerase, whereas DMAPP can be directly synthesized through the MEP pathway without isomerization of IPP. Therefore, it is unclear if IPP isomerase plays any role in the formation of DMAPP in plastids. Arabidopsis has two genes encoding putative IPP isomerases, AtIPP1 and AtIPP2. GFP fusion proteins produced in transgenic Arabidopsis showed that AtIPP1-GFP and AtIPP2-GFP were localized in plastid and mitochondria, respectively. To examine the role of IPP isomerase in plastids, we generated transgenic plants overproducing AtIPP2 that is targeted to plastids by fusing a transit peptide to this enzyme. We are currently analyzing whether AtIPP2 overproduction modulates downstream isoprenoid biosyntheses in plastids.
