Peroxisomal Localization of Arabidopsis Isopentenyl Diphosphate Isomerases Suggests That Part of the Plant Isoprenoid Mevalonic Acid Pathway Is Compartmentalized to Peroxisomes

Isoprenoids, the largest family of natural products, play numerous vital roles in basic plant processes, including photosynthesis, growth and development, reproduction, plant defense, and adaptation to environmental conditions (Gershenzon and Kreis, 1999; Rodriguez-Concepcion and Boronat, 2002). All isoprenoids are synthesized via the condensation of the five-carbon universal isoprenoid precursors, isopentenyl diphosphate (IPP) and its allylic isomer dimethylallyl diphosphate (DMAPP; McGarvey and Croteau, 1995). In higher plants, two independent pathways located in separate intracellular compartments are involved in the biosynthesis of IPP and DMAPP (see current model for plant isoprenoid pathways compartmentalization in Fig. 1 !!...!! ). In the mevalonic acid (MVA) pathway, which is referred to as the cytosolic pathway, biosynthesis of IPP/DMAPP starts from the condensation of acetyl-CoA (Qureshi and Porter, 1981; Newman and Chappell, 1999), whereas in plastids, IPP/DMAPP are formed from pyruvate and glyceraldehyde-3-P via the methylerythritol phosphate (MEP; or non-mevalonate) pathway (Lichtenthaler et al., 1997, 1999; Eisenreich et al., 1998, 2001; Rohmer, 1999). Initial research indicated that the MVA-pathway-derived pool of IPP/DMAPP serves as a precursor of farnesyl diphosphate (FPP; C15) and, ultimately, the sesquiterpenes, triterpenes, and sterols, whereas the plastidic MEP-pathway-derived pool of IPP/DMAPP provides the precursors of geranyl diphosphate (C10), geranylgeranyl diphosphate (C20), and, ultimately, the monoterpenes, diterpenes, and tetraterpenes. Although the subcellular compartmentalization of MVA and MEP pathways allows them to operate independently, metabolic cross talk between these two pathways was recently implied (Bick and Lange, 2003; Hemmerlin et al., 2003; Laule et al., 2003; Schuhr et al., 2003; Dudareva et al., 2005; Hampel et al., 2005).