Figure 9.

Schematic mode of localizations and possible functions of five GGPP synthases in Arabidopsis. The GGPS1 and GGPS3 proteins are translocated into chloroplasts for the biosynthesis of gibberellins, carotenoids, abscisic acids, and chlorophylls. The GGPS2 and GGPS4 proteins are localized on the ER membrane, and the GGPP produced by these enzymes is used for protein prenylation. The GGPS6 protein is translocated into the mitochondria, and the product could be used for ubiquinone biosynthesis. The GGR protein, for which enzymatic activity could not be detected in vitro, might stay in the cytosol to produce GPP. The differentiated subcellular localization of GGPP synthases makes it possible to have GGPP pools inside plant cells. CLA1, Putative transketolase; CPP, copalyl diphosphate; DMAPP, dimethylallyl diphosphate; GA1, CPP synthase; GA2, ent-kaurene synthase; GAP, glyceraldehyde-3-phosphate; IPP2, IPP isomerase; and MVA, mevalonate.