Figure 1.

Depiction of terpenoid biosynthesis in plants. Broken arrows indicate multiple steps or reactions. The number of carbon molecules is indicated in brackets. Question mark indicates putative exchanges of isoprenoids between the cytosol and the plastidic compartment. AcetylCoA, Acetyl coenzyme A; HMGCoA, 3-hydroxy-3 methylglutaryl coenzyme A; DMAPP, dimethylallyl pyrophosphate; GGPP, geranylgeranyl pyrophosphate. a, HMGCoA reductase. b, Plastidic 1-deoxy-d-xylulose-5-phosphate pathway. c, Isopentenyl pyrophosphate isomerase. d, Prenyl transferase (adapted from Lichtenthaler [1999]).