Two pathways are used by higher plants for the biosynthesis of isoprenoid precursors: the mevalonate pathway in the cytosol and a 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway in the plastids, with 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate reductase (HDR) catalyzing the last step in the MEP