Mevalonic acid partially restores chloroplast and etioplast development in Arabidopsis lacking the non-mevalonate pathway

Isopentenyl diphosphate (IPP) is produced via two independent biosynthetic pathways in higher plants: the mevalonate (MVA) pathway in the cytoplasm and the non-mevalonate 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway in plastids. It has been previously suggested that IPP or IPP-derived products can be exchanged between the cytoplasm and plastids. However, the issue of whether the exchanged products reflect efficient synthesis of functional isoprenoids remains unresolved. We fed exogenous mevalonic acid to the Arabidopsis thaliana (L.) Heynh. albino mutant cla1-1, a null mutant of the first-step enzyme in the MEP pathway. This resulted in the recovery of thylakoid membrane stacking in chloroplasts in the light, and the formation of prolamellar bodies and plastoglobuli in etioplasts in the dark. By contrast, exogenous lovastatin, an inhibitor of mevalonic acid biosynthesis, induced complete depigmentation and further inhibition of plastid development in both the light and the dark. These results suggest that mevalonic acid-derived products contribute to the formation of functional plastidic isoprenoids, such as the chlorophylls and carotenoids required for plastid development.