An Account of Cloned Genes of Methyl-erythritol-4-phosphate Pathway of Isoprenoid Biosynthesis in Plants

Isoprenoids, also known as terpenoids, are biosynthesized by the condensation of the two C₅ unit isopentenyl diphosphate (IPP) and isomer dimethylallyl diphosphate (DMAPP). Generally, plants use two separate pathways plastidial Methyl-erythritol-4-phosphate (MEP) and cytosolic acetate-mevalonate (MVA) pathways for formation of IPP. The genes, enzymes and intermediates of the MEP pathway have been unravelled in plants over the past few years. Interestingly, MEP pathway enzymes are encoded by nuclear genes but they function in plastids to produce precursors for isoprenes, monoterpenes, carotenoids, abscisic acid, gibberellins, and the side chain of chlorophylls, tocopherols, phylloquinones, and plastoquinone. In Arabidopsis thaliana , a complete set of genes of MEP pathway homologous to the E. coli MEP pathway genes have been identified. Although, these genes have been cloned and characterized from several other plants but overall information about them at one place is not available so far. Though, a range of reviews are available about their roles in isoprenoid biosynthesis and regulation. Therefore, we decided to compile the data on cloned and characterized genes of MEP pathway in plants. Also, we summarize the results of the previously published reports, particularly those which were based on incorporation of ¹³C-glucose or by application of specific inhibitors such as mevinolin and fosmidomycin to look into the MEP pathway in plants. In addition, we searched for the two key enzymes DXS and HMGR that could be assigned for the acetate-MVA and MEP pathway with the help of bioinformatics tools. Presence or absence of these enzymes can be correlated with respective isoprenoid biosynthetic pathways in plants.