Unravelling the regulatory mechanisms that modulate the MEP pathway in higher plants

Abstract

The methyl-D-erythritol 4-phosphate pathway is responsible for the biosynthesis of a substantial number of natural compounds of biological and biotechnological importance. In recent years, this pathway has become an obvious target to develop new herbicides and antimicrobial drugs. In addition, the production of a variety of compounds of medical and agricultural interest may be possible through the genetic manipulation of this pathway. To this end, a complete understanding of the molecular mechanisms that regulate this pathway is of tremendous importance. Recent data have accumulated that show some of the multiple mechanisms that regulate the methyl-D-erythritol 4-phosphate pathway in plants. In this review we will describe some of these and discuss their implications. It has been demonstrated that 1-deoxy-D-xylulose-5-phosphate synthase (DXS), the first enzyme of this route, plays a major role in the overall regulation of the pathway. A small gene family codes for this enzyme in most of the plants which have been analysed so far, and the members of these gene families belong to different phylogenetic groups. Each of these genes exhibits a distinct expression pattern, suggesting unique functions. One of the most interesting regulatory mechanisms recently described for this pathway is the post-transcriptional regulation of the level of DXS and DXR proteins. In the case of DXS, this regulation appears conserved among plants, supporting its importance. The evidence accumulated suggests that this regulation might link the activity of this pathway with the plant's physiological conditions and the metabolic demand for the final products of this route.

Disruption of the 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) gene results in albino, dwarf and defects in trichome initiation and stomata closure in Arabidopsis

“…The other possibility is that chemical flux from the MVA pathway is able to fulfil part of the biosynthesis requirement of the MEP pathway. As reported previously, sucrose can modulate the carbon flux through the MEP pathway, possibly either as a carbon source or as an energy indicator [53,60]. Taking into consideration that, without sucrose, the dxr null mutant plants are arrested at an early developmental stage, but with sucrose the mutant can proceed with the basic differentiation program and grow for more than 40 days, in which GAs, ABA or other important carotenoids are necessarily involved [61], the second possibility seems more likely.…”

“…There are at least two possibilities. One is posttranscriptional regulation of DXR, such as translational modulation [19,53]. In Arabidopsis, HMGR, a critical enzyme involved in the MVA pathway, has even more complicated regulation mechanisms [26,[54][55][56][57].…”

Feedback Inhibition of Deoxy-d-xylulose-5-phosphate Synthase Regulates the Methylerythritol 4-Phosphate Pathway

“…Despite the great diversity of structure and function, only two metabolic precursors, isopentenyl diphosphate (IDP) 3 and its isomer dimethylallyl diphosphate (DMADP) are used as the building blocks for all the isoprenoids (7,8). The well known acetate/mevalonate pathway was thought to be the only biochemical pathway for the synthesis of IDP (8,9).…”

“…The absence of the MEP pathway in humans and its presence in different eubacteria, various apicomplexan parasites, and photosynthetic eukaryotes make it an attractive target for drug discovery and herbicides (7,20,30). Some isoprenoids also serve as important targets for biotechnological applications because of their nutritional and medicinal benefits (7,31,32).…”

“…Some isoprenoids also serve as important targets for biotechnological applications because of their nutritional and medicinal benefits (7,31,32). Isoprene, the most abundantly produced isoprenoid in plants, significantly affects atmospheric chemistry (33).…”