Understanding the mechanisms that modulate the MEP pathway in higher plants

Abstract

The methyl-d-erythritol 4-phosphate (MEP) pathway is responsible for the biosynthesis of an impressive number of natural compounds of biological and biotechnological importance. In recent years, this pathway has become a clear target to develop new herbicides and antimicrobial drugs. Additionally, the production of a variety of compounds of medical and agricultural interest may be possible through genetic manipulation of this pathway. To this end, a full understanding of the molecular mechanisms that regulate this pathway is of tremendous importance. Our work has shown that the MEP pathway is subjected to multiple levels of regulation, some of them being conserved among different plant species. In this chapter, we describe some of these regulatory mechanisms. The first enzyme of this anabolic route is the 1-deoxy- d -xylulose 5-phosphate synthase (DXS). Our work has provided evidence of the strategic role that this enzyme plays in the overall regulation of the pathway. DXS is encoded by a small gene family, between two or three members, that belong to three major groups maintained through evolution. In some plants (e.g., maize), each of the DXS genes exhibits a unique expression pattern, supporting a particular function for each gene product during plant development. One of the most interesting regulatory events identi fi ed is the modulation of the DXS protein level in response to a blockage or decrease of the pathway fl ow. This regulation is conserved among plants, suggesting that it is an important feedback mechanism for the proper response of this pathway to the plant's metabolic demand.