Control of plastidial isoprenoid precursor supply: Divergent 1-deoxy-D-xylulose 5-phosphate synthase(DXS) isogenes regulate the allocation to primary or secondary metabolism

Abstract

Following the description of two separate pathways for isoprenoid precursor biosynthesis in plants, a new level of complexity has been introduced by the discovery of two divergent gene classes encoding the first enzyme of the plastidial methylerythritol phosphate (MEP) pathway. These nonredundant 1-deoxy-d-xylulose 5-phosphate synthase (DXS) isogenes are differentially expressed in such a way that DXS1 appears to serve housekeeping functions, whereas DXS2 is associated with the production of specialized (secondary) isoprenoids involved in ecological functions. Examples of the latter are apocarotenoid formation in roots colonized by arbuscular mycorrhizal fungi and mono- or diterpenoid biosynthesis in trichomes. Knockdown of DXS2 genes can specifically suppress secondary isoprenoid formation without affecting basic plant functions. Analyzing DXS isogenes along the progression of land plant evolution shows separation in structure and complementary expression already at the level of gymnosperms, which is maintained in all angiosperms except Arabidopsis.