Biosynthesis of Isoprene Units in Euphorbia lathyris Laticifers vs. Other Tissues: MVA and MEP Pathways, Compartmentation and Putative Endophytic Fungi Contribution

Abstract

Euphorbia species are characterized by a net of laticifers producing large amounts of triterpenes. These hydrocarbon-like metabolites can be converted into fuel by the methods of the oil industry. Euphorbia lathyris is easily grown at an industrial scale. In an attempt to increase its triterpene production, the metabolic pathways leading to isoprenoid were investigated by incorporation of 13C labeled glucose and mevalonate and 2H labeled deoxyxylulose as well as by natural abundance isotope ratio GC-MS. Latex triterpenes are exclusively synthesized via the mevalonate (MVA) pathway: this may orient future search for improving the triterpene production in E. lathyris. Phytosterols and their precursors are mainly derived from MVA pathway with a slight contribution of the methylerythritol phosphate (MEP) pathway, whereas phytol is issued from MEP pathway with a minor contribution of the MVA pathway: this is in accordance with the metabolic cross-talk between cytosolic and plastidial compartments in plants. In addition, hopenol B behaved differently from the other latex triterpenes. Its 13C isotope abundance after incorporation of 13C labeled glucose and its natural abundance δ2H signature clearly differed from those of the other latex triterpenes indicating another metabolic origin and suggesting that it may be synthesized by an endophytic fungus.

Biosynthesis and the Transcriptional Regulation of Terpenoids in Tea Plants (Camellia sinensis)

“…Sesterterpenes consist of relatively rare terpenoid substances that are formed by geranylfarnesyl diphosphate synthase (GFPPS) using GFPP as the precursor in the plastid MEP pathway [ 143 , 144 , 145 ]. Triterpenes are C 30 compounds derived from two molecules of FPP to generate the squalene catalyzed by squalene synthase (SQS) via the MVA pathway in the cytoplasm [ 26 , 146 , 147 ]. Although triterpenoids are not necessary for plant growth and development, the substances in this group have a wide range of biological activities and widespread commercial applications [ 148 , 149 , 150 , 151 ].…”

Metabolic Stimulation-Elicited Transcriptional Responses and Biosynthesis ofAcylated Triterpenoids in the Medicinal Plant Helicteres Angustifolia

“…Two units of FPP can be catalyzed by squalene synthase (SS) in a tail-to-tail manner to yield the hydrocarbon squalene. Subsequently, another important precursor 2, 3-oxidesqualene, is generated under the catalysis of the squalene monooxygenase (SM) with the presence of O2 and coenzyme NADPH [24,25]. 2, 3oxidesqualene can then be derived into various triterpenoid skeletons under the catalysis of oxidized squalene cyclases (OSCs) [26].…”