RESUMEN
Tanshinone â ¡A (Tâ ¡A), a diterpene quinone with a furan ring, is a bioactive compound found in the medicinal herb redroot sage (Salvia miltiorrhiza Bunge), in which both furan and dihydrofuran analogs are present in abundance. Progress has been made recently in elucidating the tanshinone biosynthetic pathway, including heterocyclization of the dihydrofuran D-ring by cytochrome P450s; however, dehydrogenation of dihydrofuran to furan, a key step of furan ring formation, remains uncharacterized. Here, by differential transcriptome mining, we identified six 2-oxoglutarate-dependent dioxygenase (2-ODD) genes whose expressions corresponded to tanshinone biosynthesis. We showed that Sm2-ODD14 acts as a dehydrogenase catalyzing the furan ring aromatization. In vitro Sm2-ODD14 converted cryptotanshinone to Tâ ¡A and thus was designated Tâ ¡A synthase (SmTâ ¡AS). Furthermore, SmTâ ¡AS showed a strict substrate specificity, and repression of SmTâ ¡AS expression in hairy root by RNAi led to increased accumulation of total dihydrofuran-tanshinones and decreased production of furan-tanshinones. We conclude that SmTâ ¡AS controls the metabolite flux from dihydrofuran- to furan-tanshinones, which influences medicinal properties of S. miltiorrhiza.
Asunto(s)
Dioxigenasas/genética , Dioxigenasas/metabolismo , Diterpenos/metabolismo , Furanos/metabolismo , Plantas Medicinales/metabolismo , Salvia miltiorrhiza/genética , Salvia miltiorrhiza/metabolismo , Vías Biosintéticas , Regulación de la Expresión Génica de las Plantas , Genes de Plantas , Raíces de Plantas/metabolismoRESUMEN
Coenzyme Q (CoQ) is vital for energy metabolism in living organisms. In humans, CoQ10 deficiency causes diseases and must be replenished via diet; however, CoQ content in plant foods is primarily low. Here, we report the breeding of high CoQ10 tomato lines by expressing four enzymes with a fruit-specific promoter, which modifies the chloroplast chorismate pathway, enhances cytosolic isoprenoid biosynthesis, and up-regulates the first two reactions in mitochondrion that construct the CoQ10 polyisoprenoid tail. We show that, while the level of the aromatic precursor could be markedly elevated, head group prenylation is the key to increasing the final CoQ10 yield. In the HUCD lines expressing all four transgenes, the highest CoQ10 content (0.15 mg/g dry weight) shows a seven-fold increase from the wild-type level and reaches an extraordinarily rich CoQ10 food grade. Overviewing the changes in other terpenoids by transcriptome and metabolic analyses reveals variable contents of carotenoids and α-tocopherol in the HUCD lines. In addition to the enigmatic relations among different terpenoid pathways, high CoQ10 plants maintaining substantial levels of either vitamin can be selected. Our investigation paves the way for the development of CoQ10-enriched crops as dietary supplements.