抄録
Steviol is biosynthesized from ent-kaurenoic acid, a common precursor of gibberellins (GAs), and serves as the aglycon of steviol glycosides, a class of diterpenoid natural sweeteners produced by Stevia rebaudiana and Rubus suauissimus. We have recently identified a cytochrome P450 monooxygenase that catalyzes the formation of steviol from ent-kaurenoic acid in Arabidopsis. To examine whether steviol-glucosides can be produced in Arabidopsis, we introduced the Stevia glycosyltransferase gene, UGT85C2, into Arabidopsis plants that overexpress steviol synthase gene. In vitro assay suggested that crude extracts from the double-overexpressor plants were able to produce rubusoside, a sweet steviol-glycoside, from steviol, while this enzyme activity was undetectable in extracts from wild-type plants. Our results indicate the capability of Arabidopsis plants to produce a non-sugar sweetener by modifying the GA biosynthesis pathway via the introduction of a heterologous gene. We also investigated how the engineered steviol-glucoside pathway affects endogenous GA profiles.
