Metabolic Engineering in Fragaria x ananassa for the Production of Epiafzelechin and Phenylpropenoids

摘要

To confirm the in vivo function of a recently cloned strawberry UDP-glucose:anthocyanidin glucosyltransferase (FaGTl) gene, we downregulated its expression in strawberry fruit with a transient RNA interference (RNAi) method. In about one third of the injected fruits this led to a significant downregulation of FaGTl transcript levels consistent with reduced concentrations of anthocyanin pigments. In contrast, significant levels of epiafzelechin - formed by anthocyanidin reductase (ANR) from pelargonidin - were identified in FaGTl silenced fruits. Thus, the redirection of the metabolic flux towards the flavan-3-ol through downregulation of FaGTl offers a new method to increase the levels of this bioactive metabolite in fruit crops. In addition a dormant biosynthetic pathway of strawberry volatiles was uncovered by using the transient RNAi system. Silencing of the flavonoid pathway by downregulation of the chalcone synthase gene (FaCHS) provided phenylpropenoids for the biosynthesis of chavicol and eugenol in the fruits. These studies serve as foundation for metabolic engineering of strawberry flavor.