Terpene synthases of oregano (Origanum vulgare L.) and their roles in the pathway and regulation of terpene biosynthesis
作者:Christoph Crocoll、Julia Asbach、Johannes Novak、Jonathan Gershenzon、Jörg Degenhardt
DOI:10.1007/s11103-010-9636-1
日期:2010.8
The aroma, flavor and pharmaceutical value of cultivated oregano (Origanum vulgare L.) is a consequence of its essential oil which consists mostly of monoterpenes and sesquiterpenes. To investigate the biosynthetic pathway to oregano terpenes and its regulation, we identified and characterized seven terpene synthases, key enzymes of terpene biosynthesis, from two cultivars of O. vulgare. Heterologous expression of these enzymes showed that each forms multiple mono- or sesquiterpene products and together they are responsible for the direct production of almost all terpenes found in O. vulgare essential oil. The correlation of essential oil composition with relative and absolute terpene synthase transcript concentrations in different lines of O. vulgare demonstrated that monoterpene synthase activity is predominantly regulated on the level of transcription and that the phenolic monoterpene alcohol thymol is derived from γ-terpinene, a product of a single monoterpene synthase. The combination of heterologously-expressed terpene synthases for in vitro assays resulted in blends of mono- and sesquiterpene products that strongly resemble those found in vivo, indicating that terpene synthase expression levels directly control the composition of the essential oil. These results will facilitate metabolic engineering and directed breeding of O. vulgare cultivars with higher quantity of essential oil and improved oil composition.
栽培牛至(Origanum vulgare L.)的香气、风味和药用价值主要归因于其精油,而精油主要由单萜和倍半萜组成。为了研究牛至萜的生物合成途径及其调控机制,我们从两种栽培牛至中鉴定并鉴定了7种萜类合成酶,它们是萜类生物合成的关键酶。这些酶的异源表达表明,每种酶都能形成多种单萜或倍半萜产物,它们共同负责牛至精油中几乎所有萜类的直接生产。牛至不同品系中精油成分与相对和绝对萜类合成酶转录浓度之间的相关性表明,单萜合成酶活性主要在转录水平上受到调控,而酚类单萜醇百里酚则来自γ-萜品烯,它是单萜合成酶的产物。体外实验中异源表达的萜类合成酶组合产生了与体内发现的产物非常相似的混合单萜和倍半萜产物,这表明萜类合成酶的表达水平直接控制着精油的成分。这些结果将有助于代谢工程和定向育种,培育出精油含量更高、成分更优的牛至栽培品种。