Figure 1.

Proposed biosynthesis of α- and β-thujone in WRC. The monoterpenenoids α- and β-thujone are proposed to derive from GDP through a four-step biosynthetic pathway starting with (+)-sabinene synthase (Foster et al., 2013). Sabinene may be oxidized to either (+)-cis- or (+)-trans-sabinol followed by oxidation to (+)-sabinone as the proposed direct precursor to α- and β-thujone. Here, we provide evidence for (+)-trans-sabinol but not (+)-cis sabinol as an intermediate in thujone biosynthesis in the gymnosperm WRC. In contrast, in the angiosperm common garden sage, thujone is formed by the (+)-cis-sabinol intermediate (Karp and Croteau, 1982). This article describes (+)-trans-sabinol dehydrogenase enzyme activity in WRC tissue extract and gene discovery and functional characterization of WRC (+)-sabinene-3-hydroxylase. The proposed pathway was redrawn based on Karp and Croteau (1982).