Sclareol, an antifungal specialized metabolite produced by clary sage, Salvia sclarea, is the starting plant natural molecule used for the hemisynthesis of the perfume ingredient ambroxide. Sclareol is mainly produced in clary sage flower calyces; however, the cellular localization of the sclareol biosynthesis remains unknown. To elucidate the site of sclareol biosynthesis, we analyzed its spatial distribution in the clary sage calyx epidermis using laser desorption/ionization mass spectrometry imaging (LDI–FTICR-MSI) and investigated the expression profile of sclareol biosynthesis genes in isolated glandular trichomes (GTs). We showed that sclareol specifically accumulates in GTs’ gland cells in which sclareol biosynthesis genes are strongly expressed. We next isolated a glabrous beardless mutant and demonstrate that more than 90% of the sclareol is produced by the large capitate GTs. Feeding experiments, using 1-13C-glucose, and specific enzyme inhibitors further revealed that the methylerythritol-phosphate (MEP) biosynthetic pathway is the main source of isopentenyl diphosphate (IPP) precursor used for the biosynthesis of sclareol. Our findings demonstrate that sclareol is an MEP-derived diterpene produced by large capitate GTs in clary sage emphasing the role of GTs as biofactories dedicated to the production of specialized metabolites.

中文翻译：

---

香紫苏醇和乙酸芳樟酯由腺毛通过 MEP 途径产生

香紫苏醇，一种由鼠尾草产生的抗真菌专用代谢物，丹参, 是用于半合成香料成分 ambroxide 的起始植物天然分子。香紫苏醇主要产于鼠尾草花萼中；然而，香紫苏醇生物合成的细胞定位仍然未知。为了阐明香紫苏醇生物合成的位点，我们使用激光解吸/电离质谱成像 (LDI-FTICR-MSI) 分析了其在鼠尾草花萼表皮中的空间分布，并研究了香紫苏醇生物合成基因在分离腺毛 (GTs) 中的表达谱. 我们发现香紫苏醇在 GTs 的腺细胞中特异性积累，其中香紫苏酚生物合成基因强烈表达。我们接下来分离出一个无毛的无胡子突变体并证明超过 90% 的香紫苏醇是由大头状 GT 产生的。喂食实验，使用 1-13C-葡萄糖和特异性酶抑制剂进一步揭示了甲基赤藓糖醇-磷酸 (MEP) 生物合成途径是用于生物合成香紫苏醇的异戊烯基二磷酸 (IPP) 前体的主要来源。我们的研究结果表明，香紫苏醇是一种由 MEP 衍生的二萜，由鼠尾草中的大头状 GTs 产生，强调了 GTs 作为致力于生产特殊代谢物的生物工厂的作用。