Department of Biology, University of British Columbia, Kelowna, BC, Canada.
Department of Biological Sciences, Brock University, St. Catharines, ON, Canada.
Planta. 2019 Jan;249(1):271-290. doi: 10.1007/s00425-018-2935-5. Epub 2018 Jun 9.
Using RNA-Seq, we cloned and characterized a unique monoterpene synthase responsible for the formation of a scent-determining S-linalool constituent of lavender oils from Lavandula × intermedia. Several species of Lavandula produce essential oils (EOs) consisting mainly of monoterpenes including linalool, one of the most abundant and scent-determining oil constituents. Although R-linalool dominates the EOs of lavenders, varying amounts (depending on the species) of the S-linalool enantiomer can also be found in these plants. Despite its relatively low abundance, S-linalool contributes a sweet, pleasant scent and is an important constituent of lavender EOs. While several terpene synthase genes including R-linalool synthase have been cloned from lavenders many important terpene synthases including S-linalool synthase have not been described from these plants. In this study, we employed RNA-Seq and other complementary sequencing data to clone and functionally characterize the sparsely expressed S-linalool synthase cDNA (LiS-LINS) from Lavandula × intermedia. Recombinant LiS-LINS catalyzed the conversion of the universal monoterpene precursor geranyl diphosphate to S-linalool as the sole product. Intriguingly, LiS-LINS exhibited very low (~ 30%) sequence similarity to other Lavandula terpene synthases, including R-linalool synthase. However, the predicted 3D structure of this protein, including the composition and arrangement of amino acids at the active site, is highly homologous to known terpene synthase proteins. LiS-LINS transcripts were detected in flowers, but were much less abundant than those corresponding to LiR-LINS, paralleling enantiomeric composition of linalool in L. × intermedia oils. These data indicate that production of S-linalool is at least partially controlled at the level of transcription from LiS-LINS. The cloned LiS-LINS cDNA may be used to enhance oil composition in lavenders and other plants through metabolic engineering.
利用 RNA-Seq，我们克隆并鉴定了一种独特的单萜合酶，它负责形成薰衣草油中决定香气的 S-芳樟醇成分，薰衣草油是薰衣草 × 杂种的产物。几种薰衣草属植物产生的精油（EOs）主要由包括芳樟醇在内的单萜组成，芳樟醇是最丰富和决定香气的油成分之一。尽管 R-芳樟醇主导了薰衣草的 EOs，但这些植物中也可以发现不同数量（取决于物种）的 S-芳樟醇对映体。尽管其丰度相对较低，但 S-芳樟醇具有甜美宜人的香气，是薰衣草 EOs 的重要成分。尽管已经从薰衣草中克隆了包括 R-芳樟醇合酶在内的几种萜烯合酶基因，但许多重要的萜烯合酶，包括 S-芳樟醇合酶，尚未从这些植物中描述。在这项研究中，我们采用 RNA-Seq 和其他互补测序数据从薰衣草 × 杂种中克隆并功能鉴定了表达稀疏的 S-芳樟醇合酶 cDNA（LiS-LINS）。重组 LiS-LINS 催化普遍的单萜前体香叶基二磷酸转化为 S-芳樟醇，为唯一产物。有趣的是，LiS-LINS 与其他薰衣草萜烯合酶，包括 R-芳樟醇合酶，只有约 30%的序列相似性。然而，该蛋白质的预测 3D 结构，包括活性位点处氨基酸的组成和排列，与已知的萜烯合酶蛋白高度同源。LiS-LINS 转录本在花朵中检测到，但丰度远低于对应于 LiR-LINS 的转录本，与 L. × 杂种中芳樟醇的对映体组成平行。这些数据表明 S-芳樟醇的产生至少部分受到 LiS-LINS 转录水平的控制。克隆的 LiS-LINS cDNA 可用于通过代谢工程增强薰衣草和其他植物的油组成。
