Lily, a famous cut flower with highly fragrance, has high ornamental and economic values. Monoterpenes are the main components contributing to its fragrance, and terpene synthase (TPS) genes play critical roles in the biosynthesis of monoterpenoids. To understand the function of TPS and to explore the molecular mechanism of floral scent in cultivar Lilium 'Siberia', transcriptomes of petal at different flowering stages and leaf were obtained by RNA sequencing and three unigenes related to TPS genes were selected for further validation. Quantitative real-time PCR showed that the expression level of LiTPS2 was greater than that of the other two TPS genes. Phylogenetic analysis indicated that LiTPS2 belonged to the TPSb subfamily, which was responsible for monoterpenes synthesis. Subcellular localization demonstrated that LiTPS2 was located in the chloroplasts. Furthermore, functional characterization showed that LiTPS2 utilized both geranyl pyrophosphate (GPP) and farnesyl pyrophosphate (FPP) to produce monoterpenoids such as linalool and sesquiterpenes like trans-nerolidol, respectively. Ectopic expression in transgenic tobacco plants suggested that the amount of linalool from the flowers of transgenic plants was 2-3 fold higher than that of wild-type plants. And the emissions of myrcene and (E)-β-ocimene were also accumulated from the flowers of LiTPS2 transgenic lines. Surprisingly, these three compounds were the main fragrance components of oriental lily hybrids. Our results indicated that LiTPS2 contributed to the production of monoterpenes and could effectively regulate the aroma of Lilium cultivars, laying the foundation for biotechnological modification of floral scent profiles.

中文翻译：

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百合品种（百合“西伯利亚”）中LiTPS2的过表达增强了烟草花中单萜的含量。

百合是著名的切花，香味浓郁，具有很高的观赏和经济价值。萜烯是产生其香味的主要成分，萜烯合酶（TPS）基因在萜类生物合成中起关键作用。为了了解TPS的功能并探索花香在西伯利亚百合中的分子机制，通过RNA测序获得了不同开花阶段花瓣和叶片的转录组，并选择了与TPS基因相关的三个单基因进行进一步验证。实时定量PCR表明，LiTPS2的表达水平高于其他两个TPS基因。系统发育分析表明LiTPS2属于TPSb亚家族，负责单萜的合成。亚细胞定位表明LiTPS2位于叶绿体中。此外，功能表征表明，LiTPS2同时利用了香叶基焦磷酸酯（GPP）和法呢基焦磷酸酯（FPP）来分别生产单萜类化合物，如芳樟醇和倍半萜烯，如反式橙花醇。转基因烟草植物中的异位表达表明，转基因植物花中的芳樟醇含量比野生型植物高2-3倍。LiTPS2转基因植株的花中也积累了月桂烯和（E）-β-烯菊酯的排放。令人惊讶的是，这三种化合物是东方百合杂种的主要香气成分。我们的结果表明，LiTPS2有助于单萜的产生，并可以有效调节百合属植物的香气，