Basil (Ocimum basilicum L.) contains valuable monoterpene and sesquiterpene compounds used for medical purposes. Environmental stresses are suggested to change the essential oil composition in medicinal plants. In the current investigation, an experiment was arranged in greenhouse to study the effect of cold stress on genes expression patterns of linalool synthase (LIS), β-myrcene synthase (MYS), γ-cadinene synthase (CDS), germacrene D synthase (GDS) and geraniol synthase (GES) which is involved in monoterpenes and sesquiterpenes biosynthesis in O. basilicum. The monoterpenes and sesquiterpenes composition and content were also investigated. Plants were exposed to temperatures 22 (control), 4 and 10 °C at 6 to 8 leaf stage for 12, 24 and 48 h. The genes expression levels were determined by real time PCR in plant leaves. Essential oil was extracted at flowering stage by distillation using Clevenger apparatus and its compounds were identified using gas chromatography/mass spectrometry (GC-MS). The results revealed that the LIS expression increasingly occurred to 4.86 fold at 10 °C after 12 h while that of GES reached to 5.7 fold at 10 °C after 48 h. Temperature 4 °C for 12 h increased the expression levels of MYS and GDS genes to 41.5 and 14.2 fold, respectively, while the expression level of CDS increased to 25.5 fold at 4 °C for 48 h. Significant differences (P ≤ 0.01) were observed among treatments with respect to all compounds except α-pinene and camphene. The maximum proportion of geraniol and γ-cadinene were observed at 4 °C for 24 h, while the maximum proportion of germacrene D and α-bergamotene obtained at 10 °C for 12 h. The highest proportion of 1, 8-cineole was achieved at 4 °C for 48 h. Positive associations between germacrene D content and GDS expression (r = 0.8, P ≤ 0.05) and γ-cadinene and CDS expression (r = 0.78, P ≤ 0.05) proposed that the content of terpenoid compounds in basil can be enhanced through increasing the expression levels of genes involved in their biosynthesis.

中文翻译：

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冷胁迫对罗勒单萜和倍半萜生物合成基因表达模式及其含量的影响。

罗勒 (Ocimum basilicum L.) 含有用于医疗目的的有价值的单萜和倍半萜化合物。环境压力会改变药用植物中的精油成分。本次调查在温室中安排了一项实验，研究冷胁迫对芳樟醇合酶（LIS）、β-月桂烯合酶（MYS）、γ-卡二烯合酶（CDS）、锗烯D合酶（GDS）基因表达模式的影响。 ) 和香叶醇合成酶 (GES)，该酶参与 O. basilicum 中的单萜和倍半萜生物合成。还研究了单萜和倍半萜的组成和含量。植物在 6 至 8 叶期暴露于 22（对照）、4 和 10°C 的温度下 12、24 和 48 小时。通过植物叶片中的实时PCR确定基因表达水平。在开花期使用 Clevenger 装置通过蒸馏提取精油，并使用气相色谱/质谱法 (GC-MS) 鉴定其化合物。结果表明，LIS 表达在 12 小时后在 10°C 下增加了 4.86 倍，而 GES 在 10°C 下的表达在 48 小时后达到了 5.7 倍。温度 4°C 12 小时使 MYS 和 GDS 基因的表达水平分别增加到 41.5 和 14.2 倍，而 CDS 的表达水平在 4°C 下增加到 25.5 倍，持续 48 小时。除α-蒎烯和莰烯外，所有化合物的处理之间均观察到显着差异（P ≤ 0.01）。在 4 °C 下 24 小时观察到香叶醇和 γ-卡地烯的最大比例，而在 10 °C 下 12 小时获得的锗烯 D 和 α-佛手柑的最大比例。比例最高的1，8-桉树脑在 4°C 下达到 48 小时。胚芽烯 D 含量与 GDS 表达（r = 0.8，P ≤ 0.05）和 γ-cadinene 和 CDS 表达（r = 0.78，P ≤ 0.05）呈正相关，表明罗勒中萜类化合物的含量可以通过增加表达来提高参与其生物合成的基因水平。