Xu Yanhong, Liu Juan, Liang Liang, Yang Xin, Zhang Zheng, Gao Zhihui, Sui Chun, Wei Jianhe
Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College, No. 151, Malianwa North Road, Haidian District, Beijing 100193, China.
Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College, No. 151, Malianwa North Road, Haidian District, Beijing 100193, China; Hainan Branch Institute of Medicinal Plant (Hainan Provincial Key Laboratory of Resources Conservation and Development of Southern Medicine), Chinese Academy of Medical Sciences & Peking Union Medical College, Wanning 571533, China.
Plant Physiol Biochem. 2014 Sep;82:133-41. doi: 10.1016/j.plaphy.2014.05.013. Epub 2014 Jun 7.
Agarwood is an expensive resinous heartwood derived from Aquilaria plants that is widely used in traditional medicines, incense and perfume. The major constituents of agarwood oils are sesquiterpenes, which are obtained from isopentenyl diphosphate and dimethylallyl diphosphate precursors through the plastidial methylerythritol phosphate (MEP) pathway and/or the cytosolic mevalonate pathway. 1-deoxy-d-xylulose-5-phosphate synthase (DXS) is the first rate-limiting enzyme for sesquiterpene synthesis in the MEP pathway. In this study, 3 cDNAs of DXS genes were cloned and characterized from the Aquilaria sinensis (Lour.) Gilg. These genes represent 3 phylogenetically distinct clades conserved among plants. Functional complementation in a DXS-deficient Escherichia coli strain EcAB4-2 demonstrated that they are active DXS, which rescued the E. coli mutant. Their expression profiles in different tissues and in response to different treatments were analyzed by real-time PCR. All 3 genes are highly expressed in stem, followed by leaf and root. AsDXS1 was significantly stimulated by mechanical, chemical, and H2O2 treatment, whereas AsDXS2 and AsDXS3 only responded to chemical treatment and mechanical treatment, respectively. All three genes were oscillation in respond to MJ treatment, with expression peaks occurring at different time points. Our results suggest the conservation of DXS in evolution and imply their distinct functions in primary and defensive sesquiterpene metabolism in A. sinensis.
沉香是一种昂贵的含树脂心材，源自沉香属植物，广泛用于传统医药、熏香和香水。沉香精油的主要成分是倍半萜，其通过质体甲基赤藓糖醇磷酸（MEP）途径和/或胞质甲羟戊酸途径从异戊烯基二磷酸和二甲基烯丙基二磷酸前体获得。1-脱氧-D-木酮糖-5-磷酸合酶（DXS）是MEP途径中倍半萜合成的首个限速酶。在本研究中，从白木香（Aquilaria sinensis (Lour.) Gilg.）中克隆并鉴定了3个DXS基因的cDNA。这些基因代表了植物中保守的3个系统发育上不同的分支。在DXS缺陷型大肠杆菌菌株EcAB4-2中的功能互补证明它们是有活性的DXS，挽救了大肠杆菌突变体。通过实时PCR分析了它们在不同组织中的表达谱以及对不同处理的响应。所有3个基因在茎中高表达，其次是叶和根。AsDXS1受到机械、化学和H2O2处理的显著刺激，而AsDXS2和AsDXS3分别仅对化学处理和机械处理有响应。所有三个基因对茉莉酸甲酯（MJ）处理均有振荡响应，在不同时间点出现表达峰值。我们的结果表明DXS在进化中具有保守性，并暗示它们在白木香的初级和防御性倍半萜代谢中具有不同的功能。
