Molecular Cloning and Functional Analysis of 1-Deoxy-D-Xylulose 5-Phosphate Reductoisomerase from Santalum album.
Molecular Cloning and Functional Analysis of 1-Deoxy-D-Xylulose 5-Phosphate Reductoisomerase from Santalum album.
复制标题
檀香1-脱氧-D-木酮糖5-磷酸还原异构酶的分子克隆及功能分析
作者：
Zhang Y;Yan H;Li Y;Xiong Y;Niu M;Zhang X;Teixeira da Silva JA;Ma G
檀香(Santalum Aligure L.)心材精油含有高含量的倍半萜类化合物，具有很高的经济价值，广泛应用于香料行业。倍半萜类化合物是通过甲戊酸和甲基赤藓糖醇磷酸(MEP)途径生物合成的，这两个途径也是光合色素前体的来源。1-脱氧-D-木糖-5-磷酸还原异构酶(DXR)是MEP途径中的第二限速酶。本文从7年生相思树中克隆了SaDXR的1416bp的开放阅读框及其897bp的启动子区域，其中包含与胁迫响应(HSE和富含TC的重复序列)、激素信号转导(脱落酸、赤霉素和水杨酸)和光响应相关的保守顺式元件。生物信息学分析表明，SaDXR编码一个功能保守的DXR蛋白。SaDXR在多种组织中广泛表达，包括根、树枝、茎边材、叶、花、果实和树干心材，在具有光合色素的组织中表现出明显更高的水平，如树枝、叶和花。光照下黄化幼苗中SaDXR基因的表达增加，转SaDXR基因的所有35S：：SaDXR转基因拟南芥的叶绿素和类胡萝卜素含量均增加，与SaDXR的表达水平一致。MeJA和H_2O_2对SaDXR也有刺激作用。α-桑塔洛尔的含量降低是对地塞米松的一种抑制剂的反应。这些结果表明，SaDXR在光合色素的生物合成中发挥了重要作用，将光合色素的通量转移到檀香特有的倍半萜类化合物。
Sandalwood (Santalum album L.) heartwood-derived essential oil contains a high content of sesquiterpenoids that are economically highly valued and widely used in the fragrance industry. Sesquiterpenoids are biosynthesized via the mevalonate acid and methylerythritol phosphate (MEP) pathways, which are also the sources of precursors for photosynthetic pigments. 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) is a secondary rate-limiting enzyme in the MEP pathway. In this paper, the 1416-bp open reading frame of SaDXR and its 897-bp promoter region, which contains putative conserved cis-elements involved in stress responsiveness (HSE and TC-rich repeats), hormone signaling (abscisic acid, gibberellin and salicylic acid) and light responsiveness, were cloned from 7-year-old S. album trees. A bioinformatics analysis suggested that SaDXR encodes a functional and conserved DXR protein. SaDXR was widely expressed in multiple tissues, including roots, twigs, stem sapwood, leaves, flowers, fruit and stem heartwood, displaying significantly higher levels in tissues with photosynthetic pigments, like twigs, leaves and flowers. SaDXR mRNA expression increased in etiolated seedlings exposed to light, and the content of chlorophylls and carotenoids was enhanced in all 35S::SaDXR transgenic Arabidopsis thaliana lines, consistent with the SaDXR expression level. SaDXR was also stimulated by MeJA and H2O2 in seedling roots. α-Santalol content decreased in response to fosmidomycin, a DXR inhibitor. These results suggest that SaDXR plays an important role in the biosynthesis of photosynthetic pigments, shifting the flux to sandalwood-specific sesquiterpenoids.
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