紫丁香SoDXR基因克隆及在单萜物质合成中的功能分析

【目的】探究1-脱氧木酮糖-5-磷酸还原酶（1-deoxy-D-xylulose-5-phosphate reductoisomerase, DXR）基因在紫丁香单萜物质合成中的作用，为紫丁香花香分子育种提供有效的基因资源和理论基础。【方法】本研究以紫丁香（Syringa oblata）花瓣为材料，克隆了SoDXR基因，并对其进行了生物信息学和亚细胞定位分析，不同花发育时期和器官组织中的qRT-PCR表达分析，及在金鱼草花瓣中异源瞬时过表达探究其功能。【结果】SoDXR基因全长为1 425 bp，编码474个氨基酸，编码的蛋白具有保守的DXP_reductoisom结构域，与桂花（Osmanthus fragrans）和油橄榄（Olea europaea）的相似性高达95%。亚细胞定位显示该蛋白主要定位于质体，与软件预测结果一致。伴随着开花，SoDXR表达水平呈先升高后降低的趋势，在初开期最高；在各个器官组织中均有表达，其中花瓣中表达量最高，茎中表达量最低。瞬时过表达发现，SoDXR基因的表达水平显著高于对照，促进了主要单萜成分罗勒烯和月桂烯的释放，释放量分别增加了15.03倍和4.83倍。【结论】SoDXR基因正调控紫丁香单萜物质的合成，推测DXR基因在花香次级代谢物合成中起到重要作用。

Isolation and Characterization of SoDXR Gene and Its Role on the Synthesis of Monoterpenes in Syringa oblata

Objective] The purpose of this study was to explore the role of 1-deoxy-D-xylo-5-phosphate reductoisomerase (DXR) gene in the synthesis of monoterpenes in lilac (Syringa oblata), and to provide effective genetic resources and theoretical basis for floral fragrance molecular breeding of lilac. Methods] Firstly, the SoDXR gene was cloned. Then, bioinformatics and subcellular localization were analysis, and qRT-PCR was used to analyze the gene expression patterns in different floral development stages and tissues. Finally, transient overexpression of SoDXR in the petals of snapdragon (Antirrhinum majus) was detected. Results] The open reading frame (ORF) of SoDXR was 1425bp encoding 474 amino acids. SoDXR protein contains conserved domain of DXP_reductoisom, and has a similarity of up to 95% with Osmanthus fragrans and Olea europaea. Subcellular localization indicated that the protein was mainly located in the plastids, consistent with the software prediction results. Accompanied by flowering, the expression levels of SoDXR increased and then decreased, with the highest expression level in the initial openning stage. The SoDXR was differentially expressed in various tissues with the highest expression in petal and lowest in stem. Transient overexpression revealed that the expression level of SoDXR gene was significantly higher than that of control. Moreover, the main floral volatile components in snapdragon petals, myrcene and ocimene, were significantly increased by 15.03 and 4.83 times, respectively. Conclusion] The SoDXR gene positively regulates the synthesis of monoterpenes in lilac, and SoDXR gene may play an important role in the synthesis of floral fragrance secondary metabolites.