目的 对太子参三萜类皂苷生物合成关键调控酶鲨烯环氧酶1（SQE1）基因进行全长cDNA克隆和功能分析。方法 基于其他植物SQE基因的同源序列设计简并引物，以太子参块根总RNA为模板，RT-PCR结合RACE技术克隆太子参SQE1基因的全长cDNA，并进行生物信息学分析。利用农杆菌叶盘转化法将SQE1基因转化烟草，研究其对烟草总三萜量的影响。结果 获得太子参SQE1基因全长cDNA序列2 038 bp，该序列包含1 554 bp的开放阅读框，编码517个氨基酸，相对分子质量为5.67×10⁴，等电点为8.8，与其他药用植物的SQE蛋白具有较高的同源性，含有FAD结合结构域和4个跨膜区域，转太子参SQE1基因的烟草的总三萜量明显高于非转基因植株。结论 首次克隆获得太子参SQE1基因的全长cDNA，该基因的异源表达可一定程度提高转基因植物的总三萜量，为阐明与应用太子参三萜类成分生物合成途径提供科学依据。

Objective To clone the full-length cDNA encoding squalene epoxidase 1 (SQE1), a key enzyme of triterpenes biosynthesis, from Pseudostellaria heterophylla and to perform functional analysis. Methods With the total RNA as template, the full-length cDNA of SQE1 in P. heterophylla was cloned via RT-PCR and rapid amplification of cDNA ends (RACE) techniques. The bioinformatics of the cloned SQE1 gene was performed. The target gene was transfered into tobacco by Agrobacterium-mediated transformation. Results The full-length cDNA (2 038 bp) of SQE1 gene was obtained with an open reading frame of 1 554 bp, encoding 517 amino acid polypeptides, which had higher homology with the known SQEs in other medicinal species. The calculated relative molecular mass was 5.67 × 10⁴, the isoelectric point was 8.8. The deduced protein sequence exhibited FAD-binding domains and four transmembrane regions. The content of total triterpenes was increased in transgenic tobacco plants. Conclusion This is the first report that the full-length cDNA encoding SQE1 from P. heterophylla is cloned. The ectopic expression of SQE1 could promote to increase the content of total triterpenes in transgenic plant. This work provides a foundation for exploring the biosynthetic pathway of triterpenes in P. heterophylla and their applications in bioengineering.

国家自然科学基金资助项目（30900915）；福建省教育厅资助高校重点项目（JK2012012）