Saito K, Yamazaki M, Murakoshi I
Faculty of Pharmaceutical Sciences, Chiba University, Japan.
J Nat Prod. 1992 Feb;55(2):149-62. doi: 10.1021/np50080a001.
Agrobacterium-Ti/Ri plasmids are natural gene vectors, by which a number of attempts have been made in genetic engineering of secondary metabolism in pharmaceutically important plants in the last few years. Opines are biosynthesized by transformed crown galls and hairy roots integrated with T-DNAs of Ti/Ri plasmids. These opines are classified into five families according to their structures and biogenesis. The production of opines is a natural example of genetic engineering of the biosynthetic machinery of plant cells for the benefit of the bacterial pathogen. One recent advance in transgenic technology of potential value to pharmacognosy is an application of transgenic organ cultures such as hairy roots and shooty teratomas to over-production and biotransformation of secondary metabolites. The hairy roots induced by Ri plasmid of Agrobacterium rhizogenes have been proved to be an efficient means of producing secondary metabolites that are normally biosynthesized in roots of differentiated plants. So far the specific metabolites produced by hairy root cultures and/or plants regenerated from hairy roots of 63 species have been analyzed and reported. As an alternative means of producing metabolites normally produced in leaves of plants, the shooty teratomas incited by the tumor-forming Ti plasmid or a shooty mutant of Agrobacterium tumefaciens have been used for the de novo biosynthesis and biotransformation of some specific secondary products. A second and more direct way to manipulate secondary pathways is performed by transferring and expressing specifically modified genes into medicinal plant cells with Agrobacterium vector systems. The genes encoding neomycin phosphotransferase and beta-glucuronidase have been used as model genes under the transcriptional control of appropriate promoters. Recently some specific genes that can eventually modify the fluxes of secondary metabolism have been integrated and expressed in medicinal plant cells. Future prospects are also discussed.
农杆菌Ti/Ri质粒是天然基因载体，在过去几年里，人们利用它在重要药用植物的次生代谢基因工程方面进行了多次尝试。冠瘿碱由与Ti/Ri质粒的T-DNA整合的转化冠瘿和毛状根生物合成。这些冠瘿碱根据其结构和生物合成被分为五个家族。冠瘿碱的产生是植物细胞生物合成机制为细菌病原体的利益进行基因工程的一个天然例子。转基因技术在生药学方面的一个具有潜在价值的最新进展是将转基因器官培养物，如毛状根和芽状畸胎瘤应用于次生代谢产物的过量生产和生物转化。发根农杆菌的Ri质粒诱导的毛状根已被证明是生产通常在分化植物根中生物合成的次生代谢产物的有效手段。到目前为止，已经分析并报道了63种植物的毛状根培养物和/或从毛状根再生的植物产生的特定代谢产物。作为生产通常在植物叶片中产生的代谢产物的另一种手段，由致瘤Ti质粒或根癌农杆菌的芽状突变体诱导的芽状畸胎瘤已被用于一些特定次生产物的从头生物合成和生物转化。操纵次生途径的第二种更直接的方法是通过农杆菌载体系统将经过特定修饰的基因转移并表达至药用植物细胞中。编码新霉素磷酸转移酶和β-葡萄糖醛酸酶的基因已被用作在适当启动子转录控制下的模型基因。最近，一些最终能够改变次生代谢通量的特定基因已被整合并在药用植物细胞中表达。还讨论了未来的前景。
