Gutensohn M, Dudareva N
Davis College of Agriculture, Natural Resources and Design, West Virginia University, Morgantown, WV, United States.
Purdue University, West Lafayette, IN, United States.
Methods Enzymol. 2016;576:333-59. doi: 10.1016/bs.mie.2016.03.012. Epub 2016 Apr 1.
Terpenoids are a large and diverse class of plant metabolites including mono-, sesqui-, and diterpenes. They have numerous functions in basic physiological processes as well as the interaction of plants with their biotic and abiotic environment. Due to the tight regulation of biosynthetic pathways and the resulting limited natural availability of terpenes, there is a strong interest in increasing their production in plants by metabolic engineering for agricultural, pharmaceutical, and industrial applications. The tomato fruit system was developed as a platform for metabolic engineering of terpenes to overcome detrimental effects on overall plant growth and photosynthesis traits, which are affected when terpenoid engineering is performed in vegetative tissues. Here we describe how the use of fruit-specific promoters for transgene expression can avoid these unwanted effects. In addition, targeting the expression of the introduced terpene biosynthetic gene to fruit tissue can take advantage of the large precursor pool provided by the methylerythritol-phosphate (MEP) pathway, which is highly active during tomato fruit ripening to facilitate the accumulation of carotenoids. We also discuss how the production of high levels of target terpene compounds can be achieved in fruits by the expression of individual or a combination of (i) the MEP or mevalonic acid pathway enzymes, (ii) prenyltransferases, and/or (iii) terpene synthases. Finally, we provide a brief outline of how the emitted as well as internal pools of terpenes can be analyzed in transgenic tomato fruits.
萜类化合物是一大类多样的植物代谢产物，包括单萜、倍半萜和二萜。它们在基本生理过程以及植物与其生物和非生物环境的相互作用中具有多种功能。由于生物合成途径的严格调控以及由此导致的萜类化合物天然可得性有限，人们对通过代谢工程提高其在植物中的产量以用于农业、制药和工业应用有着浓厚的兴趣。番茄果实系统被开发为萜类化合物代谢工程的平台，以克服在营养组织中进行萜类化合物工程时对植物整体生长和光合作用特性的不利影响。在这里，我们描述了使用果实特异性启动子进行转基因表达如何能够避免这些不良影响。此外，将导入的萜类生物合成基因的表达靶向果实组织可以利用由甲基赤藓糖醇磷酸（MEP）途径提供的大量前体库，该途径在番茄果实成熟期间高度活跃，有助于类胡萝卜素的积累。我们还讨论了如何通过表达（i）MEP或甲羟戊酸途径酶、（ii）异戊烯基转移酶和/或（iii）萜类合酶中的单个或组合，在果实中实现高水平目标萜类化合物的生产。最后，我们简要概述了如何在转基因番茄果实中分析释放的以及内部的萜类化合物库。
