School of Agricultural, Biological, and Environmental Sciences, Faculty of Agriculture, Tottori University, 4-101 Koyama-minami, Tottori, 680-8550, Japan.
Transgenic Res. 2013 Apr;22(2):391-402. doi: 10.1007/s11248-012-9656-5. Epub 2012 Sep 19.
Vitamin E (tocopherol: Toc) is an important lipid-soluble antioxidant synthesized in chloroplasts. Among the 8 isoforms of vitamin E, α-Toc has the highest activity in humans. To generate transgenic plants with enhanced vitamin E activity, we applied a chloroplast transformation technique. Three types of the transplastomic tobacco plants (pTTC, pTTMT and pTTC-TMT) carrying the Toc cyclase (TC) or γ-Toc methyltransferase (γ-TMT) gene and the TC plus γ-TMT genes as an operon in the plastid genome, respectively, were generated. There was a significant increase in total levels of Toc due to an increase in γ-Toc in the pTTC plants. Compared to the wild-type plants, Toc composition was altered in the pTTMT plants. In the pTTC-TMT plants, total Toc levels increased and α-Toc was a major Toc isoform. Furthermore, to use chloroplast transformation to produce α-Toc-rich vegetable, TC-overexpressing transplastomic lettuce plants (pLTC) were generated. Total Toc levels and vitamin E activity increased in the pLTC plants compared with the wild-type lettuce plants. These findings indicated that chloroplast genetic engineering is useful to improve vitamin E quality and quantity in plants.
维生素 E（生育酚：Toc）是一种在叶绿体中合成的重要脂溶性抗氧化剂。在 8 种生育酚异构体中，α-Toc 在人类中活性最高。为了生成维生素 E 活性增强的转基因植物，我们应用了叶绿体转化技术。分别携带 Toc 环化酶（TC）或γ-Toc 甲基转移酶（γ-TMT）基因以及 TC 和γ-TMT 基因作为操纵子的三种转叶绿体烟草植物（pTTC、pTTMT 和 pTTC-TMT）在质体基因组中生成。由于 pTTC 植物中γ-Toc 的增加，总Toc 水平显著增加。与野生型植物相比，pTTMT 植物中的 Toc 组成发生了改变。在 pTTC-TMT 植物中，总Toc 水平增加，且α-Toc 是主要的 Toc 同工型。此外，为了利用叶绿体转化来生产富含α-Toc 的蔬菜，我们生成了过表达 TC 的转叶绿体生菜植物（pLTC）。与野生型生菜植物相比，pLTC 植物中的总Toc 水平和维生素 E 活性增加。这些发现表明，叶绿体遗传工程有助于提高植物中维生素 E 的质量和数量。
