Institute of Genetic and Regenerative Biology, Key Laboratory for Cell and Gene Engineering of Zhejiang Province, College of Life Sciences, Zhejiang University , Hangzhou, China , 310058.
College of Pharmaceutical Science, Zhejiang University of Technology , Hangzhou, China , 310014.
J Agric Food Chem. 2017 Jun 28;65(25):5181-5187. doi: 10.1021/acs.jafc.7b00439. Epub 2017 Jun 14.
Vitamin E is a potent lipid-soluble antioxidant and essential nutrient for human health. Tocotrienols are the major form of vitamin E in seeds of most monocots. It has been known that homogentisate geranylgeranyl transferase (HGGT) catalyzes the committed step of tocotrienol biosynthesis. In the present study, we generated transgenic barley overexpressing HvHGGT under endogenous D-Hordein promoter (proHor). Overexpression of HvHGGT increased seed size and seed weight in transgenic barley. Notably, total tocotrienol content increased by 10-15% in seeds of transgenic lines, due to the increased levels of δ-, β-, and γ-tocotrienol, but not α-tocotrienol. Total tocopherol content decreased by 14-18% in transgenic lines, compared to wild type. The antioxidant activity of seeds was determined by using 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), and lipid peroxidation assays. Compared to wild type, radical scavenging activity of seed extracts was enhanced by 17-18% in transgenic lines. Meanwhile, the lipid peroxidation level was decreased by about 20% in transgenic barley seeds. Taken together, overexpression of HvHGGT enhanced the tocotrienol levels and antioxidant capacity in barley seeds.
维生素 E 是一种强效的脂溶性抗氧化剂，也是人体健康所必需的营养物质。生育三烯酚是大多数单子叶植物种子中维生素 E 的主要形式。人们已经知道，同型戊二烯基转移酶 (HGGT) 催化生育三烯酚生物合成的关键步骤。在本研究中，我们利用内源 D-类谷蛋白启动子 (proHor) 在转基因大麦中过表达 HvHGGT。HvHGGT 的过表达增加了转基因大麦种子的大小和重量。值得注意的是，由于 δ-、β-和 γ-生育三烯酚水平的增加，而 α-生育三烯酚水平没有变化，转基因系种子中的总生育三烯酚含量增加了 10-15%。与野生型相比，转基因系中的总生育酚含量下降了 14-18%。通过使用 1,1-二苯基-2-苦基肼 (DPPH)、2,2'-联氮双(3-乙基苯并噻唑啉-6-磺酸) (ABTS) 和脂质过氧化测定法来确定种子的抗氧化活性。与野生型相比，转基因系种子提取物的自由基清除活性增强了 17-18%。同时，转基因大麦种子中的脂质过氧化水平降低了约 20%。总之，HvHGGT 的过表达提高了大麦种子中的生育三烯酚水平和抗氧化能力。
