Department of Biotechnology, Interdisciplinary Program of Bioenergy and Biomaterials, Bioenergy Research Center, Chonnam National University, Gwangju, Korea.
J Pineal Res. 2014 Apr;56(3):275-82. doi: 10.1111/jpi.12120. Epub 2014 Feb 8.
A major goal of plant biotechnology is to improve the nutritional qualities of crop plants through metabolic engineering. Melatonin is a well-known bioactive molecule with an array of health-promoting properties, including potent antioxidant capability. To generate melatonin-rich rice plants, we first independently overexpressed three tryptophan decarboxylase isogenes in the rice genome. Melatonin levels were altered in the transgenic lines through overexpression of TDC1, TDC2, and TDC3; TDC3 transgenic seed (TDC3-1) had melatonin concentrations 31-fold higher than those of wild-type seeds. In TDC3 transgenic seedlings, however, only a doubling of melatonin content occurred over wild-type levels. Thus, a seed-specific accumulation of melatonin appears to occur in TDC3 transgenic lines. In addition to increased melatonin content, TDC3 transgenic lines also had enhanced levels of melatonin intermediates including 5-hydroxytryptophan, tryptamine, serotonin, and N-acetylserotonin. In contrast, expression levels of melatonin biosynthetic mRNA did not increase in TDC3 transgenic lines, indicating that increases in melatonin and its intermediates in these lines are attributable exclusively to overexpression of the TDC3 gene.
植物生物技术的一个主要目标是通过代谢工程来改善作物的营养品质。褪黑素是一种众所周知的具有多种促进健康特性的生物活性分子，包括强大的抗氧化能力。为了生成富含褪黑素的水稻植株，我们首先在水稻基因组中独立过表达了三个色氨酸脱羧酶基因。通过过表达 TDC1、TDC2 和 TDC3 来改变转基因系中的褪黑素水平；TDC3 转基因种子（TDC3-1）中的褪黑素浓度比野生型种子高 31 倍。然而，在 TDC3 转基因幼苗中，褪黑素含量仅比野生型水平增加了一倍。因此，褪黑素似乎在 TDC3 转基因系中特异性积累。除了增加褪黑素含量外，TDC3 转基因系中的褪黑素中间体水平也有所提高，包括 5-羟色氨酸、色胺、血清素和 N-乙酰血清素。相比之下，TDC3 转基因系中褪黑素生物合成 mRNA 的表达水平没有增加，这表明这些系中褪黑素及其中间体的增加完全归因于 TDC3 基因的过表达。
