China-UK HUST-RRes Genetic Engineering and Genomics Joint Laboratory, The Genetic Engineering International Cooperation Base of Ministry of Science and Technology, The Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science & Technology (HUST), Wuhan 430074, China.
J Agric Food Chem. 2009 Sep 23;57(18):8652-60. doi: 10.1021/jf9012218.
Dietary micronutrient deficiencies, such as the lack of vitamin A, are a major source of morbidity and mortality worldwide. Carotenoids in food can function as provitamin A in humans, while grains of Chinese elite wheat cultivars generally have low carotenoid contents. To increase the carotenoid contents in common wheat endosperm, transgenic wheat has been generated by expressing the maize y1 gene encoding phytoene synthase driven by a endosperm-specific 1Dx5 promoter in the elite wheat (Triticum aestivum L.) variety EM12, together with the bacterial phytoene desaturase crtI gene from Erwinia uredovora under the constitutive CaMV 35S promoter control. A clear increase of the carotenoid content was detected in the endosperms of transgenic wheat that visually showed a light yellow color. The total carotenoids content was increased up to 10.8-fold as compared with the nontransgenic EM12 cultivar. To test whether the variability of total carotenoid content in different transgenic lines was due to differences in the transgene copy number or expression pattern, Southern hybridization and semiquantitative reverse transcriptase polymerase chain reaction analyses were curried out. The results showed that transgene copy numbers and transcript levels did not associate well with carotenoid contents. The expression patterns of endogenous carotenoid genes, such as the phytoene synthases and carotene desaturases, were also investigated in wild-type and transgenic wheat lines. No significant changes in expression levels of these genes were detected in the transgenic endosperms, indicating that the increase in carotenoid transgenic wheat endosperms resulted from the expression of transgenes.
膳食微量营养素缺乏，如维生素 A 缺乏，是全世界发病率和死亡率的主要原因。食物中的类胡萝卜素在人体内可以起到维生素 A 前体的作用，而中国优质小麦品种的籽粒通常类胡萝卜素含量较低。为了提高普通小麦胚乳中的类胡萝卜素含量，通过在优质小麦（Triticum aestivum L.）品种 EM12 中表达编码八氢番茄红素合酶的玉米 y1 基因，该基因由胚乳特异性 1Dx5 启动子驱动，同时在组成型 CaMV 35S 启动子控制下表达来自欧文氏菌的细菌类胡萝卜素脱饱和酶 crtI 基因，生成了转基因小麦。在转基因小麦的胚乳中检测到类胡萝卜素含量明显增加，肉眼可见呈浅黄色。与非转基因 EM12 品种相比，总类胡萝卜素含量增加了 10.8 倍。为了测试不同转基因系中总类胡萝卜素含量的可变性是否归因于转基因拷贝数或表达模式的差异，进行了 Southern 杂交和半定量逆转录聚合酶链反应分析。结果表明，转基因拷贝数和转录水平与类胡萝卜素含量没有很好的相关性。还研究了内源类胡萝卜素基因（如八氢番茄红素合酶和类胡萝卜素脱饱和酶）在野生型和转基因小麦系中的表达模式。在转基因胚乳中未检测到这些基因表达水平的显著变化，表明转基因小麦胚乳中类胡萝卜素的增加是由于转基因的表达。
