Shewmaker CK, Sheehy JA, Daley M, Colburn S, Ke DY
Plant J. 1999 Nov;20(4):401-412X. doi: 10.1046/j.1365-313x.1999.00611.x.
A bacterial phytoene synthase (crtB) gene was overexpressed in a seed-specific manner and the protein product targeted to the plastid in Brassica napus (canola). The resultant embryos from these transgenic plants were visibly orange and the mature seed contained up to a 50-fold increase in carotenoids. The predominant carotenoids accumulating in the seeds of the transgenic plants were alpha and beta-carotene. Other precursors such as phytoene were also detected. Lutein, the predominant carotenoid in control seeds, was not substantially increased in the transgenics. The total amount of carotenoids in these seeds is now equivalent to or greater than those seen in the mesocarp of oil palm. Other metabolites in the isoprenoid pathway were examined in these seeds. Sterol levels remained essentially the same, while tocopherol levels decreased significantly as compared to non-transgenic controls. Chlorophyll levels were also reduced in developing transgenic seed. Additionally, the fatty acyl composition was altered with the transgenic seeds having a relatively higher percentage of the 18 : 1 (oleic acid) component and a decreased percentage of the 18 : 2 (linoleic acid) and 18 : 3 (linolenic acid) components. This dramatic increase in flux through the carotenoid pathway and the other metabolic effects are discussed.
一个细菌八氢番茄红素合成酶（crtB）基因以种子特异性方式过表达，其蛋白质产物靶向油菜（甘蓝型油菜）的质体。这些转基因植物产生的胚明显呈橙色，成熟种子中的类胡萝卜素含量增加了多达50倍。转基因植物种子中积累的主要类胡萝卜素是α-胡萝卜素和β-胡萝卜素。还检测到了其他前体物质，如八氢番茄红素。对照种子中的主要类胡萝卜素叶黄素在转基因种子中没有显著增加。这些种子中的类胡萝卜素总量现在等于或高于油棕中果皮中的含量。对这些种子中类异戊二烯途径中的其他代谢物进行了检测。甾醇水平基本保持不变，而生育酚水平与非转基因对照相比显著降低。发育中的转基因种子中的叶绿素水平也有所降低。此外，转基因种子的脂肪酰组成发生了变化，18:1（油酸）成分的百分比相对较高，而18:2（亚油酸）和18:3（亚麻酸）成分的百分比降低。文中讨论了通过类胡萝卜素途径通量的显著增加以及其他代谢效应。
