Chavadej S, Brisson N, McNeil J N, De Luca V
Department of Biological Sciences, Université de Montréal, Québec, Canada.
Proc Natl Acad Sci U S A. 1994 Mar 15;91(6):2166-70. doi: 10.1073/pnas.91.6.2166.
Cruciferous plants are known to produce over a hundred different mustard oil glycosides, which are derived from methionine, phenylalanine, or tryptophan. In oil-producing crops like Brassica napus (canola), the presence of indole glucosinolates in seed protein meals has decreased meal palatability and has limited their value as animal feed. We have transformed canola plants with a gene that encodes tryptophan decarboxylase (TDC) in an attempt to redirect tryptophan into tryptamine rather than into indole glucosinolates. Transgenic plants that expressed this decarboxylase activity accumulated tryptamine while correspondingly lower levels of tryptophan-derived indole glucosinolates were produced in all plant parts compared with nontransformed controls. Of particular significance, the indole glucosinolate content of mature seeds from transgenic plants was only 3% of that found in nontransformed seeds. These results demonstrate how the creation of artificial metabolic sinks could divert metabolite flow and be used to remove these undesirable indole glucosinolates, thereby increasing the value of the oilseed meals, which are produced after extraction of oil from the seed.
已知十字花科植物能产生一百多种不同的芥子油苷，这些芥子油苷由蛋氨酸、苯丙氨酸或色氨酸衍生而来。在油菜（甘蓝型油菜）等产油作物中，种子蛋白粉中吲哚硫代葡萄糖苷的存在降低了蛋白粉的适口性，并限制了其作为动物饲料的价值。我们用一个编码色氨酸脱羧酶（TDC）的基因转化了油菜植株，试图将色氨酸转化为色胺，而不是转化为吲哚硫代葡萄糖苷。表达这种脱羧酶活性的转基因植株积累了色胺，与未转化的对照相比，所有植物部位产生的色氨酸衍生的吲哚硫代葡萄糖苷水平相应降低。特别重要的是，转基因植物成熟种子中的吲哚硫代葡萄糖苷含量仅为未转化种子的3%。这些结果表明，人工代谢库的创建如何能够改变代谢物流向，并用于去除这些不良的吲哚硫代葡萄糖苷，从而提高从种子中提取油后产生的油籽粕的价值。
