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美国科学家利用基因工程技术使玉米能产生肉类中才含有的氨基酸，这提高了世界上最重要的作物之一的营养价值。
该技术通过插入一个细菌基因，使玉米能产生蛋氨酸，而蛋氨酸是皮肤、指甲和头发健康的关键营养物质。
研究人员说，这项研究将有
助于发展中国家数百万依赖玉米作为主食的人改善营养，并能降低动物饲料成本
，美国同行评审期刊《美国国家科学院学报,PNAS》报道。
摘要：
硫同化可能限制了蛋氨酸和半胱氨酸的库，可用于玉米的主要种子贮藏蛋白玉米蛋白。这一假设是通过生产转基因玉米，
通过对大肠杆菌3′- phosphoadenosine - 5′- phosphosulfate还原酶( ecpapr)的叶片特异性表达，从而提高了种子中的蛋氨酸积累，从而实现了抗硫酸盐还原能力的转基因玉米。
转基因籽粒具有较高的蛋氨酸10 -kdaδ-玉米醇溶蛋白和总蛋白硫的表达，而不降低其他玉米蛋白。这一全面的增加了s -rich玉米蛋白的表达，描述了在强化硫同化作用下这些蛋白质的调控的一个方面。与高蛋氨酸自交系b101相比，转基因株pe5的籽粒蛋氨酸积累量增加57.6%。在饲喂雏鸡的试验中，与nontransgenic粒相比，pe5玉米促进了显著的增重。因此，增
加源强度可以提高玉米的营养价值，而不明显的产量损失，并可显著降低饲料补充成本
。
Abstract
Sulfur assimilation may limit the pool of methionine and cysteine available for incorporation into zeins, the major seed storage proteins in maize. This hypothesis was tested by
producing transgenic maize with deregulated sulfate reduction capacity
achieved through
leaf-specific expression of the
Escherichia coli
enzyme 3′-phosphoadenosine-5′-phosphosulfate reductase (
Ec
PAPR) that resulted in higher methionine accumulation in seeds
. The transgenic kernels have higher expression of the methionine-rich 10-kDa δ-zein and total protein sulfur without reduction of other zeins. This overall increase in the expression of the S-rich zeins describes a facet of regulation of these proteins under enhanced sulfur assimilation.
Transgenic line PE5 accumulates 57.6% more kernel methionine than the high-methionine inbred line B101.
In feeding trials with chicks, PE5 maize promotes significant weight gain compared with nontransgenic kernels. Therefore, increased source strength can improve the nutritional value of maize without apparent yield loss and may significantly reduce the cost of feed supplementation.
Significance
Poultry feed is usually prepared as a corn–soybean mixture.
Because the only essential sulfur amino acid missing in this mixture is methionine,
it is chemically synthesized and added separately, increasing the cost of major food supply. It appears to be difficult to circumvent the regulatory aspects of sulfur metabolism, which is controlled at many levels, without damage to plant growth
. By using tissue-specific promoters to express a bacterial enzyme that increases the efficiency of assimilative sulfate reduction, seed methionine accumulation can be increased without the concomitant accumulation of toxic metabolites.
