Enhanced levels of methionine and cysteine in transgenic alfalfa (Medicago sativa L.) plants over-expressing the Arabidopsis cystathionine γ-synthase gene
Enhanced levels of methionine and cysteine in transgenic alfalfa (Medicago sativa L.) plants over-expressing the Arabidopsis cystathionine γ-synthase gene
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DOI：
10.1111/j.1467-7652.2004.00102.x
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发表时间：
2005-01-01
影响因子：
13.8
通讯作者：
Amir, R
中科院分区：
文献类型：
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作者：
Avraham, T;Badani, H;Amir, R
目的是提高紫花苜蓿(Medicago sativa L.)的蛋氨酸水平。为了改善其营养品质，我们培育出了表达拟南芥胱硫醚伽马合成酶(AtCGS)的转基因紫花苜蓿植株，AtCGS是一种控制蛋氨酸途径中第一中间代谢物合成的酶。AtCGS基因由拟南芥Rubisco小亚基启动子驱动，在叶片中获得表达。对30株转基因植株进行了转基因蛋白表达检测，筛选出4个高表达株系进行进一步的研究。与野生型相比，这些品系中的蛋氨酸、S-甲基蛋氨酸和甲硫氨酸的含量分别增加了32倍、19倍和2.2倍。值得注意的是，在这四个转基因株系中，游离半胱氨酸(蛋氨酸合成的硫供体)、谷胱甘肽(半胱氨酸的储存和运输形式)和蛋白结合半胱氨酸的水平分别比野生型植物增加了2.6倍、5.5倍和2.3倍。由于过量表达AtCGS的转基因紫花苜蓿植株的可溶性和蛋白结合蛋氨酸和半胱氨酸水平显著升高，它们可能是改良饲草作物营养品质的模式和靶标系统。
With the aim of increasing the methionine level in alfalfa (Medicago sativa L.) and thus improving its nutritional quality, we produced transgenic alfalfa plants that expressed the Arabidopsis cystathionine gamma-synthase (AtCGS), the enzyme that controls the synthesis of the first intermediate metabolite in the methionine pathway. The AtCGS cDNA was driven by the Arabidopsis rubisco small subunit promoter to obtain expression in leaves. Thirty transgenic plants were examined for the transgene protein expression, and four lines with a high expression level were selected for further work. In these lines, the contents of methionine, S-methylmethionine (SMM), and methionine incorporated into the water-soluble protein fraction increased up to 32-fold, 19-fold, and 2.2-fold, respectively, compared with that in wild-type plants. Notably, in these four transgenic lines, the levels of free cysteine (the sulphur donor for methionine synthesis), glutathione (the cysteine storage and transport form), and protein-bound cysteine increased up to 2.6-fold, 5.5-fold, and 2.3-fold, respectively, relative to that in wild-type plants. As the transgenic alfalfa plants over-expressing AtCGS had significantly higher levels of both soluble and protein-bound methionine and cysteine, they may represent a model and target system for improving the nutritional quality of forage crops.