增加谷胱甘肽含量转基因作物

谷胱甘肽在保护细胞免受生物及非生物胁迫影响方面具有重要的作用，它是细胞中对自由基和活性氧起抵抗作用的主要物质，能使细胞免受各种外源物和致癌物质的伤害。

谷胱甘肽还在诸多生化过程和新陈代谢过程中起关键作用，例如指导DNA修复、蛋白合成及氨基酸转移，控制细胞凋亡或程序性死亡，增大T细胞毒性等，它在某些国家已经作为一种黑色素抑制剂而应用于化妆品行业。

目前人们主要利用酵母来生产这种物质，也曾尝试增加植物中谷胱甘肽的含量并取得了一定的成功。最近，德国Tübingen大学的研究人员报道称他们成功的在烟草中表达了来自嗜热链球菌的谷胱甘肽合成酶——γ谷氨酰半胱氨酸连接酶（StGCL-GS），并分析发现该物质既不容易被氧化还原，也对谷胱甘肽的反馈抵制不敏感。

研究人员在Plant  Biotechnology  Journal发表文章称，表达了StGCL-GS的转基因烟草的叶子中GSH的积累量非常高（最高达12μmol  GSH/gFW，取决于不同的发育阶段），这一数值是野生品种含量的20~30倍，而且在施加硫酸盐肥料的情况下还会进一步提高。研究人员还说这种转基因作物对非生物胁迫的耐受性也得到加强。因为StGCL-GS的表达不会对植物生长产生影响，因此可与现在的酵母生产体系进行竞争。

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Exploiting plants for glutathione (GSH) production: Uncoupling GSH synthesis from cellular controls results in unprecedented GSH accumulation
Verena Liedschulte ¹ , Andreas Wachter ^1,3 , An Zhigang ² and Thomas Rausch ¹

1 HIP, Heidelberg University, INF, Heidelberg, Germany
2 Northeast Forestry University, Key Laboratory of Forest Plant Ecology, Ministry of Education, Hexing Road, Harbin, PR China
3 ZMBP, Tübingen University, Aufdev Morjenstelle, Tübingen, Germany

【Abstract】Glutathione (GSH) is a key factor for cellular redox homeostasis and tolerance against abiotic and biotic stress (May et al., 1998; Noctor et al., 1998a). Previous attempts to increase GSH content in plants have met with moderate success (Rennenberg et al., 2007), largely because of tight and multilevel control of its biosynthesis (Rausch et al., 2007). Here, we report the in planta expression of the bifunctional γ-glutamylcysteine ligase—glutathione synthetase enzyme from Streptococcus thermophilus (StGCL-GS), which is shown to be neither redox-regulated nor sensitive to feedback inhibition by GSH. Transgenic tobacco plants expressing StGCL-GS under control of a constitutive promoter reveal an extreme accumulation of GSH in their leaves (up to 12 μmol GSH/gFW, depending on the developmental stage), which is more than 20- to 30-fold above the levels observed in wild-type (wt) plants and which can be even further increased by additional sulphate fertilization. Surprisingly, this dramatically increased GSH production has no impact on plant growth while enhancing plant tolerance to abiotic stress. Furthermore, StGCL-GS-expressing plants are a novel, cost-saving source for GSH production, being competitive with current yeast-based systems .