Elevated glutathione biosynthetic capacity in the chloroplasts of transgenic tobacco plants paradoxically causes increased oxidative stress
Elevated glutathione biosynthetic capacity in the chloroplasts of transgenic tobacco plants paradoxically causes increased oxidative stress
复制标题
DOI：
10.1105/tpc.11.7.1277
复制
发表时间：
1999-07-01
期刊：
影响因子：
11.6
通讯作者：
Mullineaux, P
中科院分区：
文献类型：
--
作者：
Creissen, G;Firmin, J;Mullineaux, P
谷胱甘肽（GSH）是大多数有氧生物中的主要抗氧化剂，被认为在植物叶绿体中特别重要，因为它有助于保护光合机构免受氧化损伤。在转基因烟草植物中，过表达叶绿体靶向的γ-谷氨酰半胱氨酸合成酶（γ-ECS），叶片GSH水平提高了三倍。特别是，叶绿体GSH生物合成能力的增加导致了氧化胁迫的增强，表现为光依赖性失绿或坏死。这种表型与叶片中的GSH和γ-谷氨酰半胱氨酸（GSH的直接前体）处于更氧化的状态有关。使用除了γ-ECS水平升高之外还具有增强的谷胱甘肽合成酶或谷胱甘肽还原酶活性的杂交转基因植物，实现了叶硫醇池的含量和氧化还原状态的进一步操纵。鉴于这些实验的结果，我们认为，γ-ECS转化的植物遭受持续的氧化损伤所造成的故障的氧化还原传感过程中的叶绿体。
Glutathione (GSH), a major antioxidant in most aerobic organisms, is perceived to be particularly important in plant chloroplasts because it helps to protect the photosynthetic apparatus from oxidative damage. In transgenic tobacco plants overexpressing a chloroplast-targeted gamma-glutamylcysteine synthetase (gamma-ECS), foliar levels of GSH were raised threefold. Paradoxically, increased GSH biosynthetic capacity in the chloroplast resulted in greatly enhanced oxidative stress, which was manifested as light intensity-dependent chlorosis or necrosis. This phenotype was associated with foliar pools of both GSH and gamma-glutamylcysteine (the immediate precursor to GSH) being in a more oxidized state. Further manipulations of both the content and redox state of the foliar thiol pools were achieved using hybrid transgenic plants with enhanced glutathione synthetase or glutathione reductase activity in addition to elevated levels of gamma-ECS. Given the results of these experiments, we suggest that gamma-ECS-transformed plants suffered continuous oxidative damage caused by a failure of the redox-sensing process in the chloroplast.