EFFECTS OF ELEVATED CYTOSOLIC GLUTATHIONE-REDUCTASE ACTIVITY ON THE CELLULAR GLUTATHIONE POOL AND PHOTOSYNTHESIS IN LEAVES UNDER NORMAL AND STRESS CONDITIONS
EFFECTS OF ELEVATED CYTOSOLIC GLUTATHIONE-REDUCTASE ACTIVITY ON THE CELLULAR GLUTATHIONE POOL AND PHOTOSYNTHESIS IN LEAVES UNDER NORMAL AND STRESS CONDITIONS
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DOI：
10.1104/pp.97.3.863
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发表时间：
1991-11-01
期刊：
影响因子：
7.4
通讯作者：
KUNERT, KJ
中科院分区：
文献类型：
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作者：
FOYER, C;LELANDAIS, M;KUNERT, KJ
利用编码谷胱甘肽还原酶的细菌GOR基因转化烟草。根据转基因植株对卡那霉素的抗性和细菌gor基因的表达情况进行筛选。经等电聚焦技术分离后，同时具有天然和细菌谷胱甘肽还原酶活性的转基因植物的叶提取物，除了天然酶的六条带外，还产生了两条紧密相连的同工酶。这些源于细菌GOR基因表达的额外条带是非氯化的。转基因植株的叶片谷胱甘肽还原酶活性是非转基因对照的2到10倍。在转基因植株中获得的可提取谷胱甘肽还原酶活性取决于叶龄和叶片暴露的条件。光照和暴露于甲基紫精均可提高叶片谷胱甘肽还原酶活性。在最适条件或甲基紫精诱导的氧化条件下，转基因植株胞质谷胱甘肽还原酶活性的升高对还原型谷胱甘肽/氧化谷胱甘肽池的数量或还原状态没有影响。谷胱甘肽库没有改变，尽管参与光合作用的酶的氧化依赖于二氧化碳同化的损失和氧化。然而，在甲基紫精处理的叶盘光照后，转基因植株的抗坏血酸池的减少状态比非转基因对照的更大。因此，我们得出结论，在自然状态下，烟草中谷胱甘肽还原酶的水平高于抗坏血酸-谷胱甘肽途径最大运行所需的水平。
Tobacco (Nicotiana tabacum var Samsun) was transformed using the bacterial gor gene coding for the enzyme glutathione reductase. Transgenic plants were selected by their kanamycin resistence and expression of the bacterial gor gene. After separation by isoelectric focusing techniques, leaf extracts from transgenic plants having both native and bacterial glutathione reductase activity gave, in addition to the six bands of the native enzyme, two further closely running isoenzymes. These additional bands originating from the expression of the bacterial gor gene were nonchloroplastic. Leaves from transgenic plants had two- to 10-fold higher glutathione reductase activity than nontransgenic controls. The amount of extractable glutathione reductase activity obtained in transgenic plants was dependent on leaf age and the conditions to which leaves were exposed. Both light and exposure to methylviologen increased leaf glutathione reductase activity. Elevated levels of cytosolic glutathione reductase activity in transgenic plants had no effect on the amount or reduction state of the reduced glutathione/oxidized glutathione pool under optimal conditions or oxidative conditions induced by methylviologen. The glutathione pool was unaltered despite the oxidation-dependent loss of CO2 assimilation and oxidation of enzymes involved in photosynthesis. However, the reduction state of the ascorbate pool was greater in transgenic plants relative to nontransgenic controls following illumination of methylviologen-treated leaf discs. Therefore, we conclude that in the natural state glutathione reductase is present in tobacco at levels above those required for maximal operation of the ascorbate-glutathione pathway.