The aim of this study was to gain insight into the compartment-specific roles of ascorbate and glutathione in leaf senescence in Arabidopsis thaliana. The subcellular distribution of ascorbate, glutathione, and hydrogen peroxide (H2O2) was analyzed by transmission electron microscopy and correlated with the activity of antioxidative enzymes in wildtype plants and the ascorbate- and glutathione-deficient mutants vtc2-1 and pad2-1, respectively. Both mutants showed earlier and stronger senescence than the wildtype indicating the importance of a functioning ascorbate and glutathione cycle in the induction and regulation of senescence. Glutathione levels dropped drastically and up to 93 % in all cell compartments of wildtype plants and the vtc2-1 mutant within the first day of dark-induced senescence while ascorbate contents remained unchanged until the very end. Glutathione contents in mitochondria of pad2-1 mutants decreased more slowly over the first 7 days than compared to the other plants indicating an important role of glutathione in mitochondria in this mutant during senescence. The strongest decrease (84 %) of glutathione contents in wildtype plants at this time point was found in mitochondria indicating an important role of mitochondria for the induction of senescence and cell death events. Due to the general decrease of the antioxidative capacity, a strong accumulation of H2O2 was observed in cell walls, plastids, and the cytosol in all plants. Activities of glutathione reductase, dehydroascorbate reductase and catalase were strongly reduced while ascorbate peroxidase and monodehydroascorbate reductase were increased. The initial rapid drop of glutathione levels seemed to be the trigger for senescence, while ascorbate appeared to be the key factor in regulating senescence through controlling H2O2 levels by the oxidation of reduced ascorbate to monodehydroascorbate and the subsequent reduction to ascorbate by monodehydroascorbate reductase.

中文翻译：

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在暗诱导衰老过程中，拟南芥叶片中抗氧化剂和过氧化氢的隔室特异性研究。

本研究的目的是深入了解拟南芥中抗坏血酸和谷胱甘肽在叶衰老中的区室特异性作用。通过透射电镜分析了抗坏血酸，谷胱甘肽和过氧化氢（H2O2）的亚细胞分布，并分别与野生型植物中的抗氧化酶活性以及抗坏血酸和谷胱甘肽缺陷型突变体vtc2-1和pad2-1相关。两种突变体均显示出比野生型更早和更强的衰老，表明功能性抗坏血酸和谷胱甘肽循环在诱导和调节衰老中的重要性。在黑暗诱导的衰老的第一天，谷胱甘肽水平急剧下降，在野生型植物和vtc2-1突变体的所有细胞区室中高达93％，而抗坏血酸的含量一直保持到最后。与其他植物相比，pad2-1突变体线粒体中的谷胱甘肽含量下降的速度比其他植物要慢，这表明该突变体中谷胱甘肽在该突变体中的重要作用。在此时间点，野生型植物中谷胱甘肽含量的下降幅度最大（84％），这表明线粒体在诱导衰老和细胞死亡事件中起着重要作用。由于抗氧化能力的普遍下降，在所有植物的细胞壁，质体和胞质溶胶中均观察到了H2O2的强烈积累。谷胱甘肽还原酶，脱氢抗坏血酸还原酶和过氧化氢酶的活性大大降低，而抗坏血酸过氧化物酶和单脱氢抗坏血酸还原酶的活性增加。最初谷胱甘肽水平的快速下降似乎是衰老的诱因，而抗坏血酸似乎是通过控制还原性抗坏血酸氧化为单脱氢抗坏血酸并随后通过单脱氢抗坏血酸还原酶将其还原为抗坏血酸来控制衰老的关键因素。