Foyer C H, Souriau N, Perret S, Lelandais M, Kunert K J, Pruvost C, Jouanin L
Department of Environmental Biology, Institute of Grassland and Environmental Research, Aberystwyth, Dyfed, United Kingdom.
Plant Physiol. 1995 Nov;109(3):1047-57. doi: 10.1104/pp.109.3.1047.
A poplar hybrid, Populus tremula x Populus alba, was transformed with the bacterial genes for either glutathione reductase (GR) (gor) or glutathione synthetase (GS) (gshII). When the gor gene was targeted to the chloroplasts, leaf GR activities were up to 1000 times greater than in all other lines. In contrast, targeting to the cytosol resulted in 2 to 10 times the GR activity. GR mRNA, protein, and activity levels suggest that bacterial GR is more stable in the chloroplast. When the gshII gene was expressed in the cytosol, GS activities were up to 100 times greater than in other lines. Overexpression of GR or GS in the cytosol had no effect on glutathione levels, but chloroplastic-GR expression caused a doubling of leaf glutathione and an increase in reduction state. The high-chloroplastic-GR expressors showed increased resistance to photoinhibition. The herbicide methyl viologen inhibited CO2 assimilation in all lines, but the increased leaf levels of glutathione and ascorbate in the high-chloroplastic-GR expressors persisted despite this treatment. These results suggest that overexpression of GR in the chloroplast increases the antioxidant capacity of the leaves and that this improves the capacity to withstand oxidative stress.
一种杨树杂交种，即欧洲山杨×银白杨，用编码谷胱甘肽还原酶（GR）（gor）或谷胱甘肽合成酶（GS）（gshII）的细菌基因进行了转化。当gor基因定位于叶绿体时，叶片GR活性比所有其他株系高1000倍。相比之下，定位于细胞质导致GR活性提高2至10倍。GR的mRNA、蛋白质和活性水平表明细菌GR在叶绿体中更稳定。当gshII基因在细胞质中表达时，GS活性比其他株系高100倍。细胞质中GR或GS的过表达对谷胱甘肽水平没有影响，但叶绿体GR的表达使叶片谷胱甘肽增加一倍，并使还原状态增加。高叶绿体GR表达株系对光抑制的抗性增强。除草剂甲基紫精抑制所有株系的CO2同化，但高叶绿体GR表达株系中叶片谷胱甘肽和抗坏血酸水平增加，尽管经过这种处理仍持续存在。这些结果表明叶绿体中GR的过表达增加了叶片的抗氧化能力，并且这提高了抵御氧化应激的能力。
