Elevated glutathione biosynthetic capacity in the chloroplasts of transgenic tobacco plants paradoxically causes increased oxidative stress. [Erratum: Feb 2000, v. 12 (2), p. 301.]

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...

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Bibliographic Details
Published in:The Plant cell 1999-07, Vol.11 (7), p.1277-1291
Main Authors: Creissen, G, Firmin, J, Fryer, M, Kular, B, Leyland, N, Reynolds, H, Pastori, G, Wellburn, F, Baker, N, Wellburn, A, Mullineaux, P
Format: Article
Language:English
Subjects:
Antioxidants
biosynthesis
catalase
chemical constituents of plants
Chloroplasts
chlorosis
enzyme activity
Enzymes
Escherichia coli
gamma-glutamylcysteine
gene expression
gene transfer
genes
glutamate-cysteine ligase
glutathione
glutathione reductase (NADPH)
Leaves
ligases
light intensity
messenger RNA
necrosis
Nicotiana tabacum
oxidation
Oxidative stress
Phenotypes
photosynthesis
Plant cells
Plants
Siblings
stress
superoxide dismutase
Transgenic plants
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Summary: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.
ISSN:1040-4651
1532-298X
DOI:10.1105/tpc.11.7.1277