Regulation of glutathione synthesis in leaves of transgenic poplar (Populus tremula × P. alba) overexpressing glutathione synthetase
Plant Journal, Volume 7, No. 1, Year 1995
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The poplar hybrid Populus tremula × P. alba was transformed with the Escherichia coli gene for glutathione synthetase (gsh II] targetted to the cytosol. Leaves of five lines of transgenic plants exhibited glutathione synthetase activities 15- to 60-fold higher than those of wild-type plants. Total glutathione levels and GSH/GSSG ratios were similar in transgenic and wild-type plants. Precursor feeding experiments with cysteine and γ-glutamylcysteine suggest that glutathione synthesis in the cytoplasm is controlled by a multistep procedure that includes (i) the availability of cysteine, (ii) the availability of γ-glutamylcysteine, and (iii) regulation of the activities of both γ-glutamylcysteine synthetase and glutathione synthetase. However step (ii) may set an upper limit for the cellular glutathione content.