Abstract
Internode stem fragments of the poplar hybrid Populus tremula x Populus alba were transformed with a bacterial gene (gshl) for [gamma]-glutamylcysteine synthetase ([gamma]-ECS) targeted to the cytosol. Lines overexpressing [gamma]-ECS were identified by northern analysis, and the transformant with the highest enzyme activity was used to investigate the control of glutathione synthesis. Whereas foliar [gamma]-ECS activity was below the limit of detection in untransformed plants, activities of up to 8.7 nmol mg-1 protein min-1 were found in the transformant, in which the foliar contents of [gamma]-glutamylcysteine ([gamma]-EC) and glutathione were increased approximately 10- and 3-fold, respectively, without affecting either the reduction state of the glutathione pool or the foliar cysteine content. A supply of exogenous cysteine to leaf discs increased the glutathione content from both transformed and untransformed poplars, and caused the [gamma]-EC content of the transformant discs to increase still further. The following conclusions are drawn: (a) the native [gamma]-ECS of untransformed poplars exists in quantities that are limiting for foliar glutathione synthesis; (b) foliar glutathione synthesis in untransformed poplars is limited by cysteine availability; (c) in the transformant interactions between glutathione synthesis and cysteine synthesis operate to sustain the increased formation of [gamma]-EC and glutathione; and (d) the foliar glutathione content of the transformant is restricted by cysteine availability and by the activity of glutathione synthetase.
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- Bevan M. Binary Agrobacterium vectors for plant transformation. Nucleic Acids Res. 1984 Nov 26;12(22):8711–8721. doi: 10.1093/nar/12.22.8711. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Chen J., Goldsbrough P. B. Increased Activity of [gamma]-Glutamylcysteine Synthetase in Tomato Cells Selected for Cadmium Tolerance. Plant Physiol. 1994 Sep;106(1):233–239. doi: 10.1104/pp.106.1.233. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Foyer C. H., Souriau N., Perret S., Lelandais M., Kunert K. J., Pruvost C., Jouanin L. Overexpression of glutathione reductase but not glutathione synthetase leads to increases in antioxidant capacity and resistance to photoinhibition in poplar trees. Plant Physiol. 1995 Nov;109(3):1047–1057. doi: 10.1104/pp.109.3.1047. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Guerineau F., Woolston S., Brooks L., Mullineaux P. An expression cassette for targeting foreign proteins into chloroplasts. Nucleic Acids Res. 1988 Dec 9;16(23):11380–11380. doi: 10.1093/nar/16.23.11380. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Papen H., Kentemich T., Schmülling T., Bothe H. Hydrogenase activities in cyanobacteria. Biochimie. 1986 Jan;68(1):121–132. doi: 10.1016/s0300-9084(86)81077-x. [DOI] [PubMed] [Google Scholar]
- Rennenberg H., Polle A. Protection from oxidative stress in transgenic plants. Biochem Soc Trans. 1994 Nov;22(4):936–940. doi: 10.1042/bst0220936. [DOI] [PubMed] [Google Scholar]
- Rüegsegger A., Brunold C. Effect of Cadmium on gamma-Glutamylcysteine Synthesis in Maize Seedlings. Plant Physiol. 1992 Jun;99(2):428–433. doi: 10.1104/pp.99.2.428. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Watanabe K., Yamano Y., Murata K., Kimura A. The nucleotide sequence of the gene for gamma-glutamylcysteine synthetase of Escherichia coli. Nucleic Acids Res. 1986 Jun 11;14(11):4393–4400. doi: 10.1093/nar/14.11.4393. [DOI] [PMC free article] [PubMed] [Google Scholar]