Present address: Freie Universität Berlin, Institut für Biologie, Angewandte Genetik, Albrecht-Thaer-Weg 6, D-14195 Berlin, Germany.
Expression of a bacterial serine acetyltransferase in transgenic potato plants leads to increased levels of cysteine and glutathione
Article first published online: 25 DEC 2001
The Plant Journal
Volume 22, Issue 4, pages 335–343, May 2000
How to Cite
Harms, K., Von Ballmoos, P., Brunold, C., Höfgen, R. and Hesse, H. (2000), Expression of a bacterial serine acetyltransferase in transgenic potato plants leads to increased levels of cysteine and glutathione. The Plant Journal, 22: 335–343. doi: 10.1046/j.1365-313x.2000.00743.x
- Issue published online: 25 DEC 2001
- Article first published online: 25 DEC 2001
- Received 22 November 1999; revised 1 March 2000; accepted 3 March 2000.
The coding sequence of the wild-type, cys-sensitive, cysE gene from Escherichia coli, which encodes an enzyme of the cysteine biosynthetic pathway, namely serine acetyltransferase (SAT, EC 184.108.40.206), was introduced into the genome of potato plants under the control of the cauliflower mosaic virus 35S promoter. In order to target the protein into the chloroplast, cysE was translationally fused to the 5′-signal sequence of rbcS from Arabidopsis thaliana. Transgenic plants showed a high accumulation of the cysE mRNA. The chloroplastic localisation of the E. coli SAT protein was demonstrated by determination of enzymatic activities in enriched organelle fractions. Crude leaf extracts of these plants exhibited up to 20-fold higher SAT activity than those prepared from wild-type plants. The transgenic potato plants expressing the E. coli gene showed not only increased levels of enzyme activity but also exhibited elevated levels of cysteine and glutathione in leaves. Both were up to twofold higher than in control plants. However, the thiol content in tubers of transgenic lines was unaffected. The alterations observed in leaf tissue had no effect on the expression of O-acetylserine(thiol)-lyase, the enzyme which converts O-acetylserine, the product of SAT, to cysteine. Only a minor effect on its enzymatic activity was observed. In conclusion, the results presented here demonstrate the importance of SAT in plant cysteine biosynthesis and show that production of cysteine and related sulfur-containing compounds can be enhanced by metabolic engineering.