Enhanced levels of methionine and cysteine in transgenic alfalfa (Medicago sativa L.) plants over-expressing the Arabidopsis cystathionine γ-synthase gene
Article first published online: 21 SEP 2004
Plant Biotechnology Journal
Volume 3, Issue 1, pages 71–79, January 2005
How to Cite
Avraham, T., Badani, H., Galili, S. and Amir, R. (2005), Enhanced levels of methionine and cysteine in transgenic alfalfa (Medicago sativa L.) plants over-expressing the Arabidopsis cystathionine γ-synthase gene. Plant Biotechnology Journal, 3: 71–79. doi: 10.1111/j.1467-7652.2004.00102.x
- Issue published online: 21 SEP 2004
- Article first published online: 21 SEP 2004
- Received 2 March 2004; revised 20 June 2004; accepted 25 June 2004.
- amino acids;
- cystathionine γ-synthase;
- nutritional quality;
- transgenic alfalfa
With the aim of increasing the methionine level in alfalfa (Medicago sativa L.) and thus improving its nutritional quality, we produced transgenic alfalfa plants that expressed the Arabidopsis cystathionine γ-synthase (AtCGS), the enzyme that controls the synthesis of the first intermediate metabolite in the methionine pathway. The AtCGS cDNA was driven by the Arabidopsis rubisco small subunit promoter to obtain expression in leaves. Thirty transgenic plants were examined for the transgene protein expression, and four lines with a high expression level were selected for further work. In these lines, the contents of methionine, S-methylmethionine (SMM), and methionine incorporated into the water-soluble protein fraction increased up to 32-fold, 19-fold, and 2.2-fold, respectively, compared with that in wild-type plants. Notably, in these four transgenic lines, the levels of free cysteine (the sulphur donor for methionine synthesis), glutathione (the cysteine storage and transport form), and protein-bound cysteine increased up to 2.6-fold, 5.5-fold, and 2.3-fold, respectively, relative to that in wild-type plants. As the transgenic alfalfa plants over-expressing AtCGS had significantly higher levels of both soluble and protein-bound methionine and cysteine, they may represent a model and target system for improving the nutritional quality of forage crops.