Scientists Develop Transgenic Plants With Increased Glutathione

The tripeptide glutathione plays important roles in protecting cells from biotic and abiotic stress. It is the cell's major antioxidant, neutralizing free radicals and reactive oxygen species. It protect the cell from the harmful effects of xenobiotics and carcinogens. Glutathione also plays linchpin roles in numerous biochemical and metabolic processes, for instance in directing DNA repair, protein synthesis and amino acid transport, controlling apoptosis or cell suicide and enhancing the cytotoxic capability of T-Cells. In some countries, like the Philippines, glutathione is being used in the cosmetic industry as a melanin inhibitor.

Previous attempts to increase GSH content in plants have met with moderate success. Glutathione is currently being produced using yeast-based systems. Now researchers from the Heidelberg Institute for Plant Science at Heidelberg Uniiversity in Germany report that they have successfully expressed bifunctional γ-glutamylcysteine ligase, glutathione synthetase enzyme from the bacterium Streptococcus thermophilus (StGCL-GS), in tobacco plants. StGCL-GS has been shown to be neither redox-regulated nor sensitive to feedback inhibition by glutathione.

Reporting in the Plant Biotechnology Journal, the researchers said that transgenic tobacco plants expressing StGCL-GS show an extreme accumulation of GSH in their leaves (up to 12 μmol GSH/gFW, depending on the developmental stage), which is more than 20- to 30-fold above the levels observed in wild-type plants and which can be even further increased by additional sulphate fertilization. The researchers also said that transgenic plants showed increased abiotic stress tolerance. Since the expression of StGCL-GS had no effects on plant growth, the system can be competitive with current yeast-based systems.

The paper is available at http://dx.doi.org/10.1111/j.1467-7652.2010.00510.x