Increased resistance to oxidative stress in transgenic tobacco plants overexpressing bacterial serine acetyltransferase

Plant expression cassettes containing the Escherichia coli cysE gene allele s (encoding SAT) were constructed. After the Agrobacterium-mediated transfo rmation of tobacco, we identified stable transformed plants containing seve ral-fold higher SAT activity in comparison to the control plant. Determinat ion of nonprotein thiol contents indicated two- to threefold higher cystein e and glutathione levels in some of these transgenic plants. The maximal el evation of the cysteine level was about fourfold while that of GSH was abou t twofold higher than in the controls. The most striking physiological cons equence of the modification of sulfur metabolite levels in the transgenic p lants, however, was their several-fold increased resistance to oxidative st ress generated by exogenous hydrogen peroxide.