| Research Abstract |
Environmental pollution by sulfur-containing compounds is a serious problem for the global environment. In particular, gaseous SO_2, which is emitted mainly by both natural sources and human activities, I. E. combustion of fossil fuels, industrial refining of sulfur-containing ores, influences human health and the global ecological system of animals and plants. Phytoremediation, which uses plants to remove pollutants from the environment, has received wide attention. Cysteine synthase [ο-acetyl-L-serine(thiol)-lyase, EC 4.2.99.8] (Csase) is responsible for the final step in biosynthesis of cysteine. Transgenic tobacco(Nicotiana tabacum) (F_1)plants with enhanced Csase activities both in the cytosol and in the chloroplasts were generated by cross-fertilization of two transformants expressing either cytosolic Csase or chloroplastic Csase. The F_1 transgenic plants were highly tolerant to toxic sulfur dioxide and sulfite. Upon fumigation with 0. lμLL^<-1> sulfur dioxide, both the cysteine and glutathione contents in leaves of F_1 plants were increased significantly, but not in leaves of non-transformed control plants. Furthermore, the leaves of F_1 plants exhibited the increased resistance to paraquat, a herbicide generating active oxygen species. The transgenic Arabidopsis plants over expressing serine acetyltransferase, a key regulatory enzyme of sulfur assimilation, were also generated to examine the resistance to a heavy metal, Cd etc.
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