Phytoremediation by transgenic plants with enhanced ability of sulfur assimilation

含硫化合物对环境的污染是全球环境面临的一个严重问题。特别是二氧化硫气体，主要由自然来源和人类活动排放，如化石燃料的燃烧，含硫矿石的工业精炼，影响人类健康和全球动植物生态系统。植物修复是一种利用植物清除环境中污染物的技术，已受到广泛关注。半胱氨酸合成酶[ο-乙酰-l -丝氨酸（硫醇）裂解酶，EC 4.2.99.8] （Csase）负责半胱氨酸生物合成的最后一步。通过两个表达胞质性或叶绿体性Csase的转化体杂交，获得了细胞质和叶绿体中Csase活性均增强的转基因烟草（Nicotiana tabacum, F_1）植株。F_1转基因植株对有毒的二氧化硫和亚硫酸盐具有较高的耐受性。熏蒸0。lμLL^<-1>二氧化硫处理后，F_1植株叶片中半胱氨酸和谷胱甘肽含量均显著升高，而非转化对照植株叶片中半胱氨酸和谷胱甘肽含量无显著升高。此外，F_1植株叶片对百草枯（一种产生活性氧的除草剂）的抗性增强。以硫同化关键调控酶丝氨酸乙酰转移酶（serine acetyltransferase）转基因拟南芥植株为材料，研究其对重金属、镉等的抗性。

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.