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严重问题。特别是气态SO2，主要由自然来源和人类活动排放，即化石燃料的燃烧、含硫矿石的工业精炼等，对人类健康和全球动植物生态系统都有影响。利用植物从环境中去除污染物的植物修复技术受到了广泛的关注。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。利用胞质Csase和叶绿体Csase两个转化子进行杂交，获得了胞质Csase活性和叶绿体Csase活性均较高的烟草转基因植株(F1)。转基因F_1代植株对有毒的二氧化硫和亚硫酸盐具有高度的耐受性。熏蒸时用0。LμL1&lt；-1&gt；二氧化硫处理后，F_1代植株叶片中的半胱氨酸和谷胱甘肽含量均显著增加，而未转化对照植株叶片中的半胱氨酸和谷胱甘肽含量没有显著增加。此外，F_1代植株叶片对产生活性氧的除草剂百草枯的抗性增强。还获得了高表达丝氨酸乙酰转移酶的转基因拟南芥植株，丝氨酸乙酰转移酶是硫同化的关键调节酶，用来检测对重金属Cd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.