印度芥菜BjPCS1基因的表达提高烟草对重金属的抗性

Overexpression of BjPCS1 gene from Brassica juncea enhances the heavy metal tolerance in transgenic tobacco

在植物体内植物络合素(PC)可与重金属螯合,并进一步转运至液泡储存,使细胞质的重金属浓度降低,从而达到解毒效果。PC不是基因的直接翻译产物,而是以谷胱甘肽(GSH)为底物由植物络合素合酶催化而成。将来源于重金属超富集植物印度芥菜(Brassica juncea)的植物络合素合酶基因BjPCS1转入烟草,PCR和Northern结果表明,该基因已经整合到烟草基因组中,并在转录水平上表达。在3种重金属(200mmol/L CdCl2、400mmol/L ZnCl2、200mmol/L NiCl2)胁迫条件下,转基因烟草植株的脯氨酸含量、可溶性糖含量、丙二醛含量、相对电导率和叶绿素含量等指标均优于未转化的对照植株,表明转化BjPCS1基因提高了烟草对3种重金属的抗性,其中转基因烟草抗Cd能力最强,并且转基因烟草的T1代种子在Cd处理的情况下萌发状况明显优于对照。这些结果说明,BjPCS1基因在利用基因工程改良植物抗重金属能力和净化环境污染方面,具有良好的应用前景。

GSH is the substrate that synthesizes PC, which chelates the heavy metals. Heavy metal-PC chelatins are subsequently transported from the cytosol to the vacuole and heavy metal detoxification is thus achieved. A plantexpressed plasmid with PC synthesase from Brassica juncea （ BjPCS1 ） was constructed and transferred into tobacco. PCR and Northern blot indicated that BjPCS1 was integrated into the genome of tobacco and functioned properly. Physiological responses of the transformant to three heavy metals （200mmol/L CdCl2,400mmol/L ZnCl2,200mmol/L NiCl2 ） treatment, reflected by relative electronic conductivity （Rc/Rc＇）, chlorophyll content （Chla ＋ b）, content of dissolvent suga and MDA content, were better than those in the control plants. These results indicated that BjPCS1 transformation could improve the heavy metal tolerance of the transgenic tobaccos, especially Cd tolerance. Furthermore, the seedlings of offspring from BjPCS1 positive plants were tested for resistance to Cd. The results confirmed that the expression of BjPCS1 could enhance Cd tolerance of transgenic tobaccos. As it＇s an important role in transgenic plants, BjPCS1 gene can work as a significant gene tool in the phytoremediation of heavy metal pollution.