EDDS对印度芥菜Cu积累的影响及与P-ATPase的关系研究

EFFECT OF EDDS ON THE ACCUMULATION OF Cu IN INDIAN MUSTARD AND ITS RELATIONSHIP WITH P-TYPE ATPase

通过水培的方法研究了可降解螯合剂EDDS对印度芥菜对Cu积累的影响,分析了根系中与Cu主动排出有关的P型ATPase的活性及其基因表达。结果表明:根系中Cu的积累量随外界浓度的升高而升高,但Cu在茎杆与叶片中的积累量则变化不大。随着外加EDDS浓度的增加,根、茎、叶中的Cu的积累量均出现下降的趋势。上述结果表明,根系以Cu离子为主要的吸收形式,而不是EDDS-Cu。通过对印度芥菜根系细胞膜上P型ATPase活性及基因表达分析后发现,不加EDDS时,随着外界Cu浓度的升高,ATPase活性增强,而当Cu达到16μmol L-1时出现降低的趋势。但是,ATPase活性随着外加EDDS的浓度增加而降低,这是因为EDDS降低了外界的Cu活度。RT-PCR分析结果表明,该ATPase的基因(BjHMA)在转录水平上的表达与活性变化一致。由于P型ATPase的作用是将Cu排出细胞,因此上述结果说明,其活性大小以及转录水平的变化受到外界Cu离子活度的影响,在一定的范围内可以调节植物对Cu的积累。

Indian mustard （Brassica juncea L. ） is a model of plant used to investigate accumulation of heavy metals. In this study, a hydroponics experiment was conducted to investigate accumulation of Cu by Indian mustard applied with EDDS, a biodegradable chelator for phytoremediation. Activity of P-type ATPase, a heavy metal ATPase （HMA） responsible for Cu export, and its transcriptional expression in roots was analyzed. Results showed that increased accumulation of Cu with elevated Cu concentration in the medium was only found in roots, but not in stems or leaves. The accumulation of Cu in roots, stems and leaves decreased with elevated EDDS concentration. The results indicated that the uptake of Cu, mainly in the form of ions rather than Cu-EDDS chelator complexes, was controlled by plasma membrane of roots, where P-type ATPase increased its activity with elevated Cu concentration, but decreased with elevated EDDS concentra- tion. The expression pattern of P-type ATPase gene （BjHMA） varied similarly as its activity did. The above listed findings indicate that as P-type ATPase plays the role of actively exporting Cu out of root cells, it may regulate Cu accumulation by plants within a certain range of ambient Cu concentration.