Complexation of Arsenite with Phytochelatins Reduces Arsenite Efflux and Translocation from Roots to Shoots in Arabidopsis
Complexation of Arsenite with Phytochelatins Reduces Arsenite Efflux and Translocation from Roots to Shoots in Arabidopsis
复制标题
DOI：
10.1104/pp.109.150862
复制
发表时间：
2010-04-01
期刊：
影响因子：
7.4
通讯作者：
Feldmann, Joerg
中科院分区：
文献类型：
--
作者：
Liu, Wen-Ju;Wood, B. Alan;Feldmann, Joerg
亚砷酸盐[As(III)]与植物螯合素（PCs）络合是植物解毒砷的重要机制；这种络合如何影响As的迁移性尚不清楚。我们采用高分辨率电感耦合等离子体质谱法和精确质量电喷雾电离体质谱法结合高效液相色谱法，对砷酸盐[As(V)]暴露的拟南芥（Arabidopsis thaliana）中的As（III）硫醇配合物和游离硫醇化合物进行了鉴定和定量。As(V)在根中有效还原为As（III）。在野生型根中，69%的As络合为As(III)- pc4、As(III)- pc3和As(III)-(PC2)(2)。谷胱甘肽（GSH）缺陷突变体cad2-1和pc缺陷突变体cad1-3对As(V)的敏感性都比野生型高约20倍。在cad1-3根中，只有8%的As(III)-(GS)(3)与GSH络合，没有检测到As(III)- pcs，而在cad2-1根中，As(III)- pcs仅占总As的25%。两个突变体的As移动性均较野生型高，其茎部As（III）积累量显著高于野生型，茎根As浓度比高出野生型4.5 ~ 12倍。根也将吸收As（III）的相当一部分As(V)外排到外部培养基中，在两个突变体中这种外排量更大。此外，当野生型植物暴露于l -丁硫氨酸亚砜或硫被剥夺时，As（III）外排和根到茎的转运都增强了。结果表明，拟南芥根系中As（III）与PCs的络合降低了As（III）向外界介质的外排和根到梢转运的流动性。促进根系PC合成可能是减少砷转运到粮食作物食用器官的有效策略。
Complexation of arsenite [As(III)] with phytochelatins (PCs) is an important mechanism employed by plants to detoxify As; how this complexation affects As mobility was little known. We used high-resolution inductively coupled plasma-mass spectrometry and accurate mass electrospray ionization-mass spectrometry coupled to HPLC to identify and quantify As(III)thiol complexes and free thiol compounds in Arabidopsis (Arabidopsis thaliana) exposed to arsenate [As(V)]. As(V) was efficiently reduced to As(III) in roots. In wild-type roots, 69% of As was complexed as As(III)-PC4, As(III)-PC3, and As(III)-(PC2)(2). Both the glutathione (GSH)-deficient mutant cad2-1 and the PC-deficient mutant cad1-3 were approximately 20 times more sensitive to As(V) than the wild type. In cad1-3 roots, only 8% of As was complexed with GSH as As(III)-(GS)(3) and no As(III)-PCs were detected, while in cad2-1 roots, As(III)-PCs accounted for only 25% of the total As. The two mutants had a greater As mobility, with a significantly higher accumulation of As(III) in shoots and 4.5 to 12 times higher shoot-to-root As concentration ratio than the wild type. Roots also effluxed a substantial proportion of the As(V) taken up as As(III) to the external medium, and this efflux was larger in the two mutants. Furthermore, when wild-type plants were exposed to L-buthionine sulfoximine or deprived of sulfur, both As(III) efflux and root-to-shoot translocation were enhanced. The results indicate that complexation of As(III) with PCs in Arabidopsis roots decreases its mobility for both efflux to the external medium and for root-to-shoot translocation. Enhancing PC synthesis in roots may be an effective strategy to reduce As translocation to the edible organs of food crops.