Characterization of Cd translocation and identification of the Cd form in xylem sap of the Cd-hyperaccumulator Arabidopsis halleri
Characterization of Cd translocation and identification of the Cd form in xylem sap of the Cd-hyperaccumulator Arabidopsis halleri
复制标题
DOI：
10.1093/pcp/pcn026
复制
发表时间：
2008-04-01
影响因子：
4.9
通讯作者：
Ma, Jian Feng
中科院分区：
文献类型：
--
作者：
Ueno, Daisei;Iwashita, Takashi;Ma, Jian Feng
拟南芥是一种镉超积累植物，然而，镉从根向地上部转运的机制尚不清楚。在这项研究中，我们的特点是镉从根介质中的木质部在这个物种。拟南芥积累1,500 mg kg（1）镉在地上部没有生长抑制。一个时间过程的实验表明，释放到木质部的镉是非常迅速的，由2小时暴露于镉，在木质部汁液中的镉浓度是5倍高于在外部溶液。木质部汁液中的Cd浓度随外源Cd浓度的增加而线性增加。镉向木质部的转移被代谢抑制剂羰基氰3-氯苯腙（CCCP）完全抑制。外源Zn浓度的增加降低了木质部汁液中Cd的含量，而缺铁处理则使木质部汁液中Cd的含量增加。Cd ~（113）-NMR分析表明，Cd ~（113）在木质部汁液中的化学位移与Cd（NO_3）（2）的化学位移相同。金属形态与Geochem-PC还表明，镉主要发生在自由离子形式的木质部汁液。这些结果表明，镉在紫穗槐中是从根向木质部转移的。Halleri是一个依赖能量的过程，其部分与Zn和/或Fe运输共享。此外，镉从根转移到地上部的无机形式。
Arabidopsis halleriis a Cd hyperaccumulator; however, the mechanisms involved in the root to shoot translocation of Cd are not well understood. In this study, we characterized Cd transfer from the root medium to xylem in this species. Arabidopsis halleri accumulated 1,500 mg kg(1) Cd in the shoot without growth inhibition. A time-course experiment showed that the release of Cd into the xylem was very rapid; by 2 h exposure to Cd, Cd concentration in the xylem sap was 5-fold higher than that in the external solution. The concentration of Cd in the xylem sap increased linearly with increasing Cd concentration in the external solution. Cd transfer to the xylem was completely inhibited by the metabolic inhibitor carbonyl cyanide 3-chlorophenylhydrazone (CCCP). Cd concentration in the xylem sap was decreased by increasing the concentration of external Zn, but enhanced by Fe deficiency treatment. Analysis with Cd-113-nuclear magnetic resonance (NMR) showed that the chemical shift of Cd-113 in the xylem sap was the same as that of Cd(NO3)(2). Metal speciation with Geochem-PC also showed that Cd occurred mainly in the free ionic form in the xylem sap. These results suggest that Cd transfer from the root medium to the xylem in A. halleri is an energy-dependent process that is partly shared with Zn and/or Fe transport. Furthermore, Cd is translocated from roots to shoots in inorganic forms.