| Abstract
| - To survive in variable soil conditions, plants possesshomeostatic mechanisms to maintain a suitable concentrationof essential heavy metal ions. Certain plants, inhabitingheavy metal-enriched or -contaminated soil, thus are namedhyperaccumulators. Studying hyperaccumulators hasgreat potential to provide information for phytoremediation.To better understand the hyperaccumulating mechanism,we used an Arabidopsis cDNA microarray to compare thegene expression of the Zn/Cd hyperaccumulator Arabidopsishalleri and a nonhyperaccumulator, Arabidopsis thaliana. Byanalyzing the expression of metal-chelators, antioxidation-related genes, and transporters, we revealed a fewnovel molecular features. We found that metallothionein2b and 3, APX and MDAR4 in the ascorbate-glutathionepathway, and certain metal transporters in P1B-typeATPase, ZIP, Nramp, and CDF families, are expressed athigher levels in A. halleri than in A. thaliana. We furthervalidated that the enzymatic activity of ascorbateperoxidase and class III peroxidases are highly elevatedin A. halleri. This observation positively correlates with thehigher ability of A. halleri to detoxify H2O2 produced bycadmium and paraquat treatments. We thus suggest thathigher peroxidase activities contribute to the heavy metaltolerance in A. halleri by alleviating the ROS damage.We have revealed genes that could be candidates for thefuture engineering of plants with large biomass for usein phytoremediation.
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