© 2007 The Author(s).
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RESEARCH PAPER |
Dehydroascorbate uptake is impaired in the early response of Arabidopsis plant cell cultures to cadmium
1Department of Biology, Plant Physiology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
2Department of Biology, Ecophysiology, Biochemistry and Toxicology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
3Centre for Environmental Sciences, Environmental Biology, Hasselt University, Agoralaan Building D, 3590 Diepenbeek, Belgium
* To whom correspondence should be addressed. E-mail: nele.horemans{at}ua.ac.be
The balance between antioxidants, such as ascorbate (ASC) and glutathione, and oxidative reactive oxygen species (ROS) is known to play a pivotal role in the response of plant cells to abiotic stress. Here cell cultures of Arabidopsis thaliana were investigated with regard to their response to elevated levels of cadmium. At concentrations <100 µM, Cd induces a rapid and concentration-dependent H2O2 accumulation. This response could be inhibited by diphenylene iodonium (DPI, 20 µM). Reverse transcription-PCR analysis of three RBOH (respiratory burst oxidase homologues) genes showed an increased transcription of RBOHF after 15 min. No change in ASC concentration was observed during the first 3 h after Cd addition. In contrast, glutathione levels completely diminished within 1 h. This drop could be attributed to an increase in phytochelatin 4. At the plasma membrane, Cd further induced a significant decrease in dehydroascorbate (DHA) uptake activity (up to 90% inhibition after 4 h). This decrease is not present when cells are treated with LaCl3 before exposure to CdCl2. LaCl3 is a typical inhibitor of Ca channels and prevents Cd uptake in these cells as well as the Cd-induced ROS production. Therefore, these results appear to indicate that Cd uptake is a prerequisite for the change in DHA transport activity. However, DPI did not prevent the drop in DHA uptake activity present in Cd-treated Arabidopsis cells, indicating that this response seems to be independent of the Cd-induced H2O2 production.
Key words: Arabidopsis thaliana cell cultures, ascorbate, cadmium, DHA uptake, glutathione, reactive oxygen species
Received 6 July 2007; Revised 18 October 2007 Accepted 18 October 2007
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