JXB Advance Access published online on May 12, 2006
Journal of Experimental Botany, doi:10.1093/jxb/erj197
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1 The Edinburgh Cell Wall Group, Institute of Molecular Plant Sciences, School of Biological Sciences, The University of Edinburgh, Daniel Rutherford Building, The King's Buildings, Edinburgh EH9 3JH, UK; Present address: Department of Applied Biology, PO Box 27 (Latokartanonkaari 7), FIN-00014 University of Helsinki, Finland
* To whom correspondence should be addressed. Dehydroascorbate and traces of ascorbate were present apoplastically in living spruce (Picea abies) twigs. Since the proposed apoplastic ascorbate degradation pathway contains several steps that possibly generate H2O2, the effects of ascorbate and some of its degradation products were tested on apoplastic H2O2 concentrations in a cell culture of P. abies as a model and on non-enzymic H2O2 production in vitro. Ascorbate scavenged H2O2 in the culture medium of lignin-producing Picea cells and in spent and boiled spent medium; in the presence of Cu2+ or fresh medium, ascorbate led to the non-enzymic generation of H2O2. Preparations of dehydroascorbate (the initial oxidation-product of ascorbate), and diketogulonate (the hydrolysis-product of dehydroascorbate) induced H2O2 accumulation both non-enzymically and enzymically in Picea cell-suspensions. Paper electrophoresis showed that the dehydroascorbate and diketogulonate preparations contained several degradation products; some of these probably contributed to H2O2 production and/or scavenging in these experiments, and would also do so in vivo. These results indicate a complex ability of apoplastic ascorbate, dehydroascorbate, diketogulonate, and further products to modulate H2O2 concentrations, with potential consequences for the control of growth, development and lignification.
Received January 26, 2006
Accepted March 14, 2006
Oxygen Metabolism Special Issue
Effect of ascorbate and its oxidation products on H2O2 production in cell-suspension cultures of Picea abies and in the absence of cells
Anna Kärkönen 1
and
Stephen C. Fry 2 *
2 The Edinburgh Cell Wall Group, Institute of Molecular Plant Sciences, School of Biological Sciences, The University of Edinburgh, Daniel Rutherford Building, The King's Buildings, Edinburgh EH9 3JH, UK
Stephen C. Fry, E-mail: S.Fry{at}ed.ac.uk
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