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The properties of the Mn, Ni and Pb transport operating at plasma membranes of cucumber roots
Author(s) -
Migocka Magdalena,
Klobus Grazyna
Publication year - 2007
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.2006.00842.x
Subject(s) - antiporter , efflux , chemistry , ion transporter , membrane , metal , biophysics , cytosol , metal ions in aqueous solution , vesicle , membrane transport , nuclear chemistry , biochemistry , enzyme , biology , organic chemistry
To avoid metal toxicity, plants have developed mechanisms including efflux of metal ions from cells and their sequestration into cellular compartments. In this report, we present evidence for the role of plasma membrane efflux systems in metal tolerance of cucumber roots. We have identified the plasma membrane‐transport system participating in Cd, Pb, Mn and Ni efflux from the cytosol. Kinetic characterization of this proton‐coupled transport system revealed that it is saturable and has a different affinity for each of the metal ions used (with Km 5, 7.5 and 0.1 m M for Mn, Ni and Pb, respectively). Treatment of cucumber roots with 100 μ M Cd prior to the transport measurements caused a great increase (over 250%) in Cd antiport activity in plasmalemma vesicles. After decreasing the metal concentration to 50 μ M we still observed a large increase (over 150%) of this activity in comparison with the control. Moreover, the addition of 50 μ M Cd to the external solution stimulated not only Cd antiport in the plasmalemma vesicles but also the antiport of other metals used in the experiments. Treatment of cucumber roots with 50 μ M Ni revealed a similar effect: the antiport activity of Cd, Mn, Ni and Pb was stimulated, although to a lesser extent in comparison with stimulation by Cd. The data indicate that the root plasma membrane antiporter system is stimulated by the exogenous presence of heavy metals.