Molecular cloning, characterization and regulation by cadmium of a superoxide dismutase from the ectomycorrhizal fungus Paxillus involutus

Authors

  • Christophe Jacob,

    1. Université Henri Poincaré Nancy I, Faculté des Sciences, UMR INRA–UHP 1136 Interactions Arbres/Micro-organismes,
      Vandœuvre-les-Nancy Cedex, France;
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  • Mikaël Courbot,

    1. Université Henri Poincaré Nancy I, Faculté des Sciences, UMR INRA–UHP 1136 Interactions Arbres/Micro-organismes,
      Vandœuvre-les-Nancy Cedex, France;
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  • Annick Brun,

    1. Université Henri Poincaré Nancy I, Faculté des Sciences, UMR INRA–UHP 1136 Interactions Arbres/Micro-organismes,
      Vandœuvre-les-Nancy Cedex, France;
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  • Howard M. Steinman,

    1. Department of Biochemistry, Albert Einstein College of Medicine, New York, USA
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  • Jean-Pierre Jacquot,

    1. Université Henri Poincaré Nancy I, Faculté des Sciences, UMR INRA–UHP 1136 Interactions Arbres/Micro-organismes,
      Vandœuvre-les-Nancy Cedex, France;
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  • Bernard Botton,

    1. Université Henri Poincaré Nancy I, Faculté des Sciences, UMR INRA–UHP 1136 Interactions Arbres/Micro-organismes,
      Vandœuvre-les-Nancy Cedex, France;
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  • Michel Chalot

    1. Université Henri Poincaré Nancy I, Faculté des Sciences, UMR INRA–UHP 1136 Interactions Arbres/Micro-organismes,
      Vandœuvre-les-Nancy Cedex, France;
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M. Chalot, Université Henri Poincaré Nancy I, Faculté des Sciences, UMR INRA–UHP 1136 Interactions Arbres/Micro-organismes, F-54506 Vandœuvre-Les-Nancy Cedex, France. Fax: + 33 3 83 91 22 43, Tel.: + 33 3 83 91 27 38, E-mail: Michel.Chalot@scbiol.uhp-nancy.fr

Abstract

The gene encoding a superoxide dismutase (PiSOD) was cloned by suppressive subtractive hybridization from cDNA library of the ectomycorrhizal fungus, Paxillus involutus, grown under cadmium-stress conditions. The encoded protein was presumed to be localized in the peroxisomes because it contained a C-terminal peroxisomal localization peptide (SKL) and lacked an N-terminal mitochondrial transit peptide. Complementation of an Escherichia coli SOD null strain that is unable to grow in the presence of paraquat or cadmium indicated that cloned Pisod encoded a functional superoxide dismutase. Sensitivity of PiSOD activity to H2O2 but not KCN, and sequence homologies to other SODs strongly suggest that it is a manganese-containing superoxide dismutase. Monitoring PiSOD transcript, immunoreactive polypeptide and superoxide dismutase activity following cadmium stress suggests that the principal level of control is post-translational. This is, to our knowledge, the first insight in the characterization of molecular events that take place in an ectomycorrhizal fungus during exposure to heavy metals.

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