Heavy-Metal Regulation of Thioredoxin Gene Expression in Chlamydomonas reinhardtii |
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Authors: | Stphane Lemaire Eliane Keryer Mariana Stein Isabelle Schepens Emmanuelle Issakidis-Bourguet Catherine Grard-Hirne Myroslawa Miginiac-Maslow and Jean-Pierre Jacquot |
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Institution: | Stéphane Lemaire, Eliane Keryer, Mariana Stein, Isabelle Schepens, Emmanuelle Issakidis-Bourguet, Catherine Gérard-Hirne, Myroslawa Miginiac-Maslow, and Jean-Pierre Jacquot |
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Abstract: | Heavy metals are highly toxic compounds for cells. In this report we demonstrate that the expression of Chlamydomonas reinhardtii thioredoxins (TRX) m and h is induced by heavy metals. Upon exposure of the cells to Cd and Hg, a strong accumulation of both messengers was observed. Western-blot experiments revealed that among these two TRXs, only TRX h polypeptides accumulated in response to the toxic cations. A biochemical analysis indicated that heavy metals inhibit TRX activity, presumably by binding at the level of their active site. Sequence analysis of the C. reinhardtii TRX h promoter revealed the presence of cis-acting elements related to cadmium induction. The origins and purposes of this regulation are discussed. Our data suggest, for the first time to our knowledge, a possible implication of TRXs in defense mechanisms against heavy metals. |
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