A CDC25 homologue from rice functions as an arsenate reductase

Authors

  • Gui-Lan Duan,

    1. Department of Soil Environmental Sciences, Research Center for Eco-environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing RD, Beijing 100085, People's Republic of China;
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  • Yao Zhou,

    1. Department of Biochemistry and Molecular Biology, Wayne State University, School of Medicine, Detroit, MI 48201, USA;
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  • Yi-Ping Tong,

    1. Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100083, China
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  • Rita Mukhopadhyay,

    1. Department of Biochemistry and Molecular Biology, Wayne State University, School of Medicine, Detroit, MI 48201, USA;
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  • Barry P. Rosen,

    1. Department of Biochemistry and Molecular Biology, Wayne State University, School of Medicine, Detroit, MI 48201, USA;
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  • Yong-Guan Zhu

    1. Department of Soil Environmental Sciences, Research Center for Eco-environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing RD, Beijing 100085, People's Republic of China;
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Authors for correspondence: Yong-Guan Zhu Tel: +86 10 629 36940 Fax: +86 10 629 23563 Email: ygzhu@rcees.ac.cnBarry P. Rosen Tel: +1 313 577 1512 Fax: +1 313 577 2765 Email: brosen@med.wayne.edu

Summary

  • • Enzymatic reduction of arsenate to arsenite is the first step in arsenate metabolism in all organisms studied. The rice genome contains two ACR2-like genes, OsACR2.1 and OsACR2.2, which may be involved in regulating arsenic metabolism in rice.
  • • Here, we cloned both OsACR2 genes and expressed them in an Escherichia coli strain in which the arsC gene was deleted and in a yeast (Saccharomyces cerevisiae) strain with a disrupted ACR2 gene. OsACR2.1 complemented the arsenate hypersensitive phenotype of E. coli and yeast. OsACR2.2 showed much less ability to complement.
  • • The gene products were purified and demonstrated to reduce arsenate to arsenite in vitro, and both exhibited phosphatase activity. In agreement with the complementation results, OsACR2.1 exhibited higher reductase activity than OsACR2.2. Mutagenesis of cysteine residues in the putative active site HC(X)5R motif led to nearly complete loss of both phosphatase and arsenate reductase activities.
  • • In planta expression of OsACR2.1 increased dramatically after exposure to arsenate. OsACR2.2 was observed only in roots following arsenate exposure, and its expression was less than OsACR2.1.

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