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A nuclear gene, erd1, encoding a chloroplast-targeted Clp protease regulatory subunit homolog is not only induced by water stress but also developmentally up-regulated during senescence in Arabidopsis thaliana

Authors

  • Kazuo Nakashima,

    1. Biological Resources Division, Japan International Research Center for Agricultural Sciences (JIRCAS), 1-2, Ohwashi, Tsukuba, Ibaraki 305, Japan
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  • Tomohiro Kiyosue,

    1. Laboratory of Plant Molecular Biology, The Institute of Physical and Chemical Research (RIKEN), 3-1-1 Koyadai, Tsukuba, Ibaraki 305, Japan
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    • Present address: Department of Plant Biology, University of California, Berkeley, CA 94720, USA.

  • Kazuko Yamaguchi-Shinozaki,

    Corresponding author
    1. Biological Resources Division, Japan International Research Center for Agricultural Sciences (JIRCAS), 1-2, Ohwashi, Tsukuba, Ibaraki 305, Japan
      *For correspondence (Kazuko Yamaguchi-Shinozaki: fax +81 298 38 6643; e-mail kazukoys@jircas.affrc.go.jp; Kazuo Shinozaki: fax +81 298 4359; e-mail: sinozaki@rtc.riken.go.jp).
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  • Kazuo Shinozaki

    Corresponding author
    1. Laboratory of Plant Molecular Biology, The Institute of Physical and Chemical Research (RIKEN), 3-1-1 Koyadai, Tsukuba, Ibaraki 305, Japan
      *For correspondence (Kazuko Yamaguchi-Shinozaki: fax +81 298 38 6643; e-mail kazukoys@jircas.affrc.go.jp; Kazuo Shinozaki: fax +81 298 4359; e-mail: sinozaki@rtc.riken.go.jp).
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*For correspondence (Kazuko Yamaguchi-Shinozaki: fax +81 298 38 6643; e-mail kazukoys@jircas.affrc.go.jp; Kazuo Shinozaki: fax +81 298 4359; e-mail: sinozaki@rtc.riken.go.jp).

Summary

A cDNA, ERD1, isolated from one-hour-dehydrated plants of Arabidopsis thaliana L. encodes a putative protein that is similar to the regulatory ATPase subunit (ClpA) of the Clp protease and contains a putative chloroplast-targeting transit-peptide at the N-terminus. A chimeric gene with the putative plastid-targeting sequence of the erd1 gene fused to the synthetic green-fluorescent protein (sGFP) gene was constructed and introduced into Arabidopsis protoplasts. The N-terminal region of the ERD1 protein directed the sGFP protein into the plastids of the protoplasts, and functioned as a transit peptide. Northern blot analysis indicated that expression of the erd1 gene was induced not only by water stress, such as dehydration and high salinity, but also by natural senescence and dark-induced etiolation. The erd1 gene was not strongly induced by exogenous abscisic acid. A chimeric gene with the 0.9 kb promoter region of the erd1 gene fused to the β-glucuronidase (GUS) reporter gene was constructed, and tobacco plants transformed with the construct. The GUS reporter gene driven by the erd1 promoter was induced by dehydration and high salt stress at significant levels in the transgenic plants. The GUS gene was strongly expressed in older leaves without dehydration, and was induced by dark-induced etiolation. Furthermore, GUS activity was reduced by cytokinin treatment during dark-induced etiolation. These results indicate that expression of the erd1 gene is developmentally up-regulated by senescence as well as by water stress.

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