The calcium sensor CBL10 mediates salt tolerance by regulating ion homeostasis in Arabidopsis

Authors

  • Beom-Gi Kim,

    1. Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA,
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    • These authors contributed equally to this work.

  • Rainer Waadt,

    1. Institut für Botanik und Botanischer Garten, Universität Münster, Schlossplatz 4, 48149 Münster, Germany, and
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    • These authors contributed equally to this work.

  • Yong Hwa Cheong,

    1. Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA,
    2. Department of Bio-Environmental Science, Sunchon National University, Suncheon, Jeonnam 540-742, Korea
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    • These authors contributed equally to this work.

  • Girdhar K. Pandey,

    1. Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA,
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  • Jose R. Dominguez-Solis,

    1. Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA,
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  • Stefanie Schültke,

    1. Institut für Botanik und Botanischer Garten, Universität Münster, Schlossplatz 4, 48149 Münster, Germany, and
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  • Sung Chul Lee,

    1. Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA,
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  • Jörg Kudla,

    Corresponding author
    1. Institut für Botanik und Botanischer Garten, Universität Münster, Schlossplatz 4, 48149 Münster, Germany, and
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  • Sheng Luan

    Corresponding author
    1. Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA,
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(fax +49 251 83 23311; e-mail jkudla@uni-muenster.de; fax +1 510 642-4995; e-mail sluan@nature.berkeley.edu).

Summary

Calcium serves as a critical messenger in many adaptation and developmental processes. Cellular calcium signals are detected and transmitted by sensor molecules such as calcium-binding proteins. In plants, the calcineurin B-like protein (CBL) family represents a unique group of calcium sensors and plays a key role in decoding calcium transients by specifically interacting with and regulating a family of protein kinases (CIPKs). We report here that the CBL protein CBL10 functions as a crucial regulator of salt tolerance in Arabidopsis. Cbl10 mutant plants exhibited significant growth defects and showed hypersensitive cell death in leaf tissues under high-salt conditions. Interestingly, the Na+ content of the cbl10 mutant, unlike other salt-sensitive mutants identified thus far, was significantly lower than in the wild type under either normal or high-salt conditions, suggesting that CBL10 mediates a novel Ca2+-signaling pathway for salt tolerance. Indeed, the CBL10 protein physically interacts with the salt-tolerance factor CIPK24 (SOS2), and the CBL10–CIPK24 (SOS2) complex is associated with the vacuolar compartments that are responsible for salt storage and detoxification in plant cells. These findings suggest that CBL10 and CIPK24 (SOS2) constitute a novel salt-tolerance pathway that regulates the sequestration/compartmentalization of Na+ in plant cells. Because CIPK24 (SOS2) also interacts with CBL4 (SOS3) and regulates salt export across the plasma membrane, our study identifies CIPK24 (SOS2) as a multi-functional protein kinase that regulates different aspects of salt tolerance by interacting with distinct CBL calcium sensors.

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