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Functional characterization of the CKRC1/TAA1 gene and dissection of hormonal actions in the Arabidopsis root

Authors

  • Zhao-Yang Zhou,

    1. Institute of Cell Biology, School of Life Sciences, Lanzhou University, Lanzhou 73000, China
    2. Laboratory of Molecular and Cell Biology, Hebei Normal University, Shijiazhuang 050016, China
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    • These authors contributed equally to this work.

  • Chun-Guang Zhang,

    1. Institute of Cell Biology, School of Life Sciences, Lanzhou University, Lanzhou 73000, China
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    • These authors contributed equally to this work.

  • Lei Wu,

    1. Institute of Cell Biology, School of Life Sciences, Lanzhou University, Lanzhou 73000, China
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  • Cai-Guo Zhang,

    1. Institute of Cell Biology, School of Life Sciences, Lanzhou University, Lanzhou 73000, China
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  • Juan Chai,

    1. Institute of Cell Biology, School of Life Sciences, Lanzhou University, Lanzhou 73000, China
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  • Ming Wang,

    1. Institute of Cell Biology, School of Life Sciences, Lanzhou University, Lanzhou 73000, China
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  • Ajay Jha,

    1. Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA
    2. Department of Botany, Oklahoma State University, 104 Life Sciences East, Stillwater, OK 74078-3013, USA
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  • Peng-Fei Jia,

    1. Institute of Cell Biology, School of Life Sciences, Lanzhou University, Lanzhou 73000, China
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  • Su-Juan Cui,

    1. Laboratory of Molecular and Cell Biology, Hebei Normal University, Shijiazhuang 050016, China
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  • Ming Yang,

    1. Department of Botany, Oklahoma State University, 104 Life Sciences East, Stillwater, OK 74078-3013, USA
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  • Rujin Chen,

    Corresponding author
    1. Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA
      (fax +86 931 8912565; e-mail rchen@noble.org or +1 580 224 6692; gqguo@lzu.edu.cn).
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  • Guang-Qin Guo

    Corresponding author
    1. Institute of Cell Biology, School of Life Sciences, Lanzhou University, Lanzhou 73000, China
      (fax +86 931 8912565; e-mail rchen@noble.org or +1 580 224 6692; gqguo@lzu.edu.cn).
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(fax +86 931 8912565; e-mail rchen@noble.org or +1 580 224 6692; gqguo@lzu.edu.cn).

Summary

Cytokinin (CK) influences many aspects of plant growth and development, and its function often involves intricate interactions with other phytohormones such as auxin and ethylene. However, the molecular mechanisms underlying the role of CK and its interactions with other growth regulators are still poorly understood. Here we describe the isolation and characterization of the Arabidopsis CK-induced root curling 1 (ckrc1) mutant. CKRC1 encodes a previously identified tryptophan aminotransferase (TAA1) involved in the indole-3-pyruvic acid (IPA) pathway of indole-3-acetic acid (IAA) biosynthesis. The ckrc1 mutant exhibits a defective root gravitropic response (GR) and an increased resistance to CK in primary root growth. These defects can be rescued by exogenous auxin or IPA. Furthermore, we show that CK up-regulates CKRC1/TAA1 expression but inhibits polar auxin transport in roots in an AHK3/ARR1/12-dependent and ethylene-independent manner. Our results suggest that CK regulates root growth and development not only by down-regulating polar auxin transport, but also by stimulating local auxin biosynthesis.

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