J Integr Plant Biol. ›› 2012, Vol. 54 ›› Issue (3): 180-188.DOI: 10.1111/j.1744-7909.2012.01101.x

Special Issue: Plant Signal Transduction

• Plant-environmental Interactions • Previous Articles     Next Articles

ROP11 GTPase Negatively Regulates ABA Signaling by Protecting ABI1 Phosphatase Activity from Inhibition by the ABA Receptor RCAR1/PYL9 in Arabidopsis

Zixing Li1, Zheng Li1, Xiang Gao1, Viswanathan Chinnusamy2, Ray Bressan3, Zhi-Xin Wang1, Jian-Kang Zhu3, Jia-Wei Wu1 and Dong Liu1*   

  1. 1MOE Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing 100084, China
    2Division of Plant Physiology, Indian Agricultural Research Institute, New Delhi- 110012, India
    3Department of Horticulture and Landscape, Purdue University, West Lafayette, Indiana 47907, USA
    *Corresponding author. Tel: +86 10 6278 3603; Fax: +86 10 6278 3603; E-mail: liu-d@tsinghua.edu.cn
  • Received:2011-12-20 Accepted:2012-01-08 Published:2012-01-18

Abstract:

The phytohormone abscisic acid (ABA) regulates many key processes in plants, such as seed germination, seedling growth, and abiotic stress tolerance. In recent years, a minimal set of core components of a major ABA signaling pathway has been discovered. These components include a RCAR/PYR/PYL family of ABA receptors, a group of PP2C phosphatases, and three SnRK2 kinases. However, how the interactions between the receptors and their targets are regulated by other proteins remains largely unknown. In a companion paper published in this issue, we showed that ROP11, a member of the plant-specific Rho-like small GTPase family, negatively regulates multiple ABA responses in Arabidopsis. The current work demonstrated that the constitutively active ROP11 (CA-ROP11) can modulate the RCAR1/PYL9-mediated ABA signaling pathway based on reconstitution assays in protoplasts. Furthermore, using luciferase complementation imaging, yeast two-hybrid assays, coimmunoprecipitation assays, and bimolecular fluorescence complementation assays, we
demonstrated that CA-ROP11 directly interacts with ABI1, a signaling component downstream of RCAR1/PYL9. Finally, we provided biochemical evidence that CAROP11 protects ABI1 phosphatase activity from inhibition by RCAR1/PYL9 and thus negatively regulates ABA signaling in plant cells. A model of how ROP11 acts to negatively regulate ABA signaling is presented.

Li Z, Li Z, Gao X, Chinnusamy V, Bressan R, Wang ZX, Zhu JK, Wu JW, Liu D (2012) ROP11 GTPase negatively regulates ABA signaling by protecting ABI1 phosphatase activity from inhibition by the ABA receptor RCAR1/PYL9 in Arabidopsis. J. Integr. Plant Biol. 54(3), 180–188.

Key words: ROP11 GTPase, ABA signaling, RCAR1/PYL9A, ABI1, Arabidopsis

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