title: ROP11 GTPase negatively regulates ABA signaling by protecting ABI1 phosphatase activity from inhibition by the ABA receptor RCAR1/PYL9 in Arabidopsis.
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 Arabidopsis thaliana protoplasts. Furthermore, using luciferase complementation imaging, yeast two-hybrid assays, co-immunoprecipitation assays in Nicotiana benthamiana 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 CA-ROP11 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.
authors.affiliation: MOE Key Laboratory of Bioinformatics, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Zixing
authors.initials: Z
authors.lastname: Li
authors.forename: Zheng
authors.initials: Z
authors.lastname: Li
authors.forename: Xiang
authors.initials: X
authors.lastname: Gao
authors.forename: Viswanathan
authors.initials: V
authors.lastname: Chinnusamy
authors.forename: Ray
authors.initials: R
authors.lastname: Bressan
authors.forename: Zhi-Xin
authors.initials: ZX
authors.lastname: Wang
authors.forename: Jian-Kang
authors.initials: JK
authors.lastname: Zhu
authors.forename: Jia-Wei
authors.initials: JW
authors.lastname: Wu
authors.forename: Dong
authors.initials: D
authors.lastname: Liu
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D011523:Protoplasts / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013347:Subcellular Fractions / Q000187:drug effects / Q000201:enzymology; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C540972:RCAR1 protein, Arabidopsis; C492978:SnRK2 protein, Arabidopsis; D000040:Abscisic Acid; D017346:Protein Serine-Threonine Kinases; C087434:ABI1 protein, Arabidopsis; D010749:Phosphoprotein Phosphatases; C572957:ROP11 protein, Arabidopsis; D020741:rho GTP-Binding Proteins