Regulators of PP2C Phosphatase Activity Function as Abscisic Acid Sensors

Science  22 May 2009:
Vol. 324, Issue 5930, pp. 1064-1068
DOI: 10.1126/science.1172408

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The plant hormone abscisic acid (ABA) acts as a developmental signal and as an integrator of environmental cues such as drought and cold. Key players in ABA signal transduction include the type 2C protein phosphatases (PP2Cs) ABI1 and ABI2, which act by negatively regulating ABA responses. In this study, we identify interactors of ABI1 and ABI2 which we have named regulatory components of ABA receptor (RCARs). In Arabidopsis, RCARs belong to a family with 14 members that share structural similarity with class 10 pathogen-related proteins. RCAR1 was shown to bind ABA, to mediate ABA-dependent inactivation of ABI1 or ABI2 in vitro, and to antagonize PP2C action in planta. Other RCARs also mediated ABA-dependent regulation of ABI1 and ABI2, consistent with a combinatorial assembly of receptor complexes.

  • * These authors contributed equally to this work.

  • Present address: Plant Molecular Biology Laboratory, Public Research Centre for Health, 84, Val Fleuri, L-1526 Luxembourg, Luxembourg.

  • Present address: College of Life Sciences, Sichuan University, Chengdu, Sichuan 610064, P. R. China.

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