Abscisic acid inhibits type 2C protein phosphatases via the PYR/PYL family of START proteins.

Park, Sang-Youl; Fung, Pauline; Nishimura, Noriyuki; Jensen, Davin R; Fujii, Hiroaki; Zhao, Yang; Lumba, Shelley; Santiago, Julia et al. · Science · 2009

basic_science · Level V

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Abstract

Type 2C protein phosphatases (PP2Cs) are vitally involved in abscisic acid (ABA) signaling. Here, we show that a synthetic growth inhibitor called pyrabactin functions as a selective ABA agonist. Pyrabactin acts through PYRABACTIN RESISTANCE 1 (PYR1), the founding member of a family of START proteins called PYR/PYLs, which are necessary for both pyrabactin and ABA signaling in vivo. We show that ABA binds to PYR1, which in turn binds to and inhibits PP2Cs. We conclude that PYR/PYLs are ABA receptors functioning at the apex of a negative regulatory pathway that controls ABA signaling by inhibiting PP2Cs. Our results illustrate the power of the chemical genetic approach for sidestepping genetic redundancy.

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