title: The molecular basis of ABA-independent inhibition of PP2Cs by a subclass of PYL proteins.
abstract: PYR1/PYL/RCAR proteins (PYLs) are confirmed abscisic acid (ABA) receptors, which inhibit protein phosphatase 2C (PP2C) upon binding to ABA. Arabidopsis thaliana has 14 PYLs, yet their functional distinction remains unclear. Here, we report systematic biochemical characterization of PYLs. A subclass of PYLs, represented by PYL10, inhibited PP2C in the absence of any ligand. Crystal structures of PYL10, both in the free form and in the HAB1 (PP2C)-bound state, revealed the structural basis for its constitutive activity. Structural-guided biochemical analyses revealed that ABA-independent inhibition of PP2C requires the PYLs to exist in a monomeric state. In addition, the residues guarding the entrance to the ligand-binding pocket of these PYLs should be bulky and hydrophobic. Based on these principles, we were able to generate monomeric PYL2 variants that gained constitutive inhibitory effect on PP2Cs. These findings provide an important framework for understanding the complex regulation of ABA signaling by PYL proteins.
authors.affiliation: State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua University, Beijing 100084, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Hao
authors.forename: Ping
authors.initials: P
authors.lastname: Yin
authors.forename: Wenqi
authors.initials: W
authors.lastname: Li
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Chuangye
authors.initials: C
authors.lastname: Yan
authors.forename: Zhaohu
authors.initials: Z
authors.lastname: Lin
authors.forename: Jim Zhen
authors.initials: JZ
authors.lastname: Wu
authors.forename: Jiawei
authors.initials: J
authors.lastname: Wang
authors.forename: S Frank
authors.initials: SF
authors.lastname: Yan
authors.forename: Nieng
authors.initials: N
authors.lastname: Yan
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism / Q000494:pharmacology; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D016415:Sequence Alignment
chemical_list: D029681:Arabidopsis Proteins; C560427:PYL10 protein, Arabidopsis; D011956:Receptors, Cell Surface; D000040:Abscisic Acid; C087434:ABI1 protein, Arabidopsis; C463465:AHG3 protein, Arabidopsis; C514757:HAB1 protein, Arabidopsis; D010749:Phosphoprotein Phosphatases