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Potent and selective activation of abscisic acid receptors in vivo by mutational stabilization of their agonist-bound conformation. Proc Natl Acad Sci U S A 2011 Dec 20;108(51):20838-43

Date

12/06/2011

Pubmed ID

22139369

Pubmed Central ID

PMC3251050

DOI

10.1073/pnas.1112838108

Scopus ID

2-s2.0-84862932422   61 Citations

Abstract

Pyrabactin resistance (PYR) 1 and its relatives belong to a family of soluble abscisic acid (ABA) receptors that inhibit type 2C protein phosphatases (PP2C) when in their agonist-stabilized conformation. Given their switch-like properties, we envisioned that mutations that stabilize their agonist-bound conformation could be used to activate signaling in vivo. To identify such mutations, we subjected PYR1 to site-saturation mutagenesis at 39 highly conserved residues that participate in ABA or PP2C contacts. All 741 possible single amino acid substitutions at these sites were tested to identify variants that increase basal PYR1-PP2C interactions, which uncovered activating mutations in 10 residues that preferentially cluster in PYR1's gate loop and C-terminal helix. The mutations cause measurable but incomplete receptor activation in vitro; however, specific triple and quadruple mutant combinations were constructed that promote an agonist-bound conformation, as measured by heteronuclear single quantum coherence NMR, and lead to full receptor activation. Moreover, these mutations retain functionality when introduced into divergent family members, and can therefore be used to dissect individual receptor function in vivo, which has been problematic because of redundancy and family size. Expression of activated PYL2 in Arabidopsis seeds activates ABA signaling by a number of measures: modulation of ABA-regulated gene expression, induction of hyperdormancy, and suppression of ABA deficiency phenotypes in the aba2-1 mutant. Our results set the stage for systematic gain-of-function studies of PYR1 and related ABA receptors and reveal that, despite the large number of receptors, activation of a single receptor is sufficient to activate signaling in planta.

Author List

Mosquna A, Peterson FC, Park SY, Lozano-Juste J, Volkman BF, Cutler SR

Authors

Francis C. Peterson PhD Professor in the Biochemistry department at Medical College of Wisconsin
Brian F. Volkman PhD Professor in the Biochemistry department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Abscisic Acid
Amino Acid Sequence
Arabidopsis
Arabidopsis Proteins
DNA Mutational Analysis
Magnetic Resonance Spectroscopy
Membrane Transport Proteins
Molecular Sequence Data
Mutagenesis, Site-Directed
Mutation
Phosphoprotein Phosphatases
Protein Conformation
Protein Phosphatase 2C
Protein Structure, Tertiary
Receptors, Cytoplasmic and Nuclear
Seeds
Sequence Homology, Amino Acid
Signal Transduction
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