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Publication Abstract from PubMed

Regulation of abscisic acid (ABA) signaling is crucial in balancing responses to abiotic stresses and retaining growth in planta. An ABA receptor (PYL/RCAR) and a protein phosphatase (PP2C), a co-receptor, form a complex upon binding to ABA. Previously we reported that the second and fourth positions in the VxGPhiL motif of PP2Cs from Oryza sativa are critical in the interaction of PP2Cs with PYL/RCARs. Considering substantial effects of the VxGPhiL motif on ABA signaling outputs, further comprehensive characterization of residues in the second and fourth positions are required. Here we surveyed the second and fourth positions of the VxGPhiL motif by combination of biochemical, structural and physiological analyses. We found that the fourth position of the VxGPhiL motif, highly conserved to small hydrophobic residues, was a key determinant of the OsPP2C50:OsPYL/RCAR interactions across subfamilies. Large hydrophobic or any hydrophilic residues in the fourth position abrogated ABA responsiveness. Analysis of crystal structures of OsPP2C50 mutants, S265L/I267V ("LV"), I267L ("SL") and I267W ("SW"), in complex with ABA and OsPYL/RCAR3, along with energy calculation of the complexes, uncovered that a bulky hydrophobic residue in the fourth position of the VxGPhiL motif pushed away side chains of nearby residues, conferring side-chain rotameric energy stress. Hydrophilic residues in this position imposed solvation energy stress to the PP2C:PYL/RCAR complex. Germination and gene expression analyses corroborated that OsPP2C50 AS and AK mutants modulated ABA responsiveness in Arabidopsis. Our results suggest that ABA responsiveness could be fine-tuned by the fourth position of the VxGPhiL motif on PP2Cs. KEY MESSAGE: We comprehensively surveyed the VxGPhiL motif to find that the fourth position, highly conserved to small hydrophobic residues, was critical in regulating ABA responsiveness.

Comprehensive survey of the VxGPhiL motif of PP2Cs from Oryza sativa reveals the critical role of the fourth position in regulation of ABA responsiveness.,Han S, Lee JY, Lee Y, Kim TH, Lee S Plant Mol Biol. 2019 Nov;101(4-5):455-469. doi: 10.1007/s11103-019-00916-9. Epub , 2019 Sep 20. PMID:31541388^[4]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.