title: Modulation of drought resistance by the abscisic acid receptor PYL5 through inhibition of clade A PP2Cs.
abstract: Abscisic acid (ABA) is a key phytohormone involved in adaption to environmental stress and regulation of plant development. Clade A protein phosphatases type 2C (PP2Cs), such as HAB1, are key negative regulators of ABA signaling in Arabidopsis. To obtain further insight into regulation of HAB1 function by ABA, we have screened for HAB1-interacting partners using a yeast two-hybrid approach. Three proteins were identified, PYL5, PYL6 and PYL8, which belong to a 14-member subfamily of the Bet v1-like superfamily. HAB1-PYL5 interaction was confirmed using BiFC and co-immunoprecipitation assays. PYL5 over-expression led to a globally enhanced response to ABA, in contrast to the opposite phenotype reported for HAB1-over-expressing plants. F(2) plants that over-expressed both HAB1 and PYL5 showed an enhanced response to ABA, indicating that PYL5 antagonizes HAB1 function. PYL5 and other members of its protein family inhibited HAB1, ABI1 and ABI2 phosphatase activity in an ABA-dependent manner. Isothermal titration calorimetry revealed saturable binding of (+)ABA to PYL5, with K(d) values of 1.1 mum or 38 nm in the absence or presence of the PP2C catalytic core of HAB1, respectively. Our work indicates that PYL5 is a cytosolic and nuclear ABA receptor that activates ABA signaling through direct inhibition of clade A PP2Cs. Moreover, we show that enhanced resistance to drought can be obtained through PYL5-mediated inhibition of clade A PP2Cs.
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas - UPV, ES-46022 Valencia, Spain.
authors.forename: Julia
authors.initials: J
authors.lastname: Santiago
authors.forename: Americo
authors.initials: A
authors.lastname: Rodrigues
authors.forename: Angela
authors.initials: A
authors.lastname: Saez
authors.forename: Silvia
authors.initials: S
authors.lastname: Rubio
authors.forename: Regina
authors.initials: R
authors.lastname: Antoni
authors.forename: Florine
authors.initials: F
authors.lastname: Dupeux
authors.forename: Sang-Youl
authors.initials: SY
authors.lastname: Park
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Márquez
authors.forename: Sean R
authors.initials: SR
authors.lastname: Cutler
authors.forename: Pedro L
authors.initials: PL
authors.lastname: Rodriguez
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D055864:Droughts; D018506:Gene Expression Regulation, Plant; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D000071636:Protein Phosphatase 2C; D018749:RNA, Plant / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D018749:RNA, Plant; D011994:Recombinant Proteins; D000040:Abscisic Acid; C514757:HAB1 protein, Arabidopsis; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C