title: PYR/RCAR receptors contribute to ozone-, reduced air humidity-, darkness-, and CO2-induced stomatal regulation.
abstract: Rapid stomatal closure induced by changes in the environment, such as elevation of CO2, reduction of air humidity, darkness, and pulses of the air pollutant ozone (O3), involves the SLOW ANION CHANNEL1 (SLAC1). SLAC1 is activated by OPEN STOMATA1 (OST1) and Ca(2+)-dependent protein kinases. OST1 activation is controlled through abscisic acid (ABA)-induced inhibition of type 2 protein phosphatases (PP2C) by PYRABACTIN RESISTANCE/REGULATORY COMPONENTS OF ABA RECEPTOR (PYR/RCAR) receptor proteins. To address the role of signaling through PYR/RCARs for whole-plant steady-state stomatal conductance and stomatal closure induced by environmental factors, we used a set of Arabidopsis (Arabidopsis thaliana) mutants defective in ABA metabolism/signaling. The stomatal conductance values varied severalfold among the studied mutants, indicating that basal ABA signaling through PYR/RCAR receptors plays a fundamental role in controlling whole-plant water loss through stomata. PYR/RCAR-dependent inhibition of PP2Cs was clearly required for rapid stomatal regulation in response to darkness, reduced air humidity, and O3. Furthermore, PYR/RCAR proteins seem to function in a dose-dependent manner, and there is a functional diversity among them. Although a rapid stomatal response to elevated CO2 was evident in all but slac1 and ost1 mutants, the bicarbonate-induced activation of S-type anion channels was reduced in the dominant active PP2C mutants abi1-1 and abi2-1. Further experiments with a wider range of CO2 concentrations and analyses of stomatal response kinetics suggested that the ABA signalosome partially affects the CO2-induced stomatal response. Thus, we show that PYR/RCAR receptors play an important role for the whole-plant stomatal adjustments and responses to low humidity, darkness, and O3 and are involved in responses to elevated CO2.
authors.affiliation: Institute of Technology, University of Tartu, Tartu 50411, Estonia.
authors.forename: Ebe
authors.initials: E
authors.lastname: Merilo
authors.forename: Kristiina
authors.initials: K
authors.lastname: Laanemets
authors.forename: Honghong
authors.initials: H
authors.lastname: Hu
authors.forename: Shaowu
authors.initials: S
authors.lastname: Xue
authors.forename: Liina
authors.initials: L
authors.lastname: Jakobson
authors.forename: Ingmar
authors.initials: I
authors.lastname: Tulva
authors.forename: Miguel
authors.initials: M
authors.lastname: Gonzalez-Guzman
authors.forename: Pedro L
authors.initials: PL
authors.lastname: Rodriguez
authors.forename: Julian I
authors.initials: JI
authors.lastname: Schroeder
authors.forename: Mikael
authors.initials: M
authors.lastname: Broschè
authors.forename: Hannes
authors.initials: H
authors.lastname: Kollist
mesh_terms: D000040:Abscisic Acid / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000187:drug effects / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003624:Darkness; D006813:Humidity; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010126:Ozone / Q000378:metabolism / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D000071636:Protein Phosphatase 2C; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C540976:AT4G17870 protein, Arabidopsis; C540972:RCAR1 protein, Arabidopsis; C528438:SLAC1 protein, Arabidopsis; D002245:Carbon Dioxide; D010126:Ozone; D000040:Abscisic Acid; D011494:Protein Kinases; C472139:OST1 protein, Arabidopsis; C087434:ABI1 protein, Arabidopsis; C106443:ABI2 protein, Arabidopsis; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C