title: Elevated CO2-Induced Responses in Stomata Require ABA and ABA Signaling.
abstract: An integral part of global environment change is an increase in the atmospheric concentration of CO2 ([CO2]) [1]. Increased [CO2] reduces leaf stomatal apertures and density of stomata that plays out as reductions in evapotranspiration [2-4]. Surprisingly, given the importance of transpiration to the control of terrestrial water fluxes [5] and plant nutrient acquisition [6], we know comparatively little about the molecular components involved in the intracellular signaling pathways by which [CO2] controls stomatal development and function [7]. Here, we report that elevated [CO2]-induced closure and reductions in stomatal density require the generation of reactive oxygen species (ROS), thereby adding a new common element to these signaling pathways. We also show that the PYR/RCAR family of ABA receptors [8, 9] and ABA itself are required in both responses. Using genetic approaches, we show that ABA in guard cells or their precursors is sufficient to mediate the [CO2]-induced stomatal density response. Taken together, our results suggest that stomatal responses to increased [CO2] operate through the intermediacy of ABA. In the case of [CO2]-induced reductions in stomatal aperture, this occurs by accessing the guard cell ABA signaling pathway. In both [CO2]-mediated responses, our data are consistent with a mechanism in which ABA increases the sensitivity of the system to [CO2] but could also be explained by requirement for a CO2-induced increase in ABA biosynthesis specifically in the guard cell lineage. Furthermore, the dependency of stomatal [CO2] signaling on ABA suggests that the ABA pathway is, in evolutionary terms, likely to be ancestral.
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
authors.forename: Caspar
authors.initials: C
authors.lastname: Chater
authors.affiliation: School of Biological Sciences, Life Sciences Building, University of Bristol, Woodland Road, 24 Tyndall Avenue, Bristol BS8 1TQ, UK.
authors.forename: Kai
authors.initials: K
authors.lastname: Peng
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
authors.forename: Mahsa
authors.initials: M
authors.lastname: Movahedi
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Dunn
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Alfred Denny Building, Western Bank, Sheffield S10 2TN, UK.
authors.forename: Heather J
authors.initials: HJ
authors.lastname: Walker
authors.affiliation: State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China.
authors.forename: Yun-Kuan
authors.initials: YK
authors.lastname: Liang
authors.affiliation: School of Biological Sciences, Life Sciences Building, University of Bristol, Woodland Road, 24 Tyndall Avenue, Bristol BS8 1TQ, UK.
authors.forename: Deirdre H
authors.initials: DH
authors.lastname: McLachlan
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
authors.forename: Stuart
authors.initials: S
authors.lastname: Casson
authors.affiliation: School of Biological Sciences, Life Sciences Building, University of Bristol, Woodland Road, 24 Tyndall Avenue, Bristol BS8 1TQ, UK.
authors.forename: Jean Charles
authors.initials: JC
authors.lastname: Isner
authors.affiliation: Faculty of Health and Life Sciences, University of the West of England, Bristol Frenchay Campus, Coldharbour Lane, Bristol BS16 1QY, UK.
authors.forename: Ian
authors.initials: I
authors.lastname: Wilson
authors.affiliation: Faculty of Health and Life Sciences, University of the West of England, Bristol Frenchay Campus, Coldharbour Lane, Bristol BS16 1QY, UK.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Neill
authors.affiliation: Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, 97082 Würzburg, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Hedrich
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK. Electronic address: j.e.gray@sheffield.ac.uk.
authors.forename: Julie E
authors.initials: JE
authors.lastname: Gray
authors.affiliation: School of Biological Sciences, Life Sciences Building, University of Bristol, Woodland Road, 24 Tyndall Avenue, Bristol BS8 1TQ, UK. Electronic address: alistair.hetherington@bristol.ac.uk.
authors.forename: Alistair M
authors.initials: AM
authors.lastname: Hetherington
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D017360:Arabidopsis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D054046:Plant Stomata / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D017382:Reactive Oxygen Species; D002245:Carbon Dioxide; D000040:Abscisic Acid
keywords: ABA receptors; ABA signaling; NADPH oxidases; ROS; Rboh genes; [CO(2)] signaling; guard cells; signaling convergence; stomata; stomatal closure; stomatal density