title: Calcium specificity signaling mechanisms in abscisic acid signal transduction in Arabidopsis guard cells.
abstract: A central question is how specificity in cellular responses to the eukaryotic second messenger Ca(2+) is achieved. Plant guard cells, that form stomatal pores for gas exchange, provide a powerful system for in depth investigation of Ca(2+)-signaling specificity in plants. In intact guard cells, abscisic acid (ABA) enhances (primes) the Ca(2+)-sensitivity of downstream signaling events that result in activation of S-type anion channels during stomatal closure, providing a specificity mechanism in Ca(2+)-signaling. However, the underlying genetic and biochemical mechanisms remain unknown. Here we show impairment of ABA signal transduction in stomata of calcium-dependent protein kinase quadruple mutant plants. Interestingly, protein phosphatase 2Cs prevent non-specific Ca(2+)-signaling. Moreover, we demonstrate an unexpected interdependence of the Ca(2+)-dependent and Ca(2+)-independent ABA-signaling branches and the in planta requirement of simultaneous phosphorylation at two key phosphorylation sites in SLAC1. We identify novel mechanisms ensuring specificity and robustness within stomatal Ca(2+)-signaling on a cellular, genetic, and biochemical level.
authors.affiliation: Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, San Diego, United States.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Brandt
authors.affiliation: Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, San Diego, United States.
authors.forename: Shintaro
authors.initials: S
authors.lastname: Munemasa
authors.affiliation: Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, San Diego, United States.
authors.forename: Cun
authors.initials: C
authors.lastname: Wang
authors.affiliation: Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, San Diego, United States.
authors.forename: Desiree
authors.initials: D
authors.lastname: Nguyen
authors.affiliation: Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, San Diego, United States.
authors.forename: Taiming
authors.initials: T
authors.lastname: Yong
authors.affiliation: Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, San Diego, United States.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Yang
authors.affiliation: Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, San Diego, United States.
authors.forename: Elly
authors.initials: E
authors.lastname: Poretsky
authors.affiliation: Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, San Diego, United States.
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Belknap
authors.affiliation: Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, San Diego, United States.
authors.forename: Rainer
authors.initials: R
authors.lastname: Waadt
authors.affiliation: Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, San Diego, United States.
authors.forename: Fernando
authors.initials: F
authors.lastname: Alemán
authors.affiliation: Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, San Diego, United States.
authors.forename: Julian I
authors.initials: JI
authors.lastname: Schroeder
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D017360:Arabidopsis / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D051418:Focal Adhesion Kinase 2 / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D008565:Membrane Proteins / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D059828:Plant Cells / Q000378:metabolism / Q000502:physiology*; D054046:Plant Stomata / Q000378:metabolism / Q000502:physiology*; D000071636:Protein Phosphatase 2C; D011499:Protein Processing, Post-Translational; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D008565:Membrane Proteins; C528438:SLAC1 protein, Arabidopsis; D000040:Abscisic Acid; D051418:Focal Adhesion Kinase 2; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C; D002118:Calcium
keywords: SLAC1; SnRK; abscisic acid (ABA); arabidopsis; calcium specificity; calcium-dependent protein kinase (CPK); plant biology; protein phosphatase 2C (PP2C)