title: CO(2) signaling in guard cells: calcium sensitivity response modulation, a Ca(2+)-independent phase, and CO(2) insensitivity of the gca2 mutant.
abstract: Leaf stomata close in response to high carbon dioxide levels and open at low CO(2). CO(2) concentrations in leaves are altered by daily dark/light cycles, as well as the continuing rise in atmospheric CO(2). Relative to abscisic acid and blue light signaling, little is known about the molecular, cellular, and genetic mechanisms of CO(2) signaling in guard cells. Interestingly, we report that repetitive Ca(2+) transients were observed during the stomatal opening stimulus, low [CO(2)]. Furthermore, low/high [CO(2)] transitions modulated the cytosolic Ca(2+) transient pattern in Arabidopsis guard cells (Landsberg erecta). Inhibition of cytosolic Ca(2+) transients, achieved by loading guard cells with the calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid and not adding external Ca(2+), attenuated both high CO(2)-induced stomatal closing and low CO(2)-induced stomatal opening, and also revealed a Ca(2+)-independent phase of the CO(2) response. Furthermore, the mutant, growth controlled by abscisic acid (gca2) shows impairment in [CO(2)] modulation of the cytosolic Ca(2+) transient rate and strong impairment in high CO(2)-induced stomatal closing. Our findings provide insights into guard cell CO(2) signaling mechanisms, reveal Ca(2+)-independent events, and demonstrate that calcium elevations can participate in opposed signaling events during stomatal opening and closing. A model is proposed in which CO(2) concentrations prime Ca(2+) sensors, which could mediate specificity in Ca(2+) signaling.
authors.affiliation: Division of Biological Sciences, Cell and Developmental Biology Section and Center for Molecular Genetics 0116, University of California at San Diego, La Jolla, CA 92093-0116, USA.
authors.forename: Jared J
authors.initials: JJ
authors.lastname: Young
authors.forename: Samar
authors.initials: S
authors.lastname: Mehta
authors.forename: Maria
authors.initials: M
authors.lastname: Israelsson
authors.forename: Jan
authors.initials: J
authors.lastname: Godoski
authors.forename: Erwin
authors.initials: E
authors.lastname: Grill
authors.forename: Julian I
authors.initials: JI
authors.lastname: Schroeder
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism* / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; C511790:Gca2 protein, Arabidopsis; D002245:Carbon Dioxide; D000040:Abscisic Acid; D002118:Calcium