title: De-regulated expression of the plant glutamate receptor homolog AtGLR3.1 impairs long-term Ca2+-programmed stomatal closure.
abstract: Cytosolic Ca(2+) ([Ca(2+)](cyt)) mediates diverse cellular responses in both animal and plant cells in response to various stimuli. Calcium oscillation amplitude and frequency control gene expression. In stomatal guard cells, [Ca(2+)](cyt) has been shown to regulate stomatal movements, and a defined window of Ca(2+) oscillation kinetic parameters encodes necessary information for long-term stomatal movements. However, it remains unknown how the encrypted information in the cytosolic Ca(2+) signature is decoded to maintain stomatal closure. Here we report that the Arabidopsis glutamate receptor homolog AtGLR3.1 is preferentially expressed in guard cells compared to mesophyll cells. Furthermore, over-expression of AtGLR3.1 using a viral promoter resulted in impaired external Ca(2+)-induced stomatal closure. Cytosolic Ca(2+) activation of S-type anion channels, which play a central role in Ca(2+)-reactive stomatal closure, was normal in the AtGLR3.1 over-expressing plants. Interestingly, AtGLR3.1 over-expression did not affect Ca(2+)-induced Ca(2+) oscillation kinetics, but resulted in a failure to maintain long-term 'Ca(2+)-programmed' stomatal closure when Ca(2+) oscillations containing information for maintaining stomatal closure were imposed. By contrast, prompt short-term Ca(2+)-reactive closure was not affected in AtGLR3.1 over-expressing plants. In wild-type plants, the translational inhibitor cyclohexamide partially inhibited Ca(2+)-programmed stomatal closure induced by experimentally imposed Ca(2+) oscillations without affecting short-term Ca(2+)-reactive closure, mimicking the guard cell behavior of the AtGLR3.1 over-expressing plants. Our results suggest that over-expression of AtGLR3.1 impairs Ca(2+) oscillation-regulated stomatal movements, and that de novo protein synthesis contributes to the maintenance of long-term Ca(2+)-programmed stomatal closure.
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA.
authors.forename: Daeshik
authors.initials: D
authors.lastname: Cho
authors.forename: Sun A
authors.initials: SA
authors.lastname: Kim
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Murata
authors.forename: Sangmee
authors.initials: S
authors.lastname: Lee
authors.forename: Seul-Ki
authors.initials: SK
authors.lastname: Jae
authors.forename: Hong Gil
authors.initials: HG
authors.lastname: Nam
authors.forename: June M
authors.initials: JM
authors.lastname: Kwak
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D003600:Cytosol / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D054046:Plant Stomata / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D017470:Receptors, Glutamate / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D018749:RNA, Plant; D017470:Receptors, Glutamate; D002118:Calcium