PMID:19143998

Citation	Cho, D, Kim, SA, Murata, Y, Lee, S, Jae, SK, Nam, HG and Kwak, JM (2009) De-regulated expression of the plant glutamate receptor homolog AtGLR3.1 impairs long-term Ca2+-programmed stomatal closure. Plant J. 58:437-49
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.
Links	PubMed Online version:10.1111/j.1365-313X.2009.03789.x
Keywords	Arabidopsis/genetics; Arabidopsis/metabolism; Arabidopsis Proteins/genetics; Arabidopsis Proteins/metabolism; Calcium/metabolism; Calcium Signaling; Cytosol/metabolism; Gene Expression Regulation, Plant; Plant Stomata/metabolism; Plants, Genetically Modified/genetics; Plants, Genetically Modified/metabolism; RNA, Plant/genetics; Receptors, Glutamate/genetics; Receptors, Glutamate/metabolism
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