title: Distinct fluorescent pattern of KAT1::GFP in the plasma membrane of Vicia faba guard cells.
abstract: The organisation of membrane proteins into certain domains of the plasma membrane (PM) has been proposed to be important for signalling in yeast and animal cells. Here we describe the formation of a very distinct pattern of the K(+) channel KAT1 fused to the green fluorescent protein (KAT1::GFP) when transiently expressed in guard cells of Vicia faba. Using confocal laser scanning microscopy we observed a radially striped pattern of KAT1::GFP fluorescence in the PM in about 70% of all transfected guard cells. This characteristic pattern was found to be cell type and protein specific and independent of the stomatal aperture and the cytoskeleton. Staining of the cell wall of guard cells with Calcofluor White revealed a great similarity between the arrangement of cellulose microfibrils and the KAT1::GFP pattern. Furthermore, the radial pattern of KAT1::GFP immediately disappeared when turgor pressure was strongly decreased by changing from hypotonic to hypertonic conditions. The pattern reappeared within 15 min upon reestablishment of high turgor pressure in hypotonic solution. Evaluation of the staining pattern by a mathematical algorithm further confirmed this reversible abolishment of the radial pattern during hypertonic treatment. We therefore conclude that the radial organisation of KAT1::GFP depends on the close contact between the PM and cell wall in turgid guard cells. These results offer the first indication for a role of the cell wall in the localisation of ion channels. We propose a model in which KAT1 is located in the cellulose fibrils intermediate areas of the PM and discuss the physiological role of this phenomenon.
authors.affiliation: Institute of Botany, University of Technology Darmstadt, Schnittspahnstrasse 3-5, 64287 Darmstadt, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Homann
authors.forename: Tobias
authors.initials: T
authors.lastname: Meckel
authors.forename: Jennifer
authors.initials: J
authors.lastname: Hewing
authors.forename: Marc-Thorsten
authors.initials: MT
authors.lastname: Hütt
authors.forename: Annette C
authors.initials: AC
authors.lastname: Hurst
mesh_terms: D000199:Actins / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism; D002482:Cellulose / Q000378:metabolism; D005453:Fluorescence; D049452:Green Fluorescent Proteins / Q000378:metabolism*; D006982:Hypertonic Solutions / Q000494:pharmacology; D007038:Hypotonic Solutions / Q000494:pharmacology; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D008954:Models, Biological; D009928:Organ Specificity / Q000187:drug effects; D019441:Plant Epidermis / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018515:Plant Leaves / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D031307:Vicia faba / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000199:Actins; D006982:Hypertonic Solutions; D007038:Hypotonic Solutions; D010940:Plant Proteins; D024661:Potassium Channels, Inwardly Rectifying; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D002482:Cellulose