title: SLAH3-type anion channel expressed in poplar secretory epithelia operates in calcium kinase CPK-autonomous manner.
abstract: Extrafloral nectaries secrete a sweet sugar cocktail that lures predator insects for protection from foraging herbivores. Apart from sugars and amino acids, the nectar contains the anions chloride and nitrate. Recent studies with Populus have identified a type of nectary covered by apical bipolar epidermal cells, reminiscent of the secretory brush border epithelium in animals. Border epithelia operate transepithelial anion transport, which is required for membrane potential and/or osmotic adjustment of the secretory cells. In search of anion transporters expressed in extrafloral nectaries, we identified PttSLAH3 (Populus tremula × Populus tremuloides SLAC1 Homologue3), an anion channel of the SLAC/SLAH family. When expressed in Xenopus oocytes, PttSLAH3 displayed the features of a voltage-dependent anion channel, permeable to both nitrate and chloride. In contrast to the Arabidopsis SLAC/SLAH family members, the poplar isoform PttSLAH3 is independent of phosphorylation activation by protein kinases. To understand the basis for the autonomous activity of the poplar SLAH3, we generated and expressed chimera between kinase-independent PttSLAH3 and kinase-dependent Arabidopsis AtSLAH3. We identified the N-terminal tail and, to a lesser extent, the C-terminal tail as responsible for PttSLAH3 kinase-(in)dependent action. This feature of PttSLAH3 may provide the secretory cell with a channel probably controlling long-term nectar secretion.
authors.affiliation: University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany.
authors.forename: Mario
authors.initials: M
authors.lastname: Jaborsky
authors.affiliation: University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Maierhofer
authors.affiliation: Thünen Institute of Wood Research, Leuschnerstr. 91d, Hamburg, 21031, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Olbrich
authors.affiliation: University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany.
authors.forename: María
authors.initials: M
authors.lastname: Escalante-Pérez
authors.affiliation: University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany.
authors.forename: Heike M
authors.initials: HM
authors.lastname: Müller
authors.affiliation: Chair of Tree Physiology, University of Freiburg, Freiburg, 79110, Germany.
authors.forename: Judy
authors.initials: J
authors.lastname: Simon
authors.affiliation: University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany.
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Krol
authors.affiliation: University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany.
authors.forename: Tracey Ann
authors.initials: TA
authors.lastname: Cuin
authors.affiliation: Center for Wood Sciences, University of Hamburg, Leuschnerstr. 91, Hamburg, 21031, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Fromm
authors.affiliation: University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Ache
authors.affiliation: University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Geiger
authors.affiliation: University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Hedrich
mesh_terms: D000838:Anions / Q000378:metabolism*; D017360:Arabidopsis / Q000187:drug effects / Q000378:metabolism; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism*; D035264:Flowers / Q000187:drug effects / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects; D007473:Ion Channels / Q000378:metabolism*; D009566:Nitrates / Q000494:pharmacology; D057048:Plant Nectar; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D032107:Populus / Q000187:drug effects / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D000838:Anions; D007473:Ion Channels; D009566:Nitrates; D057048:Plant Nectar; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D011494:Protein Kinases
keywords: S-type anion channels; SLAC/SLAH; anion channels; extrafloral nectaries; poplar; transepithelial transport