title: Arabidopsis nanodomain-delimited ABA signaling pathway regulates the anion channel SLAH3.
abstract: The phytohormone abscisic acid (ABA) plays a key role in the plant response to drought stress. Hence, ABA-dependent gene transcription and ion transport is regulated by a variety of protein kinases and phosphatases. However, the nature of the membrane-delimited ABA signal transduction steps remains largely unknown. To gain insight into plasma membrane-bound ABA signaling, we identified sterol-dependent proteins associated with detergent resistant membranes from Arabidopsis thaliana mesophyll cells. Among those, we detected the central ABA signaling phosphatase ABI1 (abscisic-acid insensitive 1) and the calcium-dependent protein kinase 21 (CPK21). Using fluorescence microscopy, we found these proteins to localize in membrane nanodomains, as observed by colocalization with the nanodomain marker remorin Arabidopsis thaliana remorin 1.3 (AtRem 1.3). After transient coexpression, CPK21 interacted with SLAH3 [slow anion channel 1 (SLAC1) homolog 3] and activated this anion channel. Upon CPK21 stimulation, SLAH3 exhibited the hallmark properties of S-type anion channels. Coexpression of SLAH3/CPK21 with ABI1, however, prevented proper nanodomain localization of the SLAH3/CPK21 protein complex, and as a result anion channel activation failed. FRET studies revealed enhanced interaction of SLAH3 and CPK21 within the plasma membrane in response to ABA and thus confirmed our initial observations. Interestingly, the ABA-induced SLAH3/CPK21 interaction was modulated by ABI1 and the ABA receptor RCAR1/PYL9 [regulatory components of ABA receptor 1/PYR1 (pyrabactin resistance 1)-like protein 9]. We therefore propose that ABA signaling via inhibition of ABI1 modulates the apparent association of a signaling and transport complex within membrane domains that is necessary for phosphorylation and activation of the S-type anion channel SLAH3 by CPK21.
authors: Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, 97082 Wuerzburg, Germany.
authors: Fatih
authors: F
authors: Demir
authors: Claudia
authors: C
authors: Horntrich
authors: Jörg O
authors: JO
authors: Blachutzik
authors: Sönke
authors: S
authors: Scherzer
authors: Yvonne
authors: Y
authors: Reinders
authors: Sylwia
authors: S
authors: Kierszniowska
authors: Waltraud X
authors: WX
authors: Schulze
authors: Gregory S
authors: GS
authors: Harms
authors: Rainer
authors: R
authors: Hedrich
authors: Dietmar
authors: D
authors: Geiger
authors: Ines
authors: I
authors: Kreuzer
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D000818:Animals; D000838:Anions / Q000378:metabolism; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D003902:Detergents / Q000494:pharmacology; D031541:Fluorescence Resonance Energy Transfer; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism*; D050356:Lipid Metabolism; D013058:Mass Spectrometry; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D017434:Protein Structure, Tertiary; D018075:RNA, Complementary / Q000378:metabolism; D015398:Signal Transduction; D013261:Sterols / Q000378:metabolism; D014981:Xenopus / Q000378:metabolism
chemical_list: D000838:Anions; D029681:Arabidopsis Proteins; D003902:Detergents; D007473:Ion Channels; D018075:RNA, Complementary; C582432:SLAH3 protein, Arabidopsis; D013261:Sterols; D049452:Green Fluorescent Proteins; D000040:Abscisic Acid
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