Activity of guard cell anion channel SLAC1 is controlled by drought-stress signaling kinase-phosphatase pair.
In response to drought stress the phytohormone ABA (abscisic acid) induces stomatal closure and, therein, activates guard cell anion channels in a calcium-dependent as well as-independent manner. Two key components of the ABA signaling pathway are the protein kinase OST1 (open stomata 1) and the protein phosphatase ABI1 (ABA insensitive 1). The recently identified guard cell anion channel SLAC1 appeared to be the key ion channel in this signaling pathway but remained electrically silent when expressed heterologously. Using split YFP assays, we identified OST1 as an interaction partner of SLAC1 and ABI1. Upon coexpression of SLAC1 with OST1 in Xenopus oocytes, SLAC1-related anion currents appeared similar to those observed in guard cells. Integration of ABI1 into the SLAC1/OST1 complex, however, prevented SLAC1 activation. Our studies demonstrate that SLAC1 represents the slow, deactivating, weak voltage-dependent anion channel of guard cells controlled by phosphorylation/dephosphorylation.
Geiger
Dietmar
D
University Wuerzburg, Institute for Molecular Plant Physiology and Biophysics, Julius-von-Sachs Platz 2, D-97082 Wuerzburg, Germany.
Scherzer
Sönke
S
Mumm
Patrick
P
Stange
Annette
A
Marten
Irene
I
Bauer
Hubert
H
Ache
Peter
P
Matschi
Susanne
S
Liese
Anja
A
Al-Rasheid
Khaled A S
KA
Romeis
Tina
T
Hedrich
Rainer
R
D000040:Abscisic Acid / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D055864:Droughts; D007473:Ion Channels / Q000378:metabolism*; D008565:Membrane Proteins; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism*
D029681:Arabidopsis Proteins; D007473:Ion Channels; D008565:Membrane Proteins; C528438:SLAC1 protein, Arabidopsis; D000040:Abscisic Acid; D011494:Protein Kinases; C472139:OST1 protein, Arabidopsis; C087434:ABI1 protein, Arabidopsis; D010749:Phosphoprotein Phosphatases