A protein kinase-phosphatase pair interacts with an ion channel to regulate ABA signaling in plant guard cells.
The plant hormone abscisic acid (ABA) serves as a physiological monitor to assess the water status of plants and, under drought conditions, induces stomatal pore closure by activating specific ion channels, such as a slow-anion channel (SLAC1) that, in turn, mediate ion efflux from the guard cells. Earlier genetic analyses uncovered a protein kinase (OST1) and several 2C-type phosphatases, as respective positive and negative regulators of ABA-induced stomatal closure. Here we show that the OST1 kinase interacts with the SLAC1 anion channel, leading to its activation via phosphorylation. PP2CA, one of the PP2C phosphatase family members acts in an opposing manner and inhibits the activity of SLAC1 by two mechanisms: (1) direct interaction with SLAC1 itself, and (2) physical interaction with OSTI leading to inhibition of the kinase independently of phosphatase activity. The results suggest that ABA signaling is mediated by a physical interaction chain consisting of several components, including a PP2C member, SnRK2-type kinase (OST1), and an ion channel, SLAC1, to regulate stomatal movements. The findings are in keeping with a paradigm in which a protein kinase-phosphatase pair interacts physically with a target protein to couple a signal with a specific response.
Lee
Sung Chul
SC
Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
Lan
Wenzhi
W
Buchanan
Bob B
BB
Luan
Sheng
S
D000040:Abscisic Acid / Q000378:metabolism*; D000818:Animals; D029681:Arabidopsis Proteins; D007473:Ion Channels / Q000378:metabolism*; D008565:Membrane Proteins; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D054046:Plant Stomata / Q000378:metabolism*; D010944:Plants; D011494:Protein Kinases / Q000378:metabolism*; D015398:Signal Transduction; D014981:Xenopus; D015003:Yeasts
D029681:Arabidopsis Proteins; D007473:Ion Channels; D008565:Membrane Proteins; D010940:Plant Proteins; C528438:SLAC1 protein, Arabidopsis; D000040:Abscisic Acid; D011494:Protein Kinases; C472139:OST1 protein, Arabidopsis; C463465:AHG3 protein, Arabidopsis; D010749:Phosphoprotein Phosphatases