Early ABA Signaling Events in Guard Cells |
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Authors: | Zhen-Ming Pei Kazuyuki Kuchitsu |
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Institution: | (1) Department of Biology, Duke University, Durham, North Carolina 27708, USA;(2) Department of Applied Biological Science, and Genome and Drug Research Center, Tokyo University of Science, 2641 Yamazaki, Noda Chiba, 278-8510, Japan |
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Abstract: | The plant hormone abscisic acid (ABA) regulates a wide variety of plant physiological and developmental processes, particularly
responses to environmental stress, such as drought. In response to water deficiency, plants redistribute foliar ABA and/or
upregulate ABA synthesis in roots, leading to roughly a 30-fold increase in ABA concentration in the apoplast of stomatal
guard cells. The elevated ABA triggers a chain of events in guard cells, causing stomatal closure and thus preventing water
loss. Although the molecular nature of ABA receptor(s) remains unknown, considerable progress in the identification and characterization
of its downstream signaling elements has been made by using combined physiological, biochemical, biophysical, molecular, and
genetic approaches. The measurable events associated with ABA-induced stomatal closure in guard cells include, sequentially,
the production of reactive oxygen species (ROS), increases in cytosolic free Ca2+ levels (Ca2+]i), activation of anion channels, membrane potential depolarization, cytosolic alkalinization, inhibition of K+ influx channels, and promotion of K+ efflux channels. This review provides an overview of the cellular and molecular mechanisms underlying these ABA-evoked signaling
events, with particular emphasis on how ABA triggers an “electronic circuitry” involving these ionic components. |
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Keywords: | Abscisic acid Cytosolic Ca2+ Drought stress Guard cell Ion channel Signal transduction Stomatal closure |
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