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Abscisic Acid Activation of Plasma Membrane Ca2⁺ Channels in Guard Cells Requires Cytosolic NAD(P)H and Is Differentially Disrupted Upstream and Downstream of Reactive Oxygen Species Production in abi1-1 and abi2-1 Protein Phosphatase 2C Mutants

Yoshiyuki Murata, Zhen-Ming Pei, Izumi C. Mori and Julian Schroeder
The Plant Cell
Vol. 13, No. 11 (Nov., 2001), pp. 2513-2523
DOI: 10.2307/3871591
Stable URL: http://www.jstor.org/stable/3871591
Page Count: 11
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Abscisic Acid Activation of Plasma Membrane Ca2⁺ Channels in Guard Cells Requires Cytosolic NAD(P)H and Is Differentially Disrupted Upstream and Downstream of Reactive Oxygen Species Production in abi1-1 and abi2-1 Protein Phosphatase 2C Mutants
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Abstract

The hormone abscisic acid (ABA) regulates stress responses and developmental processes in plants. Calcium-permeable channels activated by reactive oxygen species (ROS) have been shown recently to function in the ABA signaling network in Arabidopsis guard cells. Here, we report that ABA activation of these ${\rm I}_{{\rm Ca}}\ {\rm Ca}^{2+}$ channels requires the presence of NAD(P)H in the cytosol. The protein phosphatase 2C (PP2C) mutant abi1-1 disrupted ABA activation of I Ca channels. Moreover, in abi1-1, ABA did not induce ROS production. Consistent with these findings, in abi1-1, H2 O2 activation of I Ca channels and H2 O2-induced stomatal closing were not disrupted, suggesting that abi1-1 impairs ABA signaling between ABA reception and ROS production. The abi2-1 mutation, which lies in a distinct PP2C gene, also disrupted ABA activation of I Ca. However, in contrast to abi1-1, abi2-1 impaired both H2 O2 activation of I Ca and H2 O2-induced stomatal closing. Furthermore, ABA elicited ROS production in abi2-1. These data suggest a model with the following sequence of events in early ABA signal transduction: ABA, abi1-1, NAD(P)H-dependent ROS production, abi2-1, ${\rm I}_{{\rm Ca}}\ {\rm Ca}^{2+}$ channel activation followed by stomatal closing.

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