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New Phytol. 2019 Oct;224(1):177-187. doi: 10.1111/nph.15985. Epub 2019 Jul 19.

Calcium signals in guard cells enhance the efficiency by which abscisic acid triggers stomatal closure.

Author information

1
Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Würzburg University, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany.
2
Centre for Organismal Studies, Plant Developmental Biology, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 230, D-69120 Heidelberg, Germany.
3
Institute of Technology, University of Tartu, Nooruse 1, Tartu, 50411, Estonia.

Abstract

During drought, abscisic acid (ABA) induces closure of stomata via a signaling pathway that involves the calcium (Ca2+ )-independent protein kinase OST1, as well as Ca2+ -dependent protein kinases. However, the interconnection between OST1 and Ca2+ signaling in ABA-induced stomatal closure has not been fully resolved. ABA-induced Ca2+ signals were monitored in intact Arabidopsis leaves, which express the ratiometric Ca2+ reporter R-GECO1-mTurquoise and the Ca2+ -dependent activation of S-type anion channels was recorded with intracellular double-barreled microelectrodes. ABA triggered Ca2+ signals that occurred during the initiation period, as well as in the acceleration phase of stomatal closure. However, a subset of stomata closed in the absence of Ca2+ signals. On average, stomata closed faster if Ca2+ signals were elicited during the ABA response. Loss of OST1 prevented ABA-induced stomatal closure and repressed Ca2+ signals, whereas elevation of the cytosolic Ca2+ concentration caused a rapid activation of SLAC1 and SLAH3 anion channels. Our data show that the majority of Ca2+ signals are evoked during the acceleration phase of stomatal closure, which is initiated by OST1. These Ca2+ signals are likely to activate Ca2+ -dependent protein kinases, which enhance the activity of S-type anion channels and boost stomatal closure.

KEYWORDS:

Ca2+-indicator; OST1 protein kinase; R-GECO1-mTurquoise; SLAC1 and SLAH3 anion channels; abscisic acid (ABA); cytosolic Ca2+ signals; stomata

PMID:
31179540
DOI:
10.1111/nph.15985
Free PMC Article

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