Under drought stress, the stress hormone ABA addresses the SnR kinase OST1 via its cytosolic receptor and the protein phosphatase ABI1. Upon activation, OST1 phosphorylates the guard cell S–type anion channel SLAC1. Arabidopsis ABI1 and OST1 loss-of-function mutants are characterized by an extreme wilting 'open stomata′ phenotype. Given the fact that guard cells express both SLAC- and R–/QUAC-type anion channels, we questioned whether OST1, besides SLAC1, also controls the QUAC1 channel. In other words, are ABI1/OST1 defects preventing both of the guard cell anion channel types from operating properly in terms of stomatal closure? The activation of the R–/QUAC-type anion channel by ABA signaling kinase OST1 and phosphatase ABI1 was analyzed in two experimental systems: Arabidopsis guard cells and the plant cell-free background of Xenopus oocytes. Patch-clamp studies on guard cells show that ABA activates R–/QUAC-type currents of wild-type plants, but to a much lesser extent in those of abi1–1 and ost1–2 mutants. In the oocyte system the co-expression of QUAC1 and OST1 resulted in a pronounced activation of the R–type anion channel. These studies indicate that OST1 is addressing both S–/SLAC- and R–/QUAC-type guard cell anion channels, and explain why the ost1–2 mutant is much more sensitive to drought than single slac1 or quac1 mutants.

Item Type:	Refereed Article
Keywords:	QUAC-type anion channel, ABA, ABA signaling, guard cell, patch clamp, electrophysiology TEVC
Research Division:	Physical Sciences
Research Group:	Medical and biological physics
Research Field:	Biological physics
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the biological sciences
UTAS Author:	Hedrich, R (Professor Rainer Hedrich)
ID Code:	112901
Year Published:	2013
Web of Science® Times Cited:	136
Deposited By:	Tasmanian Institute of Agriculture
Deposited On:	2016-12-02
Last Modified:	2017-11-06
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