Research ArticlePlant biology

Stomatal Closure by Fast Abscisic Acid Signaling Is Mediated by the Guard Cell Anion Channel SLAH3 and the Receptor RCAR1

Sci. Signal.  17 May 2011:
Vol. 4, Issue 173, pp. ra32
DOI: 10.1126/scisignal.2001346

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Conducting Closure

Stomata are pores in the plant epidermis that allow the movement of CO2 into the plant concomitant with the loss of water. The opening and closing of these pores is mediated by the surrounding guard cells, which respond to drought, nutrient availability, and the plant stress hormone abscisic acid (ABA). Geiger et al. identified the anion channel SLAH3 as a player in the guard cell pathway downstream of ABA and defined its mode of regulation through an ABA receptor–phosphatase RCAR1-ABI complex and a calcium-dependent kinase, CPK21. Unlike previously characterized anion channels that are regulated by ABA and contribute to stomatal closure, activation of SLAH3 was promoted by nitrate and was 20 times as permeable to nitrate ions as to chloride ions. Thus, SLAH3 may integrate nitrate signaling and metabolism with signals initiated by drought conditions to control respiration and water loss.

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