Glutamate functions in stomatal closure in Arabidopsis and fava bean.

Riichiro Yoshida,Tetsuo Shimatani,Fumika Miyata,Kenji Honda,Sumio Iwai,Yudai Shichiri,Izumi C Mori,Nobuto Kamizono

doi:10.1007/s10265-015-0757-0

Riichiro Yoshida, Tetsuo Shimatani + Show 6 more

Open Access

https://doi.org/10.1007/s10265-015-0757-0

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Abstract

Guard cells are indispensable for higher plants because they control gas exchange and water balance to maintain photosynthetic activity. The signaling processes that govern their movement are controlled by several factors, such as abscisic acid (ABA), blue light, pathogen-associated molecular patterns (PAMPs), and carbon dioxide. Herein, we demonstrated that the amino acid glutamate (Glu), a well-known mammalian neurotransmitter, functions as a novel signaling molecule in stomatal closure in both Arabidopsis and fava bean (Vicia faba L.). Pharmacological and electrophysiological analyses provided important clues for the participation of Glu-receptors, Ca2+, and protein phosphorylation during the signaling process. Genetic analyses using Arabidopsis ABA-deficient (aba2-1) and ABA-insensitive (abi1-1 and abi2-1) mutants showed that ABA is not required for Glu signaling. However, loss-of-function of the Arabidopsis gene encoding Slow Anion Channel-Associated 1 (SLAC1) and Calcium-Dependent Protein Kinase 6 (CPK6) impaired the Glu response. Moreover, T-DNA knockout mutations of the Arabidopsis Glu receptor-like gene (GLR), GLR3.5, lost their sensitivity to Glu-dependent stomatal closure. Our results strongly support functional Glu-signaling in stomatal closure and the crucial roles of GLRs in this signaling process.Electronic supplementary materialThe online version of this article (doi:10.1007/s10265-015-0757-0) contains supplementary material, which is available to authorized users.

Highlights

The amino acid glutamate (Glu) plays pivotal roles in the functioning of the central nervous system in mammals (Watkins and Jane 2006)
To ascertain whether Glu promotes stomatal closure, we applied sodium l-glutamate monohydrate to epidermal strips prepared from Arabidopsis and fava bean
We examined the effect of Glu on stomatal movement in Arabidopsis ecotypes and in fava bean

Summary

Introduction

The amino acid glutamate (Glu) plays pivotal roles in the functioning of the central nervous system in mammals (Watkins and Jane 2006). Since the discovery of GLR genes in plant cells, Glu-signaling has been studied intensively as a potential amino acid sensor, and Glu was found to cause rapid membrane depolarization and Ca2+ flux in Arabidopsis roots (Dennison and Spalding 2000). Glu has been found to have several roles in plant signaling, which include regulating hypocotyl elongation (Dubos et al 2003; Lam et al 1998), sensing mineral nutrient status (Kim et al 2001), resisting aluminum toxicity (Sivaguru et al 2003), and regulating the carbon/nitrogen balance (Kang and Turano 2003), abscisic acid (ABA) synthesis (Kang et al 2004), cold (Meyerhoff et al 2005), root meristem function

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