Chapter

Communication in Plants

pp 187-204

The Arabidopsis thaliana Glutamate-like Receptor Family (AtGLR)

  • Matthew GillihamAffiliated withDepartment of Plant Sciences, Stress Physiology Laboratory, University of Cambridge
  • , Malcolm CampbellAffiliated withDepartment of Botany, University of Toronto
  • , Christian DubosAffiliated withDepartment of Botany, University of Toronto
  • , Dirk BeckerAffiliated withJulius von Sachs Institute for Biosciences, University of Würzburg
  • , Romola DavenportAffiliated withStress Physiology Laboratory, Department of Plant Sciences, University of Cambridge

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Abstract

The 20 genes that encode the Arabidopsis thaliana glutamate-like receptor family (AtGLR) share significant similarity in amino acid coding sequence and predicted secondary structure with animal ionotropic glutamate receptor (iGluR) subunits. In animals, iGluR subunits form glutamate-gated non-selective cation channels (NSCCs) catalysing Na+ and/or Ca2+ influx into cells; in one iGluR subfamily glycine also is required as a coagonist. In Arabidopsis, both glutamate and glycine have been demonstrated to depolarise the plasma membrane and increase [Ca2+]cyt, and iGluR antagonists blocked these effects. AtGLRs are therefore predicted to function in an analogous manner to iGluR. Attempts to functionally characterise AtGLRs in heterologous expression systems have proved inconclusive with no ligand-gated activity detected. Research into the glutamate receptor-like family has been hindered by the lack of phenotypes associated with the AtGLR genes but several phenotypes associated with AtGLR overexpression and knockout have recently given hints as to their function. AtGLR have been implicated in light and C:N signalling, hypocotyl detiolation, root growth, abscisic acid (ABA) metabolism, stress responses, and general ion transport. This review will concentrate on recent developments in the AtGLR field, including the roles and effects of glutamate and glycine and related metabolites in plant physiology relative to potential roles for AtGLRs. It will examine progress made toward defining the functions of particular AtGLRs and will conclude by recommending potentially fruitful avenues of future research.