Poster: Membrane transport

Abs # 183: Determining functions of Arabidopsis glutamate receptors using electrophysiology and reverse genetics

Presenter:	Qi, Zhi , zqi@wisc.edu
Authors	Qi, Zhi  (A)   Durham, Tessa L (A)   Stephens, Nicholas R (A)   Spalding, Edgar P (A)
Affiliations:	(A): University Of Wisconsin

The Arabidopsis Glutamate-Like Receptor (AtGLR) gene family consists of twenty genes with similarity to the ionotropic glutamate receptors, which are the major excitatory ligand-gated ion channels of the mammalian central nervous system. Functional channels are hetero- or homotetramers of glutamate receptor subunits. These channels are gated by glutamate, glycine or a mixture of both ligands and, when opened, conduct cations including K⁺, Na⁺ and Ca²⁺ across the cell membrane. We are investigating the possible functions of the AtGLRs using electrophysiological tools and a collection of T-DNA insertion mutants. In wild-type seedlings, ligand application triggers large membrane depolarizations in root and hypocotyl cells. Some of the 18 T-DNA knockouts we have isolated so far display defective ligand-induced membrane depolarizations as well as aberrant electrophysiological and growth rate responses to light. To explore possible functions of AtGLRs in mineral nutrition we are screening our knockout collection for phenotypes apparent under various nutrient-limiting conditions. Data from the above screens identify Atglrs that share similar phenotypes, which guide our selection of single-knockouts to combine in double and triple mutants. When the phenotypic effect of combining two single mutations is greater than that observed in either single mutant alone, this further supports the idea that these subunits may normally interact in a functional channel. Linking membrane-level function with growth and development will allow better understanding of AtGLR physiology in the plant.