Aluminum-Activated Malate Transporters Can Facilitate GABA Transport

Plant aluminum-activated malate transporters (ALMTs) are currently classified as anion channels; they are also known to be regulated by diverse signals, leading to a range of physiological responses. Gamma-aminobutyric acid (GABA) regulation of anion flux through ALMT proteins requires a specific am...

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Bibliographic Details
Published in:The Plant cell 2018-05, Vol.30 (5), p.1147-1164
Main Authors: Ramesh, Sunita A., Kamran, Muhammad, Sullivan, Wendy, Chirkova, Larissa, Okamoto, Mamoru, Degryse, Fien, McLaughlin, Michael, Gilliham, Matthew, Tyerman, Stephen D.
Format: Article
Language:English
Subjects:
Activation
Aluminum
Amino acids
Anion channels
Anions
Binding sites
Carbon 14
Communication
Complementation
Efflux
Ion channels
Malate
Metabolism
Oocytes
Physiological responses
Proteins
Receptors
Tips
Transport
Wheat
Yeast
Yeasts
γ-Aminobutyric acid A receptors
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Summary:Plant aluminum-activated malate transporters (ALMTs) are currently classified as anion channels; they are also known to be regulated by diverse signals, leading to a range of physiological responses. Gamma-aminobutyric acid (GABA) regulation of anion flux through ALMT proteins requires a specific amino acid motif in ALMTs that shares similarity with a GABA binding site in mammalian GABAA receptors. Here, we explore why TaALMT1 activation leads to a negative correlation between malate efflux and endogenous GABA concentrations ([GABA]i) in both wheat (Triticum aestivum) root tips and in heterologous expression systems. We show that TaALMT1 activation reduces [GABA]i because TaALMT1 facilitates GABA efflux but GABA does not complex Al3+. TaALMT1 also leads to GABA transport into cells, demonstrated by a yeast complementation assay and via 14C-GABA uptake into TaALMT1-expressing Xenopus laevis oocytes; this was found to be a general feature of all ALMTs we examined. Mutation of the GABA motif (TaALMT1F213C) prevented both GABA influx and efflux, and resulted in no correlation between malate efflux and [GABA]i. We conclude that ALMTs are likely to act as both GABA and anion transporters in planta. GABA and malate appear to interact with ALMTs in a complex manner to regulate each other’s transport, suggestive of a role for ALMTs in communicating metabolic status.
ISSN:1040-4651
1532-298X
DOI:10.1105/tpc.17.00864