Aluminum-Activated Malate Transporters Can Facilitate GABA Transport([OPEN])

作者：Ramesh Sunita A; Kamran Muhammad; Sullivan Wendy; Chirkova Larissa; Okamoto Mamoru; Degryse Fien; McLaughlin Michael; Gilliham Matthew; Tyerman Stephen D^*

来源：Plant Cell, 2018, 30(5): 1147-1164.

DOI：10.1105/tpc.17.00864

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 GABA(A) 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 C-14-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 (TaALMT1(F213C)) 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.

• 出版日期2018-5