Adjusting ammonium uptake via phosphorylation
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Updated: Jun 13, 2026

Measuring Fluxes of Mineral Nutrients and Toxicants in Plants with Radioactive Tracers
Published on: August 22, 2014
Viviane Lanquar1, Wolf B Frommer
1Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, USA.
Abstract:
In plants, AMT/MEP/Rh superfamily mediates high affinity ammonium uptake. AMT/MEP transporters form a trimeric complex, which requires a productive interaction between subunits in order to be functional. The AMT/MEP C-terminal domain is highly conserved in more than 700 AMT homologs from cyanobacteria to higher plants with no cases found to be lacking this domain. AMT1;1 exists in active and inactive states, probably controlled by the spatial positioning of the C-terminus. Ammonium triggers the phosphorylation of a conserved threonine residue (T460) in the C-terminus of AMT1;1 in a time- and concentration-dependent manner. The T460 phosphorylation level correlates with a decrease of root ammonium uptake. We propose that ammonium-induced phosphorylation modulates ammonium uptake as a general mechanism to protect against ammonium toxicity.
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