Regulation of ammonium transport in Arabidopsis and Medicago
Final Report Abstract
The molecular basis of high affinity ammonium transport is relatively well understood in the model plant Arabidopsis. AMT-type ammonium transporters are regulated at the transcriptional, post-transcriptional and posttranslational level. While most research concentrated on the uptake of ammonium at low concentrations, more recently the toxicity of high concentrations of ammonium was investigated in more detail. Several novel factors important for the toxicity of ammonium have been recently identified, but a deeper understanding how plants cope with high levels of ammonium is still missing. Using a microarray approach, the physiology of plant adaptation to high ammonium was studied and identified a close relation to the plant hormone auxin. Ammonium is assimilated into glutamine and this metabolite was followed and quantified using fluorescent reporters expressed in Arabidopsis mutants. The usage of these fluorescent reporters opens novel possibilities to monitor this crucial primary metabolite not only in plants, but also for high throughput applications in other cellular and cell-free applications. Although the attempts to crystallize a plant AMT failed, structural models of plant AMTs could be generated with high confidence. These were successfully used to molecularly simulate the transport mechanism using molecular dynamics simulations on computers. Several high affinity ammonium transporters were also investigated and characterized in Medicago. The genetic architecture of ammonium transport differs considerably from that in the model Arabidopsis.
Publications
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2009. A Mycorrhizal-Specific Ammonium Transporter from Lotus japonicus Acquires Nitrogen Released by Arbuscular Mycorrhizal Fungi. Plant Physiol 150(1):73-83
Guether M, Neuhauser B, Balestrini R, Dynowski M, Ludewig U, Bonfante P
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2009. Channel-like NH3 flux by ammonium transporter AtAMT2. FEBS Lett 583(17):2833-2838
Neuhauser B, Dynowski M, Ludewig U
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2010. H-independent glutamine transport in plant root tips. PLoS One 5(1):e8917
Yang H, Bogner M, Stierhof YD, Ludewig U
