Additive contribution of AMT1;1 and AMT1;3 to high-affinity ammonium uptake across the plasma membrane of nitrogen-deficient Arabidopsis roots

作者：Loque Dominique; Yuan Lixing; Kojima Soichi; Gojon Alain; Wirth Judith; Gazzarrini Sonia; Ishiyama Keiki; Takahashi Hideki; von Wiren Nicolaus^*

来源：Plant Journal, 2006, 48(4): 522-534.

DOI：10.1111/j.1365-313X.2006.02887.x

• ammonium influx
• membrane transport
• nitrogen deficiency
• nitrogen nutrition
• nutrient uptake
• T-DNA insertion lines

In Arabidopsis four root-expressed AMT genes encode functional ammonium transporters, which raises the question of their role in primary ammonium uptake. After pre-culturing under nitrogen-deficiency conditions, we quantified the influx of N-15-labeled ammonium in T-DNA insertion lines and observed that the loss of either AMT1;1 or AMT1;3 led to a decrease in the high-affinity ammonium influx of approximately 30%. Under nitrogen-sufficient conditions the ammonium influx was lower in Columbia glabra compared with Wassilewskija (WS), and AMT1;1 did not contribute significantly to the ammonium influx in Col-gl. Ectopic expression of AMT1;3 under the control of a 35S promoter in either of the insertion lines amt1;3-1 or amt1;1-1 increased the ammonium influx above the level of their corresponding wild types. In transgenic lines carrying AMT-promoter-GFP constructs, the promoter activities of AMT1;1 and AMT1;3 were both upregulated under nitrogen-deficiency conditions and were localized to the rhizodermis, including root hairs. AMT gene-GFP fusions that were stably expressed under the control of their own promoters were localized to the plasma membrane. The double insertion line amt1;1-1amt1;3-1 showed a decreased sensitivity to the toxic ammonium analog methylammonium and a decrease in the ammonium influx of up to 70% relative to wild-type plants. These results suggest an additive contribution of AMT1;1 and AMT1;3 to the overall ammonium uptake capacity in Arabidopsis roots under nitrogen-deficiency conditions.

• 出版日期2006-11