The Organization of High-Affinity Ammonium Uptake in <i>Arabidopsis</i> Roots Depends on the Spatial Arrangement and Biochemical Properties of AMT1-Type Transporters

Yuan, Lixing; Loqué, Dominique; Kojima, Shinichi; Rauch, Sabine; Ishiyama, Keiki; Inoue, Eri; Takahashi, Hideki; Wirén, Nicolaus von

doi:10.1105/tpc.107.052134

Cited by 340 publications

(447 citation statements)

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“…We have shown a PM location of the LjAMT1;1 protein (Fig. 7), a result identical to that obtained for different AMT1 proteins in Lotus and other plant species (Ludewig et al 2003;Simon-Rosin et al 2003;Yuan et al 2007b). It has been proposed that PMlocated AMT1 proteins may play a role in recovery of ammonium lost from cells via diffusion, prior to its incorporation into amino acids (Simon-Rosin et al 2003).…”

Section: Discussionsupporting

confidence: 86%

“…7b, c). The same PM localization has been reported for AMT proteins in other plant species (Ludewig et al 2003;Simon-Rosin et al 2003;Yuan et al 2007b).…”

Section: Ljamt1;1 Expression Is Under Developmental But Not Nitrogen-supporting

confidence: 84%

“…It is imported into plant cells from the surrounding environment via transporters, in the plasma membrane (PM) of root cells (Yuan et al 2007b) and leaf cells (Husted and Schjoerring 1996). A large fraction of ammonium assimilated by plants is generated within cells by reduction of nitrate and nitrite obtained from the soil, via the photorespiratory nitrogen cycle in leaf mitochondria and by catabolism of endogenous amino compounds.…”

Section: Introductionmentioning

confidence: 99%

“…Complementary, partially overlapping gene expression patterns and kinetic properties of Arabidopsis AMT1 transporters indicate that they work cooperatively to ensure a coordinate effective high-affinity ammonium uptake in Arabidopsis roots (Yuan et al 2007b).…”

Section: Introductionmentioning

confidence: 99%

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Tissue-specific down-regulation of LjAMT1;1 compromises nodule function and enhances nodulation in Lotus japonicus

et al. 2008

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Plant ammonium transporters of the AMT1 family are involved in N-uptake from the soil and ammonium transport, and recycling within the plant. Although AMT1 genes are known to be expressed in nitrogen-fixing nodules of legumes, their precise roles in this specialized organ remain unknown. We have taken a reverse-genetic approach to decipher the physiological role of LjAMT1;1 in Lotus japonicus nodules. LjAMT1;1 is normally expressed in both the infected zone and the vascular tissue of Lotus nodules. Inhibition of LjAMT1;1 gene expression, using an antisense gene construct driven by a leghemoglobin promoter resulted in a substantial reduction of LjAMT1;1 transcript in the infected tissue but not the vascular bundles of transgenic plants. As a result, the nitrogen-fixing activity of nodules was partially impaired and nodule number increased compared to control plants. Expression of LjAMT1;1-GFP fusion protein in plant cells indicated a plasma-membrane location for the LjAMT1;1 protein.Taken together, the results are consistent with a role of LjAMT1;1 in retaining ammonium derived from symbiotic nitrogen fixation in plant cells prior to its assimilation.

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Section: Discussionsupporting

confidence: 86%

“…7b, c). The same PM localization has been reported for AMT proteins in other plant species (Ludewig et al 2003;Simon-Rosin et al 2003;Yuan et al 2007b).…”

Section: Ljamt1;1 Expression Is Under Developmental But Not Nitrogen-supporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Tissue-specific down-regulation of LjAMT1;1 compromises nodule function and enhances nodulation in Lotus japonicus

et al. 2008

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“…In Arabidopsis thaliana, the AMT family comprises six isoforms, of which three (AtAMT1;1, AtAMT1;2, and AtAMT1;3) are responsible for about 90% of the total high-affinity N uptake in roots (3). AMT gene expression in Arabidopsis roots is generally repressed by high N and induced by N deficiency (4).…”

Section: Va-tirfm | Fcsmentioning

confidence: 99%

Single-particle analysis reveals shutoff control of the Arabidopsis ammonium transporter AMT1;3 by clustering and internalization

Wang

Zhao

Luo

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Ammonium is a preferred source of nitrogen for plants but is toxic at high levels. Plant ammonium transporters (AMTs) play an essential role in NH 4 + uptake, but the mechanism by which AMTs are regulated remains unclear. To study how AMTs are regulated in the presence of ammonium, we used variable-angle total internal reflection fluorescence microscopy and fluorescence crosscorrelation spectroscopy for single-particle fluorescence imaging of EGFP-tagged AMT1;3 on the plasma membrane of Arabidopsis root cells at various ammonium levels. We demonstrated that AMT1;3-EGFP dynamically appeared and disappeared on the plasma membrane as moving fluorescent spots in low oligomeric states under N-deprived and N-sufficient conditions. Under external high-ammonium stress, however, AMT1;3-EGFPs were found to amass into clusters, which were then internalized into the cytoplasm. A similar phenomenon also occurred in the glutamine synthetase mutant gln1;2 background. Single-particle analysis of AMT1;3-EGFPs in the clathrin heavy chain 2 mutant (chc2 mutant) and Flotllin1 artificial microRNA (Flot1 amiRNA) backgrounds, together with chemical inhibitor treatments, demonstrated that the endocytosis of AMT1;3 clusters induced by high-ammonium stress could occur mainly through clathrin-mediated endocytic pathways, but the contribution of microdomain-associated endocytic pathway cannot be excluded in the internalization. Our results revealed that the clustering and endocytosis of AMT1;3 provides an effective mechanism by which plant cells can avoid accumulation of toxic levels of ammonium by eliminating active AMT1;3 from the plasma membrane. VA-TIRFM | FCSA mmonium (NH 4 + ) and nitrate (NO 3 − ) are the primary sources of nitrogen (N) for most plants growing in agricultural soils. Ammonium assimilation requires less energy than nitrate assimilation, and, thus, ammonium is absorbed preferentially when plants are N-deficient. However, high concentrations of ammonium can be toxic (1); therefore, ammonia absorption and metabolism must be strictly controlled. Understanding the mechanisms by which plant cells regulate ammonium uptake and translocation is of critical importance for agricultural improvements in N-use efficiency and avoiding ammonium toxicity.Evidence suggests that membrane ammonium transporters (AMTs) act in NH 4 + uptake into plant cells, serving as the major transporters for high-affinity ammonium uptake (2). In Arabidopsis thaliana, the AMT family comprises six isoforms, of which three (AtAMT1;1, AtAMT1;2, and AtAMT1;3) are responsible for about 90% of the total high-affinity N uptake in roots (3). AMT gene expression in Arabidopsis roots is generally repressed by high N and induced by N deficiency (4). In addition to transcriptional mechanisms, regulation of membrane transporter activity is also involved in the plant's responses to changing nutrient supplies (1). Although posttranscriptional regulation of AMT appears to be N-dependent (5), the question of how ammonium regulates AMT transporter activity, particularly t...

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Plant Nitrogen Nutrition and Transport

Miller

2010

Encyclopedia of Life Sciences

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Nitrogen (N) is a major plant nutrient and is available in soil chiefly as nitrate (NO 3 − ), ammonium and amino acids. N is acquired through roots and then transported around the plant or it can be combined with carbon to produce amino acids (assimilation) before being redistributed. Most plant cells can assimilate N and any not required for growth is stored as protein. Reserve N can be accumulated as the photosynthetic enzyme Rubisco and species‐specific storage proteins in vegetative tissue or seed endosperm. Cellular storage of NO 3 − occurs in the vacuole, where it is important for driving osmotic expansion growth. The amount of these stored forms defines a plant's N status. Some structural materials like lignin contain a high proportion of N, but this is not stored and is not remobilised. Some plants form a symbiotic relationship with bacteria in specialised nodules to enable the direct assimilation of gaseous N. Key Concepts: Nitrogen supply limits plant growth in almost all natural environments. The soil available form of N depends on factors like soil type, weather and temperature with NO 3 − dominating temperate climates. Some plants form a specialised symbiosis with bacteria to fix atmospheric N. Agriculture includes the addition of N fertiliser to optimise yield. Regulation of plant carbon and N metabolism is carefully coordinated for normal growth and development. Changes in plant N supply trigger alterations in a huge number of genes resulting in changes in morphology, growth rate and development. A change in the phosphorylation status of some plasma membrane NO 3 − and ammonium transporter proteins provides a receptor mechanism that links uptake to external availability.

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The Organization of High-Affinity Ammonium Uptake in Arabidopsis Roots Depends on the Spatial Arrangement and Biochemical Properties of AMT1-Type Transporters

Cited by 340 publications

References 65 publications

Tissue-specific down-regulation of LjAMT1;1 compromises nodule function and enhances nodulation in Lotus japonicus

Tissue-specific down-regulation of LjAMT1;1 compromises nodule function and enhances nodulation in Lotus japonicus

Single-particle analysis reveals shutoff control of the Arabidopsis ammonium transporter AMT1;3 by clustering and internalization

Plant Nitrogen Nutrition and Transport

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