Characterization of <i>Arabidopsis</i> AtAMT2, a novel ammonium transporter in plants

Sohlenkamp, Christian; Shelden, Megan C.; Howitt, Susan; Udvardi, Michael K.

doi:10.1016/s0014-5793(00)01153-4

Cited by 118 publications

(51 citation statements)

References 28 publications

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“…Whether ammonium or ammonia is the actual substrate species transported by AmtB was not determined. A similar set of ammonium transport proteins was found in Rhodobacter sphaeroides, where an ammonium-specific uptake system together with a methylammonium\ammonium permease was found (Cordts & Gibson, 1987), and in Arabidopsis thaliana where AMT1 proteins transport (methyl)ammonium (Gazzarrini et al, 1999) whilst AtAMT2 is ammoniumspecific (Sohlenkamp et al, 2000). Furthermore, the kinetic results of ammonium uptake studies indicated the presence of an additional, low-affinity ammonium transport system in C. glutamicum.…”

Section: Discussionsupporting

confidence: 56%

Multiplicity of ammonium uptake systems in Corynebacterium glutamicum: role of Amt and AmtB

et al. 2001

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In Corynebacterium glutamicum, a Gram-positive soil bacterium widely used in the industrial production of amino acids, two genes encoding (putative) ammonium uptake carriers have been described. The isolation of amt was the first report of the sequence of a gene encoding a bacterial ammonium uptake system combined with the characterization of the corresponding protein.Recently, a second amt gene, amtB, with so far unknown function, was isolated. The isolation of this gene and the suggestion of a new concept for ammonium acquisition prompted the reinvestigation of ammonium transport in C. glutamicum. In this study it is shown that Amt mediates uptake of (methyl)ammonium into the cell with high affinity and strictly depending on the membrane potential. As shown by the determination of K m at different pH values, ammonium/methylammonium, but not ammonia/methylamine, are substrates of Amt. AmtB exclusively accepts ammonium as a transport substrate. In addition, hints of another, until now unknown, low-affinity, ammonium-specific uptake system were found.

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Section: Discussionsupporting

confidence: 56%

Multiplicity of ammonium uptake systems in Corynebacterium glutamicum: role of Amt and AmtB

et al. 2001

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“…In Arabidopsis there are 6 AMT genes, while rice (Oryza sativa) has 10, and more detailed sequence comparisons have identified two distinct groups within the AMT family, denoted AMT1 and AMT2 (Shelden et al, 2001;Sohlenkamp et al, 2000). Like the NO − 3 transporters, some AMT1-type genes are expressed in root hairs, suggesting that they have a role in uptake of NH + 4 from the soil (Lauter et al, 1996;Ludewig et al, 2002).…”

Section: Ammonium Transportersmentioning

confidence: 99%

Root Nitrogen Acquisition and Assimilation

2005

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Nitrogen (N) is the main mineral element in plant tissues and almost all of this nutrient is acquired from the soil by the roots. Nitrogen is available in many different forms in the soil, but the three most abundant forms are nitrate, ammonium and amino acids. The relative importance of these different soil N pools to a plant is difficult to measure and depends on many different environmental factors. Changes in the available amounts and imbalance in the supply of some N forms can even be toxic to plants and in extreme cases can lead to changes in the vegetation. However, the importance of this element for agriculture is reflected in the amounts of N-fertiliser applied to crops and this is a major cost (economic and environmental) for world agriculture. This review covers the molecular mechanisms that the plant uses for accessing these soil N pools and briefly includes consideration of the root N assimilatory pathways that exist in the plant. The soil forms of N that are used by plants depend on many factors, but a series of different transporter and assimilatory genes that can provide access to these pools have been identified. This information can now provide the molecular tools to identify the N sources accessed by a plant and the relative importance of these different pools.

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“…The experiment was repeated twice and representative results of one experiment are shown (average values ± interval of confidence calculated for a P value of 0.05). Different letters represent a significant difference of the means at P=0.05, according to Fisher's LSD test five members of AtAMT1 gene family and the AtAMT2 gene, all six coding for NH 4 + transporters (Ninneman et al 1994;Gazzarrini et al 1999;Sohlenkamp et al 2000;von Wiren et al 2000).…”

Section: Fig 5 A-d Effects Of Nomentioning

confidence: 99%

Nitrate-dependent control of root architecture and N nutrition are altered by a plant growth-promoting Phyllobacterium sp

Mantelin

Desbrosses

Larcher

et al. 2005

Planta

117

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Both root architecture and plant N nutrition are altered by inoculation with the plant growth-promoting rhizobacteria (PGPR) Phyllobacterium strain STM196. It is known that NO3- and N metabolites can act as regulatory signals on root development and N transporters. In this study, we investigate the possible interrelated effects on root development and N transport. We show that the inhibition of Arabidopsis lateral root growth by high external NO3- is overridden by Phyllobacterium inoculation. However, the leaf NO3- pool remained unchanged in inoculated plants. By contrast, the Gln root pool was reduced in inoculated plants. Unexpectedly, NO3- influx and the expression levels of AtNRT1.1 and AtNRT2.1 genes coding for root NO3- transporters were also decreased after 8 days of Phyllobacterium inoculation. Although the mechanisms by which PGPR exert their positive effects remain unknown, our data show that they can optimize plant development independently from N supply, thus alleviating the regulatory mechanisms that operate in axenic conditions. In addition, we found that Phyllobacterium sp. elicited a very strong induction of AtNRT2.5 and AtNRT2.6, both genes preferentially expressed in the shoots whose functions are unknown.

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Characterization of Arabidopsis AtAMT2, a novel ammonium transporter in plants

Cited by 118 publications

References 28 publications

Multiplicity of ammonium uptake systems in Corynebacterium glutamicum: role of Amt and AmtB

Multiplicity of ammonium uptake systems in Corynebacterium glutamicum: role of Amt and AmtB

Root Nitrogen Acquisition and Assimilation

Nitrate-dependent control of root architecture and N nutrition are altered by a plant growth-promoting Phyllobacterium sp

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