The molecular basis of ammonium transporters in plants

The nitrogen uptake and transportation of NH4+ among different cells in plant tissues and organs are mediated by the ammonium transporters(AMTS).At the same time,the energy stored in the plasma membrane H+ gradient provides the power to drive NH4+ transport.In plant species,the ammonium transporters, each containing ten to eleven transmembrane domains,are located at the cytoplasm membrane.The molecular weight of AMT is about 48 kD.The ammonium transporters in plant species belong to a small gene family.The members in this family show different expression patterns at the transcription level.The differing affinities for NH4+ and responsiveness to nitrogen,and the varied patterns of expression among the plant ammonium transporters,suggesting that they perform different,but perhaps overlapping,physiological functions.Therefore,the regulation of the ammonium transporters at transcription and translation levels is important for plants maintaining suitable amount of nitrogen under variable NH4+ conditions and plays an important role to sustain a suitable nitrogen balance in plants under the nitrogen stress condition.