AtAMT1 gene expression and NH4+ uptake in roots of Arabidopsis thaliana: evidence for regulation by root glutamine levels

Plant J. 1999 Jul;19(2):143-52. doi: 10.1046/j.1365-313x.1999.00505.x.


The mechanisms involved in regulating high-affinity ammonium (NH4+) uptake and the expression of the AtAMT1 gene encoding a putative high-affinity NH4+ transporter were investigated in the roots of Arabidopsis thaliana. Under conditions of steady-state nitrogen (N) supply, transcript levels of the AtAMT1 gene and Vmax values for high-affinity 13NH4+ influx were inversely correlated with levels of N provision. Following re-supply of NH4NO3 to N-starved plants, AtAMT1 mRNA levels and 13NH4+ influx declined rapidly but remained high when the conversion of NH4+ to glutamine (Gln) was blocked with methionine sulfoximine (MSX). This result demonstrates that end products of NH4+ assimilation, rather than NH4+ itself, are responsible for regulating AtAMT1 gene expression. Consistent with this hypothesis, AtAMT1 gene expression and NH4+ influx were suppressed by provision of Gln alone, or together with NH4NO3 plus MSX. Furthermore, AtAMT1 transcript levels and 13NH4+ influx were negatively correlated with root Gln concentrations, following re-supply of N to N-starved plants. In addition to this level of control, the data suggest that high cytoplasmic [NH4+] may inhibit NH4+ influx.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / drug effects
  • Arabidopsis / genetics*
  • Arabidopsis / metabolism
  • Biological Transport / drug effects
  • Carrier Proteins / genetics*
  • Cation Transport Proteins*
  • Cell Membrane / metabolism
  • Cytoplasm / metabolism
  • Gene Expression Regulation, Plant
  • Glutamine / metabolism
  • Nitrates / pharmacology
  • Plant Proteins*
  • Plant Roots / metabolism*
  • Quaternary Ammonium Compounds / metabolism
  • Quaternary Ammonium Compounds / pharmacokinetics*
  • RNA, Messenger / drug effects
  • RNA, Messenger / metabolism
  • Time Factors
  • Transcription, Genetic


  • Carrier Proteins
  • Cation Transport Proteins
  • Nitrates
  • Plant Proteins
  • Quaternary Ammonium Compounds
  • RNA, Messenger
  • ammonium transporters, plant
  • Glutamine
  • ammonium nitrate