AtAMT1 gene expression and NH4+ uptake in roots of Arabidopsis thaliana: evidence for regulation by root glutamine levels
Article first published online: 5 JAN 2002
The Plant Journal
Volume 19, Issue 2, pages 143–152, July 1999
How to Cite
Rawat, S. R., Silim, S. N., Kronzucker, H. J., Siddiqi, M. Y. and Glass, A. D. M. (1999), AtAMT1 gene expression and NH4+ uptake in roots of Arabidopsis thaliana: evidence for regulation by root glutamine levels. The Plant Journal, 19: 143–152. doi: 10.1046/j.1365-313X.1999.00505.x
- Issue published online: 5 JAN 2002
- Article first published online: 5 JAN 2002
- Received 16 March 1999; revised 17 May 1999; accepted 19 May 1999.
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.