High impact information on AMT1;1

• The cDNA AMT1 contains an open reading frame of 501 amino acids and encodes a highly hydrophobic protein with 9-12 putative membrane spanning regions [1].
• Transcript levels of AtAMT1;1, which possesses an affinity in the nanomolar range, steeply increased with ammonium uptake in roots when nitrogen nutrition became limiting, whereas those of AtAMT1;3 increased slightly, with AtAMT1;2 being more constitutively expressed [2].
• Functional analysis of an Arabidopsis T-DNA "knockout" of the high-affinity NH4(+) transporter AtAMT1;1 [3].
• Removal of N to increase AtAMT1;1 expression decreased high-affinity (13)NH(4)(+) influx in the mutant by 30% compared with wild-type plants, whereas low-affinity (13)NH(4)(+) influx (250 microM-10 mM NH(4)(+)) exceeded that of wild-type plants [3].
• This result demonstrates that end products of NH4+ assimilation, rather than NH4+ itself, are responsible for regulating AtAMT1 gene expression [4].

Biological context of AMT1;1

• Consistent with this hypothesis, AtAMT1 gene expression and NH4+ influx were suppressed by provision of Gln alone, or together with NH4NO3 plus MSX [4].
• High-affinity transport and AMT1.1 expression also appear to be subject to down-regulation by glutamine [5].

Anatomical context of AMT1;1

• Electrophysiological studies of Arabidopsis AtAMT1;1 expressed in oocytes revealed passive, Deltapsi-driven transport of NH(4)(+) through this protein [6].
• Expression of AtAMT1;1 in a novel yeast mutant defective in endogenous ammonium transport and vacuolar acidification supported the above mechanism for AtAMT1;1 and revealed a central role for acid vacuoles in storage and retention of ammonia in cells [6].
• AtAMT1;1 was plasma membrane localized and expressed in the root cortex and epidermis, including root hairs [7].

Associations of AMT1;1 with chemical compounds

• However, like AtAMT2 from Arabidopsis, and unlike AMT1 transporters from several plant species, LjAMT2;1 was unable to transport methylammonium [8].
• AtAMT1 gene expression and NH4+ uptake in roots of Arabidopsis thaliana: evidence for regulation by root glutamine levels [4].
• Nitrogen deficiency-dependent accumulation of AtAMT1;1 mRNA was also observed in 35S:AtAMT1;1-transformed Arabidopsis shoots but not in roots [9].

References