Contribution of the ammonium transporter AMT1;1 to diurnallyregulated ammonium uptake in Arabidopsis roots

摘要

AMT-type ammonium transporters are suggested to represent the major entry pathways for root uptake of ammonium in plants. Ammonium influx into roots and AMTs transcript levels were shown to correlate along a diurnal cycle and under different nitrogen(N) regimes. To investigate the contribution of AMT1;1 to diurnally-regulated ammonium uptake in Arabidopsis roots, ~(15)N-labeled ammonium influx studies were conducted along a diurnal cycle in the T-DNA insertion line amtl;1-1 that no longer expressedAMT1;1. High-affinity ammonium influx in amtl;1-1 roots did not differ significantly from its corresponding wild-type. However, a significant difference in ammonium influx was observed between the T-DNA insertion line amtl;3-1 defective in AMT1;3 expression and a double insertion line (dko) generated by the cross between amtl;1-1 and amtl;3-1. In the absence of AMT1;3 ammonium influx mediated by AMT1;1 followed a diurnal rhythm. These data suggest that AMT1;1 contributes to diurnally-regulated ammoniumuptake in Arabidopsis roots in dependence of AMT1;3.