Reciprocal regulation between AtNRT2.1 and AtAMT1.1 expression and the kinetics of NH4+ and NO3− influxes

Abstract

b s t r a c tOur results show that AtNRT2.1 expression has a positive effect on the NH 4 + ion influx, mediated by the HATS, as also occurs with AtAMT1.1 expression on the NO 3 − ion influx. AtNRT2.1 expression plays a key role in the regulation of AtAMT1.1 expression and in the NH 4 + ion influx, differentiating the nitrogen source, and particularly, the lack of it. Nitrogen starvation produces a compensatory effect by AtAMT1.1 when there is an absence of the AtNRT2.1 gene. Our results also show that, in the atnrt2 mutant lacking both AtNRT2.1 and AtNRT2.2, gene functions present different kinetic parameters on the NH 4 + ion influx mediated by the HATS, according to the source and availability of nitrogen. Finally, the absence of AMT1.1 also produces changes in the kinetic parameters of the NO 3 − influx, showing different V max values depending on the source of nitrogen available.

Transcriptome and metabolite analysis identifies nitrogen utilization genes in tea plant (Camellia sinensis)

“…Our results are from two weeks adaptation to ammonium instead of less than hour in previous publication 15 . We proposed that this result could be caused by the reciprocal repression of NRT and AMT 12, 46 . The higher AMT expression in HJ indicated a stronger repression of NRT , leading to decreased NRT expression in the HJ roots (Table 3, Fig.…”

“…AMT expression is dependent on N signal in roots and spatial arrangement 10 while NRT expression is regulated by the N signal of the whole plant in Arabidopsis 11 . A reciprocal regulation between homologs of AMT or NRT and between AMT and NRT was reported 9, 11, 12 . Nitrate can enhance the uptake of ammonium while the latter will repress the uptake of nitrate in rice 13, 14 .…”

Disruption of the ammonium transporter AMT1.1 alters basal defenses generating resistance against Pseudomonas syringae and Plectosphaerella cucumerina

“…Although the ammonium supply may affect the plant responses to pathogens, to the best of our knowledge, no NH + 4 transporter is involved in the plant immune system. NRT2.1 and AMT1.1 are the primary high-affinity transport systems (HATS) involved in NO − 3 and NH + 4 uptake, respectively (Cerezo et al, 2001; Kaiser et al, 2002), and reciprocal regulation between AtNRT2.1 and AtAMT1.1 expression has been observed (Camañes et al, 2012a). High-affinity ammonium and nitrate transporters act as sensors of low NH + 4 and NO − 3 in the root environment; therefore, thus the gene expression of AMT1.1 and NRT2.1 is enhanced upon low fertilization.…”

A phospho-switch in the N-terminus of NRT2.1 affects nitrate uptake by controlling the interaction of NRT2.1 with NAR2.1

“…NRT2.1 here was found to be multiphosphorylated in the N- and C-terminus. At the same time, the regulatory pattern of NRT2.1 turned out to be very complex and under transcriptional and posttranscriptional control of external nitrate supply as well as the metabolic C/N status of the plant (Gansel et al, 2001; Wirth et al, 2007; Camanes et al, 2012; Li et al, 2016). Therefore, it is to no surprise at all to find highly complex regulatory mechanisms involving a yin-yang like phosphoswitch to control NRT2.1 activity at the protein level.…”

“…In contrast, NRT2.1 gene expression was up-regulated by light and sugars (Lejay et al, 1999; Lejay et al, 2003) and in general is well known to be affected by the C/N status of the plant (Girin et al, 2007; Krouk et al, 2010). Reciprocal regulation of NRT2.1 and ammonium transporters upon nitrate and ammonium influx was described (Gansel et al, 2001; Camanes et al, 2012).…”