Characterization of nitrite uptake in Arabidopsis thaliana: evidence for a nitrite‐specific transporter

Abstract

SummaryNitrite-specific plasma membrane transporters have been described in bacteria, algae and fungi, but there is no evidence of a nitrite-specific plasma membrane transporter in higher plants. We have used 13 NO À 2 to characterize nitrite influx into roots of Arabidopsis thaliana. Hydroponically grown Arabidopsis mutants, defective in high-affinity nitrate transport, were used to distinguish between nitrate and nitrite uptake by means of the short-lived tracers 13 NO À 2 and 13 NO À 3 . This approach allowed us to characterize a nitrite-specific transporter. The Atnar2.1-2 mutant, lacking a functional high-affinity nitrate transport system, is capable of nitrite influx that is constitutive and thermodynamically active. The corresponding fluxes conform to a rectangular hyperbola, exhibiting saturation at concentrations above 200 lM (K m = 185 lM and V max = 1.89 lmol g À1 FW h À1

Ectopic expression of a cyanobacterial flavodoxin in creeping bentgrass impacts plant development and confers broad abiotic stress tolerance

“…To investigate what caused the enhanced NUE in Fld transgenics, we examined the transcript levels of the genes encoding a high affinity nitrate transporter and the NiR, the key enzymes in N assimilation pathway. As shown in Figure c, the expression of the nitrite transporter (Kotur et al ., ) gene, AsNRT , was significantly up‐regulated in TG plants in comparison with WT controls. Further analysis revealed that there was no significant difference in AsNiR (KR911829) expression between TG and WT control plants (Figure d).…”

Nitrogen and sulfur assimilation in plants and algae

“…It is important to note that there are nitrite-specific transporters in the plasmalemma of both C. reinhardtii (Galván et al, 1996) and A. thaliana (Kotur et al, 2013), with half-saturation values of 3.5 mmol m −3 and 185 mmol m −3 respectively. Neither of these transporters seem to have been completely characterized genetically.…”

“…The most common forms of inorganic N utilized by photosynthetic organisms are combined N compounds, mostly NO 3 − and NH 4 + , occasionally as NO 2 − ; (Kotur et al, 2013). In oxygenated soils, NO 3 − (+V) is the main source of combined N for plants; in the ocean, the production based on nitrate is high in upwelling zones, but lower in the rest of the ocean, where most of the productivity involves recycled N (Falkowski and Raven, 2007;Raven et al, 1992a,b).…”

Fetal-maternal nitrite exchange in sheep: Experimental data, a computational model and an estimate of placental nitrite permeability

“…Other options include specific transport proteins in cell membranes that would transport nitrite ions and indeed there is evidence for accelerated flux across red cell membranes but findings differ with regard to the effectiveness of various blockers [38]. Specific nitrite transport proteins have been identified in bacteria [39, 40] and plant cells [41, 42] but in animal cells the mechanism of trans-membrane nitrite movement remains poorly understood [36]. Particularly in the multilayered placenta nothing appears to be known about nitrite transfer across the endothelial, syncytio- and cytotrophoblastic layers of the placental membrane.…”