Rice OsNAR2.1 interacts with OsNRT2.1, OsNRT2.2 and OsNRT2.3a nitrate transporters to provide uptake over high and low concentration ranges

Abstract

Plants take up both nitrate and ammonium as main nitrogen (N) sources. Although ammonium is the predominant form in anaerobic-flooded paddy soil, it has been proposed that rice and other wetland plants may take up significant amounts of nitrate formed by nitrification of ammonium in the rhizosphere. A two-component system for nitrate transport including NRT2s with a partner protein (NAR2 or NRT3.1) has been identified in Arabidopsis. We report the physiological function of another member of the NAR2 family, OsNAR2.1 in rice (Oryza sativa, ssp. Japonica, cv. Nipponbare). OsNAR2.1 was mainly expressed in roots and induced by nitrate and suppressed by ammonium and some amino acids. Knockdown of OsNAR2.1 by RNA interference synchronously suppressed expression of OsNRT2.1, OsNRT2.2 and OsNRT2.3a in the osnar2.1mutants. Both high-and low-affinity nitrate transports were greatly impaired by OsNAR2.1 knockdown. Yeast two hybridization showed that OsNAR2.1 not only interacted with OsNRT2.1/OsNRT2.2, but also with OsNRT2.3a. Taken together, the data demonstrate that OsNAR2.1 plays a key role in enabling the plant to cope with variable nitrate supply.

Overexpression of a pH-sensitive nitrate transporter in rice increases crop yields

“…Previous studies have shown a major difference between OsNRT2.3a and OsNRT2.3b, with OsNRT2.3a requiring a partner protein, OsNAR2.1, for functional nitrate transport (13)(14)(15). In contrast, OsNRT2.3b does not require the OsNAR2.1 partner protein for nitrate membrane transport (13).…”

“…1D and in the first 7 min of the recording in SI Appendix, Fig. S3A), indicating that nitrate/proton cotransport resulted in cytosolic acidification (14,16). The nitrate-elicited cytosolic acidification was reversed by washing the oocyte with pH 8 saline.…”

“…S1 A and B). OsNRT2.3a encodes a plasma membrane protein of 516 amino acids that functions in long-distance nitrate transport in the xylem from root to shoot (12,14), whereas OsNRT2.3b encodes a shorter 486-aa plasma membrane protein expressed moderately in the phloem of the shoot and faintly in the root (12) (SI Appendix, Fig. S1C).…”

LeNRT2.3 functions in nitrate acquisition and long‐distance transport in tomato

“…NAR2 may also be required in high-affinity nitrate transport regulated by LeNRT2.3. NAR2 is involved in high-affinity nitrate uptake as a partner with NRT2 to establish HATS activity in several plant species [20,[40][41][42][43][44]. HATS is reduced in nar2.1 mutant in Arabidopsis [45].…”

Isolation and characterization of the Chrysanthemum nitrate transporter CmNRT1

“…CHL1 homologous proteins in other plants, such as LeNrt1.1 of tomato, OsNRT1 of rice and BcNRT1 of Chinese cabbage, are also low-affinity transporters (Lauter et al, 1996;Lin et al, 2000;. Only low-affinity nitrate uptake activity was observed in OsNRT1-injected oocytes and BcNRT1 can restore chl1-5 nitrate uptake at 10 mM but not at 0.2 mM nitrate (Lin et al, 2000;Yan et al, 2011). Nitrate uptake in A. thaliana heterologously expressing CmNRT1 (Figure 3) showed that CmNRT1 has a similar function to OsNRT1 and BcNRT1.…”