Involvement of plasma membrane H+-ATPase in the nitrate-nutrition uptake and utilization in indica rice

Utilization of nitrogen by crops is essential for sustainable agriculture. The transport of nitrate (NO₃⁻) across the plasma membrane is a critical gateway for N uptake and subsequent utilization. This process requires proton (H⁺) coupled cotransport, which is driven by proton motive force, provided by plasma membrane (PM) H⁺-ATPase. In this report, two indica rice varieties [Meixiangzhan 2 (MXZ) and Jifengyou 1002 (JFY)] in South China were selected and cultivated in hydroponic solution with 0.5 mM or 2.0 mM NO₃⁻ as the N source. The JFY exhibited stronger growth with higher biomass than MXZ under both 0.5 mM and 2.0 mM NO₃⁻. PM H⁺-ATPase activity of JFY roots was significantly higher than that of MXZ. The higher PM H⁺-ATPase activity in JFY was consistent with a higher abundance of PM H⁺-ATPase protein and higher transcription levels of OSAs, such as OSA2, OSA7 and OSA8 in roots, OSA3, OSA7 and OSA8 in leaves. The expression of nitrate transporters (OsNRT1;1b, OsNRT2.1, OsNRT2.2, and OsNAR2.1) were also higher in roots or shoots of JFY than those in MXZ. Under 0.5 mM and 2.0 mM NO₃⁻, the NO₃⁻ absorption and translocation rate, nitrate content, as well as nitrate reductase (NR) activity were all significantly higher in JFY, as compared to those in MXZ. Taken together, in JFY and MXZ, a higher level of PM H⁺-ATPase protein and higher activity coupled with greater efficiency in nitrate uptake, translocation and assimilation, suggesting the existence of a close correlation between PM H⁺-ATPase and nitrate utilization in indica rice. PM H⁺-ATPase may one of the elite genes that can contribute to nitrate use efficiency in rice.