Overexpression of the nitrate transporter, OsNRT2.3b, improves rice phosphorus uptake and translocation.

KEY MESSAGE: Overexpression of OsNRT2.3b in rice can increase Pi uptake and accumulation through advanced root system, enhanced OsPT and OsPHR genes expression, and the phloem pH homeostasis. Nitrogen (N) and phosphorus (P) are two essential macronutrients for plants. Overexpression of the rice nitrate transporter, OsNRT2.3b, can improve rice grain yield and nitrogen use efficiency (NUE). Here, OsNRT2.3b overexpression resulted in increased grain yield, straw yield, and grain:straw ratio, accompanied by increased P concentrations in the leaf blade, leaf sheath, culm, and unfilled rice hulls. Overexpression of OsNRT2.3b significantly increased 33Pi uptake compared with WT under 300-μM Pi but not 10-μM Pi condition in 24 h. Moreover, the OsNRT2.3b-overexpressing rice lines showed increased root and shoot biomass, root:shoot ratio, total root length root surface area and N, P accumulation under 300- and 10-μM Pi supply in hydroponic solution. The levels of OsPT2, OsPT8, and OsPHR2 expression in roots and of OsPT1 and OsPHR2 in shoots were upregulated in OsNRT2.3b-overexpressing rice. These results indicated that OsNRT2.3b overexpression can improve rice P uptake and accumulation, partially through the advanced root system, enhanced gene expression, and the phloem pH regulation function.