Cassava Nitrate Transporter NPF5.4 promotes both yield potential and salt tolerance in rice

Abstract Nitrogen is a major driving force for the improvement of crop yield worldwide, but brings detrimental effects on ecosystems, thus future agricultural sustainability demands enhanced nitrogen use efficiency (NUE). The nitrate transporter (NRT/NPF) family associated with nitrogen uptake and utilization is indispensable to the improvement of NUE in crops. Because cassava (Manihot esculenta) has high-affinity to absorb nitrate, the NUE of the NPF genes in cassava might be higher than other crops. Here we identified and systematically analyzed the NPF gene family in cassava, including phylogenetic relationship, chromosome location, gene duplication, and gene expression in response to different nitrogen supply. Gene expression analysis revealed that MeNPF5.4 and MeNPF6.2 were specifically expressed in stem, and have diverse expression in different nitrogen conditions. To well study the roles of these two genes, we constructed their overexpression (OE) lines in rice. A NO3− flux assay showed that MeNPF5.4 OE lines exhibited a significant NO3− influx, which suggests that they might have contributed to NUE improvement of rice. Notably, overexpressing MeNPF5.4 not only results in increased grain size and weight but also enhanced tolerance to salt. Compared with MeNPF5.4, MeNPF6.2 OE lines showed higher salt stress tolerance but had smaller grain size. Taken together, our results demonstrated that MeNPF5.4 can potentially improve the NUE and salt stress tolerance of rice, which reveals valuable breeding targets to improve crop yield and stress tolerance.