Genome‐wide identification of nitrate transporter 1/peptide transporter family (NPF) in cassava (Manihot esculenta) and functional analysis of MeNPF5.4 and MeNPF6.2 in response to nitrogen and salinity stresses in rice

Abstract

AbstractNitrogen is a major driving force for the improvement of crop yield worldwide but brings detrimental effects on ecosystems. Therefore, enhancing nitrogen use efficiency (NUE) is vital for sustainable agriculture. The nitrate transporter (NRT1/NPF) family associated with nitrogen uptake and utilization is indispensable to the improvement of NUE in crops. As an important food security crop, cassava (Manihot esculenta) produces an acceptable yield in nutrient‐deficient soil. 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 supplies. The stem is involved in nitrogen transportation and remobilization. Gene expression analysis revealed that MeNPF5.4 and MeNPF6.2 were specifically expressed in the stem, and have diverse expression in different nitrogen conditions. To facilitate the functional analysis of MeNPF5.4 and MeNPF6.2, we constructed their overexpression (OE) lines in rice. A NO3− flux assay showed that MeNPF5.4 and MeNPF6.2 OE lines exhibited a marked decrease in NO3− efflux and significant NO3− influx compared with WT, which suggests that they might have contributed to the NUE improvement of rice. Notably, overexpressing MeNPF5.4 showed increased grain size, grain number, and grain weight per panicle. More importantly, the MeNPF5.4 OE line contributed to salt tolerance. Nevertheless, an obvious reduction in grain number and grain weight per panicle was detected in the MeNPF6.2 OE line compared with WT. Strikingly, the MeNPF6.2 OE line showed higher salt stress tolerance than WT in LN conditions. 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.