Identification and characterization of the NPF, NRT2 and NRT3 in spinach

Nitrate transporters (NRTs) participate in nitrate uptake, transport and allocation within the plant. However, this gene family has not been studied thoroughly in spinach. This study provided the general information about spinach SoNRTs and their transcriptional and functional responses to different levels of nitrate supplies. Resultes showed that fifty-seven NPF (also known as NRT1), nine NRT2 and one NRT3 were identified in spinach homologous to characterized Arabidopsis NRT genes. Phylogenetic analysis organized the SoNRT family into three clades: NPF with three subclades, NRT2, and NRT3. The tested SoNRT genes showed the various expression profiles in relation to tissue specificity and nitrate supply, indicating their functional diversity in response to external nitrate supply. Among them, transgenic Arabidopsis plants overexpressing SoNPF30 showed improved biomass, decreased shoot nitrate contents but no significant difference of (NO3-)-N-15 uptake rates when compared with those of the wild type in response to high N treatment. Under low N treatment, overexpressing of SoNRT3 significantly increased whole plant biomass, root nitrate contents and (NO3-)-N-15 uptake rates. These demonstrated that SoNPF30 and SoNRT3 confer greater capacity for nitrate translocation or nitrate uptake, and could help to improve the ability of plant nitrogen utilization under those conditions. Our findings provide a valuable basis for future research on this family of genes in spinach.

Automated summary

Nitrate transporters play crucial roles in nitrate uptake, transport, and allocation in plants. This study identified and characterized SoNRT gene family in spinach, showing their diverse responses to nitrate supplies. Overexpressing SoNPF30 and SoNRT3 in Arabidopsis plants demonstrated their potential roles in improving nitrate translocation or uptake, enhancing plant nitrogen utilization under different conditions. This research lays a foundation for further exploration of this gene family in spinach.