OsBTBZ1 Regulates Nitrate Transport in Arabidopsis thaliana via NRT2.1 Modulation Under Salt Stress

Nitrogen availability and salinity are two major environmental factors affecting plant growth and development. Nitrate uptake is strictly regulated through transcriptional networks that balance nutrient assimilation and stress responses. The role of BTB-ZF transcription factors, which have been implicated in various abiotic stress responses, in coordinating nitrate uptake remains largely unknown; specifically, the precise molecular mechanisms through which OsBTBZ1, a BTB-ZF transcription factor from Oryza sativa, confers salt tolerance remain to be fully elucidated. Here, we characterize the function of OsBTBZ1 in Arabidopsis thaliana under nitrate and salt stress conditions. Transcriptomic analysis of the bt3 mutant and revertant lines expressing OsBTBZ1 in the bt3 mutant background indicated a relationship with NRT2.1, which encodes a high-affinity nitrate transporter. The bt3 mutant exhibited severe root growth inhibition under low nitrate and salt stress; however, expression of OsBTBZ1 restored root growth under combined stress, supporting a role for AtBT3 in stress adaptation. Our findings suggest that OsBTBZ1 may contribute to the coordination of nitrate-responsive pathways and root plasticity under stress, potentially through regulation of nitrate transport-related processes, including those associated with NRT2.1. These findings highlight the potential of OsBTBZ1-mediated regulatory mechanisms for improving nitrogen use efficiency and stress tolerance in future crops.