Nitrate-Inducible NIGT1 Proteins Modulate Phosphate Uptake and Starvation Signaling via Transcriptional Regulation of SPX Genes

The study revealed that nitrogen sources, particularly nitrate, played a crucial role in modulating phosphate starvation responses in plants. NIGT1 proteins, which are nitrate-inducible transcriptional repressors, were found to bind to and repress SPX gene promoters, affecting the phosphate starvation signaling network. This interaction influenced the activity of PHR1, a key regulator of phosphate responses. The research demonstrated that nitrate enhanced phosphate starvation responses, such as anthocyanin accumulation and root hair growth, which were diminished in the nigt1.1–nigt1.4 quadruple mutant. Overexpression of NIGT1 improved phosphate uptake even under phosphate-replete conditions. The study highlighted the NIGT1–SPX–PHR cascade as a mediator of nitrogen-responsive regulation of phosphate uptake, providing insights into the balanced acquisition of nitrogen and phosphorus in plants.