Antagonistic regulation of nitrogen and drought signaling mediated by NIN-like protein 7 transcription factor in <i>Arabidopsis thaliana</i>.

Abstract

Plants face the constant challenge of reconciling antagonistic environmental signals, such as nutrient-driven growth and water deficit-induced stress responses. However, the molecular mechanisms that integrate these conflicting pathways remain poorly understood. Through a comprehensive transcriptomic meta-analysis in <i>Arabidopsis thaliana</i>, we show that nitrogen (N) supply and water deficit signaling exhibit overlapping and often opposing gene expression responses. Regulatory network modeling identifies the NIN-LIKE PROTEIN 7 (NLP7) transcription factor (TF) as a central integrator of these convergent transcriptional responses. Through combinatorial water deficit and N supply treatments in wild-type and <i>nlp7</i> mutant plants, we find that NLP7 accounts for 85% of the transcriptional interaction between these pathways. Chromatin immunoprecipitation and sequencing and a cell TF assay to detect TF regulation genome-wide reveal that NLP7 directly downregulate the expression of TFs such as <i>HB6</i>, <i>NAC6</i>, <i>NAP</i>, and <i>WRKY18</i>, which are central regulators of water deficit-mediated stress signaling. Repression of these secondary TFs has distinct downstream effects on gene expression, influencing shared and water deficit-specific responses. Loss of NLP7 enhances water deficit tolerance, characterized by increased water retention, reduced abscisic acid-mediated stomatal aperture, and altered expression of stress-responsive genes. These findings establish NLP7 as a central hub balancing growth and stress responses, providing insight into how plants integrate competing environmental cues.