The regulatory mechanism of the low-nitrogen-responsive MADS-box transcription factor <i>PpAGL24</i> in peach root system development and nitrogen utilization

Nitrogen critically regulates peach yield formation and fruit quality development through multifaceted physiological mechanisms. In peach production, the problems of large nitrogen input and low Nitrogen Use Efficiency (NUE) are more prominent. Therefore, mining key genes for efficient nitrogen utilization in peach is crucial for improving NUE and reducing nitrogen use. Integrated transcriptomic profiling of peach rootstock 'Shannong-1' under low-nitrogen (0.1 mM) treatment identified the MADS-box transcription factor <italic>PpAGL24</italic>. Functional characterization revealed that <italic>PpAGL24</italic> modulates root system architecture and coordinates nitrogen uptake-assimilation pathways, suggesting its pivotal role in enhancing NUE. <italic>PpAGL24</italic> expressed in peach roots and overexpressed in <italic>Arabidopsis thaliana</italic> both resulted in an increased number of lateral roots and higher nitrogen content. Transcriptome sequencing of <italic>PpAGL24</italic>-overexpressing peach roots revealed its putative regulatory network governing 'lateral root development', 'nitrate assimilation', and 'nitrogen metabolism', suggesting its hierarchical coordination in root developmental plasticity and nitrogen remodeling. Dual-luciferase and yeast one-hybrid assays showed that <italic>PpAGL24</italic> can activate the transcription of the nitrite reductase-encoding gene <italic>PpNiR1</italic>. This study reveals a new mechanism by which the MADS-box transcription factor <italic>PpAGL24</italic> regulates root growth and nitrogen assimilation in peach trees by modulating the <italic>PpNiR1</italic> gene, which provides theoretical support for the improvement of NUE and the reduction of nitrogen inputs in peach orchards.