Transcriptional regulation of <i>GmNAC3</i> -mediated drought stress tolerance in soybean

Drought stress is a major limiting factor that adversely affects both the yield and quality of soybean crops. Transcription factors (TFs) play a pivotal role in regulating gene expression, facilitating plant adaptation and response to various abiotic stresses. Among the 179 <i>NAC</i> TFs encoded in the soybean genome, several are differentially expressed under stress conditions; however, the functional role of <i>GmNAC3</i> in drought tolerance remains largely unknown. In this study, we cloned the 840 bp coding sequence of <i>GmNAC3</i> and developed transgenic soybean hairy roots via <i>Agrobacterium</i>-mediated transformation to explore its role in drought response. The physiological and molecular responses of <i>GmNAC3</i> overexpression (OE) chimeric soybean plants were assessed under polyethylene glycol (PEG)-simulated drought stress using Hoagland nutrient solution. Compared to empty vector (EV) controls, OE plants exhibited enhanced drought tolerance, including improved phenotypic traits, better root development, and stress resilience. Notably, OE plants showed a 23.9% reduction in hydrogen peroxide accumulation and a 31.25% decrease in superoxide anion levels. Biomass analysis on MS medium revealed significantly higher fresh and dry weights of OE hairy roots across different mannitol concentrations compared to EV roots. Furthermore, <i>GmNAC3</i> overexpression led to the upregulation of key downstream genes involved in stress response, particularly <i>GmLAC5</i> and <i>GmLAC7</i>. These findings suggest that <i>GmNAC3</i> enhances drought tolerance in soybean by regulating both physiological and molecular pathways. Overall, GmNAC3 represents a promising target for genetic engineering aimed at improving drought resistance in soybean and potentially other crops.