Transcriptional regulation of GmNAC3-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 NAC TFs encoded in the soybean genome, several are differentially expressed under stress conditions; however, the functional role of GmNAC3 in drought tolerance remains largely unknown. In this study, we cloned the 840 bp coding sequence of GmNAC3 and developed transgenic soybean hairy roots via Agrobacterium-mediated transformation to explore its role in drought response. The physiological and molecular responses of GmNAC3 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, GmNAC3 overexpression led to the upregulation of key downstream genes involved in stress response, particularly GmLAC5 and GmLAC7. These findings suggest that GmNAC3 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.