Natural variation in ZmNAC087 contributes to total root length regulation in maize seedlings under salt stress

Soil salinity poses a significant challenge to crop growth and productivity, particularly affecting the root system, which is vital for water and nutrient uptake. To identify genetic factors that influence root elongation in stressful environments, we conducted a genome-wide association study (GWAS) to investigate the natural variation associated with total root length (TRL) under salt stress and normal conditions in maize seedlings. Our study identified 69 genetic variants associated with 38 candidate genes, among which a specific single nucleotide polymorphism (SNP) in ZmNAC087 was significantly associated with TRL under salt stress. Transient expression and transactivation assays revealed that ZmNAC087 encodes a nuclear-localized protein with transactivation activity. Further candidate gene association analysis showed that non-coding variations in ZmNAC087 promoter contribute to differential ZmNAC087 expression among maize inbred lines, potentially influencing the variation in salt-regulated TRL. In addition, through nucleotide diversity analysis, neutrality tests, and coalescent simulation, we demonstrated that ZmNAC087 underwent selection during maize domestication and improvement. These findings highlight the significance of natural variation in ZmNAC087, particularly the favorable allele, in maize salt tolerance, providing theoretical basis and valuable genetic resources for the development of salt-tolerant maize germplasm.