ZmbHLH164, a Drought-Induced bHLH Transcription Factor from Maize, Confers Enhanced Drought Tolerance in Transgenic Tobacco and Modulates Abscisic Acid-Related Gene Expression

ZmbHLH164, a drought-induced nuclear bHLH transcription factor identified via transcriptomic screening in a drought-tolerant maize line, functions as a positive regulator of drought tolerance. Heterologous overexpression in tobacco elevated abscisic acid (ABA) levels, accelerated stomatal closure, reduced water loss, enhanced osmolyte accumulation, and suppressed reactive oxygen species and lipid peroxidation under drought. RNA-seq and qRT-PCR confirmed upregulation of ABA biosynthesis and signaling genes. Conversely, the <i>zmbhlh164</i> maize loss-of-function mutant displayed severe wilting, chlorosis, and physiological deterioration under water deficit. These integrated findings demonstrate that ZmbHLH164 enhances drought resilience primarily through ABA-mediated stomatal regulation and activation of antioxidant/osmotic adjustment pathways, establishing its value as a candidate gene for molecular breeding of drought-resilient crops.