Genome-wide identification and functional characterization of the ABF gene family in maize reveals ZmABF8 as a key regulator of drought tolerance

Abscisic acid (ABA) plays a pivotal role in plant adaptation to abiotic stresses, with ABA-responsive element binding factors (ABFs) serving as central regulators in ABA signaling pathways. Despite their importance, the ABF gene family in maize (Zea mays L.) remains poorly characterized. Here, we performed the first comprehensive genome-wide analysis of the maize ABF gene family, identifying 18 ZmABF members distributed across 9 chromosomes. Phylogenetic analysis classified these genes into four distinct subgroups, all containing conserved bZIP domains and predicted nuclear localization. Promoter analysis revealed abundant ABA-responsive cis-elements, particularly ABRE and ARE motifs, suggesting strong ABA-mediated regulation. Expression profiling demonstrated tissue-specific patterns, with predominant expression in roots and leaves, and significant upregulation under drought, cold, and heat stresses. Notably, protein-protein interaction analysis revealed that all ZmABFs interact with SnRK2 kinases, confirming their integration into the core ABA signaling network. Functional validation focused on ZmABF8, which showed the most pronounced induction under drought stress. Overexpression of ZmABF8 in maize significantly enhanced drought tolerance, as evidenced by improved seed germination, reduced seedling damage, and increased activities of antioxidant enzymes (POD and SOD) under water deficit conditions. These findings not only provide a systematic genomic resource for the maize ABF family but also identify ZmABF8 as a promising genetic target for developing drought-resistant maize varieties in the face of climate change.