ZmCYB5-1, a cytochrome b5 Gene, negatively regulates drought stress tolerance in maize

Cytochrome b5 proteins (CYB5s), integral components of electron transport systems, are well-documented mediators in plant-specific fatty acid biogenesis and cuticular lipid deposition. However, the mechanisms through which CYB5 genes modulate drought stress responses in maize remain poorly understood. In this study, we identified a novel drought-responsive gene designated as ZmCYB5-1 and characterized its role in drought adaptation. The transcriptional profile of ZmCYB5-1 was found to be significant down-regulated by both drought stress and abscisic acid (ABA). Sequence analysis revealed that ZmCYB5-1 possesses the conserved cytochrome b5 domain characteristic of this protein family. Transient expression assays in tobacco epidermal cells confirmed that ZmCYB5-1 is predominantly localized in the cytoplasm and nucleus. Strikingly, transgenic maize plants overexpressing ZmCYB5-1 displayed markedly reduced drought tolerance compared to wild-type controls. Transcriptomic profiling under drought stress conditions demonstrated that the overexpression line exhibited significant downregulation of genes related to three key biological processes: ABA signal transduction pathways, stress response mechanisms, and photosynthetic apparatus. Collectively, our findings provide compelling evidence that ZmCYB5-1 acts as a negative regulator of drought stress responses in maize, highlighting its potential as a promising genetic engineering target for improving drought resistance through gene-editing approaches.