Maize ZmEREB199 transcription factor negatively regulates plant salt tolerance

With the escalating soil salinization, salt stress has emerged as a critical constraint on plant growth and development, reducing crop productivity and impeding agricultural advancement. The AP2/EREBP transcription factors play a key role in regulating plant growth and abiotic stress responses. However, the role of DREB subclade within the AP2/EREBP superfamily in regulating salt stress response in maize remains largely elusive. In this study, the maize ZmEREB199 gene was cloned, and its expression profiles, sequence features, subcellular localization, transcriptional activation activity, and function in mediating salt stress tolerance were investigated. It was found that the ZmEREB199 gene is intronless, encodes a 230-amino-acid protein containing a single conserved AP2 domain, belongs to the DREB subfamily, localizes to the nucleus, and shows transcriptional activation activity. RT-qPCR analysis revealed that ZmEREB199 expression in maize was significantly upregulated under salt stress. Overexpression of ZmEREB199 significantly impaired salt tolerance in transgenic Arabidopsis and rice, as evidenced by marked reductions in root length, decreases in chlorophyll a, chlorophyll b, and total chlorophyll contents, lower relative water content (RWC), and superoxide dismutase (SOD) and peroxidase (POD) activities, accompanied by significant increases in relative electrical conductivity (REC), malondialdehyde (MDA) and H₂O₂ contents, as well as deeper NBT and DAB staining, under salt stress conditions. Integrated analyses of RNA-seq, RT-qPCR, and dual-luciferase (dual-LUC) reporter assays demonstrated that ZmEREB199 modulates salt stress tolerance by regulating the transcription of stress-responsive genes. This study provides insights into the function and regulatory mechanism of ZmEREB199 in mediating maize responses to salt stress.