The Maize WRKY Transcription Factor ZmWRKY4 Confers Lead Tolerance by Regulating ZmCAT1 Expression

Lead (Pb) severely impairs plant growth, yet the role of WRKY transcription factors in Pb tolerance in maize remains largely unknown. Here, we identified a Pb-responsive WRKY transcription factor, ZmWRKY4, whose transcript levels were rapidly and strongly induced in maize leaves following Pb exposure. Physiological and biochemical analyses showed that overexpression of ZmWRKY4 substantially enhanced Pb tolerance in maize. Transgenic lines exhibited significantly lower malondialdehyde (MDA) levels and reduced electrolyte leakage than wild-type plants. In addition, ZmWRKY4 overexpression increased catalase (CAT) activity and effectively limited H₂O₂ accumulation. Further analyses revealed that ZmWRKY4 positively regulates ZmCAT1, a key antioxidant gene involved in H₂O₂ scavenging, under Pb stress. Electrophoretic mobility shift assays and ChIP-qPCR collectively confirmed that ZmWRKY4 directly binds to W-box elements within the ZmCAT1 promoter in vivo and in vitro, thereby activating its transcription. Together, these findings define a previously uncharacterized ZmWRKY4-ZmCAT1 regulatory module that enhances antioxidant capacity and mitigates oxidative damage during Pb stress. This work provides new insights into the molecular mechanisms underlying heavy metal tolerance in maize and identifies a promising genetic target for developing Pb-resilient crop varieties.