Positive regulation of maize resistance to Bipolaris maydis by the cell death suppressor ZmDAD1

Defender Against Cell Death 1 (DAD1) is a conserved negative regulator of programmed cell death (PCD), with homologs widely present in plants that modulate immune-related cell death. However, the role and underlying mechanism of DAD1 in maize resistance to Bipolaris maydis, which causes southern corn leaf blight (SCLB) remain unclear. Here, the maize DAD1 gene was characterized, and its predicted amino acid sequence contains a conserved oligosaccharyltransferase (OST) subunit domain. Subcellular localization assays showed that ZmDAD1 primarily localizes to the endoplasmic reticulum (ER), aligning with the documented localization of its orthologs in other species and suggesting a conserved functional role. Gene expression analysis showed that ZmDAD1 is significantly induced following B. maydis infection, with its expression peaking at 12 h post-inoculation (hpi), supporting that ZmDAD1 is related to the early defense response. Further functional validation confirmed that the transient overexpression of ZmDAD1 effectively suppressed cell death in both Nicotiana benthamiana and maize protoplasts. Conversely, Silencing ZmDAD1 through virus-induced gene silencing (VIGS) compromised maize resistance to B. maydis, whereas its transient overexpression enhanced resistance. Protein-Protein interaction predictions suggested that ZmDAD1 may associate with multiple OST complex subunits and ER stress-related proteins. Transcriptome profiling further revealed that ZmDAD1 transient overexpression plants showed significant enrichment of differentially expressed genes involved in glutathione metabolism, glycosyltransferase activity, and cellulose synthase. Collectively, ZmDAD1 plays a crucial role in the maize-B. maydis interaction. It enhances plant immune defense responses by suppressing cell death, providing new insights into the molecular mechanisms underlying disease resistance in maize.