Mutation of ZmDIR5 Reduces Maize Tolerance to Waterlogging, Salinity, and Drought

The <i>DIR</i> (Dirigent) gene family plays a multifaceted role in plant growth, development, and stress responses, making it one of the key gene families for plant adaptation to environmental changes. However, research on <i>ZmDIRs</i> in maize remains limited. In this study, we identified a member of the maize <i>DIR</i> gene family, <i>ZmDIR5</i>, whose promoter region contains numerous elements associated with responses to abiotic stresses. <i>ZmDIR5</i> is upregulated in response to waterlogging, salt, and drought stresses, and its protein is localized in the endoplasmic reticulum. Subsequent studies revealed that ZmDIR5-EMS (ethyl methane sulfonate) mutant lines exhibited reduced growth compared to WT (wild-type) plants under waterlogging, salt, and drought stress conditions. The mutant lines also demonstrated a relatively higher accumulation of malondialdehyde and reactive oxygen species, lower synthesis of proline and total lignans, and decreased antioxidant enzyme activity under these stress conditions. Additionally, the mutant lines displayed impaired sodium and potassium ion transport capabilities, reduced synthesis of abscisic acid and zeatin, and decreased expression of related genes. The mutation of <i>ZmDIR5</i> also inhibited the phenylpropanoid biosynthesis pathway in maize. These results indicate that <i>ZmDIR5</i> serves as a positive regulator of maize tolerance to waterlogging, salt, and drought stresses.