A Dirigent Gene, ZmDIR11, Positively Regulates Drought Tolerance in Maize

The DIR gene family, which encodes Dirigent proteins, plays a crucial role in plant development and stress responses. However, the functions and mechanisms of this family in maize remained underexplored. This study identified ZmDIR11, a member of the maize Dirigent protein family, and explored its role in drought tolerance. ZmDIR11 shared conserved regions with homologous proteins in wheat, rice, and Arabidopsis. RT-qPCR analysis revealed that ZmDIR11 expression is upregulated in leaves under drought and PEG stress, while subcellular localization confirmed its presence in the endoplasmic reticulum. Virus-induced gene silencing (VIGS) and EMS mutagenesis demonstrated that ZmDIR11 silencing or mutation significantly reduces drought tolerance in maize seedlings, indicating its positive regulatory role. Silencing or mutation of ZmDIR11 led to decreased growth parameters (plant height, root length, fresh weight, dry weight, and chlorophyll content) under drought stress, alongside a reduced antioxidant capacity, as evidenced by increased levels of MDA and ROS and decreased activities of SOD, CAT, and POD. Furthermore, ZmDIR11 mutation impaired the synthesis of ABA and zeatin, downregulating key genes in the ABA (ZmABA1, ZmNCED3, ZmSnRK2.6) and zeatin (ZmIPT4, ZmCKO5, ZmCKO4b) pathways. Drought-responsive genes (ZmRD20, ZmRD22, ZmDREB2A) and lignan biosynthesis genes (Zm4CL, ZmC3H, ZmCAD1) are also downregulated in ZmDIR11 mutants. In conclusion, ZmDIR11 enhances drought tolerance in maize by regulating antioxidant capacity, ABA and zeatin synthesis, and lignan metabolism. This study provides new insights into the role of DIR genes in drought tolerance and offers a potential genetic resource for breeding drought-resistant maize varieties.