ZmEXPB7, a β-expansin gene, contributes to drought tolerance in Arabidopsis

Drought stress poses a significant threat to maize productivity, highlighting the need to elucidate molecular mechanisms underlying drought tolerance. Previous studies identified <i>ZmLBD33</i> as a regulator of drought stress responses that interacts with the cell wall-loosening gene <i>ZmEXPB7</i>. To elucidate the function of <i>ZmEXPB7</i> in drought tolerance, we conducted heterologous expression studies in Arabidopsis. The results demonstrated that <i>ZmEXPB7</i> expression was rapidly induced under PEG₆₀₀₀-simulated stress, reaching peak levels within 1 h. Overexpression of <i>ZmEXPB7</i> in Arabidopsis significantly enhanced drought tolerance, improved root growth, and increased survival rates under osmotic and soil drought conditions. Transgenic plants exhibited reduced water loss, decreased stomatal density, and enhanced stomatal closure. DAB and NBT staining demonstrated that the ROS accumulated in <i>ZmEXPB7</i>-overexpressed Arabidopsis. A physiological index assay also revealed that SOD and POD activities in <i>ZmEXPB7</i>-overexpressed Arabidopsis were lower than those in wild-type Arabidopsis. These findings indicate that <i>ZmEXPB7</i> positively regulates drought tolerance by modulating stomatal aperture and H₂O₂ signaling. This study highlights the crucial role of expansin genes in stress adaptation and positions <i>ZmEXPB7</i> as a potential target for engineering drought-resilient crops.