ZmLBD5 Increases Drought Sensitivity by Suppressing ROS Accumulation in Arabidopsis

Abstract

Drought stress is known to significantly limit crop growth and productivity. Lateral organ boundary domain (LBD) transcription factors-particularly class-I members-play essential roles in plant development and biotic stress. However, little information is available on class-II <i>LBD</i> genes related to abiotic stress in maize. Here, we cloned a maize class-II LBD transcription factor, <i>ZmLBD5,</i> and identified its function in drought stress. Transient expression, transactivation, and dimerization assays demonstrated that <i>ZmLBD5</i> was localized in the nucleus, without transactivation, and could form a homodimer or heterodimer. Promoter analysis demonstrated that multiple drought-stress-related and ABA response cis-acting elements are present in the promoter region of <i>ZmLBD5</i>. Overexpression of <i>ZmLBD5</i> in Arabidopsis promotes plant growth under normal conditions, and suppresses drought tolerance under drought conditions. Furthermore, the overexpression of <i>ZmLBD5</i> increased the water loss rate, stomatal number, and stomatal apertures. DAB and NBT staining demonstrated that the reactive oxygen species (ROS) decreased in <i>ZmLBD5</i>-overexpressed Arabidopsis. A physiological index assay also revealed that SOD and POD activities in <i>ZmLBD5</i>-overexpressed Arabidopsis were higher than those in wild-type Arabidopsis. These results revealed the role of <i>ZmLBD5</i> in drought stress by regulating ROS levels.