ZmHB53, a Maize Homeodomain‐Leucine Zipper I Transcription Factor Family Gene, Contributes to Abscisic Acid Sensitivity and Confers Seedling Drought Tolerance by Promoting the Activity of ZmPYL4.

Plant‐specific homeodomain‐leucine zipper I (HD‐Zip I) transcription factors (TFs) crucially regulate plant drought tolerance. However, their specific roles in maize (Zea mays L.) regulating drought tolerance remain largely unreported. Here, we screened a maize HD‐Zip I TF family gene, ZmHB53, and clarified its role in drought stress. ZmHB53 overexpression maize plants exhibited sensitivity to abscisic acid (ABA), tolerant to polyethylene glycol (PEG 6000)‐induced stress during germination, along with improved seedling drought resistance. Compared to the wild‐type, ZmHB53 overexpression lines show higher water retention, biomass, and survival rates, and reduced water loss and stomatal size under drought, suggesting ZmHB53′s role in drought adaptation. DNA affinity purification sequencing (DAP‐Seq), yeast one hybrid, electrophoretic mobility shift assay (EMSA), and dual luciferase showed that ZmHB53 directly bound to and upregulated the expression of ABA receptor ZmPYL4. Meanwhile, transgenic plants overexpressing ZmPYL4 also exhibit ABA sensitivity and drought tolerance. The research results provide novel insights into the regulatory role of ZmHB53 and ZmPYL4 in enhancing maize's drought tolerance, establishing a foundation for future validation and potential application of ZmHB53 in strategies to improve maize resistance to drought. Summary statement: The study highlights ZmHB53′s crucial role in maize drought resistance, likely involving ABA‐responsive elements in its promoter. ZmHB53 overexpression maize plants exhibited sensitivity to abscisic acid (ABA), tolerant to polyethylene glycol (PEG 6000)‐induced stress during germination, along with improved seedling drought resistance. These plants show higher water retention, biomass, and survival rates, and reduced water loss and stomatal size under drought, suggesting ZmHB53′s role in drought adaptation. Furthermore, DNA affinity purification sequencing (DAP‐Seq), yeast one hybrid, electrophoretic mobility shift assay (EMSA) and dual luciferase showed that ZmHB53 directly bound to and upregulated the expression of ABA receptor ZmPYL4. Most importantly, we obtained homozygous genetic materials of ZmPYL4 gene based on overexpression (OE) lines, And the functional analysis showed that overexpression of ZmHB53/ZmPYL4 significantly enhanced maize drought tolerance, primarily by promoting root elongation and facilitating stomatal closure, thus helping the plant better conserve water and maintain growth under drought conditions. Overall, this study uncovers the synergistic effect of ZmHB53 and ZmPYL4 in modulating drought tolerance in maize, offering a theoretical framework and practical guidance for future research dedicated to enhancing maize's drought resistance through this biological mechanism [ABSTRACT FROM AUTHOR]