Functional study of ZmHDZ4 in maize (Zea mays) seedlings under drought stress

Maize is a major feed and industrial crop and pivotal for ensuring global food security. In light of global warming and climate change, improving maize tolerance to water deficit is crucial. Identification and functional analysis of drought tolerance genes have potential practical importance in understanding the molecular mechanisms of drought stress. Here, we identified a maize Homeodomain-Leucine Zipper I, ZmHDZ4, in maize seedlings that is associated with drought tolerance. We demonstrated that ZmHDZ4 has transcriptional activation activity, exclusively localized in the nucleus. Several Cis-acting elements associated with abiotic stress have been identified in the core promoter region of ZmHDZ4. Under drought-stressed conditions, transgenic maize plants overexpressing ZmHDZ4 exhibited significantly higher relative water content and peroxidase (POD) and superoxidase dismutase (SOD) activities compared to wide-type plants, while displaying lower malondialdehyde (MAD) content. The expressions of ZmMFS1-88, ZmGPM573, and ZmPHD9 were significantly repressed in the ZmHDZ4-OE plants under drought-stressed conditions, indicating that ZmMFS1-88, ZmGPM573, and ZmPHD9 were the candidate target genes of ZmHDZ4. ZmHDZ4 is involved in the regulation of drought stress tolerance in maize by participating in osmotic regulation, sugar metabolism pathways, and hormone regulation.