Overexpression of Maize ZmHDZIV14 Increases Abscisic Acid Sensitivity and Mediates Drought and Salt Stress in Arabidopsis and Tobacco

Abstract

Homeodomain-leucine zipper (HD-Zip) IV transcription factors are integral in the plant response to abiotic stressors. In maize, few HD-Zip IV proteins have yet been reported, and the functions are not well understood. In the current study, we isolated ZmHDZIV14 from the HD-Zip IV transcription factor family from maize and characterized its role in the stress response. We conducted a phylogenetic analysis showing that there was high homology and thus likely similar functions between ZmHDZIV14 and AtHDG11. Heterologous overexpression of ZmHDZIV14 in Arabidopsis caused increased sensitivity to abscisic acid (ABA), tolerance of salt and mannitol at germination stage, and drought tolerance of seedlings. ZmHDZIV14 transgenic Arabidopsis lines placed under drought stress additionally displayed lower levels of malondialdehyde, higher proline, and relative water content, compared to the wild-type. Further, modified tobacco plants (35S::ZmHDZIV14) responded to drought conditions with appropriate stomatal changes. After drought was relieved, expression of P5CS1, RD22, RD29B, RAB18, NCED3, and ERD1 were upregulated in transgenic Arabidopsis. It can be seen ZmHDZIV14 expression resulted in physiological and molecular changes in the transgenic lines, which improved overall drought tolerance. In summary, our results indicate that ZmHDZIV14 is a transcriptional regulator that modifies an ABA-dependent signaling pathway to regulate the drought response in plants.