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

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 isolatedZmHDZIV14from 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 betweenZmHDZIV14andAtHDG11. Heterologous overexpression ofZmHDZIV14inArabidopsiscaused increased sensitivity to abscisic acid (ABA), tolerance of salt and mannitol at germination stage, and drought tolerance of seedlings.ZmHDZIV14transgenicArabidopsislines 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 ofP5CS1,RD22,RD29B,RAB18,NCED3, andERD1were upregulated in transgenicArabidopsis. It can be seenZmHDZIV14expression resulted in physiological and molecular changes in the transgenic lines, which improved overall drought tolerance. In summary, our results indicate thatZmHDZIV14is a transcriptional regulator that modifies an ABA-dependent signaling pathway to regulate the drought response in plants.