Expression of ZmHDZ4 , a Maize Homeodomain-Leucine Zipper I Gene, Confers Tolerance to Drought Stress in Transgenic Rice

Climate change is predicted to be a major threat to crop yield due to increasing global temperatures and periods of unpredictable rainfall. Therefore, it is important to identify some new genes that can help plants cope with drought stress. In this study, a drought-induced homeodomain-leucine zipper (HD-Zip) I gene, ZmHDZ4 , was isolated from maize and characterized for its role in drought stress. Transient expression experiments showed that ZmHDZ4 is localized to the nucleus. Yeast one-hybrid assays demonstrated that ZmHDZ4 has trans-activation activity, and that the minimal activation domain was ZmHDZ4-1. We found that overexpression of ZmHDZ4 in rice can enhance tolerance to drought and increase sensitivity to abscisic acid (ABA). Compared to wild-type plants, ZmHDZ4 -expressing transgenic plants had lower relative electrolyte leakage (REL), lower malondialdehyde (MDA) levels, and increased proline contents under drought stress conditions, all of which may contribute to enhanced drought tolerance. Taken together, these results suggest that ZmHDZ4 functions as a transcriptional regulator that can positively affect plant drought tolerance. Thus, ZmHDZ4 is an excellent candidate gene with potential applications in molecular breeding to improve crop drought tolerance.