MsHDZ23, a Novel Miscanthus HD-ZIP Transcription Factor, Participates in Tolerance to Multiple Abiotic Stresses.

ABSTRACT

The homeodomain-leucine zipper (HD-ZIP) transcription factors, representing one of the largest plant-specific superfamilies, play important roles in the response to various abiotic stresses. However, the functional roles of HD-ZIPs in abiotic stress tolerance and the underlying mechanisms remain relatively limited in Miscanthus sinensis. In this study, we isolated an HD-ZIP TF gene, MsHDZ23, from Miscanthus and ectopically expressed it in Arabidopsis. Transcriptome and promoter analyses revealed that MsHDZ23 responded to salt, alkali, and drought treatments. The overexpression (OE) of MsHDZ23 in Arabidopsis conferred higher tolerance to salt and alkali stresses compared to wild-type (WT) plants. Moreover, MsHDZ23 was able to restore the hb7 mutant, the ortholog of MsHDZ23 in Arabidopsis, to the WT phenotype. Furthermore, MsHDZ23-OE lines exhibited significantly enhanced drought stress tolerance, as evidenced by higher survival rates and lower water loss rates compared to WT. The improved drought tolerance may be attributed to the significantly smaller stomatal aperture in MsHDZ23-OE lines compared to WT. Furthermore, the accumulation of the malondialdehyde (MDA) under abiotic stresses was significantly decreased, accompanied by dramatically enhanced activities in several antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in the transgenic plants. Collectively, these results demonstrate that MsHDZ23 functions as a multifunctional transcription factor in enhancing plant resistance to abiotic stresses.