Cloning and Characterization of IbDREB1d and Its Role in Plant Growth Regulation in Sweet Potato

DREB (Dehydration-Responsive Element-Binding Protein) transcription factors are a subfamily of the AP2/ERF transcription factor family and play a crucial role in the regulation of plant responses to abiotic stress. In this study, we successfully cloned the IbDREB1d gene from the leafy sweet potato cultivar Fucaishu18. The open reading frame (ORF) of the IbDREB1d gene comprises 792 base pairs and encodes a protein consisting of 263 amino acids. Protein sequence analysis indicates that IbDREB1d is characterized by acidic, hydrophilic, and unstable properties, with its closest phylogenetic relationships to Ipomoea trifida and Ipomoea triloba. Quantitative real-time PCR (RT-qPCR) analysis revealed that IbDREB1d is expressed in the roots, stems, and leaves of sweet potato, with increased expression under low temperature, hydrogen peroxide (H₂O₂), and drought conditions. Overexpression of IbDREB1d in sweet potato resulted in transgenic plants exhibiting dwarfism, shortened internode lengths, smaller leaf size, and microscopic evidence of impaired vascular tissue development. Hormonal analysis indicated significant reductions in the levels of indole-3-acetic acid, indole-3-butyric acid, salicylic acid, and zeatin in these transgenic plants. These decreases may explain the observed phenotypic changes, such as inhibited growth and reduced leaf size. This study provides novel theoretical insights into the role of IbDREB1d in stress-responsive expression and modulating plant growth in sweet potato.