The bHLH Transcription Factor DkLHW Is a Positive Regulator of Plant Height in Persimmon

Dwarfism is an important agronomic trait in perennial fruit trees, although its molecular regulatory mechanism in persimmon remains poorly understood. In this study, we identified a bHLH transcription factor, DkLHW, which functions as a positive regulator of plant height in persimmon. Yeast two-hybrid (Y2H), bimolecular fluorescence complementation (BiFC), and pull-down assays demonstrated that DkLHW interacts with DkMYB117. Electrophoretic mobility shift (EMSA) assays showed that DkLHW enhances the DNA-binding ability of DkMYB117 to the DkGA2ox2 promoter. Dual-luciferase reporter assays further demonstrated that this enhanced binding leads to stronger transcriptional repression of DkGA2ox2. Heterologous overexpression of DkLHW in tobacco resulted in increased plant height, longer internodes, and elevated levels of active GAs. Similarly, transient overexpression of DkLHW in persimmon leaves down-regulated DkGA2ox2 expression and increased active GA content. Expression analysis showed that DkLHW transcript levels were significantly lower in the dwarf cultivar 'Nantongxiaofangshi' (Diospyros kaki Linn.cv. Nantongxiaofangshi) compared with standard cultivars. These results indicate that DkLHW positively regulates persimmon plant height by forming a functional module with DkMYB117 to repress DkGA2ox2 expression and modulate gibberellin homeostasis. Our findings provide new insights into the transcriptional network controlling dwarfism in persimmon and identify DkLHW as a potential target for molecular breeding of plant architecture.