The regulatory role of DELLA protein DkGAI1 in persimmon dwarfism

Persimmon (Diospyros kaki Thunb.) is an important fruit crop in East Asia with significant commercial potential. However, dwarfing cultivation in persimmon trees is rarely applied due to the lack of excellent dwarfing rootstocks and cultivars. 'Nantongxiaofangshi' (Diospyros kaki Linn.cv. Nantongxiaofangshi) is an excellent persimmon cultivar suitable for dwarfing cultivation due to its distinct dwarfing characteristics, but the underlying mechanism remains unclear. In this study, we further identified the DkGAI1 gene, which encodes a DELLA protein, as a candidate gene regulating dwarfing in 'Nantongxiaofangshi' persimmon. Transgenic D. lotus (Diospyros lotus L.) overexpressing DkGAI1 exhibited significant dwarfing and reduced levels of bioactive GAs. Biochemical analyses revealed that DkGAI1 interacts with DkMYB117. Moreover, DkGAI1 interferes with the DNA-binding activity of DkMYB117, thereby alleviating the repression of DkGA2ox2. The DkGAI1-DkMYB117-DkGA2ox2 module promotes gibberellin metabolism, ultimately contributing to the dwarfing of 'Nantongxiaofangshi'. Our findings elucidate the molecular basis of dwarfing in 'Nantongxiaofangshi' and provide valuable insights for the development of dwarf persimmon cultivars.