DoHY5/DoPIF5- DoPHT1 Module Mediates Red-Light Modulation of Phosphorus Homeostasis in Dendrobium officinale Kimura et Migo

Dendrobium officinale Kimura et Migo, a valuable medicinal orchid, thrives in mountainous environments, the specific habitat factors promoting polysaccharide accumulation in wild plants. This study explored how light regulates phosphorus uptake in D. officinale and how light and phosphorus interact to influence polysaccharide synthesis. We found that red light promoted phosphorus absorption and induced polysaccharide accumulation under low phosphorus. Transcriptomic analysis revealed the upregulated expression of phosphate transporters DoPHT1;2 and DoPHT1;6 under red light. Transcription factors DoHY5 and DoPIF5 directly bound to the promoters of DoPHT1 genes and regulated the transporter expression. Additionally, DoPHT1;2 and DoPHT1;6 localized to the cell membrane and functioned as high-affinity phosphate transporters. Overexpression of DoHY5 enhanced phosphorus uptake and DoPHT1 expression in both Arabidopsis thaliana and D. officinale, whereas DoPIF5 inhibited these processes. In conclusion, the DoHY5/DoPIF5-DoPHT1 module mediates the red-light regulation of phosphorus uptake, providing a theoretical foundation for improving the cultivation and quality of D. officinale.