StNF-YC9 and StWRKY75 synergistically regulate StPAP10b -mediated root phosphatase activity to drive soil organic phosphorus mobilization in potato

Phosphate limitation represents a major constraint for crop production worldwide. Potato (Solanum tuberosum L.), a globally essential staple crop, is highly susceptible to low inorganic phosphate (LP) stress, yet the underlying molecular responses remain poorly understood. Here, we report that StPAP10b, a purple acid phosphatase gene, is strongly upregulated in roots under LP stress. Among 16 StPAPs analyzed, StPAP10b localizes to the cell wall and exhibits a broad substrate specificity, efficiently hydrolyzing organic phosphorus (Po) sources into bioavailable inorganic phosphorus (Pi). Functional studies confirm that the release of the StPAP10b protein into the rhizosphere enhances root acid phosphatases (APase) activity, facilitating Po utilization under LP. Furthermore, we identify a transcriptional regulatory module in which StWRKY75 directly activates StPAP10b expression by binding to its promoter. This regulation is potentiated by StNF-YC9, which interacts with StWRKY75 and synergistically amplifies StPAP10b transcription. Silencing StPAP10b in StWRKY75-overexpressing roots demonstrated that StWRKY75-mediated LP adaptation partially depends on StPAP10b. Together, these findings reveal the StNF-YC9-StWRKY75-StPAP10b axis as a key regulatory module that enhances extracellular APase activity and Po acquisition, providing strategic insights for improving phosphorus use efficiency in potato.