PagSND1-B1 Regulates Wood Formation by Influencing Phosphorus Absorption and Distribution in Poplar

In natural environments, the growth and development of trees are continuously affected by phosphorus (P) starvation stress. However, the mechanisms through which trees balance stem growth and P distribution remain unknown. This study found that in the woody model species poplar, the P loss in stems is more severe than that in roots and leaves under P starvation conditions, thereby inhibiting stem development and reducing the expression of numerous genes related to wood formation, including PagSND1-B1. Intriguingly, overexpression of PagSND1-B1 in poplar enhances resistance to P starvation and promotes xylem development. Further analysis demonstrated that PagSND1-B1 can directly and positively regulate the phosphorus transporter PagPHT1;5a. Analysis of P content changes in leaves, stems and roots of transgenic poplar before and after treatment indicated that overexpression of PagSND1-B1 disrupts the normal P redistribution procedure, leading to increased P accumulation in stems, which is beneficial for xylem development. Therefore, PagSND1-B1 participates in the phosphorus absorption and homoeostasis of poplar by modulating PagPHT1;5a. This study provides valuable insights into the regulatory function of PagSND1-B1 in wood formation and the process by which trees balance phosphorus distribution and xylem development.