| Phosphorus plays an important role in plants’growth and development, but the phosphate in soil is often limited for plant uptake. Plants have developed a variety of strategies to enhance Pi acquisition and efficiency. AtPHRl and its homolog OsPHR2 in rice regulate the systemic phosphate (Pi) starvation signaling. Most of PSI (Pi starvation induced) genes are regulated by AtPHRl/OsPHR2. It has been reported that the Pi starvation can induce the sucrose accumulation and the increased sucrose can enhance the relative expression of PSI (Pi starvation induced) genes and influence the root morphology in Arabidopsis. However, whether the Pi starvation can induce sucrose accumulation therefore enhance Pi signaling in rice are still unknown.To determine whether the Pi starvation can induce sucrose accumulation for Pi signaling in rice, we measured the sucrose accumulation accumulation and determined the effects of exogenous sucrose treatment on Pi signaling in rice plants. To understand the possible molecular mechanism, we further determined the sucrose content and Pi signaling in the Osphr2 and Ossut2 mutants. Finally, to explore the possible molecular mechanism of Pi starvation induced sucrose accumulation and its effect on Pi signaling in rice, we determined the function of OsSPPl by analyzing its expression pattern and the performances of the Ossppl mutant under Pi starvationstress.The following results are obtained:1. Pi starvation can induce sucrose accumulation in rice shoot. The expression of PSI genes can be enhanced by exogenous sucrose application partially dependent on OsPHR2 under Pi starvation stress. Moreover, the Pi signaling might not be enhanced by the sucrose accumulated in vacuole.2. The OsSPPl encodes a sucrose phosphate phosphatase. The expression of OsSPPl was significantly induced by Pi starvation. This induction by Pi starvation was regulated by OsPHR2. OsSPPl is presented in leaves, and root and its abandance was enhance by Pi starvation. OsSPPl is localized to the cytoplasm.3. The Osppl mutant is a T-DNA insertional mutant. It showed that Pi starvation induced sucrose accumulation and expression of PSI genes in shoots were partially compromised in the Ossppl mutant. The Pi concentration in the Ossppl mutant was higher than that in WT. Moreover, the Pi starvation lead to an enhancement of root-shoot ratio in WT, while this enhancement was partially compromised in the Ossppl mutant.Together, we demonstrated that Pi sharvation can induce the expression of OsSPPl to enhance the sucrose accumulation, therefore modulate the Pi signaling in rice. |
