The Rice CK2 Kinase Regulates Trafficking of Phosphate Transporters in Response to Phosphate Levels

摘要

Phosphate transporters () mediate phosphorus uptake and are regulated at the transcriptional and posttranslational levels. In one key mechanism of posttranslational regulation, phosphorylation of affects their trafficking from the endoplasmic reticulum () to the plasma membrane. However, the kinase(s) mediating phosphorylation and the mechanism leading to retention of phosphorylated remain unclear. In this study, we identified a rice (Oryza sativa) kinase subunit, CK2β3, which interacts with PT2 and PT8 in a yeast two-hybrid screen. Also, the CK2α3/β3 holoenzyme phosphorylates PT8 under phosphate-sufficient conditions. This phosphorylation inhibited the interaction of PT8 with PHOSPHATE TRANSPORTER TRAFFIC FACILITATOR1, a key cofactor regulating the exit of from the to the plasma membrane. Additionally, phosphorus starvation promoted CK2β3 degradation, relieving the negative regulation of phosphorus-insufficient conditions. In accordance, transgenic expression of a nonphosphorylatable version of OsPT8 resulted in elevated levels of that protein at the plasma membrane and enhanced phosphorus accumulation and plant growth under various phosphorus regimes. Taken together, these results indicate that CK2α3/β3 negatively regulates and phosphorus status regulates CK2α3/β3.