The phosphorylation of phosphatidylinositol (PI) to PI4P is the first committed step in the generation of phosphatidylinositol 4,5-bisphosphate (PIP2), a precursor of the second messenger inositol 1,4,5-trisphosphate (InsP3) (By similarity). Involved in the control of flowering under long day conditions by promoting degradation of FTIP1 (PubMed:28254780). Recruits FTIP1 for degradation by the 26S proteasome in leaves, which affects RFT1 transport to the shoot apical meristem (SAM) (PubMed:28254780). a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol) + ATP = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol 4-phosphate) + ADP + H(+) Interacts with FTIP1 and RPN10. Specifically expressed in the phloem including companion cells. Early flowering phenotype under long day conditions. Belongs to the PI3/PI4-kinase family. Type II PI4K subfamily.