Abstract
Phosphatidylinositol(4,5)-bisphosphate (PtdIns(4,5)P2) is synthesized by phosphatidylinositol4-phosphate5-kinase (PIP5K) and regulates activity and intracellular localization of various proteins. The PIP5K plays a pivotal role in phospholipid-mediated signal transduction with G-proteins and phospholipaseDs. In plant cell morphogenesis, involvements of low molecular weight G-protein(ROP1,2), phospholipaseDζ1(PLDζ1), and PtdIns(4,5)P2 to tip-growth of root-hair or pollen-tube have been reported. Thus, phospholipid-mediated signal transduction is believed to control plant cell tip-growth. However the molecular characteristics and physiological roles of PIP5Ks have not been elucidated well as far in plants. Previously we reported the involvement of AtPIP5K3 in root-hair elongation among eleven PIP5K genes in Arabidopsis. In this work, we revealed that AtPIP5K3 was preferentially localized to a growing root-hair tip region. Furthermore, we found that two or more root-hairs were generated from one root-hair cell overexpressing AtPIP5K3. These results suggest that AtPIP5K3 is involved in root-hair initiation as well as elongation by synthesizing PtdIns(4,5)P2 in the tip region.
