The Arabidopsis Phosphatidylinositol Phosphate 5-Kinase PIP5K3 is a key regulator of root hair tip growth.
Phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] functions as a site-specific signal on membranes to promote cytoskeletal reorganization and membrane trafficking. Localization of PtdIns(4,5)P2 to apices of growing root hairs and pollen tubes suggests that it plays an important role in tip growth. However, its regulation and mode of action remain unclear. We found that Arabidopsis thaliana PIP5K3 (for Phosphatidylinositol Phosphate 5-Kinase 3) encodes a phosphatidylinositol 4-phosphate 5-kinase, a key enzyme producing PtdIns(4,5)P2, that is preferentially expressed in growing root hairs. T-DNA insertion mutations that substantially reduced the expression of PIP5K3 caused significantly shorter root hairs than in the wild type. By contrast, overexpression caused longer root hairs and multiple protruding sites on a single trichoblast. A yellow fluorescent protein (YFP) fusion of PIP5K3, driven by the PIP5K3 promoter, complemented the short-root-hair phenotype. PIP5K3-YFP localized to the plasma membrane and cytoplasmic space of elongating root hair apices, to growing root hair bulges, and, notably, to sites about to form root hair bulges. The signal was greatest in rapidly growing root hairs and quickly disappeared when elongation ceased. These results provide evidence that PIP5K3 is involved in localizing PtdIns(4,5)P2 to the elongating root hair apex and is a key regulator of the machinery that initiates and promotes root hair tip growth.
Kusano
Hiroaki
H
Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
Testerink
Christa
C
Vermeer
Joop E M
JE
Tsuge
Tomohiko
T
Shimada
Hiroaki
H
Oka
Atsuhiro
A
Munnik
Teun
T
Aoyama
Takashi
T
D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D030821:Plants, Genetically Modified; D020133:Reverse Transcriptase Polymerase Chain Reaction
D029681:Arabidopsis Proteins; D017853:Phosphotransferases (Alcohol Group Acceptor); C020077:1-phosphatidylinositol-4-phosphate 5-kinase