title: A Sec14p-nodulin domain phosphatidylinositol transfer protein polarizes membrane growth of Arabidopsis thaliana root hairs.
abstract: Phosphatidylinositol (PtdIns) transfer proteins (PITPs) regulate signaling interfaces between lipid metabolism and membrane trafficking. Herein, we demonstrate that AtSfh1p, a member of a large and uncharacterized Arabidopsis thaliana Sec14p-nodulin domain family, is a PITP that regulates a specific stage in root hair development. AtSfh1p localizes along the root hair plasma membrane and is enriched in discrete plasma membrane domains and in the root hair tip cytoplasm. This localization pattern recapitulates that visualized for PtdIns(4,5)P2 in developing root hairs. Gene ablation experiments show AtSfh1p nullizygosity compromises polarized root hair expansion in a manner that coincides with loss of tip-directed PtdIns(4,5)P2, dispersal of secretory vesicles from the tip cytoplasm, loss of the tip f-actin network, and manifest disorganization of the root hair microtubule cytoskeleton. Derangement of tip-directed Ca2+ gradients is also apparent and results from isotropic influx of Ca2+ from the extracellular milieu. We propose AtSfh1p regulates intracellular and plasma membrane phosphoinositide polarity landmarks that focus membrane trafficking, Ca2+ signaling, and cytoskeleton functions to the growing root hair apex. We further suggest that Sec14p-nodulin domain proteins represent a family of regulators of polarized membrane growth in plants.
authors.affiliation: Department of Cell and Developmental Biology, Michael Hooker Microscopy Facility, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA. patrick_vincent@med.unc.edu
authors.forename: Patrick
authors.initials: P
authors.lastname: Vincent
authors.forename: Michael
authors.initials: M
authors.lastname: Chua
authors.forename: Fabien
authors.initials: F
authors.lastname: Nogue
authors.forename: Ashley
authors.initials: A
authors.lastname: Fairbrother
authors.forename: Hal
authors.initials: H
authors.lastname: Mekeel
authors.forename: Yue
authors.initials: Y
authors.lastname: Xu
authors.forename: Nina
authors.initials: N
authors.lastname: Allen
authors.forename: Tatiana N
authors.initials: TN
authors.lastname: Bibikova
authors.forename: Simon
authors.initials: S
authors.lastname: Gilroy
authors.forename: Vytas A
authors.initials: VA
authors.lastname: Bankaitis
mesh_terms: D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000254:growth & development*; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D003593:Cytoplasm / Q000648:ultrastructure; D003599:Cytoskeleton / Q000378:metabolism; D017930:Genes, Reporter; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D049294:Phospholipid Transfer Proteins / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development* / Q000648:ultrastructure; D017434:Protein Structure, Tertiary
chemical_list: D000199:Actins; D049294:Phospholipid Transfer Proteins; D002118:Calcium
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