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A Sec14p-nodulin domain phosphatidylinositol transfer protein polarizes membrane growth of Arabidopsis thaliana root hairs.

Vincent P, Chua M, Nogue F, Fairbrother A, Mekeel H, Xu Y, Allen N, Bibikova TN, Gilroy S, Bankaitis VA - J. Cell Biol. (2005)

Bottom Line: 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.

View Article: PubMed Central - PubMed

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

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 izygosity 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.

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F-actin imaging in root hairs. (A) The peripheral actin cables are revealed by talin-GFP imaging as is the fine tip-directed f-actin network (arrow). F-actin imaging in mutant single (B) and double (C) root hairs. Arrows indicate compromise of the fine tip-directed f-actin network. Bars, 20 μm.
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fig6: F-actin imaging in root hairs. (A) The peripheral actin cables are revealed by talin-GFP imaging as is the fine tip-directed f-actin network (arrow). F-actin imaging in mutant single (B) and double (C) root hairs. Arrows indicate compromise of the fine tip-directed f-actin network. Bars, 20 μm.

Mentions: Vacuolation of Atsfh1::T-DNA root hair tip cytoplasm recapitulated the effects recorded in root hairs where the actin cytoskeleton was disrupted (Čiamporová et al., 2003). To assess f-actin status in Atsfh1::T-DNA root hairs, we used GFP-talin as a reporter for f-actin. These imaging experiments indicated that wild-type root hairs exhibit a discrete cortical actin meshwork and a tip-concentrated f-actin microfilament network in the VRZ (Fig. 6 A and Video 5, available at http://www.jcb.org/cgi/content/full/jcb.200412074/DC1), as described previously (Baluška et al., 2000; Smith, 2003). However, selective defects in the f-actin cytoskeleton were apparent in mutant root hairs. Although the cortical actin cytoskeleton of mutant root hairs remained intact, the tip-directed f-actin microfilament component was lost (Fig. 6, B and C; and Videos 6 and 7, available at http://www.jcb.org/cgi/content/full/jcb.200412074/DC1). As tip f-actin microfilament networks focus transport vesicle delivery to the hair apex (Mathur and Hülskamp, 2002; Ketelaar et al., 2003), defects in this actin network are expected to result in dispersal of transport vesicles throughout the root hair cytoplasm. Indeed, loss of the f-actin microfilament network in Atsfh1::T-DNA root hairs coincides with loss of PHPLCδ1–YFP fluorescence in the tip cytoplasm.


A Sec14p-nodulin domain phosphatidylinositol transfer protein polarizes membrane growth of Arabidopsis thaliana root hairs.

Vincent P, Chua M, Nogue F, Fairbrother A, Mekeel H, Xu Y, Allen N, Bibikova TN, Gilroy S, Bankaitis VA - J. Cell Biol. (2005)

F-actin imaging in root hairs. (A) The peripheral actin cables are revealed by talin-GFP imaging as is the fine tip-directed f-actin network (arrow). F-actin imaging in mutant single (B) and double (C) root hairs. Arrows indicate compromise of the fine tip-directed f-actin network. Bars, 20 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171805&req=5

fig6: F-actin imaging in root hairs. (A) The peripheral actin cables are revealed by talin-GFP imaging as is the fine tip-directed f-actin network (arrow). F-actin imaging in mutant single (B) and double (C) root hairs. Arrows indicate compromise of the fine tip-directed f-actin network. Bars, 20 μm.
Mentions: Vacuolation of Atsfh1::T-DNA root hair tip cytoplasm recapitulated the effects recorded in root hairs where the actin cytoskeleton was disrupted (Čiamporová et al., 2003). To assess f-actin status in Atsfh1::T-DNA root hairs, we used GFP-talin as a reporter for f-actin. These imaging experiments indicated that wild-type root hairs exhibit a discrete cortical actin meshwork and a tip-concentrated f-actin microfilament network in the VRZ (Fig. 6 A and Video 5, available at http://www.jcb.org/cgi/content/full/jcb.200412074/DC1), as described previously (Baluška et al., 2000; Smith, 2003). However, selective defects in the f-actin cytoskeleton were apparent in mutant root hairs. Although the cortical actin cytoskeleton of mutant root hairs remained intact, the tip-directed f-actin microfilament component was lost (Fig. 6, B and C; and Videos 6 and 7, available at http://www.jcb.org/cgi/content/full/jcb.200412074/DC1). As tip f-actin microfilament networks focus transport vesicle delivery to the hair apex (Mathur and Hülskamp, 2002; Ketelaar et al., 2003), defects in this actin network are expected to result in dispersal of transport vesicles throughout the root hair cytoplasm. Indeed, loss of the f-actin microfilament network in Atsfh1::T-DNA root hairs coincides with loss of PHPLCδ1–YFP fluorescence in the tip cytoplasm.

Bottom Line: 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.

View Article: PubMed Central - PubMed

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

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 izygosity 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.

Show MeSH
Related in: MedlinePlus