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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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AtSfh1p function is essential for proper root hair development. (A) Genomic structure of AtSFH1. Sites of T-DNA insertion and the LBD coding regions are indicated. The Atsfh1::T-DNA allele harbors three T-DNA copies at the single site of insertion. (B) Root hair profiles of wild-type (top) and Atsfh1::T-DNA (bottom) plants. Corresponding profiles of 3-d-old seedlings (left) and adult plants (right) are shown. (C) ESEM of living 3-d-old wild-type (left) and Atsfh1::T-DNA (right) seedlings. Bars, 200 μm. (D) Frequencies of single, double, and triple root hairs in 3-d-old wild-type (black bars) and Atsfh1::T-DNA (gray bars) seedlings as determined by ESEM of 250 root hairs of each genotype (25 root hairs from each of 10 seedlings). Frequencies of each class of root hair morphology were determined for each individual seedling and the average frequencies and standard errors are given. (E) Nomarski images of wild-type (left) and Atsfh1::T-DNA (right) root epidermal cells initiating root hair growth. Vertical arrows identify cell plates. Horizontal arrows identify direction of primary root growth. Bars = 50 μm. (F) Root hair profiles of 3-d-old seedlings. (left) Atsfh1::T-DNA (*) and transgenic derivative bearing an ectopic wild-type gene (TgAtSFH1). (right) Transgenic Atsfh1::T-DNA seedling expressing an NH2-terminal (TgGFP-AtSFH1) gene fusion.
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fig4: AtSfh1p function is essential for proper root hair development. (A) Genomic structure of AtSFH1. Sites of T-DNA insertion and the LBD coding regions are indicated. The Atsfh1::T-DNA allele harbors three T-DNA copies at the single site of insertion. (B) Root hair profiles of wild-type (top) and Atsfh1::T-DNA (bottom) plants. Corresponding profiles of 3-d-old seedlings (left) and adult plants (right) are shown. (C) ESEM of living 3-d-old wild-type (left) and Atsfh1::T-DNA (right) seedlings. Bars, 200 μm. (D) Frequencies of single, double, and triple root hairs in 3-d-old wild-type (black bars) and Atsfh1::T-DNA (gray bars) seedlings as determined by ESEM of 250 root hairs of each genotype (25 root hairs from each of 10 seedlings). Frequencies of each class of root hair morphology were determined for each individual seedling and the average frequencies and standard errors are given. (E) Nomarski images of wild-type (left) and Atsfh1::T-DNA (right) root epidermal cells initiating root hair growth. Vertical arrows identify cell plates. Horizontal arrows identify direction of primary root growth. Bars = 50 μm. (F) Root hair profiles of 3-d-old seedlings. (left) Atsfh1::T-DNA (*) and transgenic derivative bearing an ectopic wild-type gene (TgAtSFH1). (right) Transgenic Atsfh1::T-DNA seedling expressing an NH2-terminal (TgGFP-AtSFH1) gene fusion.

Mentions: Atsfh1::T-DNA plants (Fig. 4 A) were substantially normal and fertile. However, mutant plants elaborated short root hairs. Mutant single root hairs from 3-d-old seedlings were one-third the length of age-matched wild-type structures (69 ± 13 vs. 224 ± 51 μm, n = 55) and exhibited half the surface area (3494 ± 902 vs. 6924 ± 1045 μm2, n = 55). Mutant and wild-type single root hairs exhibited similar volumes (14866 ± 5550 vs. 17113 ± 3510 μm3, n = 55), as did double root hairs (unpublished data). These disparities persisted throughout the lifetime of the plant (Fig. 4 B). In addition, Atsfh1::T-DNA root hairs appeared flaccid. This observation was in contrast to the rigid profiles exhibited by age-matched wild-type root hairs (Fig. 4 C). Although there is robust AtSFH1 expression in apical cells of the root cap, Atsfh1::T-DNA primary roots exhibit no defects in gravitropism (unpublished data).


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)

AtSfh1p function is essential for proper root hair development. (A) Genomic structure of AtSFH1. Sites of T-DNA insertion and the LBD coding regions are indicated. The Atsfh1::T-DNA allele harbors three T-DNA copies at the single site of insertion. (B) Root hair profiles of wild-type (top) and Atsfh1::T-DNA (bottom) plants. Corresponding profiles of 3-d-old seedlings (left) and adult plants (right) are shown. (C) ESEM of living 3-d-old wild-type (left) and Atsfh1::T-DNA (right) seedlings. Bars, 200 μm. (D) Frequencies of single, double, and triple root hairs in 3-d-old wild-type (black bars) and Atsfh1::T-DNA (gray bars) seedlings as determined by ESEM of 250 root hairs of each genotype (25 root hairs from each of 10 seedlings). Frequencies of each class of root hair morphology were determined for each individual seedling and the average frequencies and standard errors are given. (E) Nomarski images of wild-type (left) and Atsfh1::T-DNA (right) root epidermal cells initiating root hair growth. Vertical arrows identify cell plates. Horizontal arrows identify direction of primary root growth. Bars = 50 μm. (F) Root hair profiles of 3-d-old seedlings. (left) Atsfh1::T-DNA (*) and transgenic derivative bearing an ectopic wild-type gene (TgAtSFH1). (right) Transgenic Atsfh1::T-DNA seedling expressing an NH2-terminal (TgGFP-AtSFH1) gene fusion.
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Related In: Results  -  Collection

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fig4: AtSfh1p function is essential for proper root hair development. (A) Genomic structure of AtSFH1. Sites of T-DNA insertion and the LBD coding regions are indicated. The Atsfh1::T-DNA allele harbors three T-DNA copies at the single site of insertion. (B) Root hair profiles of wild-type (top) and Atsfh1::T-DNA (bottom) plants. Corresponding profiles of 3-d-old seedlings (left) and adult plants (right) are shown. (C) ESEM of living 3-d-old wild-type (left) and Atsfh1::T-DNA (right) seedlings. Bars, 200 μm. (D) Frequencies of single, double, and triple root hairs in 3-d-old wild-type (black bars) and Atsfh1::T-DNA (gray bars) seedlings as determined by ESEM of 250 root hairs of each genotype (25 root hairs from each of 10 seedlings). Frequencies of each class of root hair morphology were determined for each individual seedling and the average frequencies and standard errors are given. (E) Nomarski images of wild-type (left) and Atsfh1::T-DNA (right) root epidermal cells initiating root hair growth. Vertical arrows identify cell plates. Horizontal arrows identify direction of primary root growth. Bars = 50 μm. (F) Root hair profiles of 3-d-old seedlings. (left) Atsfh1::T-DNA (*) and transgenic derivative bearing an ectopic wild-type gene (TgAtSFH1). (right) Transgenic Atsfh1::T-DNA seedling expressing an NH2-terminal (TgGFP-AtSFH1) gene fusion.
Mentions: Atsfh1::T-DNA plants (Fig. 4 A) were substantially normal and fertile. However, mutant plants elaborated short root hairs. Mutant single root hairs from 3-d-old seedlings were one-third the length of age-matched wild-type structures (69 ± 13 vs. 224 ± 51 μm, n = 55) and exhibited half the surface area (3494 ± 902 vs. 6924 ± 1045 μm2, n = 55). Mutant and wild-type single root hairs exhibited similar volumes (14866 ± 5550 vs. 17113 ± 3510 μm3, n = 55), as did double root hairs (unpublished data). These disparities persisted throughout the lifetime of the plant (Fig. 4 B). In addition, Atsfh1::T-DNA root hairs appeared flaccid. This observation was in contrast to the rigid profiles exhibited by age-matched wild-type root hairs (Fig. 4 C). Although there is robust AtSFH1 expression in apical cells of the root cap, Atsfh1::T-DNA primary roots exhibit no defects in gravitropism (unpublished data).

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