Arabidopsis Trichome Morphogenesis and the Role of Microtubules in Controlling Trichome Branch Formation

N-methyl-d-aspartate receptors (NMDARs) are known to regulate axonal refinement and dendritic branching. However, because NMDARs are abundantly present as tri-heteromers (e.g., NR1/NR2A/NR2B) during development, the precise role of the individual subunits NR2A and NR2B in these processes has not been elucidated. Ventral spinal cord neurons (VSCNs) provide a unique opportunity to address this problem, because the expression of both NR2A and NR2B (but not NR1) is downregulated in culture. Exogenous NR2A or NR2B were introduced into these naturally NR2-null neurons at 4 DIV, and electrophysiological recordings at 11 DIV confirmed that synaptic NR1NR2A receptors and NR1NR2B receptors were formed, respectively. Analysis of the dendritic architecture showed that introduction of NR2B, but not NR2A, dramatically increased the number of secondary and tertiary dendritic branches of VSCNs. Whole cell patch-clamp recordings further indicated that the newly formed branches in NR2B-expressing neurons were able to establish functional synapses because the frequency of miniature AMPA-receptor synaptic currents was increased. Using previously described mutants, we also found that disruption of the interaction between NR2B and RasGRF1 dramatically impaired dendritic branch formation in VSCNs. The differential role of the NR2A and NR2B subunits and the requirement for RasGRF1 in regulating branch formation was corroborated in hippocampal cultures. We conclude that the association between NR1NR2B-receptors and RasGRF1 is needed for dendritic branch formation in VSCNs and hippocampal neurons in vitro. The dominated NR2A expression and the limited interactions of this subunit with the signaling protein RasGRF1 may contribute to the restricted dendritic arbor development in the adult CNS.

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Revisiting the Growth Mechanism of Hierarchical Semiconductor Nanostructures: The Role of Secondary Nucleation in Branch Formation

The Journal of Physical Chemistry Letters ◽

10.1021/acs.jpclett.9b02110 ◽

2019 ◽

Vol 10 (21) ◽

pp. 6827-6834 ◽

Cited By ~ 8

Author(s):

Lili Liu ◽

Maria L. Sushko ◽

Edgar C. Buck ◽

Xin Zhang ◽

Libor Kovarik ◽

...

Keyword(s):

Growth Mechanism ◽

Semiconductor Nanostructures ◽

Secondary Nucleation ◽

Branch Formation

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Faculty Opinions recommendation of Pivotal role of VASP in Arp2/3 complex-mediated actin nucleation, actin branch-formation, and Listeria monocytogenes motility.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1000640.13709 ◽

2001 ◽

Author(s):

Pascale Cossart

Keyword(s):

Listeria Monocytogenes ◽

Pivotal Role ◽

Actin Nucleation ◽

Branch Formation

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Arp2/3 Complex and Actin Depolymerizing Factor/Cofilin in Dendritic Organization and Treadmilling of Actin Filament Array in Lamellipodia

The Journal of Cell Biology ◽

10.1083/jcb.145.5.1009 ◽

1999 ◽

Vol 145 (5) ◽

pp. 1009-1026 ◽

Cited By ~ 781

Author(s):

Tatyana M. Svitkina ◽

Gary G. Borisy

Keyword(s):

Actin Filaments ◽

Leading Edge ◽

Actin Network ◽

Actin Depolymerizing Factor ◽

Nucleation Model ◽

Branch Formation ◽

Cell Front ◽

Dendritic Organization ◽

Pointed End

The leading edge (∼1 μm) of lamellipodia in Xenopus laevis keratocytes and fibroblasts was shown to have an extensively branched organization of actin filaments, which we term the dendritic brush. Pointed ends of individual filaments were located at Y-junctions, where the Arp2/3 complex was also localized, suggesting a role of the Arp2/3 complex in branch formation. Differential depolymerization experiments suggested that the Arp2/3 complex also provided protection of pointed ends from depolymerization. Actin depolymerizing factor (ADF)/cofilin was excluded from the distal 0.4 μm of the lamellipodial network of keratocytes and in fibroblasts it was located within the depolymerization-resistant zone. These results suggest that ADF/cofilin, per se, is not sufficient for actin brush depolymerization and a regulatory step is required. Our evidence supports a dendritic nucleation model (Mullins, R.D., J.A. Heuser, and T.D. Pollard. 1998. Proc. Natl. Acad. Sci. USA. 95:6181–6186) for lamellipodial protrusion, which involves treadmilling of a branched actin array instead of treadmilling of individual filaments. In this model, Arp2/3 complex and ADF/cofilin have antagonistic activities. Arp2/3 complex is responsible for integration of nascent actin filaments into the actin network at the cell front and stabilizing pointed ends from depolymerization, while ADF/cofilin promotes filament disassembly at the rear of the brush, presumably by pointed end depolymerization after dissociation of the Arp2/3 complex.

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Regulation of Cell Polarity by Microtubules in Fission Yeast

The Journal of Cell Biology ◽

10.1083/jcb.142.2.457 ◽

1998 ◽

Vol 142 (2) ◽

pp. 457-471 ◽

Cited By ~ 106

Author(s):

Kenneth E. Sawin ◽

Paul Nurse

Keyword(s):

Cell Cycle ◽

Fission Yeast ◽

Cell Polarity ◽

High Frequency ◽

Fluorescent Protein ◽

Physiological Importance ◽

Normal Transition ◽

Branch Formation ◽

Green Fluorescent

To investigate the role of microtubules in regulating cell polarity in Schizosaccharomyces pombe, we have developed a system in which normally cylindrical fission yeast synchronously form branched cells at high frequency upon treatment with the microtubule-depolymerizing drug thiabendazole (TBZ). Branching depends on both elevated temperature and cell cycle state and occurs at high frequency only when TBZ is added to cells that have not yet passed through New-End Take-Off (NETO), the normal transition from monopolar to bipolar growth. This suggests that microtubules may be of greatest physiological importance for the maintenance of cell shape at specific points in the cell cycle. The localization of three different proteins normally found at cell ends—cortical F-actin, tea1, and an ral3 (scd2)–green fluorescent protein (GFP) fusion—is disrupted by TBZ treatment. However, these proteins can eventually return to cell ends in the absence of microtubules, indicating that although their localization to ends normally depends on microtubules, they may recover by alternative mechanisms. In addition, TBZ induces a shift in ral3–GFP distribution from cell ends to the cell middle, suggesting that a protein complex containing ral3 may be part of the cue that specifies the position of branch formation.

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Pivotal role of VASP in Arp2/3 complex–mediated actin nucleation, actin branch-formation, and Listeria monocytogenes motility

The Journal of Cell Biology ◽

10.1083/jcb.200106061 ◽

2001 ◽

Vol 155 (1) ◽

pp. 89-100 ◽

Cited By ~ 90

Author(s):

Justin Skoble ◽

Victoria Auerbuch ◽

Erin D. Goley ◽

Matthew D. Welch ◽

Daniel A. Portnoy

Keyword(s):

Listeria Monocytogenes ◽

Actin Filament ◽

Actin Filaments ◽

Actin Monomer ◽

Wild Type ◽

Binding Region ◽

Actin Nucleation ◽

Branch Formation

The Listeria monocytogenes ActA protein mediates actin-based motility by recruiting and stimulating the Arp2/3 complex. In vitro, the actin monomer-binding region of ActA is critical for stimulating Arp2/3-dependent actin nucleation; however, this region is dispensable for actin-based motility in cells. Here, we provide genetic and biochemical evidence that vasodilator-stimulated phosphoprotein (VASP) recruitment by ActA can bypass defects in actin monomer-binding. Furthermore, purified VASP enhances the actin-nucleating activity of wild-type ActA and the Arp2/3 complex while also reducing the frequency of actin branch formation. These data suggest that ActA stimulates the Arp2/3 complex by both VASP-dependent and -independent mechanisms that generate distinct populations of actin filaments in the comet tails of L. monocytogenes. The ability of VASP to contribute to actin filament nucleation and to regulate actin filament architecture highlights the central role of VASP in actin-based motility.

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Overexpression of The AtWUSCHEL Gene Promotes Somatic Embryogenesis And Lateral Branch Formation In Birch (Betula Platyphylla Suk.)

10.21203/rs.3.rs-1033825/v1 ◽

2021 ◽

Author(s):

Hu Lou ◽

Weizhi Wang ◽

Linlin Yang ◽

Zhiyong Cai ◽

Huiying Cai ◽

...

Keyword(s):

Somatic Embryogenesis ◽

Stem Cell ◽

Deciduous Tree ◽

Stem Cell Population ◽

Betula Platyphylla ◽

Limiting Step ◽

Branch Formation ◽

Betula Platyphylla Suk ◽

Lateral Branches

Abstract Birch (Betula platyphylla Suk.) is a deciduous tree with the value of medicinal and ornamental greening. Plant somatic embryogenesis is a limiting step in birch genetic breeding. As a transcription factor, the Arabidopsis thaliana WUSCHEL (AtWUS) gene plays an important role in maintaining and regulating stem cell characteristics. It determines whether the stem cell population is differentiated. To explore the method of inducing somatic embryogenesis in birch. We overexpressed the AtWUS gene and transferred it into birch. The expression of AtWUS increased the somatic embryogenesis rate from 101.4% to 717.1%. The expression of the AtWUS gene in calli and globular embryos led to the downregulation of the BpWUS gene. The BpLEC1, BpLEC2, BpFUS3 and BpABI3 genes were upregulated. In addition, overexpression of AtWUS increased the number of lateral branches and bud meristem in birch. Similarly, the BpWUS gene was downregulated in the bud meristem. The BpLEC1, BpLEC2, BpFUS3, BpSTM and BpCUC2 genes were upregulated. This result indicated that overexpression of the AtWUS gene promoted somatic embryogenesis (SE) by increasing the expression of SE-related genes. In conclusion, this study focused on the role of the AtWUS gene in birch SE and the molecular mechanism of promoting SE.

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Trichome morphogenesis: a cell–cycle perspective

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2002.1087 ◽

2002 ◽

Vol 357 (1422) ◽

pp. 823-826 ◽

Cited By ~ 44

Author(s):

A. Schnittger ◽

M. Hülskamp

Keyword(s):

Cell Cycle ◽

Spatial Information ◽

Epidermal Cells ◽

Branching Pattern ◽

Microtubule Cytoskeleton ◽

Leaf Hairs ◽

Cell Divisions ◽

Branch Formation ◽

A Cell

Arabidopsis leaf hairs (trichomes) are polyploid epidermal cells with a predictable branching pattern. More than 15 genes have been identified that are involved in the regulation of branching. The cloning of the ZWICHEL , ANGUSTIFOLIA and STICHEL genes points to two mechanistic aspects of branch formation: (i) a role of the microtubule cytoskeleton; and (ii) a link to the regulation of cell divisions. The latter aspect is supported by the recent identification of an Arabidopsis mutant with multicellular trichomes, the siamese mutant, suggesting that Arabidopsis trichomes are evolutionarily derived from multicellular forms. We speculate that the spatial information for branch formation is derived from mechanisms employed in cell divisions.

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