Faculty Opinions recommendation of Statolith sedimentation kinetics and force transduction to the cortical endoplasmic reticulum in gravity-sensing Arabidopsis columella cells.

Ptc1p, a type 2C protein phosphatase, is required for a late step in cortical endoplasmic reticulum (cER) inheritance in Saccharomyces cerevisiae. In ptc1Δ cells, ER tubules migrate from the mother cell and contact the bud tip, yet fail to spread around the bud cortex. This defect results from the failure to inactivate a bud tip–associated pool of the cell wall integrity mitogen-activated protein kinase, Slt2p. Here we report that the polarisome complex affects cER inheritance through its effects on Slt2p, with different components playing distinct roles: Spa2p and Pea2p are required for Slt2p retention at the bud tip, whereas Bni1p, Bud6p, and Sph1p affect the level of Slt2p activation. Depolymerization of actin relieves the ptc1Δ cER inheritance defect, suggesting that in this mutant the ER becomes trapped on the cytoskeleton. Loss of Sec3p also blocks ER inheritance, and, as in ptc1Δ cells, this block is accompanied by activation of Slt2p and is reversed by depolymerization of actin. Our results point to a common mechanism for the regulation of ER inheritance in which Slt2p activity at the bud tip controls the association of the ER with the actin-based cytoskeleton.

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Ultrastructural and Morphometric Observations of Cortical Endoplasmic Reticulum in Arbacia, Spisula and Mouse Eggs*. (egg cortex/endoplasmic reticulum/plasma membrane/cortical granules)

Development Growth & Differentiation ◽

10.1111/j.1440-169x.1985.00349.x ◽

1985 ◽

Vol 27 (3) ◽

pp. 349-359 ◽

Cited By ~ 19

Author(s):

SHIRLEY LUTTMER ◽

FRANK J. LONGO

Keyword(s):

Endoplasmic Reticulum ◽

Plasma Membrane ◽

Cortical Granules ◽

Cortical Endoplasmic Reticulum ◽

Mouse Eggs ◽

Egg Cortex

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FrontiERs: movers and shapers of the higher plant cortical endoplasmic reticulum

Current Opinion in Plant Biology ◽

10.1016/j.pbi.2011.07.006 ◽

2011 ◽

Vol 14 (6) ◽

pp. 658-665 ◽

Cited By ~ 33

Author(s):

Imogen Sparkes ◽

Chris Hawes ◽

Lorenzo Frigerio

Keyword(s):

Endoplasmic Reticulum ◽

Higher Plant ◽

Cortical Endoplasmic Reticulum

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Membrane junctions in xenopus eggs: their distribution suggests a role in calcium regulation

The Journal of Cell Biology ◽

10.1083/jcb.96.4.1159 ◽

1983 ◽

Vol 96 (4) ◽

pp. 1159-1163 ◽

Cited By ~ 92

Author(s):

DM Gardiner ◽

RD Grey

Keyword(s):

Endoplasmic Reticulum ◽

Plasma Membrane ◽

Intracellular Calcium ◽

Calcium Release ◽

Egg Activation ◽

Electron Dense Material ◽

Intracellular Calcium Release ◽

Cortical Endoplasmic Reticulum ◽

Center Distance ◽

Lines Of Evidence

We have observed the presence of membrane junctions formed between the plasma membrane and cortical endoplasmic reticulum of mature, unactivated eggs of xenopus laevis. The parallel, paired membranes of the junction are separated by a 10-mn gap within which electron-dense material is present. This material occurs in patches with an average center-to-center distance of approximately 30 nm. These junctions are rare in immature (but fully grown) oocytes (approximately 2 percent of the plasma membrane is associated with junctions) and increase dramatically during progesterone-induced maturation. Junctions in the mature, unactivated egg are two to three times more abundant in the animal hemisphere (25-30 percent of the plasma membrane associated with junction) as compared with the vegetal hemisphere (10-15 percent). Junction density decreases rapidly to values characteristic of immature oocytes in response to egg activation. The plasma membrane-ER junctions of xenopus eggs are strikingly similar in structure to membrane junctions in muscle cells thought to be essential in the triggering of intracellular calcium release from the sarcoplasmic reticulum. In addition, the junctions' distinctive, animal-vegetal polarity of distribution, their dramatic appearance during maturation, and their disapperance during activation are correlated with previously documented patterns of calcium-mediated events in anuran eggs. We discuss several lines of evidence supporting the hypothesis that these junctions in xenopus eggs are sites that transduce extracellular events into intracellular calcium release during fertilization and activation of development.

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