10 citations found on Fucus polarity (4/28/97):
Development 122 (9): 2623-2630 (1996)
The role of targeted secretion in the establishment of cell polarity
and the orientation of the division plane in Fucus zygotes.
Shaw SL, Quatrano RS
Department of Biology, University of North Carolina, Chapel Hill 27599-3280,
USA.
In this study, we investigate the role of polar secretion and the resulting
asymmetry in the cell wall in establishing polarity in Fucus zygotes. We
have utilized brefeldin-A to selectively interrupt secretion of Golgi-derived
material into the cell wall as assayed by toluidine blue O staining of
sulfated fucoidin. We show that the polar secretion of Golgi-derived material
is targeted to a cortical site of the zygote identified by the localization
of actin filaments and dihydropyridine receptors. The deposition of Golgi-derived
material into the cell wall at this target site is temporally coincident
with and required for polar axis fixation. We propose that local secretion
of Golgi-derived material into the cell wall transforms the target site
into the fixed site of polar growth. We also found that polar secretion
of Golgi-derived material at the fixed site is essential for growth and
differentiation of the rhizoid, as well as for the proper positioning of
the first plane of cell division. We propose that the resulting asymmetry
in the cell wall serves as positional information for the underlying cortex
to initiate these polar events. Our data supports the hypothesis that cell
wall factors in embryos, previously shown to be responsible for induction
of rhizoid cell differentiation, are deposited simultaneously with and
are responsible for polar axis fixation. Furthermore, the pattern of polar
growth is attributable to a positional signal at the fixed site and appears
to be independent of the orientation of the first cell division plane.
Thus, the establishment of zygotic cell polarity and not the position of
the first division plane, is critical for the formation of the initial
embryonic pattern in Fucus.
J Cell Sci 109 ( Pt 2): 335-342 (1996)
Polar localization of a dihydropyridine receptor on living Fucus zygotes.
Shaw SL, Quatrano RS
Department of Biology, University of North Carolina, Chapel Hill 27599-3280,
USA.
We have used a fluorescently-labeled dihydropyridine (FL-DHP) to vitally
stain living Fucus zygotes during the establishment of cell polarity. Localization
of FL-DHP is primarily at the plasma membrane and FL-DHP binding is competitively
blocked by an unlabeled dihydropyridine. Distribution of FL-DHP is initially
symmetrical before fixation of the polar axis, but becomes asymmetrical
in response to a unilateral light gradient. The distribution of FL-DHP
receptors can be relocalized when the direction of the photopolarizing
stimulus is changed. Treatment of cells with cytochalasin B prior to axis
fixation reversibly prevents localization of FL-DHP receptors. Observation
of FL-DHP labeling by time-lapse fluorescence microscopy indicates that
the existing receptors are redistributed during polar axis formation. The
asymmetric distribution of FL-DHP receptors coincides temporally and spatially
with increased local intracellular calcium ion concentrations, as measured
by calcium green dextran. Based on the site, timing, photo-reversibility,
and actin dependence of the asymmetric localization of FL-DHP receptors,
we conclude that FL-DHP is a vital probe for the later stage of polar axis
formation in Fucus zygotes. Furthermore, we propose that FL-DHP receptors
correspond to ion channels that are transported to the future site of polar
growth to create the changes in local calcium concentration required for
polarity establishment.
Dev Biol 171 (1): 258-261 (1995)
Spatial redistribution of poly(A)+ RNA during polarization of the Fucus
zygote is dependent upon microfilaments.
Bouget FY, Gerttula S, Quatrano RS
Department of Biology, University of North Carolina, Chapel Hill 27599-3280,
USA.
Asymmetrical distribution of mRNA has been associated with polarization
and cell fate determination during early development of animal embryos.
In this report we determine the distribution pattern of poly(A)+ RNA during
early embryogenesis of the brown alga Fucus. Poly(A)+ RNA is symmetrically
distributed in the egg and early zygote. Shortly after the polar axis is
established, poly(A)+ RNA becomes segregated to the thallus pole of the
zygote. Following cytokinesis, most of poly(A)+ RNA is partitioned into
the thallus cell. We show that the spatial redistribution of poly(A)+ RNA
requires intact microfilaments and the fixation of the polar axis, but
is not dependent upon polarized growth of the rhizoid, intact microtubules,
or orientation of the division plane.
Zygote 1 (1): 9-15 (1993)
Ratio confocal imaging of free cytoplasmic calcium gradients in polarising
and polarised Fucus zygotes.
Berger F, Brownlee C
Ecole Normale Suprieure de Lyon, France.
In the marine brown alga, Fucus, two poles are differentiated before cell
division determining the future rhizoid or thallus. We have used a combination
of the Ca(2+)-sensitive dye Calcium Green and the pH-sensitive dye SNARF
monitored at pH-insensitive wavelengths to obtain confocal ratio images
of free cytoplasmic calcium distribution at different stages in polarising
Fucus zygotes. These dyes have the advantage that they can be used in most
confocal microscopes and their longer excitation wavelengths greatly reduce
autofluorescence problems. Dyes of varying molecular weights (free acid
form, 10,000 mol.wt or 70,000 mol.wt dextran-conjugated) were pressure
microinjected into early zygotes which were allowed to polarise in unidirectional
light. Dextran-conjugated dyes remained non-compartmentalised and fluorescence
could be monitored for up to 3 days following microinjection. Currently
we have been able to detect Ca2+ gradients at the tip of the rhizoid, confirming
earlier results. Localised Ca2+ elevations have also been observed at the
rhizoid pole of the polarising zygote before the onset of rhizoid germination.
Limitations of this technique and the significance of these Ca2+ gradients
are discussed.
Dev Suppl 1: 11-16 (1991)
Polar axis fixation in Fucus zygotes: components of the cytoskeleton
and extracellular matrix.
Quatrano RS, Brian L, Aldridge J, Schultz T
Department of Biology, University of North Carolina, Chapel Hill 27599-3280.
Polar axis formation and polar axis stabilization (or fixation) can be
separated and analyzed in synchronously developing zygotes of the brown
alga Fucus. Extensive experimental evidence points to a role for both the
cytoskeleton and the extracellular matrix (ECM) in the process of axis
fixation in Fucus. A structural complex composed of the cytoskeleton and
the ECM has been postulated to stabilize membrane asymmetries generated
as a result of axis-forming vectors. This axis stabilizing complex (ASC)
may take the form of transmembrane connections between the cytoskeleton
on the cytoplasmic face and the ECM on the external side of the plasma
membrane, similar to focal contacts in animal cells. At present we know
of two components in the proposed ASC of Fucus: an adhesive sulfated glycoprotein
which is localized in the ECM, and an actin network which is localized
on the adjoining cytoplasmic face. This preliminary report describes evidence
for the presence of molecules in two-celled Fucus embryos that are similar
to those found in focal contacts in animal cells, i.e. vinculin, integrin
and vitronectin. However, their localization and interaction with each
other relative to the polar axis has yet to be determined. These initial
observations will provide the basis to pursue further an analysis of these
components in the process of polar axis fixation.
Dev Biol 134 (2): 451-461 (1989)
Protein synthesis and morphogenesis are not tightly linked during embryogenesis
in Fucus.
Kropf DL, Hopkins R, Quatrano RS
Department of Botany and Plant Pathology, Oregon State University, Corvallis
97331.
Fertilized eggs of the brown alga Fucus have long been used as model organisms
for investigating the early events in the establishment of polarity and
subsequent embryogenesis since large numbers of zygotes can easily be obtained.
We have analyzed protein synthesis in eggs and embryos during the first
day of development using two-dimensional gels and found that synthesis
of 12 of the 60 most prominent proteins changed either qualitatively or
quantitatively. Actin and beta-tubulin were identified by immunoblotting;
synthesis of these cytoskeletal proteins was initiated at different times
during the first 12 hr of development. Unique, reproducible patterns of
protein synthesis observed during development in the light permitted accurate
staging of developing embryos. Inhibitors such as cytochalasin and sucrose,
however, blocked morphogenesis without affecting protein synthesis, and,
conversely, growth in the dark delayed protein synthesis but had very little
effect on the timing of morphogenesis. The data are consistent with morphogenesis
and protein synthesis being relatively independent during early embryogenesis.
Actinomycin D added soon after fertilization had no effect on protein synthesis
1 day later, indicating that the proteins analyzed were encoded by maternal
mRNA stored in the egg.
J Cell Sci Suppl 2: 129-141 (1985)
Cytological and biochemical requirements for the establishment of a
polar cell.
Quatrano RS, Griffing LR, Huber-Walchli V, Doubet RS
Our research is aimed at understanding the biochemical and cytological
basis of cell polarity in zygotes of the brown alga, Fucus distichus L.
Powell. One manifestation of this polar cell is the localization of a sulphated
fucan polysaccharide (F2) in only one region of the zygote cell surface,
the rhizoid cell wall. The focus of this paper is centered around the mechanism
responsible for the directional transport of Golgi vesicles containing
F2 and the biochemical properties of F2 that might specify its localized
fate. Recent findings indicate that the various sulphated polysaccharides
in the brown algae are complexes resulting from linkages of two basic polymers:
an alpha-(1----2)-linked fucan that contains high levels of ester sulphate
(F3), and a uronic acid-rich polymer (F1). The fucan complex F2, which
is localized in the rhizoid wall, is composed of a fucan sulphate core
(F3) to which uronic acid polymers (similar to F1) are attached. Our results,
using a purified endoguluronate lyase, indicate that guluronate bridges
link these subunits of F2. The carbon backbone of F2 is not synthesized
de novo after fertilization. However, F2 is sulphated, and possibly assembled,
beginning 10 h after fertilization, after which it is locally inserted
into the rhizoid wall, and held in the wall structure only by calcium ionic
bonds. Although sulphation is required for localization of F2, it is not
known if the uronic acid side-chains are also assembled at the time of
sulphation, and/or required for localization. The fact that F3 (F2 without
the side-chains) is secreted uniformly into the zygote wall suggests that
the uronic acid chains of F2 may play a critical role in its localization.
A sulphated F2 alone is not sufficient for its localization since in the
presence of cytochalasin, vesicles containing F2 are not transported to
the rhizoid. Recent studies point to a central role for a cytoskeletal
element, possibly microfilaments, in the directional transport of these
vesicles. We have used the techniques of isoelectric focusing and electrophoretic
mobility to study surface charge of these Golgi vesicles to determine if
charge might be one factor that specifies their localization. Vesicles
that contain the sulphated fucan F3 are secreted randomly and have the
same surface charge as those containing F2 that are directionally transported.
However, there is no stable endogenous electrical current at the time when
F3 vesicles are randomly secreted, whereas a current is detectable when
F2 vesicles are localized.
Dev Biol 40 (1): 162-173 (1974)
The relationship between changes in cell wall composition and the establishment
of polarity in Fucus embryos.
Novotny AM, Forman M
Biophysik 9 (3): 253-260 (1973)
Orientation of Fucus egg polarity by electric a.c. and d.c. fields.
Novak B, Bentrup FW
Naturwissenschaften 53 (5): 138 (1966)
Regional concentration of cytoplasmic RNA in fucus eggs in relation
to polarity.
Nakazawa S