scholarly journals Sperm entry induces polarity in fucoid zygotes

Development ◽  
2000 ◽  
Vol 127 (3) ◽  
pp. 493-501 ◽  
Author(s):  
W.E. Hable ◽  
D.L. Kropf
Keyword(s):  
Environmental Cues ◽  
Entry Site ◽  
Environmental Signals ◽  
Growth Axis ◽  
Low Sodium ◽  
Extrinsic Cues ◽  
Sperm Entry ◽  
Actin Patch ◽  
Adhesive Secretion ◽  
Lines Of Evidence

Fucoid zygotes establish a rhizoid-thallus growth axis in response to environmental signals; however, these extrinsic cues are not necessary for polarization, suggesting that zygotes may have inherent polarity. The hypothesis that sperm entry provides a default pathway for polarization of zygotes cultured in the absence of environmental signals was tested, and was supported by several lines of evidence. First, an F-actin patch, a cortical marker of the rhizoid pole, formed at the sperm entry site within minutes of fertilization. Second, the sperm entry site predicted the site of polar adhesive secretion (the first morphological manifestation of the rhizoid pole) and the position of rhizoid outgrowth. Third, when fertilization was restricted to one hemisphere of the egg, rhizoid outgrowth always occurred from that hemisphere. Fourth, delivery of sperm to one location within a population of eggs resulted in polarization of both adhesive secretion and rhizoid outgrowth toward the sperm source. Finally, induction of polyspermy using low sodium seawater increased the frequency of formation of two rhizoids. Sperm entry therefore provides an immediate default axis that can later be overridden by environmental cues.

scholarly journals Regulation of clathrin coat assembly by Eps15 homology domain–mediated interactions during endocytosis

2012 ◽  
Vol 23 (4) ◽  
pp. 687-700 ◽  
Author(s):  
Ryohei Suzuki ◽  
Junko Y. Toshima ◽  
Jiro Toshima
Keyword(s):  
Functional Diversity ◽  
Protein Interaction ◽  
Interaction Domain ◽  
Protein Protein Interaction ◽  
Molecular Events ◽  
Biological Studies ◽  
Eh Domain ◽  
Actin Patch ◽  
Lines Of Evidence

Clathrin-mediated endocytosis involves a coordinated series of molecular events regulated by interactions among a variety of proteins and lipids through specific domains. One such domain is the Eps15 homology (EH) domain, a highly conserved protein–protein interaction domain present in a number of proteins distributed from yeast to mammals. Several lines of evidence suggest that the yeast EH domain–containing proteins Pan1p, End3p, and Ede1p play important roles during endocytosis. Although genetic and cell-biological studies of these proteins suggested a role for the EH domains in clathrin-mediated endocytosis, it was unclear how they regulate clathrin coat assembly. To explore the role of the EH domain in yeast endocytosis, we mutated those of Pan1p, End3p, or Ede1p, respectively, and examined the effects of single, double, or triple mutation on clathrin coat assembly. We found that mutations of the EH domain caused a defect of cargo internalization and a delay of clathrin coat assembly but had no effect on assembly of the actin patch. We also demonstrated functional redundancy among the EH domains of Pan1p, End3p, and Ede1p for endocytosis. Of interest, the dynamics of several endocytic proteins were differentially affected by various EH domain mutations, suggesting functional diversity of each EH domain.

scholarly journals Combinatorial Control of Gene Expression

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Soumya Bhattacharjee ◽  
Kaushik Renganaath ◽  
Rajesh Mehrotra ◽  
Sandhya Mehrotra
Keyword(s):  
Gene Expression ◽  
Short Description ◽  
Controlling Factors ◽  
Environmental Cues ◽  
Control Of Gene Expression ◽  
Environmental Signals ◽  
Combinatorial Control ◽  
Sense And Respond ◽  
Eukaryotic Organisms

The complexity and diversity of eukaryotic organisms are a feat of nature’s engineering. Pulling the strings of such an intricate machinery requires an even more masterful and crafty approach. Only the number and type of responses that they generate exceed the staggering proportions of environmental signals perceived and processed by eukaryotes. Hence, at first glance, the cell’s sparse stockpile of controlling factors does not seem remotely adequate to carry out this response. The question as to how eukaryotes sense and respond to environmental cues has no single answer. It is an amalgamation, an interplay between several processes, pathways, and factors—a combinatorial control. A short description of some of the most important elements that operate this entire conglomerate is given in this paper.

scholarly journals Spatiotemporal Analysis of Ca2+ Waves in Relation to the Sperm Entry Site and Animal–Vegetal Axis during Ca2+ Oscillations in Fertilized Mouse Eggs

2000 ◽  
Vol 218 (2) ◽  
pp. 299-313 ◽  
Author(s):  
Ryusaku Deguchi ◽  
Hideki Shirakawa ◽  
Shoji Oda ◽  
Tatsuma Mohri ◽  
Shunichi Miyazaki
Keyword(s):  
Spatiotemporal Analysis ◽  
Entry Site ◽  
Sperm Entry ◽  
Mouse Eggs

scholarly journals BdlA, a Chemotaxis Regulator Essential for Biofilm Dispersion in Pseudomonas aeruginosa

2006 ◽  
Vol 188 (21) ◽  
pp. 7335-7343 ◽  
Author(s):  
Ryan Morgan ◽  
Steven Kohn ◽  
Sung-Hei Hwang ◽  
Daniel J. Hassett ◽  
Karin Sauer
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Gene Product ◽  
Signaling Cascade ◽  
Environmental Cues ◽  
Environmental Sensing ◽  
Environmental Signals ◽  
Isogenic Mutant ◽  
Biofilm Detachment ◽  
Biofilm Dispersion ◽  
Do So

ABSTRACT Multiple environmental cues have been shown to trigger biofilm detachment, the transition from surface-attached, highly organized communities known as biofilms to the motile lifestyle. The goal of this study was to identify a gene product involved in sensing environmental cues that trigger biofilm dispersion in Pseudomonas aeruginosa. To do so, we focused on novel putative chemotaxis transducer proteins that could potentially be involved in environmental sensing. We identified a locus encoding such a protein that played a role in detachment, as indicated by the observation that an isogenic mutant biofilm could not disperse in response to a variety of environmental cues. The locus was termed bdlA for biofilm dispersion locus. The BdlA protein harbors an MCP (methyl-accepting chemotaxis protein) domain and two PAS (Per-Arnt-Sint) domains that have been shown to be essential for responding to environmental signals in other proteins. The dispersion-deficient phenotype of the bdlA mutant was confirmed by treatment with the biocide H2O2 and by microscopic observations. The dispersion response was independent of motility. bdlA mutant biofilms were found to have increased adherent properties and increased intracellular levels of cyclic di-GMP (c-di-GMP). Our findings suggest that BdlA may be a link between sensing environmental cues, c-di-GMP levels, and detachment. Based on our findings, a possible involvement of BdlA in a signaling cascade resulting in biofilm dispersion is discussed.

scholarly journals Deviating from the Beaten Track: New Twists in Brassinosteroid Receptor Function

2020 ◽  
Vol 21 (5) ◽  
pp. 1561 ◽  
Author(s):  
Sebastian Wolf
Keyword(s):  
Conceptual Models ◽  
Signalling Pathways ◽  
Environmental Cues ◽  
Receptor Complex ◽  
Environmental Signals ◽  
Surface Receptors ◽  
The Core ◽  
Beaten Track ◽  
Multiple Levels ◽  
New Evidence

A key feature of plants is their plastic development tailored to the environmental conditions. To integrate environmental signals with genetic growth regulatory programs, plants rely on a number of hormonal pathways, which are intimately connected at multiple levels. Brassinosteroids (BRs), a class of plant sterol hormones, are perceived by cell surface receptors and trigger responses instrumental in tailoring developmental programs to environmental cues. Arguably, BR signalling is one of the best-characterized plant signalling pathways, and the molecular composition of the core signal transduction cascade seems clear. However, BR research continues to reveal new twists to re-shape our view on this key signalling circuit. Here, exciting novel findings pointing to the plasma membrane as a key site for BR signalling modulation and integration with other pathways are reviewed and new inputs into the BR signalling pathway and emerging “non-canonical” functions of the BR receptor complex are highlighted. Together, this new evidence underscores the complexity of plant signalling integration and serves as a reminder that highly-interconnected signalling pathways frequently comprise non-linear aspects which are difficult to convey in classical conceptual models.

The sperm entry site during fertilization of the zebrafish egg: Localization of actin

1992 ◽  
Vol 32 (3) ◽  
pp. 217-228 ◽  
Author(s):  
Nathan H. Hart ◽  
Karen A. Becker ◽  
Joseph S. Wolenski
Keyword(s):  
Entry Site ◽  
Sperm Entry

scholarly journals Genetic Locus Required for Antigenic Maturation of Rhizobium etli CE3 Lipopolysaccharide

2001 ◽  
Vol 183 (20) ◽  
pp. 6054-6064 ◽  
Author(s):  
Dominik M. Duelli ◽  
Andrea Tobin ◽  
Jodie M. Box ◽  
V. S. Kumar Kolli ◽  
Russell W. Carlson ◽  
...  
Keyword(s):  
Genetic Locus ◽  
Low Ph ◽  
Open Reading Frames ◽  
Site Directed Mutagenesis ◽  
Nodule Development ◽  
Environmental Cues ◽  
Rhizobium Etli ◽  
Wild Type ◽  
Specific Expression ◽  
Environmental Signals

ABSTRACT Rhizobium etli modifies lipopolysaccharide (LPS) structure in response to environmental signals, such as low pH and anthocyanins. These LPS modifications result in the loss of reactivity with certain monoclonal antibodies. The same antibodies fail to recognize previously isolated R. etli mutant strain CE367, even in the absence of such environmental cues. Chemical analysis of the LPS in strain CE367 demonstrated that it lacked the terminal sugar of the wild-type O antigen, 2,3,4-tri-O-methylfucose. A 3-kb stretch of DNA, designated as lpe3, restored wild-type antigenicity when transferred into CE367. From the sequence of this DNA, five open reading frames were postulated. Site-directed mutagenesis and complementation analysis suggested that the genes were organized in at least two transcriptional units, both of which were required for the production of LPS reactive with the diagnostic antibodies. Growth in anthocyanins or at low pH did not alter the specific expression ofgusA from the transposon insertion of mutant CE367, nor did the presence of multiple copies of lpe3 situated behind a strong, constitutive promoter prevent epitope changes induced by these environmental cues. Mutations of the lpe genes did not prevent normal nodule development on Phaseolus vulgaris and had very little effect on the occupation of nodules in competition with the wild-type strain.

scholarly journals An elevated free cytosolic Ca2+ wave follows fertilization in eggs of the frog, Xenopus laevis.

1985 ◽  
Vol 100 (4) ◽  
pp. 1325-1329 ◽  
Author(s):  
W B Busa ◽  
R Nuccitelli
Keyword(s):  
Protein Synthesis ◽  
Xenopus Laevis ◽  
Transient Increase ◽  
Cortical Granule ◽  
Entry Site ◽  
Cleavage Division ◽  
Present Evidence ◽  
Granule Exocytosis ◽  
Sperm Entry ◽  
Cortical Granule Exocytosis

The eggs of most or all animals are thought to be activated after fertilization by a transient increase in free cytosolic Ca2+ concentration ([Ca2+]i). We have applied Ca2+-selective microelectrodes to detect such an increase in fertilized eggs of the frog, Xenopus laevis. As observed with an electrode in the animal hemisphere, [Ca2+]i increased from 0.4 to 1.2 microM over the course of 2 min after fertilization, and returned to its original value during the next 10 min. No further changes in [Ca2+]i were detected through the first cleavage division. In eggs impaled with two Ca2+ electrodes, the Ca2+ pulse was observed to travel as a wave from the animal to the vegetal hemisphere, propagating at a rate of approximately 10 microns/s across the animal hemisphere. The apparent delay between the start of the fertilization potential and initiation of the Ca2+ wave at the sperm entry site as approximately 1 min. Through these observations describe only the behavior of subcortical [Ca2+]i, we suggest that our data represent the subcortical extension of the cortical Ca2+ wave thought to trigger cortical granule exocytosis, and we present evidence that both the timing and magnitude of the Ca2+ pulse we observed are consistent with this identity. This first quantification of subcortical [Ca2+]i during fertilization indicates that the Ca2+ transient is available to regulate processes (e.g., protein synthesis) in the subcortical cytosol.

scholarly journals The effects of microenvironment on the redifferentiation of regenerating neurones: neurite architecture, acetylcholine receptors and Ca2+ channel distribution

1987 ◽  
Vol 132 (1) ◽  
pp. 111-131
Author(s):  
M. E. Spira ◽  
D. Zeldes ◽  
B. Hochner ◽  
A. Dormann
Keyword(s):  
Action Potentials ◽  
Acetylcholine Receptors ◽  
Membrane Properties ◽  
Environmental Cues ◽  
Freezing And Thawing ◽  
Intrinsic Factors ◽  
Extrinsic Cues ◽  
Voltage Dependent ◽  
Synaptic Receptors ◽  
Ca2 Channels

Severed adult neurones, which are capable of regrowth, encounter different microenvironments from those encountered during development. Moreover, adult neurones may respond in a different manner from developing neurones to the same environmental cues. Thus, the recovery of the integrative and transmission capabilities (which depend on the neuronal architecture, passive and active membrane properties, and synaptic receptor distribution) by a regenerating adult neurone may not be complete. In the present review, we examine several aspects of the outcome of the interaction between the microenvironment and regrowing neurones using the cockroach giant interneurones (GINs) as a model system. We demonstrate that whereas extrinsic cues govern the morphological redifferentiation and distribution of synaptic receptors, the distribution of voltage-dependent Ca2+ channels is to a large extent determined by intrinsic factors. The pathway of regrowth and the architecture of regenerating GINs were studied by examination of intracellularly stained fibres. The environments provided by the connectives and ganglia are different. The elongating sprouts in the connective appeared as smooth cylinders. Within the ganglionic domain, the main longitudinal sprouts emitted neurites which extended and branched into the neuropile. The local cues for branching of neurites were eliminated by freezing and thawing of the ganglia prior to the arrival of the growing tips. The failure to extend neurites under these conditions is attributed to the elimination of extrinsic signals for morphological redifferentiation of the fibres, since the same fibres emit neurites in anterior ganglia which have not been subjected to freezing and thawing. The distribution of acetylcholine receptors (AChRs) on the GINs was mapped by ionophoretic application of ACh. In both the intact and regenerating GINs receptors were located only on the neurites. Freezing and thawing of a ganglion eliminated the local signals for insertion and/or activation of AChRs on the neurites. Thus, both the morphological redifferentiation and the distribution of AChRs are affected by the microenvironment. Voltage-dependent Ca2+ channels were detected after intracellular injection of tetraethylammonium into the GIN and in the presence of tetrodotoxin (TTX) and Ba2+ in the extracellular space. The regrowing axon tips always revealed large barium action potentials independent of the CNS microenvironment. This observation is consistent with the hypothesis that Ca2+ plays an important role in the growth process. However, increased Ba2+ responsiveness was also observed in axonal segments proximal to the region of neuronal extension.(ABSTRACT TRUNCATED AT 400 WORDS)

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