The role of the fibrillar component of the surface sheath in the morphogenesis of Dictyostelium discoideum

While the role of myosin II in muscle contraction has been well characterized, less is known about the role of myosin II in non-muscle cells. Recent molecular genetic experiments on Dictyostelium discoideum show that myosin II is necessary for cytokinesis and multicellular development. Here we use immunofluorescence microscopy with monoclonal and polyclonal antimyosin antibodies to visualize myosin II in cells of the multicellular D. discoideum slug. A subpopulation of peripheral and anterior cells label brightly with antimyosin II antibodies, and many of these cells display a polarized intracellular distribution of myosin II. Other cells in the slug label less brightly and their cytoplasm displays a more homogeneous distribution of myosin II. These results provide insight into cell motility within a three-dimensional tissue and they are discussed in relation to the possible roles of myosin II in multicellular development.

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cAMP induces a rapid and reversible modification of the chemotactic receptor in Dictyostelium discoideum.

The Journal of Cell Biology ◽

10.1083/jcb.100.3.715 ◽

1985 ◽

Vol 100 (3) ◽

pp. 715-720 ◽

Cited By ~ 39

Author(s):

C Klein ◽

J Lubs-Haukeness ◽

S Simons

Keyword(s):

Dictyostelium Discoideum ◽

Concentration Dependence ◽

Time Course ◽

Camp Synthesis ◽

Sds Page ◽

Reversible Modification ◽

Camp Receptor ◽

Camp Stimulation ◽

Stimulation Of

Stimulation, within 1 min after cAMP stimulation, of aggregation-competent Dictyostelium discoideum amebae was found to cause a rapid (within 1 min) modification of the cell's surface cAMP receptor. The modified receptor migrated on SDS PAGE as a 47,000-mol-wt protein, as opposed to a 45,000-mol-wt protein labeled on unstimulated cells. The length of time this modified receptor could be detected depended upon the strength of the cAMP stimulus: 3-4 min after treatment with 10(-7) M cAMP, cells no longer possessed the 47,000-mol-wt form of the cAMP receptor. Instead, the 45,000-mol-wt form was present. Stimulation of cells with 10(-5) M cAMP, however, resulted in the persistent (over 15 min) expression of the modified receptor. The time course, concentration dependence, and specificity of stimulus for this cAMP-induced shift in the cAMP receptor were found to parallel the cAMP-stimulated phosphorylation of a 47,000-mol-wt protein. In addition, both phenomena were shown to occur in the absence of endogenous cAMP synthesis. The possibility that the cAMP receptor is phosphorylated in response to cAMP stimulation, and the role of this event in cell desensitization, are discussed.

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Role of epigenetics in unicellular to multicellular transition in Dictyostelium

Genome Biology ◽

10.1186/s13059-021-02360-9 ◽

2021 ◽

Vol 22 (1) ◽

Author(s):

Simon Yuan Wang ◽

Elizabeth Ann Pollina ◽

I-Hao Wang ◽

Lindsay Kristina Pino ◽

Henry L. Bushnell ◽

...

Keyword(s):

Dictyostelium Discoideum ◽

Orthologous Gene ◽

Chromatin Accessibility ◽

Critical Event ◽

H3k4 Methylation ◽

Social Amoeba ◽

The Social ◽

Conserved Genes ◽

Multicellular Organisms

Abstract Background The evolution of multicellularity is a critical event that remains incompletely understood. We use the social amoeba, Dictyostelium discoideum, one of the rare organisms that readily transits back and forth between both unicellular and multicellular stages, to examine the role of epigenetics in regulating multicellularity. Results While transitioning to multicellular states, patterns of H3K4 methylation and H3K27 acetylation significantly change. By combining transcriptomics, epigenomics, chromatin accessibility, and orthologous gene analyses with other unicellular and multicellular organisms, we identify 52 conserved genes, which are specifically accessible and expressed during multicellular states. We validated that four of these genes, including the H3K27 deacetylase hdaD, are necessary and that an SMC-like gene, smcl1, is sufficient for multicellularity in Dictyostelium. Conclusions These results highlight the importance of epigenetics in reorganizing chromatin architecture to facilitate multicellularity in Dictyostelium discoideum and raise exciting possibilities about the role of epigenetics in the evolution of multicellularity more broadly.

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The role of cyclic nucleotides and cell agglomeration in postaggregative enzyme synthesis in Dictyostelium discoideum

Developmental Biology ◽

10.1016/0012-1606(78)90145-8 ◽

1978 ◽

Vol 63 (2) ◽

pp. 412-420 ◽

Cited By ~ 69

Author(s):

Chris Town ◽

Julian Gross

Keyword(s):

Dictyostelium Discoideum ◽

Cyclic Nucleotides ◽

Enzyme Synthesis

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Stimulation of calcium influx by platelet activating factor in Dictyostelium

Journal of Cell Science ◽

10.1242/jcs.108.4.1597 ◽

1995 ◽

Vol 108 (4) ◽

pp. 1597-1603

Author(s):

R. Schaloske ◽

C. Sordano ◽

S. Bozzaro ◽

D. Malchow

Keyword(s):

Plasma Membrane ◽

G Protein ◽

Dictyostelium Discoideum ◽

Calcium Influx ◽

Platelet Activating Factor ◽

Inactive Compound ◽

Time Period ◽

Dependent Pathway ◽

Stimulation Of

Platelet activating factor (PAF) induces Ca2+ influx in Dictyostelium discoideum. In this investigation we used this activity to analyze the mechanism of PAF action. We found that PAF activity was confined to the period of spike-shaped oscillations and suggest that the role of PAF is to augment cAMP relay. PAF seems to act only a few times during this time period of two hours, since Ca2+ entry adapted to a subsequent stimulus for about 30 minutes. PAF showed a reduced response in the G protein beta- strain LW14 and was unable to induce Ca2+ influx in the G alpha 2- strains HC85 and JM1. The latter expresses the cAMP receptors cAR1 constitutively, and exhibits cAMP-induced Ca2+ influx, albeit at a reduced level. In order to decide whether the inability of PAF to elicit a Ca2+ response in JM1 cells was due to the lack of differentiation and/or the lack of G alpha 2, we inhibited the IP3-dependent pathway with compound U73122 and found that Ca2+ entry was blocked, whereas a closely related inactive compound, U73343, did not alter the response. In agreement with this, NBD-Cl, an inhibitor of Ca2+ uptake into the IP3-sensitive store in Dictyostelium, also abolished PAF activity. The latter was not inhibited by the plasma membrane antagonists BN-52021 or WEB 2170. Therefore PAF seems to operate intracellularly via the IP3-signalling pathway at or upstream of the IP3-sensitive store.

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An analysis of culmination in Dictyostelium using prestalk and stalk-specific cell autonomous markers

Development ◽

10.1242/dev.111.3.779 ◽

1991 ◽

Vol 111 (3) ◽

pp. 779-787 ◽

Cited By ~ 19

Author(s):

K.A. Jermyn ◽

J.G. Williams

Keyword(s):

Gene Expression ◽

Extracellular Matrix ◽

Dictyostelium Discoideum ◽

Tube Formation ◽

Matrix Proteins ◽

Specific Cell ◽

Primary Role ◽

Fusion Genes ◽

Spore Mass

The ecmA (pDd63) and ecmB (pDd56) genes encode extracellular matrix proteins of the slime sheath and stalk tube of Dictyostelium discoideum. Using fusion genes containing the promoter of one or other gene coupled to an immunologically detectable reporter, we previously identified two classes of prestalk cells in the tip of the migrating slug; a central core of pstB cells, which express the ecmB gene, surrounded by pstA cells, which express the ecmA gene. PstB cells lie at the position where stalk tube formation is initiated at culmination and we show that they act as its founders. As culmination proceeds, pstA cells transform into pstB cells by activating the ecmB gene as they enter the stalk tube. The prespore region of the slug contains a population of cells, termed anterior-like cells (ALC), which have the characteristics of prestalk cells. We show that the ecmA and ecmB genes are expressed at a low level in ALC during slug migration and that their expression in these cells is greatly elevated during culmination. Previous observations have shown that ALC sort to surround the prespore cells during culmination (Sternfeld and David, 1982 Devl Biol. 93, 111–118) and we find just such a distribution for pstB cells. We believe that the ecmB protein plays a structural role in the stalk tube and its presence, as a cradle around the spore head, suggests that it may play a further function, perhaps in ensuring integrity of the spore mass during elevation. If this interpretation is correct, then a primary role of anterior-like cells may be to form these structures at culmination. We previously identified a third class of prestalk cells, pstO cells, which lie behind pstA cells in the slug anterior and which appeared to express neither the ecmA nor the ecmB gene. Using B-galactosidase fusion constructs, which give more sensitive detection of gene expression, we now find that these cells express the ecmA gene but at a much lower level than pstA cells. We also show that expression of the ecmA gene becomes uniformly high throughout the prestalk zone when slugs are allowed to migrate in the light. Overhead light favours culmination and it may be that increased expression of the ecmA gene in the pst ‘O’ region is a preparatory step in the process.

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The role of phosphodiesterase in aggregation of Dictyostelium discoideum

Journal of Cell Science ◽

10.1242/jcs.31.1.233 ◽

1978 ◽

Vol 31 (1) ◽

pp. 233-243

Author(s):

M. Darmon ◽

J. Barra ◽

P. Brachet

Keyword(s):

Dictyostelium Discoideum ◽

Direct Contact ◽

Signal To Noise Ratio ◽

Signal To Noise ◽

Extracellular Medium ◽

Camp Phosphodiesterase ◽

Cellular Slime Mould ◽

Cellular Slime ◽

Mutant Cells

The role of cAMP phosphodiesterase in the cAMP-mediated aggregation of the cellular slime mould Dictyostelium discoideum was investigated with a morphogenetic mutant defective in phosphodiesterase production. Mutant cells become capable of aggregating normally when incubated in the presence of exogenous phosphodiesterase isolated from Idictyostelium or rat brain. Direct contact between enzyme and the cell membrane is not required for this phenotypic suppression. The aggregateless character of this strain presumably results from an over-accumulation of cAMP in the extracellular medium since aggregation can be induced in the absence of added phosphodiesterase under conditions facilitating diffusion of the nucleotide. This suggests that phosphodiesterase is not involved in the generation or recognition of cAMP signals, but that the enzyme is essential in the control of the cAMP signal-to-noise ratio.

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The FtsZ Homolog, FszB, Inhibits Mitochondrial Dynamics in Dictyostelium discoideum

Cells ◽

10.3390/cells9010064 ◽

2019 ◽

Vol 9 (1) ◽

pp. 64 ◽

Cited By ~ 1

Author(s):

Ericka Vogel ◽

Pristine Bay Pittman ◽

Kari Naylor

Keyword(s):

Dictyostelium Discoideum ◽

Mitochondrial Dynamics ◽

Model System ◽

Membrane Remodeling ◽

Positive Role ◽

Actual Mechanism

Dictyostelium discoideum is a well-established mitochondrial model system for both disease and dynamics, yet we still do not understand the actual mechanism of mitochondrial dynamics in this system. The FtsZ proteins are known to mediate membrane remodeling events such as cytokinesis in bacteria and fission of chloroplasts; D. discoideum has two FtsZ proteins, FszA and FszB. To determine the role of these proteins in mitochondrial dynamics we overexpressed FszB-GFP and determined its effect on fission, fusion, and motility in the presence of intact and disrupted cytoskeletal filaments. Here we show that overexpression of FszB-GFP decreases mitochondrial dynamics and suggest that actin may play a positive role driving fission in the context of excessive inhibition by overexpressed FszB-GFP.

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