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Aggregation
Aggregation

 

Dictyostelium discoideum

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Taxonomy

D. discoideum belongs to the order of Dictyosteliida (dictyostelid cellular slime molds or social amoebae). Dictyosteliida contains organisms that hover on the borderline between uni- and multicellularity. Each organism starts its life as a unicellular amoeba, but they aggregate to form a multicellular fruiting body when starved. Traditionally, social amoebas have been classified according to their most notable trait, fruiting body morphology. Based on this, three genera have been proposed: Dictyostelium, with unbranched or laterally branched fruiting bodies; Polysphondylium, whose fruiting bodies consist of repetitive whorls of regularly spaced side branches; and Acytostelium, which, unlike the other genera, forms acellular fruiting body stalks.

Taxonomic lineage

cellular organisms - Eukaryota - Amoebozoa - Mycetozoa - Dictyosteliida - Dictyostelium - Dictyostelium discoideum

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Brief facts

Related organisms:

Dictyostelium discoideum life cycle

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Essentials Laboratory Exercises for General Biology

Essentials Laboratory Exercises for General Biology

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Life cycle

Dictyostelium has 3 modes of reproduction: sexual, asexual (spores) and vegetative - mitotic division of unicellular organisms.

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Appendix 1: anatomy ontologies

Gaudet P, Williams JG, Fey P, Chisholm RL. An anatomy ontology to represent biological knowledge in Dictyostelium discoideum. BMC Genomics. 2008; 9: 130.

Dictyostelium cell cycle

Dictyostelium life cycle and the corresponding anatomical structures from the Dictyostelium anatomy ontology. A. Vegetative amoebae (DDANAT:0000002). B. Aggregation territory (DDANAT:0000003). C. Loose aggregate (DDANAT:0000004) with stream (DDANAT:0000013). D. Mound (DDANAT:0000005). E. Tipped mound (DDANAT:0000006). F. Standing slug (DDANAT:0000007). G. Migratory slug (DDANAT:0000008). H. Early culminant (DDANAT:0000009). I. Mid culminant (DDANAT:0000010). J. Fruiting body (DDANAT:0000010) with spores (DDANAT:0000414).

Dictyostelium Migrating slug anatomy

Subdivisions of the multicellular organism. The prestalk and prespore zones are recognizable from the tipped mound stage. This diagram represents the different subdivisions of the multicellular organism at the migratory slug stage. The subdivisions remain in the same relative positions and proportions until culmination.

Culminating body anatomy

Cell movements during culmination. Terminal cell differentiation takes place during the culmination stage and is correlated with cellular movements within the organism, as shown here for an early culminant. PstAB cells present in the slug are the first to migrate down the stalk tube and terminally differentiate into stalk cells, hence referred to as primary prestalk cells. They are replaced by pstA cells, which start expressing ecmB and in turn become stalk cells (secondary prestalk cells). PstA cells are in turn replaced by pstO cells. This process continues until all prestalk cells have been incorporated into the stalk.

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Appendix 2: P450 oxidoreductase (RedA) controls development beyond the mound stage

Gonzalez-Kristeller DC et al. The P450 oxidoreductase, RedA, controls development beyond the mound stage in Dictyostelium discoideum. BMC Dev Biol. 2008; 8: 8.

Disruption of redA impairs development at mound stage

Disruption of redA impairs development at mound stage. (A) Exponentially growing AX4 wild type cells and the mutants redA- and redA-KO were starved on filter pads and photographed at the indicated times (h) after starvation. (B) AX4 fruiting bodies and redA- yellow mounds after 48 hours starvation on filter pads are shown at lower (left) and at 5x higher magnification (right).

AX4 cells do not rescue redA- phenotype

AX4 cells do not rescue redA- phenotype. Exponentially growing redA- and AX4 wild type cells were starved on filter pads mixed at the indicated proportions. At the indicated times (h) after starvation cells were photographed.

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References

Websites

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