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Dictyostelium discoideum, slime mold

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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


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Model organism

Related organisms:

Dictyostelium discoideum life cycle


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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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Appendix 3: duplications in the genomes of laboratory stocks of Dictyostelium discoideum

Gareth Bloomfield, Yoshimasa Tanaka, Jason Skelton, Alasdair Ivens, and Robert R Kay.
Widespread duplications in the genomes of laboratory stocks of Dictyostelium discoideum. Genome Biol. 2008; 9(4)

Relationships between the most commonly used Dictyostelium strains

Relationships between the most commonly used Dictyostelium strains.
(a) Simplified genealogical tree showing the relationships between common laboratory strains derived from NC4. The branch marked 'Ax3' is more complex than shown here: sub-lineages have been given the names KAx3 and Ax4. The auxotrophic strain DH1 was engineered in an 'Ax3' background, and JH10 from 'Ax4.'
(b) Plaque morphologies. Cells were plated clonally in association with Klebsiella aerogenes on SM agar. Plaques were photographed after 4 days. Small DH1 plaques are indicated with arrowheads. Variation in diameter is a function of the rate of feeding and of the motility of the amoebae. Where the bacteria are cleared the amoebae aggregate in streams; this process had not yet begun in the slow-growing DH1 plaques.
(c) Fruiting bodies. Wild type cells - in this instance NC4(Dee) - form larger, more robust fruiting bodies than axenic mutants.


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References

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