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Dictyostelium discoideum is a soil-living amoeba-like organism commonly known as slime mold or slime mould. It consumes bacteria found in soil. Its life cycle begins as a spore is released from a mature fruiting body (sorocarp) and then this sorocarp the spore hatches under warm and moist conditions to give rise to Myxamoebae. Myxamoeba is the vegetative stage where they feed on bacteria but get together for aggregation during starvation. The life cycle of Dictyostelium is shown in the below figure.
<img style="display: block; margin-left: auto; margin-right: auto;" src="https://vediphlie-aws.s3.ap-south-1.amazonaws.com/Dictyostelium_amoeba_showing_cell_aggregation_and_differentiation_977c4e4175.PNG" alt="Dictyostelium (amoeba) showing cell aggregation and differentiation" />
Fig.: Dictyostelium (amoeba) showing cell aggregation and differentiation.
<h2 style="text-align: left;">Mechanism of aggregation -</h2>
The molecular mechanism for the aggregation in Myxamoebae is dependent on the cAMP signaling. One cell that is termed the founder of the colony, initially secrets the cAMP because of stress during starvation and the other cell responds to this signal either by secreting more cAMP or by migrating towards the cAMP source cell. The cAMP molecule acts as a signal molecule for each cell in the following manner&ndash;&nbsp;
<img style="display: block; margin-left: auto; margin-right: auto;" src="https://vediphlie-aws.s3.ap-south-1.amazonaws.com/Molecular_mechanism_of_aggregation_by_c_AMP_GPCR_Signaling_in_Dictyostelium_7caa0540dd.PNG" alt="Molecular mechanism of aggregation by cAMP (GPCR) Signaling in Dictyostelium" />
Fig.: Molecular mechanism of aggregation by cAMP (GPCR) Signaling in Dictyostelium.
1. A GPCR-protein receptor is activated on cAMP reception
2. Receptor stimulates the Adenylate cyclase
3. cAMP diffuses out of the cell
4. Internal cAMP desensitizes the cAMP- GPCR receptor.
5. Another G-protein stimulates phospholipase C
6. Calcium ion released by IP3 induction
7. Calcium ions rearrange the cytoskeleton to bear pseudopodia.
Because of receptor desensitization, cells show oscillatory behavior and produce beautiful spirals seen in converging colonies. The aggregated amoebae work as pseudoplasmodium and are known as a slug. This slug is having 100,000 cells and a 2-4mm long body. The cAMP and DIF (differentiation-inducing factor) are responsible for the differentiation of slug into the prestalk and the prespore cells that switch the positions in the culmination stage and form the mature fruiting body (sorocarp).
The fruiting body stalk is formed by cells from the anterior end of the slug and the spores of the fruiting body are formed by the cells from the posterior end of the slug. After some hours the fruiting body has the ability to release mature spores, leading to Myxamoebae.

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In this topic of Cell Aggregation and Differentiation in Dictyostelium, we will cover the life cycle of Dictyostelium & the Mechanism of aggregation. 

Cell Aggregation and Differentiation in Dictyostelium

The molecular mechanism for the aggregation in Myxamoebae is dependent on the cAMP signalling. In this topic of Cell Aggregation and Differentiation in Dictyostelium, we will cover the life cycle of Dictyostelium & the Mechanism of aggregation. 

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