From unicellular to multicellular organisation in the social amoeba dictyostelium discoideum

The development of the social amoeba Dictyostelium discoideum Development of a vertebrate embryo typically involves the generation of millions of cells that differentiate into hundreds of cell types to form a wide variety of different tissues and organs. Some cell types arise and differentiate in situ at the right position at the right time of development; however, many cell types have to migrate during development over considerable distances to reach their final destination. One of the best understood mechanisms guiding long-range cell movement is chemotaxis. Chemotactic cell movement is a key mechanism in the multicellular development of the social amoeba Dictyostelium discoideum. Its development is in many respects much simpler and more amenable to experimental analysis than that of vertebrates. The cells proliferate in the vegetative stage as single amoebae, which live in the soil and feed on bacteria. When the population size increases, the cells in the centre of the colony will start to starve, and starvation for amino acids acts as a signal for the cells to enter a multicellular developmental phase. Up to 10⁵ cells aggregate to form a multicellular aggregate which transforms into a cylindrical slug. The slug migrates under the control of environmental signals such as light and temperature gradients to the soil surface, where low humidity and overhead light trigger the conversion of the slug into a fruiting body. The fruiting body consists of a stalk of dead cells supporting a mass of spores.