Early Dictyostelium Development: Control Mechanisms Bypassed by Sequential Mutagenesis

Dictyostelium discoideum is a microorganism that has chosen an unusual way to reach multicellularity: Its ameboid cells stay single during growth and, after nutrient exhaustion, aggregate into a multicellular body, the slug. Eventually, the cells differentiate into spores and stalk cells, the two major constituents of the fruiting body formed at the end of development. Although Dictyostelium represents a side branch of evolution that has not given rise to higher multicellular organisms, the mechanisms of its development may help to define general principles by which the interaction of cells is controlled and by which their differentiation is programmed in time and ordered in space. In this paper we concentrate on the early stages of development.