Specific examples of pattern formation

Abstract

The slime mould species Dictyostelium discoideum has the simplest known cellular pattern. The pattern manifests itself during formation of the fruiting body which consists of only two cell types, spore and stalk. Fruiting bodies vary greatly in size, but spore and stalk cells are always formed in the same ratio, which is about 2:1 in the wild type: the pattern is size invariar [18]. The fruiting body is formed from a slugshaped migrating mass of amoeboid cells, the grex or pseudoplasmodium. Although the grex appears homogeneous, it can be demonstrated by a number of techniques, immunological, histochemical, ultrastructural and behavioural, that the pattern normally originates during grex migration (see [18]). The cells at the front of the grex become prestalk cells and those at the back, prespore cells.