Cell sorting out during the differentiation of mixtures of metabolically distinct populations of<i>Dictyostelium discoideum</i>

Abstract

ABSTRACT The behaviour, during the multicellular phase of the life-cycle, of amoebae of Dictyostelium discoideum grown indifferent media is described. Amoebal populations were marked by growthtemperature-sensitive genetic lesions which do not interfere with developmental phenomena. The fate of cell populations was determined by measuring the relative number of mutant and wild-type cells at various stages in the life-cycle. Cells sort out during development in such a way that they may be ordered in a sequence in which those given early in the following list preferentially appear in the spore population when mixed with those given later in the list: cells grown in axenic medium + 86 mM glucose and harvested when in the exponential phase of growth ; cells grown in axenic medium and harvested when in the exponential phase of growth ; cells grown on bacteria and harvested when in the exponential phase of growth; cells grown in axenic medium+ 86 mM glucose and harvested when in the stationary phase of growth. Chemotactic aggregation and grex migration are not essential for sorting-out to occur but, in the normal life-cycle, the cells of a grex formed from amoebae grown in different media have sorted out anteroposteriorly. The relationship between this sorting out behaviour and the mechanism of pattern formation in fruiting-body morphogenesis is discussed. Differences in density of the amoebae cannot account for the sorting out predispositions we observe.