International Journal of Developmental Biology, in press. In Dictyostelium discoideum the initial differentiation of cells is regulated by the phase of the cell cycle at starvation. Seen thus, it appears that while the notion of morphogens and positional information is a useful way of describing collective behaviour during the later stages of differentiation and pattern formation in D. discoideum, the essence of that behaviour must be sought in the myriad and interlocking ways in which cells differ from each other at all stages of the life cycle. Both represented insertions in the same gene, named PHG1. This gene encodes a polytopic membrane protein with an N-terminal lumenal domain and nine potential transmembrane segments.
Homologous genes can be identified in many species, however their function is yet to be elucidated.
Disruption of PHG1 caused a selective defect in phagocytosis of latex beads and E. coli, but not K. aerogenes bacteria. This defect in phagocytosis was caused by a decrease in the adhesion of mutant cells to phagocytosed particles. These results indicate that the Phg1 protein is involved in the adhesion of Dictyostelium to various substrates, a crucial event of phagocytosis and demonstrate the usefulness of a genetic approach to dissect the molecular events involved in the phagocytic process. To elucidate the diversity of secondary metabolites of Dictyostelium cellular slime molds and search for physiologically active substances affecting their development, we investigated the constituents of D. medium. Biological evaluation of the compounds showed that they delayed the differentiation of D. discoideum cells.