Development of Dictyostelium discoideum: Chemotaxis, Cell-cell Adhesion, and Gene Expression

Abstract

INTRODUCTION AND OVERVIEW
The cellular slime mold Dictyostelium discoideum has attracted the interest of developmental biologists for many years. Starvation of this unicellular, eukaryotic organism triggers a program of differentiation during which cells undergo chemotaxis to form a multicellular aggregate, followed by differentiation of two new cell types: spores and stalks. This developmental program exhibits many features seen during development of higher eukaryotic organisms: A homogeneous population of cells differentiate into two new cell types; developing cells communicate with each other via extracellular hormones; specific cell-cell contacts are formed during the multicellular stage of development; and a specific arrangement of spore and stalk cells form during morphogenesis. Yet Dictyostelium is haploid and amenable to mutational analysis; stocks of developmental lethal mutations can be propagated vegetatively and the developmental defects studied in detail. As differentiation occurs only when growth and DNA replication have ceased, one can concentrate on the developmental process in the absence of cell growth. Additionally, the two differentiated cell types and their precursors can be isolated in quantity, allowing biochemical analysis.

Here we review our current understanding of the developmental program of Dictyostelium, focusing on the signals that regulate differentiation, the changes in gene expression, and the molecular mechanisms used by Dictyostelium to regulate the levels of gene products during development. Morphogenesis and pattern formation are considered in a separate paper in this volume (MacWilliams and David). Several excellent reviews consider other aspects of Dictyostelium development and, in particular, two books edited by Loomis provide an excellent starting...