A Molecular Analysis of G Proteins and Control of Early Gene Expression by the Cell-surface cAMP Receptor in Dictyostelium

Abstract

Dictyostelium grows as single-celled, vegetative amoebas that initiate multicellular development upon starvation. Multicellularity is achieved by the aggregation of ∼105 individual cells in response to the chemotactic agent cAMP. The aggregate undergoes a series of defined morphological changes that result in the formation of a mature fruiting body containing a sorocarp of ∼8 × 104 spores atop a slender stalk composed of ∼2 × 104 stalk cells. A molecular analysis of the developmental process has shown that sets of genes are preferentially expressed at different morphological stages. The expression of these genes is directly coupled to morphological differentiation and is regulated at the transcriptional level, in part by extracellular morphogenetic factors secreted by cells at specific developmental stages (Loomis 1975, 1982; Gomer et al. 1985; Klein et al. 1985; Schaap 1986; Williams et al. 1986; Datta et al. 1987; Mann et al. 1987).