Developmental gene regulation by an ancient intercellular communication system in social amoebae Dictyostelids live as single cells for most of their life time but under unfavourable conditions they can aggregate to form multicellular fruiting bodies. The aggregative chemoattractant glorin (N propionyl γ L glutamyl L ornithine δ lactam ethyl ester) was originally isolated from Polysphondylium violaceum. In this study chemotaxis of amoebae to glorin is determined in species from all four major phylogenetic groups of Dictyostelids. Effects of glorin as a modulator of gene regulation in the early multicellular development are studied in the species Polysphondylium pallidum PN500. This study implies that glorin is the most ancient intercellular communication molecule that mediates not only chemotactic aggregation but also prepares amoebae to post aggregative development by inducing genes required for intra and intercellular signaling in the multicellular organism.