Dictyostelid social amoebas display an early form of multicellularity, where amoebas aggregate to form fruiting bodies, which contain only spores or up to four additional cell-types. different cell types throughout the organism. Dictyostelid social amoebas display an early form of multicellularity, where amoebas aggregate to form fruiting bodies, which contain only spores or up to LY2365109 hydrochloride four additional cell-types. These cell types will form the stalk and support structures for the stalk and spore head. Phylogenetic inference subdivides Dictyostelia into four major groups, with the model organism residing in group 4. In differentiation of its five Rabbit Polyclonal to OR2L5 cell types is dominated by lateral inhibition-type mechanisms that trigger scattered cell differentiation, with tissue patterns being formed by cell sorting. Results To reconstruct the evolution of pattern formation in Dictyostelia, we used cell-type specific antibodies and promoter-reporter fusion constructs to investigate pattern formation in 98 species that represent all groupings. Our results indicate that in all early diverging Dictyostelia and most members of groups 1C3, cells differentiate into maximally two cell types, prestalk and prespore cells, with pattern formation being dominated by position-dependent transdifferentiation of prespore cells into prestalk cells. In clade 2A, prestalk and stalk cell differentiation are lost and the prespore cells construct an acellular stalk. Group 4 species set aside correct proportions of prestalk and prespore cells early in development, and differentiate into up to three more supporting cell types. Conclusions Our experiments show that positional transdifferentiation is the ancestral mode of pattern formation in Dictyostelia. The early specification of a prestalk population equal to the number of stalk cells is a derived trait that emerged in group 4 and LY2365109 hydrochloride a few late diverging species in the other groups. Group 4 spore masses are larger than those of other groups and the differentiation of supporting cell types by lateral inhibition may have facilitated this increase in size. The signal DIF-1, which is secreted by prespore LY2365109 hydrochloride cells, triggers differentiation of supporting cell types. The synthesis and degradation of DIF-1 were shown to be restricted to group 4. This suggests that the emergence of DIF-1 signalling caused increased cell-type specialization in this group. Electronic supplementary material The online version of this article (doi:10.1186/2041-9139-5-34) contains supplementary material, which is available to authorized users. development, prespore and prestalk cells differentiate in well-regulated proportions that reflect the ratio of spores and stalk cells in the fruiting body [3, 4]. Initially, the prestalk and prespore cells differentiate intermixed with each other. They next sort out by differential chemotaxis and cell adhesion to form anterior prestalk and posterior prespore tissues [5, 6]. The cells that will form the basal disc and lower and upper cup differentiate among the prespore cells, and then sort to either the anterior boundary of the prespore region, or to the rearguard [7, 8]. Polyketide based signals such as DIF-1 (Differentiation inducing factor 1), which are produced by prespore cells [9] cause the differentiation of these support cells [10]. All these studies have been focussed on a single species, and indicate that cell-type specification mainly occurs by positional transdifferentiation of prespore cells into stalk cells [11, 12]. These conflicting results have thus far not been placed into an evolutionary context. Molecular phylogenetic studies showed that the Dictyostelia can be subdivided into two branches each containing two major groups and some group-intermediate species, which may represent additional groupings [13C15]. is a member of group 4, a set that contains species which form robust fruiting bodies with large spore LY2365109 hydrochloride heads. In this work we investigated patterns of cell differentiation in 98 species across all LY2365109 hydrochloride groupings. The results were mapped onto the molecular phylogeny in order to identify trends in the evolution of cell-type proportioning and pattern formation. Our results indicate that position-dependent transdifferentiation of prespore cells into stalk cells is the ancestral mechanism for cell-type specialization in Dictyostelia, with position-independent proportioning of prestalk and prespore cells and additional cell-type diversification occuring mainly in group 4. Methods Cell culture Most species were grown in association with on one fifth SM agar with 0.5% charcoal and some on one third LP with 0.5% charcoal [15]. Cells were harvested from growth plates, washed with phosphate buffer (PB) (10?mM Na/K-phosphate, pH?6.5) and distributed at 5??106 to 3??107 cells/cm2 on 2??2?cm squares of dialysis.