A well supported multi gene phylogeny of 52 dictyostelia.

The Dictyostelid social amoebas are a popular model system for cell- and developmental biology and for evolution of sociality. Small subunit (SSU) ribosomal DNA-based phylogenies subdivide the known 150 species into four major and some minor groups, but lack resolution within groups, particularly group 4, and, as shown by genome-based phylogenies of 11 species, showed errors in the position of the root and nodes separating major clades. We are interested in the evolution of cell-type specialization, which particularly expanded in group 4.

Species recognition in social amoebae.

Aggregative multicellularity requires the ability of cells to recognise conspecifics. Social amoebae are among the best studied of such organisms, but the mechanism and evolutionary background of species recognition remained to be investigated. Here we show that heterologous expression of a single gene is sufficient for cells to efficiently make chimaeric fruiting bodies with cells.

Alkylbenzoquinone involved in development of cellular slime molds.

The structure of the prespore-cell-promoting factor from Dictyostelium discoideum was determined to be 2-hydroxy-5-methyl-6-pentylbenzoquinone. The synthetic compound has prespore-cell-promoting activity similar to the natural one, with half-maximal induction at a concentration as low as 40 pM. It was also found that the factor induces aggregation in an aggregation-deficient mutant of a related species, Polysphodilium violaceum.

Talin couples the actomyosin cortex to the plasma membrane during rear retraction and cytokinesis.

Contraction of the cortical actin cytoskeleton underlies both rear retraction in directed cell migration and cytokinesis. Here, we show that talin, a central component of focal adhesions, has a major role in these processes. We found that Dictyostelium talin A colocalized with myosin II in the rear of migrating cells and the cleavage furrow.

Origin and function of the stalk-cell vacuole in Dictyostelium.

Large vacuoles are characteristic of plant and fungal cells, and their origin has long attracted interest. The cellular slime mould provides a unique opportunity to study the de novo formation of vacuoles because, in its life cycle, a subset of the highly motile animal-like cells (prestalk cells) rapidly develops a single large vacuole and cellulosic cell wall to become plant-like cells (stalk cells). Here we describe the origin and process of vacuole formation using live-imaging of Dictyostelium cells expressing GFP-tagged ammonium transporter A (AmtA-GFP), which was found to reside on the membrane of stalk-cell vacuoles.

SunB, a novel Sad1 and UNC-84 domain-containing protein required for development of Dictyostelium discoideum.

A gene, sunB, encoding a novel class of Sad1 and UNC-84 (SUN) domain, was isolated from a cDNA screen for suppressors of a mutation in Dd-STATa - a Dictyostelium homologue of metazoan STAT (signal transducers and activators of transcription). The SunB protein localized in the area around the nucleus in growing cells, but in the multicellular stages it was predominantly found in prespore vacuoles (PSVs). A disruptant of sunB was multinucleated in the vegetative phase; during development it formed mounds with multiple tips and failed to culminate.

The trishanku gene and terminal morphogenesis in Dictyostelium discoideum.

Multicellular development in the social amoeba Dictyostelium discoideum is triggered by starvation. It involves a series of morphogenetic movements, among them being the rising of the spore mass to the tip of the stalk. The process requires precise coordination between two distinct cell types-presumptive (pre-) spore cells and presumptive (pre-) stalk cells.

Talin B is required for force transmission in morphogenesis of Dictyostelium.

Talin plays a key role in the assembly and stabilisation of focal adhesions, but whether it is directly involved in force transmission during morphogenesis remains to be elucidated. We show that the traction force of Dictyostelium cells mutant for one of its two talin genes talB is considerably smaller than that of wild-type cells, both in isolation and within tissues undergoing morphogenetic movement. The motility of mutant cells in tightly packed tissues in vivo or under strong resistance conditions in vitro was lower than that of wild-type cells, but their motility under low external force conditions was not impaired, indicating inefficient transmission of force in mutant cells.

Cell sorting by differential cell motility: a model for pattern formation in Dictyostelium.

In the slug stage of the cellular slime mold Dictyostelium discoideum, prespore cells and four types of prestalk cells show a well-defined spatial distribution in a migrating slug. We have developed a continuous mathematical model for the distribution pattern of these cell types based on the balance of force in individual cells. In the model, cell types are assumed to have different properties in cell motility, i.

Possible role of contact following in the generation of coherent motion of Dictyostelium cells.

After aggregation by chemotaxis, cells of the cellular slime mold Dictyostelium discoideum form a multicellular structure and show coherent motion such as vortices. Here, we present a mathematical model to explain both aggregation and coherent motion of cells in two-dimensional space. The model incorporates chemotactic response of cells and the cell's property, called "contact following", to follow the other cells with which they are in contact.