CSM News Electronic Edition Volume 5, number 5 August 19, 1995 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to CSM-News@worms.cmsbio.nwu.edu. Back issues of CSM-News, the CSM Reference database and other useful information is available by anonymous ftp from worms.cmsbio.nwu.edu [165.124.233.50], via Gopher at the same address, or by World Wide Web at the URL "http://worms.cmsbio.nwu.edu/dicty.html" =========== Abstracts =========== Evidence for positional differentiation of prestalk cells and for a morphogenetic gradient in Dictyostelium. Anne Early, Tomo Abe and Jeffrey Williams MRC Laboratory of Molecular Cell Biology and Dept of Biology, University College London, Gower St, London WC1E 6BT Summary We present evidence that Dictyostelium slug tip cells, the pstA cells, may arise by positional differentiation but at a site remote from that which they will eventually occupy. When first detectable, the pstA cells form a peripheral ring surrounding the other prestalk cell sub-type, the pstO cells, but subsequently they move above the pstO cells to form the tip. Because pstA cell differentiation requires a ten fold higher concentration of DIF, the stalk cell inducer, the initial patterning seems likely to reflect the existence of a morphogenetic gradient. The subsequent redistribution of the two cell types is explicable by their different rates of chemotaxis to cAMP. These results help reconcile the two apparently opposing views of pattern formation in Dictyostelium; that there is positional differentiation or that pattern formation occurs by cell sorting. ------------------------------------------------------------------------ pDcsA Vectors for Strictly regulated Protein Synthesis during Early Development of Dictyostelium discoideum Jan Faix, Werner Dittrich, Josef Prassler, Monika Westphal, and Guenther Gerisch Max-Planck-Institut fuer Biochemie, D-82152 Martinsried, Germany Plasmid, in press. Summary Two expression vectors have been constructed to express proteins exclusively in developing cells of Dictyostelium discoideum. In these Escherichia coli/D. discoideum shuttle vectors proteins are synthesized under control of the promoter of the contact site A (csA) gene, which is efficiently suppressed during growth and becomes strongly activated during early development of D. discoideum. The pDcsA vectors appear to be valuable tools for the production of proteins that are not compatible with growth of D. discoideum cells. ------------------------------------------------------------------------ Involvement of Cyanide-resistant Respiration in Cell-Type Proportioning during the Dictyostelium Development Shin-Ichi Matsuyama and Yasuo Maeda Biological Institute, Faculty of Science, Tohoku University, Aoba, Sendai 980-77, Japan Developmental Biology, in press. ABSTRACT Involvement of cyanide (CN)- resistant respiration in cell-type proportioning was analysed using the developmental system of Dictyostelium discoideum. When migrating slugs were vitally-stained with rhodamine 123, which is known to stain actively respirating mitochondria coupled with elevated electronic potential of the inner membrane, the posterior prespore region was stained more strongly than the anterior prestalk region. Application of benzohydroxamic acid (BHAM) and propyl gallate (PG), a specific inhibitors of CN-resistant respiration, to starved Dictyostelium cells induced formation of unique cell masses, in which almost all of the cells differentiated into stalk-like cells with a large vacuole and thick cell wall. BHAM was also found to enhance the expressions of prestalk-specific genes such as ecmA and ecmB in the unique cell mass in a position-dependent manner. In contrast, the expression of a prespore-specific gene, Dp87, was almost completely inhibited by BHAM. Taken together these results strongly suggest the involvement of CN-resistant respiration in the proportion-regulation of cell-types differentiating during the Dictyostelium development. ------------------------------------------------------------------------- [End CSM News, volume 5, number 5]