CSM News Electronic Edition Volume 4, number 12 June 10, 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 =========== INTEGRATED MAPS OF THE CHROMOSOMES IN DICTYOSTELIUM DISCOIDEUM William F. Loomis*, Dennis Welker#, Joanne Hughes#, Dawn Maghakian*, and Adam Kuspa@ *Center for Molecular Genetics, Department of Biology, UCSD, La Jolla , CA 92093; # Molecular Biology Program,Department of Biology, Utah State University, Logan, Utah 84322-5305; and @Department of Biochemistry, Baylor College of Medicine, Houston, Texas 77030 Genetics, in press ABSTRACT Detailed maps of the 6 chromosomes that carry the genes of Dictyostelium discoideum were constructed by correlating physically mapped regions with parasexually determined linkage groups. Chromosomally assigned regions were ordered and positioned by the pattern of altered fragment sizes seen in a set of REMI-RFLP strains each harboring an inserted plasmid that carries sites recognized by NotI, SstII, SmaI, BglI and ApaI. These restriction enzymes were used to digest high molecular weight DNA prepared from over 100 REMI-RFLP strains and the resulting fragments were separated and sized by pulsed-field gels. Over 150 gene probes were hybridized to blots of these gels and used to map the insertion sites relative to flanking restriction sites. In this way we have been able to restriction map the 35 Mb genome as well as determine the map position of over 150 genes to with ~40 kb resolution. These maps provide a framework for subsequent refinement. ---------------------------------------------------------------------- Activation of adenylate cyclase by divalent cations and polyamines in saponin-treated Dictyostelium discoideum cells Masakazu Oyama and Kou Kubota Department of Life Science, Faculty of Science, Himeji, Institute of Technology, Shosha 2167, Himeji 671-22 Japan J. Biochem., in press. SUMMARY Binding of an intrinsic agonist (cyclic AMP) to specific receptors on the cell surface induces transmembrane signals for activation of adenylate cyclase in the cellular slime mold, Dictyostelium discoideum. We found that stimulation by CaCl2, MgSO4 or polyamines having two to four positive charges induced the activation of adenylate cyclase in cells treated with saponin. The activation was roughly identical to the stimulation of the intrinsic agonist both in amount and in time course. The intact cells (saponin-untreated cells) responded to neither divalent cations nor polyamines. While saponin is known to have a detergent like effect and to make the plasma membrane permeable, low molecular weight dyes did not penetrate the plasma membrane under our conditions for the saponin-treatment. Caffeine is known to inhibit the cAMP-induced activation of adenylate cyclase by blocking signal transduction, but not by acting directly on the enzyme (Brenner, M. and Thoms, S. D. (1984) Develop. Biol. 101, 136-146). We found that caffeine inhibited the cation-induced activation. These results suggest that these divalent and polyvalent cations do not act directly on adenylate cyclase but that they mimic or induce the transmembrane activation signal for adenylate cyclase in the saponin-treated cells. ----------------------------------------------------------------------- [End CSM News, volume 4, number 21]