Dicty News Electronic Edition Volume 24, number 5 March 4, 2005 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu or by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. Back issues of Dicty-News, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. ============= Abstracts ============= PldB, a putative phospholipase D homologue in Dictyostelium discoideum mediates quorum sensing during development Yi Chen, Vanessa Rodrick, Yi Yan, and Derrick Brazill* Department of Biological Sciences Hunter College 695 Park Avenue New York, NY 10021 Eukaryotic Cell, in press Quorum sensing, also known as cell-density sensing in the unicellular eukaryote Dictyostelium discoideum, is required for efficient entry into the differentiation and development segment of its life cycle. Quorum sensing is accomplished by simultaneously secreting and sensing the glycoprotein Conditioned Medium Factor, or CMF. When the density of starving cells is high, CMF levels are high, which leads to aggregation followed by development. Here, we describe the role of pldB, a gene coding for a putative phospholipase D homologue, in quorum sensing. We find that in submerged culture, adding butanol, an inhibitor of PLD-catalyzed phosphatidic acid production, allows cells to bypass the requirement for CMF mediated quorum sensing and aggregate at low cell density. Deletion of pldB mimics the presence of butanol, allowing cells to aggregate at low cell density. pldB- cells also initiate and finish aggregation rapidly. Analysis of early developmental gene expression in pldB- cells reveals that the cAMP receptor cAR1 is expressed at higher levels, earlier than in wild type cells, which could explain the rapid aggregation phenotype. As would be predicted, cells overexpressing pldB are unable to aggregate even at high cell density. Adding CMF to these pldB-overexpressing cells does not rescue aggregation. Both of these phenotypes are cell autonomous, as mixing a small number of pldB- cells with wild-type cells does not cause the wild type cells to behave like pldB- cells. Submitted by: Derrick Brazill [brazill@genectr.hunter.cuny.edu] ----------------------------------------------------------------------------- The Intracellular Role of Adenylyl Cyclase in the Regulation of Lateral Pseudopod Formation During Dictyostelium Chemotaxis Vesna Stepanovic, Deborah Wessels, Karla Daniels, William F. Loomis and David R. Soll W.M. Keck Dynamic Image Analysis Facility, Department of Biological Sciences, The University of Iowa, Iowa City, IA 52242 and Department of Biology, University of California-San Diego, La Jolla, CA 92037 Eukaryotic Cell, in press Cyclic AMP (cAMP) functions as the extracellular chemoattractant in the aggregation phase of Dictyostelium development. There is some question, however, concerning what role, if any, it plays intracellularly in motility and chemotaxis. To test for such a role, the behavior of null mutants of acaA, the adenylyl cyclase gene which encodes the enzyme responsible for cAMP synthesis during aggregation, was analyzed in buffer, and in response to experimentally generated spatial and temporal gradients of extracellular cAMP. acaA- cells were defective in suppressing lateral pseudopods in response to a spatial gradient of cAMP and to an increasing temporal gradient of cAMP. acaA- cells were unable to chemotax in natural waves of cAMP generated by majority control cells in mixed cultures. These results indicate that intracellular cAMP, and hence adenylate cyclase, plays an intracellular role in the chemotactic response. The behavioral defects of acaA- cells were surprisingly similar to those of cells of null mutants of regA, which encodes the phosphodiesterase that hydrolyzes cAMP and, hence, functions opposite ACA. This result is consistent with the hypothesis that ACA and REGA are components of a receptor-regulated intracellular circuit that controls protein kinase A activity. In this model, the suppression of lateral pseudopods in the front of a natural wave depends on a complete circuit. Hence, deletion of any component of the circuit (i.e., REGA or ACA) would result in the same chemotactic defect. Submitted by: Deborah Wessels [deborah-wessels@uiowa.edu] ----------------------------------------------------------------------------- The genome of the social amoeba Dictyostelium discoideum L. Eichinger1,  , J.A. Pachebat2,1,  , G. Glšckner3,  , M.-A. Rajandream4,  , R. Sucgang5,  , M. Berriman4, J. Song5, R. Olsen6, K. Szafranski3, Q. Xu7, 8, B. Tunggal1, S. Kummerfeld2, M. Madera2, B. A. Konfortov2, F. Rivero1, A. T. Bankier2, R. Lehmann3, N. Hamlin4, R. Davies4, P. Gaudet9, P. Fey9 , K. Pilcher9, G. Chen5, D. Saunders4, E. Sodergren7,10, P. Davis4, A. Kerhornou4, X. Nie5, N. Hall4, a, C. Anjard6, L. Hemphill5, N. Bason4, P. Farbrother1, B. Desany5, E. Just9, T. Morio11, R. Rost12, C. Churcher4, J. Cooper4, S. Haydock13, N. van Driessche7, A. Cronin4, I. Goodhead4, D. Muzny10, T. Mourier4, A. Pain4, M. Lu5, D. Harper4, R. Lindsay5, H. Hauser4, K. James4, M. Quiles10, M. Madan Babu2, T. Saito14, C. Buchrieser15, A. Wardroper16, 2, M. Felder3, M. Thangavelu17, D. Johnson4, A. Knights4, H. Loulseged10, K. Mungall4, K. Oliver4, C. Price4, M.A. Quail4, H. Urushihara11, J. Hernandez10, E. Rabbinowitsch4, D. Steffen10, M. Sanders4, J. Ma10, Y. Kohara18, S. Sharp4, M. Simmonds4, S. Spiegler4, A. Tivey4, S. Sugano19, B. White4, D. Walker4, J. Woodward4, T. Winckler20, Y. Tanaka11, G. Shaulsky7,8, M. Schleicher12, G. Weinstock7, 10, A. Rosenthal3, E.C. Cox21, R. L. Chisholm9, R. Gibbs7, 10, W. F. Loomis6, M. Platzer3, ā, R. R. Kay2, ā, J. Williams22, ā, P. H. Dear2, ā,¤, A. A. Noegel1, ā, B. Barrell4, ā and A. Kuspa5, 7, ā 1Center for Biochemistry and Center for Molecular Medicine Cologne, University of Cologne, Joseph-Stelzmann-Str. 52, 50931 Cologne, Germany 2Laboratory of Molecular Biology, MRC Centre, Cambridge CB2 2QH, UK 3Genome Analysis, Institute for Molecular Biotechnology, Beutenbergstr. 11, D-07745 Jena, Germany 4The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridgeshire CB10 1SA, UK 5Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX77030, USA 6Section of Cell and Developmental Biology, Division of Biology, University of California, San Diego, La Jolla, CA 92093, USA 7Dept. of Human and Molecular Genetics, Baylor College of Medicine, Houston, TX 77030, USA 8Graduate Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, Houston TX 77030, USA 9dictyBase, Center for Genetic Medicine, Northwestern University, 303 E Chicago Ave, Chicago, IL 60611, USA 10Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX 77030, USA 11Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan 12Adolf-Butenandt-Institute/Cell Biology, Ludwig-Maximilians-University, 80336 Munich, Germany 13Biochemistry Department, University of Cambridge, Cambridge CB2 1QW, UK. 14Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810 Japan 15UnitŽ de Genomique des Microorganismes Pathogenes, Institut Pasteur, 28 rue du Dr. Roux, 75724 Paris Cedex 15, France. 16Department of Biology, University of York, York YO10 5YW, UK. 17MRC Cancer Cell Unit, Hutchison/MRC Research Centre, Hills Road, Cambridge CB2 2XZ, UK. 18Centre for Genetic Resource Information, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan 19Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Minato, Tokyo 108-8639, Japan 20Institut fŸr Pharmazeutische Biologie, UniversitŠt Frankfurt (Biozentrum), Frankfurt am Main, 60439, Germany 21Department of Molecular Biology, Princeton University, Princeton, NJ08544-1003, USA 22School of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK aPresent address: The Institute for Genomic Research, 9712 Medical Center Drive, Rockville MD 20850, USA  These authors contributed equally. āCo-senior authors ¤Corresponding author. Telephone: [0044] 1223 402190 Fax: [0044] 1223 412178 Email: phd@mrc-lmb.cam.ac.uk Nature, in press The social amoebae are exceptional in their ability to alternate between unicellular and multicellular forms. Here we describe the genome of the best-studied member of this group, Dictyostelium discoideum. The gene-dense chromosomes encode ~12,500 predicted proteins, a high proportion of which have long repetitive amino acid tracts. There are many genes for polyketide synthases and ABC transporters, suggesting an extensive secondary metabolism for producing and exporting small molecules. The genome is rich in complex repeats, one class of which is clustered and may serve as centromeres. Partial copies of the extrachromosomal rDNA element are found at the ends of each chromosome, suggesting a novel telomere structure and the use of a common mechanism to maintain both the rDNA and chromosomal termini. A proteome-based phylogeny shows that the amoebozoa diverged from the animal/fungal lineage after the plant/animal split, but Dictyostelium appears to have retained more of the diversity of the ancestral genome than either of these two groups. Submitted by: Paul Dear [phd@mrc-lmb.cam.ac.uk] ============================================================================== [End Dicty News, volume 24, number 5]