iDicty News Electronic Edition Volume 21, number 16 November 21, 2003 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 ============= Two Dictyostelium Orthologs of the Prokaryotic Cell Division Protein, FtsZ, Localize to Mitochondria and Are Required for the Maintenance of Normal Mitochondrial Morphology Paul R. Gilson,1* Xuan-Chuan Yu,2 Dale Hereld,2 Christian Barth,3 Amelia Savage,1 Ben R. Kiefel,1 Sui Lay,3 Paul R. Fisher,3 William Margolin,2 and Peter L. Beech1 Centre for Cellular and Molecular Biology, School of Biological and Chemical Sciences, Deakin University, Victoria 3125,1 and Department of Microbiology, La Trobe University, Bundoora, Victoria 3083,3 Australia, and Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, Texas 770302 Eukaryotic Cell, in press In bacteria, the protein FtsZ is the principal component of a ring that constricts the cell at division. Though all mitochondria probably arose through a single, ancient bacterial endosymbiosis, the mitochondria of only certain protists appear to have retained FtsZ and the protein is absent from the mitochondria of fungi, animals and higher-plants. We have investigated the role FtsZ plays in mitochondrial division in the genetically-tractable protist Dictyostelium discoideum, which encodes two nuclear-encoded FtsZs, FszA and FszB, that are targeted to the inside of mitochondria. In most wild-type amoebae, the mitochondria are spherical or rod-shaped, but in fsz-null mutants they become elongated into tubules - indicating a decrease in mitochondrial division has occurred. In support of this role in organelle division, antibodies to FszA, and FszA-GFP, show belts and puncta at multiple places along the mitochondria, which may define future or recent sites of division. FszB-GFP, in contrast, locates to an electron-dense, sub-mitochondrial body usually located at one end of the organelle but how it functions during division is unclear. This is the first demonstration of two differentially localised FtsZs within the one organelle, and points to a divergence in the roles of these two proteins.Ê Submitted by: Paul Gilson [gilson@wehi.edu.au] ----------------------------------------------------------------------------- Surrogate hosts: protozoa and invertebrates as models for studying pathogen-host interactions Michael Steinert, Matthias Leippe, Thomas Roeder Int. J. Med. Microbiol., in press Animal models, primary cell culture systems and permanent cell lines have provided important information on virulence properties of pathogenic microorganisms. Recently, it has been shown that some inherent limitations of such models can be circumvented by using non-vertebrate hosts such as Caenorhabditis elegans, Drosophila melanogaster and Dictyostelium discoideum. These new models are helpful to follow infection processes at the molecular level. Persuasive support comes from the fact that processes such as phagocytosis, cell signaling or innate immunity can be studied in these surrogate hosts. This review describes the establishment and application of each of the three aforementioned and genetically tractable hosts. In addition, we will report on a number of approaches that led to the identification of host cell factors which influence the susceptibility of the hosts to infection. Submitted by: Matthias Leippe [mleippe@zoologie.uni-kiel.de] ----------------------------------------------------------------------------- The Ca2+/Calcineurin-regulated cup Gene Family in Dictyostelium discoideum and Its Possible Involvement in Development Barrie Coukell, Yi Li, John Moniakis and Anne Cameron Department of Biology, York University, 4700 Keele, St., Toronto, ON, M3J 1P3, CANADA Eukaryotic Cell, in press Changes in free intracellular Ca2+ are thought to regulate several major processes during Dictyostelium development including cell aggregation and cell type-specific gene expression, but the mechanisms involved are unclear. To learn more about Ca2+ signalling and Ca2+ homeostasis in this organism, we used suppression subtractive hybridization to identify genes up-regulated by high extracellular Ca2+. Unexpectedly, many of the genes identified belong to a novel gene family (termed cup) with seven members. In vegetative cells, the cup genes were up-regulated by high Ca2+, but not by other ions or by heat, oxidative or osmotic stress. cup induction by Ca2+ was blocked completely by inhibitors of calcineurin and protein synthesis. In developing cells, cup expression was high during aggregation and late development, but low during the slug stage. This pattern correlates closely with reported levels of free intracellular Ca2+ during development. The cup gene products are highly homologous, acidic proteins possessing putative ricin domains. BLAST searches failed to reveal homologs in other organisms but Western analyses suggested that cup-like proteins might exist in certain other cellular slime mold species. Localization experiments indicated that cup proteins are primarily cytoplasmic, but become cell membrane-associated during Ca2+ stress and cell aggregation. When cup expression was down-regulated by antisense RNA, the cells failed to aggregate. However, this developmental block was overcome by partially up-regulating cup expression. Together, these results suggest that the cup proteins in Dictyostelium might play an important role in stabilizing/regulating the cell membrane during Ca2+ stress and/or certain stages of development. Submitted by: Barrie Coukell [bcoukell@yorku.ca] ----------------------------------------------------------------------------- Defect in Peroxisomal Multifunctional Enzyme MFE1 Affects cAMP Relay in Dictyostelium #1Satomi Matsuoka, #$1Hidekazu Kuwayama, 1Daisuke Ikeno, 2Masakazu Oyama, and 1*Mineko Maeda Develop. Growth Differ., in press We have previously reported that cells of Dictyostelium discoideum lacking the fatty acid oxidation enzyme MFE1 accumulate excess cyclopropane fatty acids from ingested bacteria. Cells in which mfeA- is disrupted fail to develop when grown in association with bacteria but form normal fruiting bodies when grown in axenic media. Bacterially grown mfeA- cells express the genes for the cAMP receptor (carA) and adenylyl cyclase (acaA) but fail to respond to a cAMP pulse by synthesis of additional cAMP which normally relays the signal. Moreover, they do not accumulate the adhesion protein, gp80, which is encoded by the cAMP-induced gene, csaA. As a consequence they do not acquire developmentally regulated EDTA-resistant cell-cell adhesion. When mutant cells are mixed with wild type cells and allowed to develop together, they co-aggregate and differentiate into both spores and stalk cells. Thus, most of the developmental consequences of excess cyclopropane fatty acids appear to result from impaired cAMP relay. Submitted by: Mineko Maeda [mmaeda@bio.sci.osaka-u.ac.jp] =============================================================================== [End Dicty News, volume 21, number 16]