Control of enzyme synthesis by cellular interaction during development of the cellular slime mold Dictyostelium discoideum |
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| Authors: | P C Newell M Longlands M Sussman |
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| Affiliation: | 1. Microbiology Unit, Department of Biochemistry University of Oxford, OX1 3QU, England;2. Department of Biology, Brandeis University Waltham, Mass. 02154, U.S.A.;1. Arid Land and Oasis Cropping Laboratory, Institute of Arid Land, Route Eljorf, University of Gabes, 4119, Medenine, Tunisia;2. Department of Analytical Chemistry, Faculty of Pharmacy, Süleyman Demirel University, Isparta, Turkey;3. Laboratoire Energie, Eau, Environnement et Procèdes, (LEEEP), LR18ES35, Ecole Nationaled''Ingénieurs de Gabès, Université de Gabès, 6072, Gabès, Tunisia;4. Department of Chemistry, Faculty of Science and Literature, Manisa Celal Bayar University, Manisa, Turkey;1. Department of Pharmacy, Health and Nutritional Sciences, Università della Calabria, Arcavacata di Rende, Cosenza, Italy;2. Institute of General Pathology, Università Cattolica del Sacro Cuore, Roma, Italy;3. Fondazione Policlinico Universitario A. Gemelli IRCCS, Roma, Italy;1. Department of Mining and Environmental Geology, University of Venda, Thohoyandou, 0950, South Africa;3. Department of Geochemistry, Geological Survey of Denmark and Greenland (GEUS), 10, Øster Voldgade, DK-1350, Copenhagen K, Denmark;1. Department of Nanotechnology, University of Kashmir, Srinagar, Jammu and Kashmir, India;2. Department of Chemistry, DAV College, Sector -10, Chandigarh, India;3. Department of Mechanical Engineering, National Institute of Technology Srinagar, Jammu and Kashmir, India;4. Department of Physics, National Institute of Technology Srinagar, Jammu and Kashmir, India;1. Department of Surgery, Osaka University Graduate School of Medicine Japan;2. Graduate School of Biomedical and Health Sciences, Hiroshima University, Japan;1. Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany;2. Bundeswehr Medical Academy, Munich, Germany |
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| Abstract: | The cellular slime mold Dictyostelium discoideum exists during part of its life cycle as a population of separate ameboid cells without obvious cellular interactions and at other times as an organized multicellular assembly of closely interacting cells capable of developing into either stalk cells or spores. The influence of cell interactions on this development was studied by measuring the accumulation of the enzyme UDP-glucose pyrophosphorylase, a pivotal enzyme needed for polysaccharide synthesis, during development. When partially developed cell aggregates were disaggregated to single cells and replated on a solid substratum, they reaggregated, rapidly recapitulated their previous morphological development, and then completed fruit construction with approximately normal timing. During this time they also repeated the program of enzyme accumulation forming an additional 300 units of UDP-glucose pyrophosphorylase activity regardless of the amount accumulated before disaggregation. In undisturbed developing cells the presence of actinomycin D did not affect pyrophosphorylase accumulation for several hours after its administration, indicating the prior accumulation of stable messenger RNA. After disaggregation, however, the presence of actinomycin inhibited any further increase in pyrophosphorylase activity, reaggregating cells being dependent on further RNA synthesis for the additional accumulation of this enzyme. This effect of disaggregation was not due to cell damage or to non-specific loss of RNA, as the rate of incorporation of [35S]methionine into trichloroacetic acid-insoluble protein was the same in reaggregating cells as before disaggregation and was not affected for several hours by the presence of actinomycin. Disaggregated cells which were prevented from reforming normal cell contacts by EDTA formed little further enzyme and cells whose reaggregation was completely prevented by spatial separation formed none. The results indicate the need for cellular interaction to maintain the synthesis of this developmental enzyme even if the messenger RNA for the enzyme has already been formed. |
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