Mapping the Germ-Line and Somatic Genomes of a Ciliated Protozoan,Tetrahymena thermophila

Selected contributions to fundamental research and potential biotechnological applications exploiting unique or special features of the biology of Tetrahymena and other ciliates1.  Current research on general problems of fundamental significance.  •  Ribozymes: Codiscovery in the self-splicing intron of the 28S ribosomal RNA (Kruger et al. 1982). TheTetrahymena macronucleus as the eukaryotic nucleus most actively synthesizing RNAs.  •  Eukaryotic telomeres: Discovery of telomere molecular basis (Blackburn and Gall 1978) and telomerase (Greider and Blackburn 1985); template role of telomerase RNA (Yu et al. 1990) in Tetrahymena (see alsoBlackburn and Greider 1995). Tetrahymena has 20,000 copies of the DNA telomere per cell and, during MAC differentiation, has high levels of telomerase activity to carry out rapid de novo synthesis of >4000 telomeres.  •  Chromatin structure and function (e.g., Roth and Allis 1996; Shen and Gorovsky 1996): The ciliates represent an experiment of nature, as they maintain within the same cell a MIC, with chromatin always condensed and not expressed, and a MAC, with chromatin always extended and actively expressed.  •  Site-specific chromosome diminution: Mechanisms of diminution as well as understanding of epigenetic control and transposon relationships in Tetrahymenaand other ciliates (e.g., Prescott 1994; Coyne et al. 1996; Meyer and Duharcourt 1996; Klobutcher and Herrick 1997). Thousands of site-specific diminution events occur per haploid genome during MAC differentiation.  •  Regulated secretion (e.g.,Chilcoat et al. 1996 in Tetrahymena; Madeddu et al. 1994 inParamecium): These ciliates have thousands of secretory vesicles; their release can be induced in large number and synchronously.  •  Membrane excitability and chemosensory signaling in Paramecium (e.g., Saimi et al. 1994; Van Houten 1994): These large cells have striking and easily observed swimming behavior that indicates the state of depolarization of the membrane.  •  Cytokines: Studies are facilitated inTetrahymena by availability of nutritionally complete, chemically defined growth media (e.g., Rasmussen et al. 1996); inEuplotes (e.g., Luporini et al.         1996), where the easily observable mating reaction is induced by pheromones secreted in large amounts.  •  Cellular morphogenesis and polarity control (e.g., Frankel 1989): In addition to available genetic approaches, ciliates can be surgically manipulated.  •  Role of post-translational modifications of tubulin in Tetrahymena (e.g., Gaertig et al. 1995): Tetrahymena possesses a remarkable variety of tubulin-based structures formed from a minimal number of tubulin genes. 2.  Applications related to nutritional, environmental, and occupational health sciences based onTetrahymena as a eukaryote useful for rapid, reliable, sensitive, and inexpensive bioassays.  •  Determining the protein nutritional value of human foods, based on similarity of nutritional requirements (e.g., Koehler et al. 1987).  •  Sensitive biosensor for biotoxin detection (e.g., Martin Gonzalez et al. 1997).  •  Determining quantitative structure-activity relationship (QSAR) for the toxicity of human-made chemical compounds in the environment or the pharmacopoeia (e.g., Pauli et al. 1994; Sinks et al. 1997).  •  Monitoring water quality (e.g., Slabbert and Morgan 1982).  •  Alternative host for the growth ofLegionella, the causative agent of Legionnaire’s disease (e.g., Kikuhara et al. 1994).  •  Alternative to vertebrate animals or cells for testing cleaning products for eye irritation (e.g., Bagley et al. 1994). 3.  Potential for biotechnological applications.  •  Industrial production of enzymes and pharmaceuticals (e.g., Ropenga and Lenfant 1987; Kiy et al. 1996).  •  Biological control of mosquitoes, intermediate hosts for major worldwide human diseases: malaria, yellow fever (e.g., Manasherob et al. 1996; Narain et al. 1996).  •  Fighting epidemics of the closely related ciliate Icthyophthirius in fish hatcheries and pet stores (e.g., Ling et al. 1993).