We propose to study the regulation of two sets of genes in Dictyostelium discoideum those coding for heat shock proteins and those coding for spore coat proteins. Both sets of proteins have been isolated and partially characterized in this laboratory. The expression of the heat shock genes can be experimentally controlled by altering the temperature of incubation. The spore coat genes are expressed only at late stages of development and the proteins may accumulate only in posterior (pre-spore) cells. We plan to study the heat shock responses by isolating mutants in which it is altered. Heat shock at 30 degrees for 30 min. or more protects Dictyostelium cells from the lethal effects of incubation at 34 degrees. We have isolated a mutant which is partially unprotected and plan to isolate more of this class of mutants, hopefully including completely unprotected strains. We will also select for mutant strains which are protected by incubation at only 22 degrees. The heat shock proteins will be analyzed by 2D gel electrophoresis, for phos-phorylation, methylation, and glycosidation, and subcellular localization and compared to wild-type. The heat shock proteins and responses are very highly conserved in all eukaryotes and undoubted play central roles in cellular physiology. Dictyostelium provides a way to elucidate the control and function of heat shock genes. The spore coat proteins are the major proteins synthesized during culmination and provide useful markets for terminal differentiation of one of the two cell types. The temporal and spatial regulation of their genes will be studied in wild-type and pattern mutants by well-characterized antibodies to the proteins. The dependence on cell-cell interaction will be investigated. These studies will aid us in our understanding of regulation of specific gene expression in this multicellular developmental system and will provide models for similar processes in higher organisms.
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