Prespore cell inducing factor, ψ factor,controls both prestalk and prespore gene expression in Dictyostelium development |
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Authors: | Yoko Yamada Hiroshi Minamisawa Masashi Fukuzawa Takefumi Kawata Akiko A Oohata |
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Institution: | 1. Biological Laboratory, Kansai Medical University, Hirakata, Osaka 573‐1136;2. Present address: College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, UK.;3. Department of Biology, Faculty of Science, Toho University, Funabashi, Chiba 274‐8510;4. Department of Biology, Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki, Aomori 036‐8561, Japan |
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Abstract: | Prespore cell‐inducing (psi, ψ) factor (PsiA), encoded by the psiA gene of Dictyostelium, is a secreted signal glycoprotein that induces prespore cell differentiation when added to monolayer cultures. In situ hybridization during normal development showed that the psiA gene is highly expressed in scattered cells at the mound stage and in prespore cells at the onset of culmination. The conventional prespore‐cell marker genes, cotC and pspA, were expressed normally in psiA? and psiA overexpressing strains. Expressions of rnrB and cudA are repressed in the prestalk cells of a wild type slug to render prespore specific pattern. However, a promoter‐reporter fusion gene, rnrB:lacZ, showed an ectopic expression in the prestalk cells of the psiA? strain while cudA(psp):lacZ did so in those of the psiA overexpressing strain. Overexpression of psiA delayed expression of the prestalk specific gene, ecmB, during development, while knocking out psiA promoted its expression. In addition, overexpression inhibited DIF‐1‐induced stalk formation in monolayer cultures. Together with the known prespore inducing activity, the results indicate that PsiA regulates both prespore and prestalk/stalk cell differentiation. These results indicate that PsiA is also involved in prestalk cell differentiation. |
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Keywords: | cell‐type differentiation Dictyostelium discoideum extracellular signal growth factor ψ factor |
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