A pleiotropic defect in cAMP-regulated gene expression in the Dictyostelium agg- mutant synag 7 |
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Authors: | I A Drummond R L Chisholm |
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Institution: | Department of Cell, Molecular, and Structural Biology, Northwestern University Medical School, Chicago, Illinois 60611. |
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Abstract: | During differentiation of Dictyostelium discoideum, cAMP functions as a diffusible, extracellular signal to direct chemotaxis and regulate developmental gene expression. The availability of signal-transduction mutants of Dictyostelium now makes it feasible to pursue a genetic analysis of cAMP signaling. The synag 7 mutant is defective in receptor-mediated adenylate cyclase stimulation and cannot relay a cAMP signal. To further characterize this mutant, mRNA levels of several cAMP-regulated genes were measured during development. cAMP-regulated gene expression was found to be dramatically altered in synag 7:several different genes which require cAMP for expression in wild-type cells were induced in synag 7 in the absence of cAMP. In addition, the gene-encoding discoidin I, which is normally expressed in starved cells and repressed by cAMP, is expressed at very low levels in starved synag 7 cells, possibly due to precocious repression. These results suggest that a pleiotropic regulator of cAMP-regulated gene expression is uncoupled from its normal controls during development in synag 7. |
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