Analysis of the ras Gene Function in Dictyostelium Discoideum
The Dictyostelium discoideum genome contains a single ras gene encoding a putative protein related to mammalian ras (1) . This gene is expressed in vegetative cells, growing in the presence of a food source. Upon starvation cell division stops and a specific developmental cycle is induced which leads to the formation of a fruiting body composed of only two parts, stalk and spores. The latter cells can give rise to vegetative cells in the presence of a new food source (for review see 2) . Transcripts from the Dictyostelium ras gene can be detected in vegetatively growing cells and accumulate during late development only in prestalk cells. At that stage two mRNAs of different size can be detected. The ras protein steady state level present in vegetative cells decreases steadily during early development, then more abruptly passed the pseudoplasmodium stage. Studies by others showed that the ras protein is mainly synthesized in vegetative cells and during late development, corresponding to the detection of ras mRNA (3).
KeywordsGuanylate Cyclase Dictyostelium Discoideum Dictyostelium Cell Inositol Polyphosphate Prespore Cell
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