Expression of activated Ras during Dictyostelium development alters cell localization and changes cell fate

There is now a body of evidence to indicate that Ras proteins play importan t roles in development. Dictyostelium expresses several I as genes and each appears to perform a distinct function. Previous data had indicated that t he overexpression of an activated form of the major developmentally regulat ed gene, rasD, caused a major aberration in morphogenesis and cell type det ermination. We now show that the developmental expression of an activated r asG gene under the control of the rasD promoter causes a similar defect. Ou r results indicate that the expression of activated rasG in prespore cells results in their transdifferentiation into prestalk cells, whereas activate d rasG expression in prestalk causes gross mislocalization of the prestalk cell populations.