Cyclic AMP dependent protein kinase and prestalk-cell gene expression in Dictyostelium

Abstract

Cyclic AMP-dependent protein kinase (PKA) is required for aggregation of starved amoebae during development of Dictyostelium discoideum as well as for prespore gene expression and for maturation of stalk cells and spores. It has not been clear until now whether it plays any role in the stalk pathway prior to the final maturation of stalk cells. We have examined stalk cell formation and prestalk cell gene expression in a mutant of Dictyostelium that has an inactive PKA regulatory subunit and therefore has unrestrained catalytic activity (Nature 356 (1992) 171–172). We show that when mutant amoebae are incubated under buffer in the absence of cAMP they accumulate transcripts of the prestalk-cell-specific ecmA gene and form stalk cells, whereas the parental cells neither accumulate ecmA transcripts nor form stalk cells. These findings indicate that constitutive PKA activity renders cells able to express prestalk-cell-specific genes under conditions where wild-type cells cannot do so, and hence that PKA is probably implicated in prestalk gene expression during normal development.