Stage-specific changes in protein phosphorylation during spore germination in Dictyostelium: role of calmodulin.

Extensive protein phosphorylation occurs during all phases of spore germination in Dictyostelium discoideum. The developmental changes were prevented when germination was inhibited by inhibitors of calmodulin function. In addition, differences in patterns of phosphorylation were detected based upon the method of spore activation. Several phosphoproteins were lost in heat activated as compared to autoactivated spores. In spite of the fact that several aspects (i.e. autoactivation, emergence) are calmodulin-dependent, there was no evidence that calcium- or calmodulin-dependent protein kinase activity is present during any phase of spore germination. This suggests that other CaM-dependent processes mediate the diverse aspects of spore germination in D. discoideum.