The genesis of the spore coat of Dictyostelium represents an exquisite exam
ple of developmentally regulated protein secretion. The proteins that are d
estined to be assembled into the extracellular matrix of the spore coat are
stored in unique prespore vesicles that are triggered to secrete their con
tents at terminal differentiation. The regulation of this process is being
revealed by the identification of the individual proteins in these vesicles
.