Phosphorelay protein that supplies phosphate to regA or accepts phosphate from regA; depending on the relative concentration of the phosphodonor proteins. In vitro, acts as a substrate for cheA (bacterial kinase). Plays a role in the development. ypd1 (yeast) can complement rdeA defect. Expressed early in development in the form of precocious cell aggregation. Expressed at a significant level during vegetative growth and peaks at 8-16 hours of development. Even at its peak, the level of expression is low. The phosphorelay mechanism involves the sequential transfer of a phosphate group from 'Asp-212' of pde2 to His-65 of rdeA. In vitro, dephosphorylated by dokA. Final morphogenesis aberrant, rapid development (body formation accelerated), premature spore maturation and elevated levels of cAMP. PkaR and rdeA double mutants are rapidly developing and sporogenous. acaA and rdeA double mutant forms only a very small number of spores and no cAMP synthesis.