Ca2+ chemotaxis in Dictyostelium discoideum

Abstract

Using a newly developed microfluidic chamber, we have demonstrated in vitro that Ca2+ functions as a chemoattractant of aggregation-competent Dictyostelium discoideum amoebae, that parallel spatial gradients of cAMP and Ca2+ are more effective than either alone, and that cAMP functions as a stronger chemoattractant than Ca2+. Effective Ca2+ gradients are extremely steep compared with effective cAMP gradients. This presents a paradox because there is no indication to date that steep Ca 2+ gradients are generated in aggregation territories. However, given that Ca2+ chemotaxis is co-acquired with cAMP chemotaxis during development, we speculate on the role that Ca2+ chemotaxis might have and the possibility that steep, transient Ca2+ gradients are generated during natural aggregation in the interstitial regions between cells.