Involvement of cyanide-resistant respiration in cell-type proportioning during Dictyostelium development

Involvement of cyanide (CN)-resistant respiration in cell-type proportioning was analyzed using the developmental system of Dictyostelium discoideum. When migrating slugs were vitally stained with rhodamine 123, which is known to stain actively respirating mitochondria coupled with an elevated electronic potential of the inner membrane, the posterior prespore region was stained more strongly than the anterior prestalk region. Application of benzohydroxamic acid (BHAM) and propyl gallate, specific inhibitors of CN-resistant respiration, to starved Dictyostelium cells induced formation of unique cell masses, in which almost all of the cells differentiated into stalk-like cells with a large vacuole and thick cell wall. BHAM was also found to enhance the expressions of prestalk-specific genes such as ecmA and ecmB in the unique cell mass in a position-dependent manner. In contrast, the expression of a prespore-specific gene, Dp87, was almost completely inhibited by BHAM. Taken together these results strongly suggest the involvement of CN-resistant respiration in the proportion regulation of cell types differentiating during the Dictyostelium development.