Calcium and malate are sporulation-promoting factors of Physarum polycephalum

Fruiting body formation (sporulation) is a distinctive, irreversible differ entiation process in the life cycle of the slime mold Physarum polycephalum , The most important requirement for sporulation of Physarum is a period of starvation, and normally sporulation proceeds in the tight. It is shown he re that by omitting the liquid sporulation medium and elevating the tempera ture from 21 to 25 degreesC, sporulation can occur routinely in the dark. I t is further shown that this autocrine signaling in the dark requires calci um ions and malate, A putative sporulation control factor was detected in c onditioned media derived from plasmodia starved in the dark, which was then identified as polymalate, As an additional role for this previously detect ed polyanion, specific for the plasmodial state of Physarum, it is suggeste d that the secreted compound serves as a source for both malate and calcium ions and thus promotes sporulation without light signaling.