Oscillations in Intracellular ATP, cAMP and cGMP Concentration in Relation to Rhythmical Sporulation under Continuous Light in the Myxomycete Physarum polycephalum

Abstract

The times of sporulation in populations of plasmodia derived from single starving plasmodia and the variation in intracellular ATP, cAMP and cGMP concentrations were determined from the time when the plasmodia were exposed to continuous light. Sporulation occurred from about 10 h after illumination, with further intermittent sporulation at 5 h or 10 h intervals. Intracellular ATP, cAMP and cGMP concentrations oscillated, usually in phase, with a period of 4–5 h until the irreversible commitment to sporulation occurred. The ATP concentration stopped oscillating, remained at the same level for a few hours and decreased gradually during sporangium formation. Oscillations in cAMP and cGMP concentrations continued, little affected by commitment to sporulate or subsequent sporulation. The period of ATP oscillation did not differ over a wide range of temperature. In plasmodia which were starved only for 1 d and therefore unable to sporulate, light failed to induce ATP oscillation. The concentrations of cAMP and cGMP oscillated but not in phase.