Different developmental programs for amoebal and plasmodial encystment in Physarum polycephalum

Summary Amoebal and plasmodial encystment (spherulation) of Physarum polycephalum were compared. Encystment of amoebae was induced by the addition of glucose to a dense culture. A change in cellular proteins during the amoeba to rnicrocyst transition was demonstrated by SDS-polyacrylamide gel electrophoresis. We also observed that the encystment of amoebae did not involve the accumulation of the proteins which accompany plasmodial encystment. A cDNA library was constructed from poly(A)⁺ RNA of encysted amoebae and was screened by differential hybridization. Two different mRNAs, specific to mature microcysts were identified. These mRNAs were not found in encysted plasmodia. Likewise, four encysted plasmodial mRNAs were absent from microcysts. These results show that different developmental programs are used for amoebal and plasmodial encystment.