CHANGES IN RNA SYNTHESIS ASSOCIATED WITH DIFFERENTIATION (SPORULATION) IN PHYSARUM-POLYCEPHALUM

Sporulation (differentiation) of the slime mold Physarum polycephalum occurs synchronously, is independent of growth, is irreversible, and is sensitive to actinomycin D. A large portion of the RNA synthesized after illumination, which triggers sporulation, is ribosomal RNA (rRNA). The microsomal RNA from sporulating cultures revealed characteristic differences in the light region of sucrose gradients (4-16 S); this region also contained labile RNA fractions that hybridized to a greater extent than rRNA. The pattern of hybridization of total RNA obtained from sporulating cultures and fractionated on sucrose gradient was also distinct from that of starved plasmodia. Hybridization-competition experiments suggest a different RNA moiety in starving and growing plasmodia but have failed to distinguish between microsomal RNA from starving and that from sporulating cultures. © 1969.