Changes in gene expression during spherulation in Physarum polycephalum

Abstract

Variation of gene expression during spherulation of Physarum polycephalum microplasmodia has been studied by two-dimensional gel electrophoresis of proteins synthesized in vivo and in vitro. The electrophoretic pattern of total cellular proteins has also been analyzed during the course of differentiation. In all cases, major variations were observed and correlated with the formation of biologically mature spherules. After 24 h of differentiation, numerous specific proteins started to accumulate. After 48 h, a time at which viable spherule formation was complete, the synthesis of a set of late proteins was observed. It has also been shown that the synthesis of actin, the most abundant protein in this organism, was significantly repressed during the period at which the cells accumulated the spherule-specific proteins. The results showed that the spherulation of Physarum involves complex and major changes of protein synthesis, which occur in a temporal sequence. These variations are also observed in the population of translatable mRNA, thus suggesting an important role for RNA transcription.