Changes in protein and RNA during asexual differentiation of Physarum polycephalum

Abstract

Some of the events during the growth and asexual differentiation of Physarum polycephalum amoebae are described. Encysted amoebae contain low levels of protein and RNA. When these cells are mixed with bacteria and inoculated onto agar plates, there is an increase in cellular RNA content followed by an increase in protein content. The cellular RNA and protein contents of all strains tested decrease during the subsequent cell divisions. In nondifferentiating cells (strain CI at 30 °C and strain LU648), RNA and protein contents continue to decrease, and the cells eventually encyst. In the asexually differentiating strain CI grown at 26 °C, the cellular RNA and protein contents stop decreasing and begin to increase when the first amoebae become committed to form Plasmodia. At early stages of differentiation a new 36 000 molecular weight polypeptide appears. In fully formed plasmodia another polypeptide of 38 000 molecular weight is observed. These two plasmodial-specific polypeptides are among the most abundant plasmodial proteins.