RNA differences between spherulating and growing microplasmodia of Physarum polycephalum as revealed by sedimentation pattern and DNA-RNA hybridization

I. Chet*, H. P. Rusch

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

The pattern of RNA during growth and during spherule formation (spherulation) was investigated in the plasmodia of the slime mold Physarum polycephalum. Spherulation was induced by exposing microplasmodia to 0.5 M mannitol. The RNA pattern was determined by the radioactivity profiles with sucrose density gradients, and by RNA-DNA competition-hybridization experiments. RNA degradation was minimized by extraction with diethyl pyrocarbonate-sodium dodecylsulfate. The radioactivity profiles of RNA extracted from both growing and spherulating microplasmodia after 20 min of labeling showed high specific activity in a fraction heavier than ribosomal RNA, but only the profiles of RNA extracted during spherulation showed high specific activity in the "lighter" region of the gradients. The specific activity of the soluble RNA, extracted at intervals following the induction of spherulation, progressively increased for 3 h, suggesting that the pool of ribonucleotides increased during this period. Actinomycin D inhibited the incorporation of [3H]protein hydrolysate into protein during spherulation but not during growth, thus indicating the necessity of new RNA synthesis during spherulation. Competition-hybridization experiments with RNA extracted from growing and spherulating microplasmodia, and performed both on filters and in liquid, suggested that some classes of RNA were depressed during spherulation and that some new classes were synthesized. It was concluded that transcription plays an important role in the control of spherulation in P. polycephalum.

Original languageEnglish
Pages (from-to)559-568
Number of pages10
JournalBBA Section Nucleic Acids And Protein Synthesis
Volume209
Issue number2
DOIs
StatePublished - 17 Jun 1970
Externally publishedYes

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