Transcription of ribosomal RNA in the life cycle of Physarum may be regulated by a specific nucleolar initiation inhibitor

Nuclear polyphosphate as a possible source of energy during the sporulation of Physarum polycephalum

31P NMR spectroscopic analysis of the polyphosphate pool in cellular and nuclear extracts of Physarum polycephalum demonstrates that plasmodia and cysts contain inorganic polyphosphates with an average chain length of about 100 phosphates. However, only during sporulation are these high-molecular-weight polyphosphates degraded to a lower molecular weight corresponding to an average chain length of about 10 phosphates. Since polyphosphates are degraded even in the presence of a sufficiently large pool of inorganic phosphate, produced by intracellular injection, we conclude that the degradation of polyphosphates serves in supplying energy for biosynthesis during sporulation rather than in increasing the availability of phosphate.

Starvation phase of Physarum polycephalum: characterization of transfer ribonucleic acid

We have begun a series of studies designed to characterize gene expression during differentiation in the slime mold Physarum polycephalum. This work concerns the starvation phase of the sporulation sequence and describes some of the quantitative changes which occur in plasmodial constituents during the 3-day starvation period and also describes alterations in the transfer ribonucleic acid (tRNA) population. The results show that whereas the plasmodial tRNA content decreased by 75% during starvation, concurrent de novo synthesis of tRNA also occurred, and they also show that overall amino acid acceptor activity of the starvation-phase tRNA population did not differ significantly from that found in the growth phase. Of the 19 starvation-phase tRNA families assayed, however, 6 were found to have consistently lower acceptor activities than did their growth-phase counterparts. Reverse-phase (RPC-5) chromatographic analysis of five of those families failed to reveal any major differences between growth- and starvation-phase isoacceptors. The data suggest that the depletion and resynthesis of tRNA during the starvation phase results in a quantitative alteration in the composition of the tRNA population and that the alteration is tRNA family and not tRNA isoacceptor specific.

Starvation phase of Physarum polycephalum: characterization of transfer ribonucleic acid

We have begun a series of studies designed to characterize gene expression during differentiation in the slime mold Physarum polycephalum. This work concerns the starvation phase of the sporulation sequence and describes some of the quantitative changes which occur in plasmodial constituents during the 3-day starvation period and also describes alterations in the transfer ribonucleic acid (tRNA) population. The results show that whereas the plasmodial tRNA content decreased by 75% during starvation, concurrent de novo synthesis of tRNA also occurred, and they also show that overall amino acid acceptor activity of the starvation-phase tRNA population did not differ significantly from that found in the growth phase. Of the 19 starvation-phase tRNA families assayed, however, 6 were found to have consistently lower acceptor activities than did their growth-phase counterparts. Reverse-phase (RPC-5) chromatographic analysis of five of those families failed to reveal any major differences between growth- and starvation-phase isoacceptors. The data suggest that the depletion and resynthesis of tRNA during the starvation phase results in a quantitative alteration in the composition of the tRNA population and that the alteration is tRNA family and not tRNA isoacceptor specific.

Incorporation of 32Pi into nucleotides, polyphosphates, and other acid-soluble compounds by Myxococcus xanthus during myxospore formation

When glycerol was used to induce myxospore formation in Myxococcu xanthus in the presence of 32Pi, the label was incorporated into a variety of acid-soluble compounds. Incorporation into ribonucleotides was approximately fivefold greater than in vegetative cells or noninducible mutants grown in glycerol. The label was also incorporated into some unknown compounds and material tentatively identified as guanosine tetraphosphate. Marked accumulation into polyphosphates, which were present mainly in culture supernatants, occurred relatively late during myxospore formation. The kinetics of accumulation of some of these compounds and their distribution into acid-soluble cell extracts and culture supernatants are described and compared with those in vegetative cells and noninducible mutants.

A new method for the purification of RNA polymerase II (or B) from the lower eukaryote Physarum polycephalum. The presence of subforms

The DNA-dependent RNA polymerase II or B from the lower eukaryote Physarum polycephalum has been purified to apparent homogeneity by a new method employing poly(ethylene imine) precipitation and elution, and heparin-Sepharose affinity chromatography. The method is readily scaled up or down and affords a purification of over 5000-fold with a yield of 35-45%. The procedure is easy to perform and can be carried out in less than three days even on a large scale. Furthermore, it gives enzyme of higher purity and in at least 10-fold greater yield than previously published procedures for its purification from this organism. These improvements have allowed the detection of a series of subforms of the enzyme. The combination of precipitation using poly(ethylene imine) with chromatography on heparin-Sepharose may prove useful in the preparation of other proteins which interact with nucleic acids.