Nature of ribonucleic acid synthesis during early sporulation in Saccharomyces cerevisiae.

Phosphate uptake in sporulating cultures of Saccharomyces cerevisiae has been found to occur approximately 2 h after the transfer to sporulation medium. Early ribonucleic acid synthesis begins at approximately 4 h and continues to 8 h. Incorporation of phosphate into acid-extractable precursor pools parallels phosphate uptake. In triple-labeling experiments it was observed that the breakdown of vegetatively synthesized ribonucleic acid is not a significant source of precursors for ribonucleic acid synthesis during sporulation. The majority of the ribonucleic acid made in a 10-min period during sporulation does not migrate on gels with precursor or mature ribosomal ribonucleic acid.