Polyamine biosynthesis during germination of yeast ascospores

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Abstract
The role of the diamine putrescine during germination and outgrowth of ascospores of S. cerevisiae was examined. Ornithine decarobxylase activity increased and declined rapidly during germination and outgrowth; peak activity was attained after the cells had proceeded through the G1 interval of the cell cycle, whereas minimal activity was present at the completion of the 1st cell division. .alpha.-Methylornithine inhibited ornithine decarboxylase activity and the in vivo accumulation of putrescine. In the presence of .alpha.-methylornithine or methylglyoxal bis(guanylhydrazone), spores were unaffected in their ability to break dormancy and proceed through 1 cell division. Subsequent cellular growth, however, was retarded but not completely inhibited. The supplementation of methylglyoxal bis(guanylhydrazone) to sporulation medium greatly inhibited this sexual process. The synthesis of putrescine is apparently not required for the breaking of spore dormancy, but polyamine biosynthesis may be essential for meiosis and sporulation.