mRNA decay is rapidly induced after spore germination of Saccharomyces cerevisiae

Spores from the yeast Saccharomyces cerevisiae can germinate and resume their vegetative growth when placed in favorable conditions. Biochemical studies on germination have been limited by the difficulty of obtaining a pure population of spores germinating synchronously. Here, we report that spores can be purified and sorted according to their size by centrifugal elutriation and that these spores are able to germinate synchronously. Synchronizing their development has allowed reevaluating certain parameters of germination, and we demonstrate that both transcription and translation are induced very rapidly after germination induction. Spores contain mRNAs that are stable for several months in spores kept at 4 degrees C. Germination induction leads to very rapid degradation of these mRNAs, thus providing a simple model to study induction of mRNA decay in eukaryotes. mRNAs from the spore are polyadenylated, capped, and cosediment on sucrose gradients with ribosomes and polysomes and with components of the mRNA degradation machinery. The presence of polysomes in the spores led us to evaluate the activity of the translation apparatus in these cells. We present evidence that there is ongoing transcription and translation in nongerminating yeast spores incubated in water at 30 degrees C, suggesting that these activities could play a role in spore long term survival.