Isolation of DNA sequences preferentially expressed during sporulation in Saccharomyces cerevisiae.

A differential hybridization screen has been used to identify genes cloned from the yeast Saccharomyces cerevisiae that are expressed preferentially during sporulation. Duplicate copies of a partial Sau3A yeast DNA library prepared in the vector pBR322 were hybridized with radioactive cDNA probes representing the mRNA populations of sporulating a alpha cells and asporogenous alpha alpha cells at various times after transfer to sporulation medium. Thirty-eight clones showed an enhanced hybridization signal with the a alpha sporulation probe relative to the alpha alpha control cDNA probe. A comparison of the array of fragments produced by restriction endonuclease digestion of these plasmids suggested that 15 different sequences had been cloned. An RNA blot analysis using these cloned DNAs to probe RNAs purified from aa, a alpha, and alpha alpha cells harvested either during vegetative growth or at 10 h after transfer to sporulation medium indicated that 14 different sporulation-specific genes had been identified. Transcripts complementary to these genes are present only in a alpha cells after transfer to sporulation medium. Three of these clones contain two sporulation-specific genes. Three genes have been identified that are expressed in all cell types during vegetative growth and only in a alpha cells in sporulation medium.