FATE AND ROLE OF PEROXISOMES DURING THE LIFE-CYCLE OF THE YEAST SACCHAROMYCES-CEREVISIAE - INHERITANCE OF PEROXISOMES DURING MEIOSIS

Sporulation in the yeast Saccharomyces cerevisiae is a meiotic develop mental process that occurs in MATa/MAT alpha heterozygotes in response to nutrient deprivation. Here, the fate and role of peroxisomes durin g sporulation and germination has been examined by a combination of im munoelectron microscopy and the use of per mutants defective in peroxi somal functions. Using a green fluorescent protein probe targeted to p eroxisomes we show that peroxisomes are inherited through meiosis and that they do not increase in number either during sporulation or spore germination. In addition, there is no requirement for peroxisome degr adation prior to spore packaging. Unlike the situation in filamentous fungi, peroxisomes do not proliferate during the yeast life cycle. Fun ctional peroxisomes are dispensable for efficient meiotic development on acetate medium since homozygous Delta pex6 diploids sporulated well and produced mature spores that were resistant to diethyl ether. Like haploids, diploid cells can proliferate their peroxisomes in response to oleate as sole carbon source in liquid medium, but under these con ditions they do not sporulate. On solid oleate medium, homozygous pex5 , Delta pex6, and pex7 cells were unable to sporulate efficiently, whe reas the wild type was. The results presented here are discussed in te rms of the transmission of organelles to progeny cells.