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 developmental process that occurs in MATa/MAT alpha heterozygotes in response to nutrient deprivation. Here, the fate and role of peroxisomes during sporulation and germination has been examined by a combination of immunoelectron microscopy and the use of per mutants defective in peroxisomal functions. Using a green fluorescent protein probe targeted to peroxisomes 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 degradation prior to spore packaging. Unlike the situation in filamentous fungi, peroxisomes do not proliferate during the yeast life cycle. Functional 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 conditions they do not sporulate. On solid oleate medium, homozygous pex5, Delta pex6, and pex7 cells were unable to sporulate efficiently, whereas the wild type was. The results presented here are discussed in terms of the transmission of organelles to progeny cells.