Regulation of peroxisome size and number by fatty acid beta-oxidation in the yeast Yarrowia lipolytica

The Yarrowia lipolytica MFE2 gene encodes peroxisomal beta-oxidation multif unctional enzyme type 2 (MFE2). MFE2 is peroxisomal in a wild-type strain b ut is cytosolic in a strain lacking the peroxisomal targeting signal-1 (PTS 1) receptor. MFE2 has a PTS1, Ala-Lys-Leu, that is essential for targeting to peroxisomes. MFE2 lacking a PTS1 can apparently oligomerize with full-le ngth MFE2 to enable targetting to peroxisomes. Peroxisomes of an oleic acid -induced MFE2 deletion strain, mfe2-KO, are larger and more abundant than t hose of the wild-type strain. Under growth conditions not requiring peroxis omes, peroxisomes of mfe2-KO are larger but less abundant than those of the wild-type strain, suggesting a role for MFE2 in the regulation of peroxiso me size and number. A nonfunctional version of MFE2 did not restore normal peroxisome morphology to mfe2-KO cells, indicating that their phenotype is not due to the absence of MFE2, mfe2-KO cells contain higher amounts of bet a-oxidation enzymes than do wild-type cells. We also show that increasing t he level of the beta-oxidation enzyme thiolase results in enlarged peroxiso mes. Our results implicate peroxisomal beta-oxidation in the control of per oxisome size and number in yeast.