Peroxisomal ABC transporters and beta-oxidation during the life cycle of the filamentous fungus Podospora anserina

ATP-binding cassette transporters are ubiquitous proteins that facilitate transport of diverse substances across a membrane. However, their exact role remains poorly understood. In order to test their function in a fungus life cycle, we deleted the two Podospora anserina peroxisomal ABC transporter pABC1 and pABC2 genes as well as the three genes involved in peroxisomal (fox2) and mitochondrial (scdA and echA) beta-oxidation. Analysis of the single and double mutants shows that fatty acid beta-oxidation occurs in both organelles. Furthermore, the peroxisomal and mitochondrial fatty acid beta-oxidation pathways are both dispensable for vegetative and sexual development. They are, however, differently required for ascospore pigmentation and germination, this latter defect being restored in a DeltapABC1 and DeltapABC2 background. We report also that lack of peroxisomal ABC transporters does not prevent peroxisomal long-chain fatty acid oxidation, suggesting the existence of another pathway for their import into peroxisomes. Finally, we show that some aspects of fatty acid degradation are clearly fungus species specific.