Peroxisomes, ubiquitous organelles in eukaryotic cells, typically contain enzymes involved inÂ β 8208;oxidation of fatty acids, and play diverse roles in different eukaryotic organisms. In filamentous fungi, for example, they are required for the formation of Woronin body that is an organelle specific to filamentous ascomycetes and functions in the septal pore plugging upon hyphal injury. Furthermore, peroxisomes are reported to play fundamental roles during growth in humans, plants and also filamentous fungi. However, molecular mechanisms responsible for the severe growth defects of peroxisomal deficiency remain unknown. Here we generated the Aspergillus oryzae strains with deleted Aopex5 and Aopex7 genes encoding the receptors for peroxisomal targeting signals PTS1 and PTS2, respectively. In addition to their growth defects in the minimal medium containing oleic acid as a carbon source, surprisingly, they exhibited growth defects on the glucose medium. By screening for required nutrient supplements, we found that the addition of biotin restores their growth defects. Genome database searches revealed that BioF protein/KAPA (78208;keto8208;88208;aminopelargonic acid) synthase, one of the biotin biosynthetic enzymes, has a PTS1 sequence. BothÂ 916;AobioF and AobioF916;PTS1 strains exhibited growth defects in the absence of biotin, indicating that peroxisomal targeting of BioF is crucial for the biotin biosynthesis. In conclusion we demonstrate a novel role for peroxisomes in biotin biosynthesis, of which steps are upstream of the terminal reactions in mitochondria.
Full conference title:
11 th European Conference on Fungal Genetics
- ECFG 11th (2012)