|
内容記述 |
Filamentous fungi elongate their hyphal tips continuously for a long period. Neurospora crassa (N. crassa), one of the model fungi, has been reported to grow hyphae for more than 2 years, reaching a length of about 70 m. The interior of the mycelium is separated by perforated septa, and each cellular compartment is a cytoplasmic continuum containing multiple nuclei. These unique features allow fungi to recycle or replace aged or dysfunctional organelles to fresh ones by migration of functional copies from other compartments, contributing to immortality of hyphae. Short-lifespan N. crassa mutants that cease their hyphal growth at an early period have been analyzed to elucidate the mechanism of hyphal immortality more detail. From this analysis, it has been indicated that mutants deficient in the gene related to maintenance for mitochondrial DNA (mtDNA) are shorten their lifespan. These facts suggest that maintenance of mtDNA is also important for fungal hyphal immortality. Mitochondria is one of the organelles for production of ATP and essential for normal growth and life cycle of fungi. Mitochondria is a double membrane-bound organelle in eukaryotic cell and has its own circular DNA known as mtDNA. Maintenance of mtDNA is important for mitochondrial function and defect of maintenance system of mtDNA is known to cause severe diseases in human. Currently, three genes including mammalian TFAM homolog can be identified as essential genes for normal growth of hyphae in our laboratory. Phenotypic analysis of each N. crassa mutant and functional analysis of these three genes were conducted in this study. |
