Mitochondrial fusion and inheritance of the mitochondrial genome

Abstract

Although maternal or uniparental inheritance of mitochondrial genomes is a general rule, biparental inheritance is sometimes observed in protists and fungi,including yeasts. In yeast, recombination occurs between the mitochondrial genomes inherited from both parents.Mitochondrial fusion observed in yeast zygotes is thought to set up a space for DNA recombination. In the last decade,a universal mitochondrial fusion mechanism has been uncovered, using yeast as a model. On the other hand, an alternative mitochondrial fusion mechanism has been identified in the true slime mold Physarum polycephalum.A specific mitochondrial plasmid, mF, has been detected as the genetic material that causes mitochondrial fusion in P. polycephalum. Without mF, fusion of the mitochondria is not observed throughout the life cycle, suggesting that Physarum has no constitutive mitochondrial fusion mechanism.Conversely, mitochondria fuse in zygotes and during sporulation with mF. The complete mF sequence suggests that one gene, ORF640, encodes a fusogen for Physarum mitochondria. Although in general, mitochondria are inherited uniparentally, biparental inheritance occurs with specific sexual crossing in P. polycephalum.An analysis of the transmission of mitochondrial genomes has shown that recombinations between two parental mitochondrial genomes require mitochondrial fusion,mediated by mF. Physarum is a unique organism for studying mitochondrial fusion.

Secrets of the subterranean pathosystem of Armillaria

“…The genetic basis of this phenomenon in Armillaria is not known. In other study systems, for example the protist Physarum , mating‐type alleles interact with mitochondrial plasmids to either permit or prevent mitochondrial recombination after the fusion of gametes (Takano et al ., 2010). It is possible that mitochondrial recombination helps to restore function to a mitochondrial genome degraded over the many mitotic divisions expected during the long‐lived diploid stage of Armillaria , a hypothesis that has been postulated to explain an increased rate of mitochondrial recombination among older individuals of the filamentous ascomycete Podospora anserina (van Diepeningen et al ., 2010).…”

Review of cytological studies on cellular and molecular mechanisms of uniparental (maternal or paternal) inheritance of plastid and mitochondrial genomes induced by active digestion of organelle nuclei (nucleoids)

“…similar to bacterial conjugation (sexuality), which is related to the F-plasmid. Cellular and molecular mechanisms of biparental inheritance of mitochondrial genomes related to mF plasmid in P. polycephalum are described in detail in this issue by Takano et al (2010). When the cell lacks an mF-plasmid, the mitochondrial genome shows uniparental inheritance with a particular hierarchy ( Fig.…”

What Uses Are Mating Types? The “Developmental Switch” Model

“…Second, in some organisms (such as in the yeast Saccharomyces cerevisiae ), both mating types transmit mitochondria. Potential conflicts are solved by mitochondrial fusion and mitochondrial DNA (mtDNA) recombination (Takano et al 2010). In the brown alga Ectocarpus siliculosus , both mating types transmit chloroplasts, which then segregate in different parts of the sporophyte after zygotic division (Peters et al 2004).…”