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Sexuality of mitochondria: fusion, recombination, and plasmids
S Kawano1, H Takano, T Kuroiwa
1Department of Biological Sciences, Graduate School of Science, University of Tokyo, Japan.
Abstract:
Mitochondrial fusion, recombination, and mobile genetic elements, which are essential for mitochondrial sexuality, are well established in various organisms. The recombination of mitochondrial DNA (mtDNA) depends upon fusion between parental mitochondria, and between their mtDNA-containing areas (mt-nuclei), to allow pairing between the parental mtDNAs. Such mitochondrial fusion followed by recombination may be called "mitochondrial sex." We have identified a novel mitochondrial plasmid named mF. This plasmid is apparently responsible for promoting mitochondrial fusion and crosses over with mtDNA in successive sexual crosses with mF- strains. Only in mF+ strains carrying the mF plasmid did small spherical mitochondria fuse which subsequently underwent fusion between the mt-nuclei that contained the mtDNA derived from individual mitochondria. Several successive mitochondrial divisions followed, accompanied by mt-nuclear divisions. The resulting mitochondria contained recombinant mtDNA with the mF plasmid. Such features remind us also of the bacterial conjugative plasmids such as F plasmid. Therefore, in the final part of this chapter, we discuss the origin of sex and its relationship to the sexuality of mitochondria.
Insights
Researchers discovered a novel mitochondrial plasmid, mF, that promotes mitochondrial fusion and DNA recombination, akin to bacterial conjugation. This finding sheds light on the origins of mitochondrial sex and its evolutionary relationship to sexual reproduction.
Area of Science:
- Mitochondrial biology
- Genetics
- Evolutionary biology
Background:
- Mitochondrial fusion and recombination are crucial for mitochondrial sexuality.
- Mitochondrial DNA (mtDNA) recombination requires fusion of parental mitochondria and their mtDNA-containing regions (mt-nuclei).
- This process, termed 'mitochondrial sex,' facilitates pairing of parental mtDNAs.
Purpose of the Study:
- To identify novel factors involved in mitochondrial fusion and recombination.
- To investigate the role of a newly discovered mitochondrial plasmid, mF, in these processes.
- To explore the evolutionary implications of mitochondrial sexuality.
Main Methods:
- Identification and characterization of a novel mitochondrial plasmid (mF).
- Observational studies of mitochondrial fusion and division in mF+ and mF- strains.
- Analysis of mtDNA recombination events in successive sexual crosses.
Main Results:
- A novel mitochondrial plasmid, mF, was identified.
- The mF plasmid promotes mitochondrial fusion and subsequent mt-nuclear fusion in mF+ strains.
- Recombination of mtDNA occurs, incorporating the mF plasmid into the resulting mitochondria.
Conclusions:
- The mF plasmid plays a key role in facilitating mitochondrial fusion and recombination, analogous to bacterial conjugative plasmids.
- These findings provide insights into the mechanisms of mitochondrial sex.
- The study discusses the potential evolutionary origins of sex and its connection to mitochondrial sexuality.