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Constitutive homologous recombination between mitochondrial DNA and a linear mitochondrial plasmid in Physarum
H Takano1, S Kawano, T Kuroiwa
1Department of Biology, Faculty of Science, University of Tokyo, Japan.
Abstract:
In one particular myxamoebal strain (NG7; mF+) of Physarum polycephalum, a linear mitochondrial plasmid (mF plasmid) which promotes mitochondrial fusion has been identified. A mating between mF- strains, that do not carry the mF plasmid, resulted in uniparental inheritance of the mtDNA. In matings between mF+ and mF- strains a recombination occurred between the mtDNA and the mF plasmid, and recombinant mtDNA was generated with the end of the mF plasmid as its ends. The DNA sequences of the recombination site in the mtDNA and the mF plasmid, and of the recombinant mtDNA, revealed that the mF plasmid had a 473-bp sequence that was identical to, but slightly shorter than, a 477-bp sequence of the mtDNA. This so-called identical sequence was found at the junction between unique sequences of the mF plasmid and the mtDNA in the recombinant mtDNA. Thus, the recombination between the mtDNA and the mF plasmid was due to reciprocal crossing-over at the identical sequence.
Insights
A mitochondrial plasmid in Physarum polycephalum promotes mitochondrial fusion. This mF plasmid recombines with mitochondrial DNA (mtDNA), creating new mtDNA through reciprocal crossing-over at an identical sequence.
Area of Science:
- Cell Biology
- Molecular Genetics
- Mycology
Background:
- Physarum polycephalum is a model organism for studying nuclear and mitochondrial genetics.
- Mitochondrial fusion is a critical process for maintaining mitochondrial health and function.
- A specific linear mitochondrial plasmid, termed the mF plasmid, has been identified in certain strains.
Purpose of the Study:
- To investigate the role of the mF plasmid in mitochondrial fusion.
- To elucidate the mechanism of interaction and recombination between the mF plasmid and mitochondrial DNA (mtDNA).
Main Methods:
- Mating experiments between different strains of Physarum polycephalum (mF+ and mF-).
- DNA sequence analysis of mtDNA, mF plasmid, and recombinant mtDNA.
- Identification of recombination sites and sequence homology.
Main Results:
- Uniparental inheritance of mtDNA was observed in matings of mF- strains.
- Recombination occurred between the mF plasmid and mtDNA in matings of mF+ and mF- strains.
- Recombinant mtDNA was generated with the mF plasmid sequence integrated at its ends, resulting from reciprocal crossing-over at a shared 473-bp sequence.
Conclusions:
- The mF plasmid actively participates in recombination with the host mtDNA.
- This recombination process, driven by sequence homology, generates novel mtDNA molecules.
- The mF plasmid's ability to recombine with mtDNA may be linked to its role in promoting mitochondrial fusion.