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Linear kalilo DNA is a Neurospora mitochondrial plasmid that integrates into the mitochondrial DNA
C J Myers1, A J Griffiths, H Bertrand
1Department of Botany, University of British Columbia, Vancouver, Canada.
Abstract:
The linear autonomous form of kalilo DNA (previously called AR-kalDNA) is shown to be resident within mitochondria rather than nuclei, as had been suggested by previous experiments. This form has been renamed mtAR-kalDNA, to signify its mitochondrial location. Experiments are described that illustrate the inheritance and somatic transmission patterns of the mitochondrial kalilo plasmid and the mitochondrial inserted form of kalilo DNA (mtIS-kalDNA). Progeny of a cross with a pre-senescent subculture as the female parent inherited mtAR-kalDNA only; mtIS-kalDNA was not transmitted sexually. During somatic propagation of the ascospore cultures, novel kalilo DNA inserts appeared and most of them persisted until death. We propose that these inserts originated from de novo integration of mtAR-kalDNA into the mitochondrial DNA. In two of the ascopore-derived series analyzed, the first inserts detected were seen only transiently and inserts appearing subsequent to the transient inserts were retained until death. We propose that these enduring inserts originated either from rearrangements of the transient inserts or from novel integration events, either from mtAR-kalDNA or from transposition of the transient inserts.
Insights
The linear autonomous kalilo DNA (mtAR-kalDNA) resides in mitochondria, not nuclei. Novel mitochondrial kalilo DNA inserts appear during somatic propagation and often persist, suggesting de novo integration and rearrangements.
Area of Science:
- Mitochondrial genetics
- Molecular biology
- DNA dynamics
Background:
- Previous research suggested AR-kalDNA was nuclear.
- Mitochondrial DNA (mtDNA) is crucial for cellular energy production.
- Plasmids can influence host cell function and evolution.
Purpose of the Study:
- To determine the correct cellular localization of the linear autonomous form of kalilo DNA.
- To investigate the inheritance and transmission patterns of mitochondrial kalilo DNA.
- To characterize the formation and persistence of kalilo DNA inserts within mitochondria.
Main Methods:
- Genetic crosses involving pre-senescent subcultures.
- Analysis of somatic propagation in ascospore cultures.
- Molecular characterization of kalilo DNA forms and their integration into mtDNA.
Main Results:
- The linear autonomous kalilo DNA (renamed mtAR-kalDNA) is localized in mitochondria.
- mtAR-kalDNA is inherited sexually, while the mitochondrial inserted form (mtIS-kalDNA) is not.
- Novel kalilo DNA inserts arise during somatic propagation, with some persisting until death, suggesting de novo integration and rearrangements.
Conclusions:
- The mitochondrial localization of mtAR-kalDNA is confirmed.
- Somatic integration and potential rearrangements of mitochondrial kalilo DNA contribute to its diversity.
- These findings provide insights into extrachromosomal DNA dynamics within mitochondria.