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Temperature-dependency of electron-transport activity in mitochondria with exogenous mitochondrial DNA in Drosophila
1Department of Biology, Ochanomizu University, Tokyo, Japan.
Abstract:
In mitochondrial DNA (mtDNA) heteroplasmy induced artificially in Drosophila melanogaster (Matsuura et al., 1989), foreign mtDNA derived from D. mauritiana was selectively transmitted at 25 degrees C but was lost at 19 degrees C (Niki et al., 1989; Matsuura et al., 1990, 1991). To investigate temperature-dependent factors in the selective transmission of mtDNA, the temperature-dependency of electron-transport activity of mitochondria from D. melanogaster in which endogenous mtDNA was completely replaced by the foreign mtDNA was compared with that of D. melanogaster and D. mauritiana. For NADH-oxidase activity, the optimum temperature of D. mauritiana mitochondria was 35 degrees C while for two types of mitochondria from D. melanogaster each possessing either endogenous or exogenous mtDNA, maximum activity was noted at 32 degrees C. This observation suggests that the temperature-dependency of mitochondrial electron-transport activity is mainly determined by a nuclear genome. NADH-cytochrome c reductase and cytochrome c oxidase activities were not significantly different among the three types of mitochondria. The temperature-dependency of mitochondrial function apparently is not involved in the temperature-dependent selective transmission of mtDNA in the heteroplasmic state.
Insights
Temperature affects mitochondrial DNA (mtDNA) transmission in fruit flies. Mitochondrial electron transport activity, influenced by nuclear genes, does not explain this temperature-dependent selective transmission of mtDNA.
Area of Science:
- Genetics
- Mitochondrial Biology
- Drosophila melanogaster Research
Background:
- Mitochondrial DNA (mtDNA) heteroplasmy in Drosophila melanogaster shows temperature-dependent selective transmission.
- Foreign mtDNA from D. mauritiana is transmitted at 25°C but lost at 19°C.
Purpose of the Study:
- To investigate the role of temperature-dependent mitochondrial electron-transport activity in the selective transmission of mtDNA.
- To determine if nuclear or mitochondrial genomes primarily influence temperature-dependent mitochondrial function.
Main Methods:
- Comparing temperature-dependency of electron-transport activity in D. melanogaster mitochondria with replaced mtDNA to native D. melanogaster and D. mauritiana mitochondria.
- Assessing NADH-oxidase, NADH-cytochrome c reductase, and cytochrome c oxidase activities across different temperatures.
Main Results:
- Optimum temperature for NADH-oxidase activity differed: 35°C for D. mauritiana, 32°C for D. melanogaster (both endogenous and foreign mtDNA).
- Nuclear genome appears to primarily determine temperature-dependency of mitochondrial electron-transport activity.
- No significant differences in NADH-cytochrome c reductase and cytochrome c oxidase activities were observed.
Conclusions:
- Temperature-dependency of mitochondrial function is mainly determined by the nuclear genome.
- Mitochondrial function's temperature-dependency is not the reason for temperature-dependent selective mtDNA transmission in heteroplasmic states.