| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1996: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1995: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
In order to study the molecular mechanisms of the temperature-dependent selection in the transmission of mitochondrial DNA (mtDNA) in Drosophila, we tried to identify both genes in the nuclear genome and DNA regions in the mitochondrial genome which are responsible for the selection. The results are as follows.
1. Chromosomes which have effects on the temperature-dependent selection were investigated. The transmission of mtDNA was examined in artificial heteroplasmy constructed using strains in which chromosomes were substituted reciprocally between the two strains of D.melanogaster. Each of the X,second, and third chromosome was shown to have effects on the temperature-dependent selection, when D.mauritiana mtDNA coexisted. These results suggest that the selection in mtDNA transmission is regulated by gene products which are encoded by the X,second and third chromosomes. Further investigation to identifysuch genes is now in progress.
2. Using mitochondrial proteins extracted from eggs of D.melanogaster, the replication of mtDNA was examined in vitro to detect directly its temperature-dependency. At present, the activity of mtDNA synthesis is not obtained. It is necessary to improve the methods of the procedure of protein extraction and activity assay.
3. Nucleotide sequences of the A+T-rich region of mtDNA which includes the replication origin of mtDNA were determined in D.simulans and D.mauritiana. For a total of about 3kb, nucleotide substitutions were analyzed by comparing with the corresponding regions of D.melanogaster and D.yakuba. With regard to the temperature-dependency, no characteristic sequences which are suggested to be involved in the selection was detected in the A+T-rich region examined by comparing the sequences of D.simulans and D.mauritiana. Further sequences are necessary to infer the DNA region (s) responsible for the temperature-dependent selection in the transmission of mtDNA.
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