Philippe Lachaume | Search PubMed

PubMed2004

Coordinated decrease of the expression of the mitochondrial and nuclear complex I genes in a mitochondrial mutant of Drosophila.

We have studied a mutant strain of Drosophila in which 80% of the mitochondrial DNA molecules have lost over 30% of their coding region through deletion. This deletion affects genes encoding five subunits of complex I of the respiratory chain (NADH:ubiquinone oxidoreductase). The enzymatic activity of complex I in the mutant strain is half that in the wild strain, but ATP synthesis is unaffected. The drop in enzymatic activity of complex I in the mutant strain is associated with a 50% decrease in the quantity of constitutive proteins of the complex. Moreover, in the mutant strain there is a 50% decrease in the steady-state concentration of the transcripts of the mitochondrial genes affected by the deletion. This decrease is also observed for the transcripts of the nuclear genes coding for the subunits of complex I. These results suggest a coordination of the expression of the mitochondrial and nuclear genes coding for mitochondrial proteins.

Animals↗

PubMed2002

The nuclear genome of a Drosophila mutant strain increases the frequency of rearranged mitochondrial DNA molecules.

We studied a mutant strain of Drosophila subobscura, in which 80% of the mitochondrial genomes (mtDNA) have lost over 30% of the coding region. The mutation is stable and is transmitted identically to offspring. The putative role of the mutant nuclear genome in the production of rearranged mtDNA was investigated using reciprocal crosses, to place the mitochondria of the wild strain in a mutant nuclear context. Nested PCR was used to screen for rearrangements in different regions of mtDNA; and rearrangements were detected in some individuals from the F6 generation. The frequency of these deleted mtDNAs then increased progressively in the population; and they were present in nearly all individuals in the F11 generation. They were not transmissible. Direct repeats were present at the deletion boundaries. These mutated genomes disappeared on reversion to a wild-type nuclear genome. Deletions were detected in a very small fraction of the wild population (0.7% of individuals). The mutant nuclear genome therefore does not promote a particular deletion but increases the frequency of different mtDNA rearrangements. The potential involvement of different candidate nuclear genes is discussed.

Animals↗