Single Nucleotides in the mtDNA Sequence Modify Mitochondrial Molecular Function and Are Associated with Sex-Specific Effects on Fertility and Aging

http://www.cell.com/current-biology/abstract/S0960-9822%2815%2901091-X

M. Florencia Camus, Jochen B.W. Wolf, Edward H. Morrow, Damian K. Dowling 

In this study, the authors bred flies containing the same nuclear genome, but different mitochondrial genomes, corresponding to different mitochondrial haplotypes from across the world. In doing this, the authors were able to demonstrate how the mitochondrial genotype can affect the phenotype of the fly, without considering the effect of nuclear DNA.

In 7 of the 13 haplotypes considered, the authors found that mtDNA copy number was increased in females above males, with the effect becoming stronger with age. Conversely (and strikingly), across 9 of the 13 mitochondrial genes tested, mitochondrial gene expression was higher in males, in all 9 genes, across all 13 haplotypes.

The authors found that mean longevity was higher in female flies. This intriguing finding, although only correlative, suggests that differences in the expression of the mitochondrial genome between males and females, may result in increased female longevity, as this may provide a selective advantage for such haplotypes (as mtDNA is maternally inherited). As an additional curiosity, the authors found that the Brownsville haplotype in this nuclear background induces cytoplasmic male sterility (male infertility, due to an interaction between mtDNA and nucleus). This is the only known case in metazoans.