Evolved genetic variation due to epistatic mitochondrial-nuclear interactions
Authors: Samantha Sierra-Martinez; Douglas Crawford; Marjorie Oleksiak
Affiliation: University of Miami
Keywords: Comparative genomics & genome evolution
One explanation for large standing genetic variation and the diversity of nucleotide polymorphisms responding to similar evolutionary pressures is epistasis. If the adaptive value of a nucleotide polymorphism is context dependent (dependent on genetic background), then more than one adaptive solution is likely, providing a mechanism to maintain standing genetic variation. That is, the interactions among nucleotide polymorphisms define their adaptive value, which translates into more than one adaptive solution. One of the more approachable genetic interactions occurs between the two cellular genomes: nuclear and mitochondrial. These two genomes define the 96 proteins that interact within the oxidative phosphorylation pathway to produce most cellular ATP. These interactions could affect ATP production, altering an individual’s fitness. To examine mito-nuclear interactions, I analyzed nucleotide polymorphisms among pairs of polluted and non-polluted populations, where there is an adaptive divergence between populations. There are three predictions: 1) population pairs will differ in the frequencies of mito-haplotypes, 2) population pairs will have significant allele frequency differences in nuclear OxPhos genes, and 3) within a population between mitochondrial haplotypes significant differences will occur in the nuclear polymorphism frequencies. These data suggest that adaptation involves mitochondrial genomic changes that alter the adaptive importance of nuclear polymorphisms.