Mitochondrial Heteroplasmy and Non-Maternal Inheritance
Populations of mitochondria reside within individuals. Among angiosperms, these populations are rarely considered as genetically variable entities and typically are not found to be heteroplasmic in nature, leading to the widespread assumption that plant mitochondrial populations are homoplasmic. However, empirical studies of mitochondrial variation in angiosperms are relatively uncommon due to a paucity of sequence variation. Recent greenhouse studies of Silene vulgaris suggested that heteroplasmy might occur in this species at a level that it is biologically relevant. We have established a novel quantitative PCR method to study the intraindividual population genetics of mitochondria across two generations in natural populations of S. vulgaris. We show incidences of heteroplasmy for mitochondrial atpA and patterns of inheritance that are suggestive of more widespread heteroplasmy at both atpA and cox1. We have also demonstrated that quantitative levels of mitochondrial variation within individuals are high, constituting 26% of the total in one population. These findings are most consistent with a biparental model of mitochondrial inheritance. However, selection within individuals may be instrumental in the maintenance of variation because S. vulgaris is gynodioecious. Male sterility is in part, regulated by the mitochondrial genome, and strong selection pressures appear to influence the frequency of females in these populations.
Plant Mitochondrial Recombination
The McCauley lab is interested in the impact of intergenic recombination on the population genetics of plant mitochondrial genomes. The plant mitochondrial genome is capable of both intra- and intermolecular recombination. Intergenic recombination has the potential to create novel multilocus genotypes given the loci involved have intermolecular sequence differences. Recent studies have suggested that heteroplasmy and recombination could play a role in the mitochondrial population genetics of natural populations of plants in the genus Silene. The lab is interested in some related questions 1) what is the magnitude of linkage disequilibrium among mitochondrial genes in S. vulgaris? and 2) what is the role of population structure in generating recombinatorial novelty?
