The maternal transmission of organelles sets the stage for conflict between nuclear and cytoplasmic genomes. An organellar mutation that improves female fitness will spread, even if that same mutation decreases male fertility. In plants, this conflict leads to a widespread phenomenon called cytoplasmic male sterility (CMS), whereby plants are unable to produce functional pollen due to maternally-inherited cytoplasm. Because CMS reduces fertility in numerous species of plant, it is a central issue in both evolutionary genetics and agriculture.
In the Finseth lab, we are interested in understanding the causes and consequences of cyto-nuclear conflict. CMS is pervasive and highly variable across Mimulus, providing fertile ground for understanding nucleo-mitochondrial conflict, mating system evolution, and the origin of hybrid sterilities.
Chromosome 7 of M. guttaus contains a nuclear region that restores fertility resulting from CMS (Rf2). Consistent with a model of selfish evolution of the restorer, we see an extended haplotype structure (purple and red) and a reduction in nucleotide diversity (not shown). Vertical lines represent genes (N = 1,352), horizontal lines represent re-sequenced inbred lines a population with CMS (N = 10), colors show the proportion of variant sties per gene matching the reference genome.