Summary
The presence of both cytoplasmic and nuclear genomes within eukaryotic cells raises fascinating
questions about co-evolution between genomic compartments that experience fundamentally
different mutation rates and modes of inheritance. The highly mutagenic environments found in
the mitochondria of some eukaryotes have generated interest in the role that mitochondrial
mutation accumulation plays in phenomena such as intracellular gene transfer, compensatory
evolution in the nucleus and the evolution of reproductive isolation. Although plant systems have
played an important historical role in the study of cytonuclear co-evolution, they remain
underutilized in many respects. In particular, the enormous natural variation inDNAsubstitution
rates, gene content and genome architecture in plant mitochondria – much of which has even
been found within a single genus – provides opportunities to resolve longstanding evolutionary
questions about the consequences of mitochondrial mutation accumulation. This review
summarizes some of the classic questions about cytonuclear co-evolution that could be
addressed by taking advantage of the variation in plants and highlights a recent analysis of the
effect of mitochondrial mutation accumulation on rates of molecular evolution in the nucleus.