Patterns and Mechanisms of Mitogenome Rearrangement in the Crayfishes

Science Center, Bent Corridor

Within Metazoa, the structure of the mitochondrial genome is remarkably consistent. It is typically comprised of 37 genes arranged in a circular chromosome (22 tRNA, 2 rRNA, and 13 protein coding regions), as well as a single large non-coding region. The order of these features on the mitogenome, however, can vary substantially between taxa and this variation serves as a reliable phylogenetic signal. Mitochondrial rearrangements may involve duplications, inversions, translocations, and deletions, but the underlying mechanisms causing these changes remain largely uncharacterized. Thus, our ability to model the evolution of gene order is limited. Palindromic sequences in mtDNA may play an important role, as they can form hairpin secondary structures and also potentially increase the likelihood of strand slippage during replication. Additionally, proximity of a gene to the non-coding control region appears to increase its likelihood of involvement in rearrangement events, although the exact function of the control region remains unclear. The crayfishes represent a model system with which to approach the study of mitochondrial rearrangement because they include clades with both highly conserved and highly variable mitochondrial gene orders. Using a set of crayfish mitogenomes, we examine the role of palindromic elements in mitochondrial gene rearrangement and analyze the organization of genes and pseudogenes with the goal of elucidating possible mechanisms of rearrangement in animal mitochondria.