Insect mitochondrial control region: A review of its structure, evolution and usefulness in evolutionary studies

The control region is the only major non-coding region in the mitochondrial genome of insects. It is heavily biased to A+T nucleotides and seems to evolve under a strong directional mutation pressure. Among insects, this region is variable in both size and nucleotide sequence and may contain tandem repetition which is often associated with heteroplasmy. Tandem repetition appears to undergo concerted evolution and copy number variation indicates a high mutation rate. In contrast, the nucleotide substitution rate in this region is likely to be much reduced due to high A+T content and directional mutation pressure. Insect mitochondrial control regions are not necessarily the most variable region in the genome in terms of nucleotide substitution, and may not evolve faster than single-copy nuclear non-coding sequences. These observations have implications for the use of this region as a genetic marker in evolutionary studies. Contrary to earlier expectation, this region may have limited usefulness for both inter- and intra-specific analyses, depending on the structure and evolutionary patterns of a particular sequence. As some structural elements have been observed to be highly conserved between phylogenetically very distant insect taxa, it is of great interest to study the molecular evolution of this region in the entire class, Insecta.