Molecular evolution of mitochondrial translocations within the Arvicolinae

Deborah A Triant, Purdue University

Abstract

The mitochondrial and nuclear genomes have been linked since the historic transfer and integration of proto-mitochondrial DNA to the nucleus. Within the cell, the two genomes are physically separated but maintain complex pathways that allow for the transport of mitochondrial proteins, which are encoded in the nucleus. Despite this extensive interaction, it was traditionally thought that the two genomes were distinct until it was discovered that mitochondrial DNA was able to escape the confines of the organelle to be later integrated into the nuclear genome. The reasons as to why and how these mitochondrial transfers occur are not yet fully understood but they likely have influenced the evolution of the two genomes. Mitochondrial transfers (numts) are widespread in a variety of taxa but do not exhibit any prominent patterns related to their integration or accumulation. Within this dissertation, I isolated and examined numt sequences from a group of arvicoline rodents, most specifically within voles of the genus Microtus. Microtine voles are an excellent system in which to study numts because they have evolved faster than most rodents and have elevated rates of speciation and karyotypic evolution. The first chapter herein describes my sequencing of a Microtus mitochondrial genome. I use this genome sequence as a basis for comparison with all numt sequences and to examine Microtus mitochondrial substitution rates relative to other mammals. The second chapter outlines measures for detecting and avoiding numts during mitochondrial studies and tests for expression of a cytochrome b numt. In the next chapter, I characterized a numt found within M. rossiaemeridionalis that encompasses over 25% of the mitochondrial genome. Additionally, I isolated a portion of that numt in multiple Microtus species to date the translocation to the nucleus, assess numt orthology and estimate rates of neutral substitution. In the last chapter, I characterize multiple numts within M. rossiaemeridionalis and provide evidence that they are the result of both independent insertions and duplications events. This study demonstrates that there has been extensive and ongoing numt integration within Microtus and the results may eventually assist in understanding the evolutionary dynamics of mitochondrial transfers.

Degree

Ph.D.

Advisors

DeWoody, Purdue University.

Subject Area

Genetics

COinS