Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Biology

Supervisor

Smith, David R.

2nd Supervisor

Lachance, MA.

Co-Supervisor

Abstract

Mitochondrial genomes are known for their diverse characteristics and are an attractive model to study genome evolution. Draft nuclear genomes of 71 Metschnikowia yeast strains are publicly available but their mitochondrial genome assemblies are incomplete, thereby making genome studies difficult. To remediate this shortcoming, complete mitochondrial genomes of 71 Metschnikowia strains were assembled from the draft nuclear genomes. Metschnikowia mitochondrial genomes exhibit an unprecedented amount of diversity, particularly with respect to the frequency and distribution of introns, which is often reflected upon overall genome size variations. Additionally, loss of synteny between strains of the same species further strengthens the notion that mitochondrial genomes evolve differently from their host genomes. Diversities shown from multiple genome characteristics explored in this thesis therefore highlights importance of mitochondrial genomes for studying evolution and diversity of genomes that were often neglected.

Summary for Lay Audience

Mitochondria are important organelles responsible for the production of energy in eukaryotic cells. Mitochondria differ from many other organelles by possessing their own genome. Early studies have focused on nuclear genomes, but there is now increasing interest in mitochondrial genomes, as the two are presumed to share similar, but somewhat independent evolutionary histories. Metschnikowia species are yeasts commonly found in the guts of beetles that inhabit morning glories and other flowers around the world. The nuclear genomes from various Metschnikowia are available, but their mitochondrial counterpart is known mostly from raw sequence reads that require careful assembly in order to extract useful information on their diversity. My thesis focused on constructing and analyzing mitochondrial genomes of these yeasts. I have found that the mitochondrial genomes of these species exhibit a remarkable amount of architectural diversity, such as how genes are oriented across mitochondrial genomes and how their overall distributions differ from other species, as well as how segments that are not converted into proteins (introns) are present within a gene. All these diversities contribute towards incredible overall size differences of mitochondrial genomes of Metschnikowia species. In many cases, even individuals belong to same species showed vast differences that were rare in nuclear genomes. In conclusion, my thesis shed a light on how amazing these non-nuclear genomes are and why they should be studied more in detail in hopes of further our understanding of how genomes evolve.

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