Evolutionary dynamics of selfish mitochondrial mutations in Caenorhabditis elegans
Abstract
Despite mitochondrial DNA being one of the most popular and powerful molecular markers used to study eukaryotic evolution, much about its biology remains poorly understood. Mitochondrial genomes are challenging to engineer, reducing the power of experiments aimed at disentangling mitochondria’s complex and dynamic biology. In this dissertation, we take advantage of both long-term mutation accumulation experiments — which spontaneously generate new deletion-bearing mitotypes in Caenorhabditis elegans — and the large catalog of C. elegans natural isolates. This allows us to avoid the difficulty of engineering mitochondrial genomes and explore how selection shapes the fate of new mitochondrial mutations. We first demonstrate the selfish nature of a mitotype bearing a deletion in the ctb-1 gene (∆ctb-1), namely its transmission advantage and host fitness costs. ∆ctb-1 is then used to highlight the importance of population size for the intracellular dynamics of mitochondrial mutations. Next, we disentangle the mutational history of ∆ctb-1. In doing so, we found that selfish drive can be seen in a variety of classes of mitochondrial mutations, and that some mutations may hitchhike to high frequency by arising on a mitotype bearing a selfish mutation. We then demonstrate the selfish nature of another deletion-bearing mitotype and compare its intracellular dynamics to that of ∆ctb-1. Finally, we created lines of C. elegans bearing mutations in their sex determination pathways, and in key components of the electron transport chain. We then used these lines to determine if any of the electron transport chain mutations had sex system-specific or male-specific detrimental effects.
Subject
heteroplasmyselection
mitochondrial deletion
fitness
selfish genetic element
genomic conflict
sex
Citation
Dubie, Joseph James (2022). Evolutionary dynamics of selfish mitochondrial mutations in Caenorhabditis elegans. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /197106.