Open Access Thesis
A typical animal mitochondrial genome consists of a single circular chromosome with 37 genes (Shao et al. 2015). Atypical mitochondrial genomic arrangements have been found in some lice species, including some species with minichromosomes with only a single protein-coding or ribosomal RNA gene (Cameron et al. 2011). Mitochondrial genome data from two species of chewing lice from pocket gophers have been reported to date. For both species, Geomydoecus aurei and Thomomydoecus minor (order Phthiraptera, suborder Ischnocera, family Trichodectidae), the cox1 gene occurs on a small (less than 2,000 base-pair [bp]) minichromosome (Pietan et al. 2016).
Eight additional mitochondrial chromosomes of the louse, G. aurei are characterized here, one of which is derived from unpublished work of Andersen and Spradling (2017). For three additional minichromosomes, primers anchored in a conserved sequence region were used to amplify the majority of the circle. The four other minichromosomes were characterized using genomic sequence data annotated for mitochondrial sequences, which allowed the design of primers to amplify a portion of the circle. Seven protein-coding genes, two rRNA genes, and 16 tRNA genes were annotated.
The nucleotide lengths of G. aurei minichromosomes ranged from 1,318-1,922 bp. Each minichromosome had 1-2 protein-coding or rRNA genes with 1-3 tRNA genes. An identical 79-bp nucleotide sequence was present in all of the G. aurei minichromosomes along with three additional conserved sequence blocks that were shared among chromosomes, making the architecture of these minichromosomes similar to those of other lice in the family Trichodectidae (Song et al. 2018). All G. aurei minichromosomes had a 19-bp and an 11-bp sequence within the 79-bp conserved sequence block that was identical to the other pocket gopher louse species, T. minor, studied by Pietan et al. (2016). Given the differentiation otherwise observed between these species, the presence of stretches of identical nucleotide sequences suggests functional importance. The G. aurei cox2 minichromosome has a reduced gene content compared to other trichodectids, yet the total size of the minichromosome is similar among species, supporting suggestions by Shao et al. (2017) and Song et al. (2018) that selective pressure regulates overall size of minichromosomes in lice.
Year of Submission
Master of Science
Department of Biology
Theresa Spradling, Chair
1 PDF file (vii, 47 pages)
©2019 Alexandra Cleone Place
Place, Alexandra Cleone, "Analysis of a fragmented mitochondrial genome in a chewing louse, Geomydoecus aurei" (2019). Dissertations and Theses @ UNI. 980.
Available for download on Friday, August 07, 2020