| dc.description | To better understand how mitochondrial genomes evolve, I investigated the structure, organization, expression and evolutionary affiliations of mitochondrial genes in the non-photosynthetic dinoflagellate Crypthecodinium cohnii. In each of the two closest relatives of the dinoflagellates, apicomplexans (a group of intracellular parasites) and ciliates, mitochondrial DNA (mtDNA) has been characterized. Therefore, the specific question that this thesis addresses is: Is the mitochondrial genome of C. cohnii more similar to that of the apicomplexans or the ciliates? To answer this question, the DNA sequences of cox1 and cob genes as well as flanking sequences were determined from C. cohnii mtDNA. The cox1 gene exists in four distinct but related contexts in C. cohnii mtDNA, with a central repeat unit flanked by one of two possible upstream (flanking domain 1 or 2) and downstream (flanking domain 3 or 4) regions. The majority of the cox1 coding sequence is located within the central repeat: however, the C-terminal portion of the open reading frame extends into flanking domains 3 and 4, thereby creating two distinct cox1 ORFs. Sequence analysis showed that the C-terminal end of one of the cox1 ORFs can fold into a highly stable RNA structure, presumably allowing it to form a stable mRNA. A similar pattern is seen with cob, with the exception that cob-containing elements exhibit five different C-terminal flanking regions, generating three distinct ORFs. The arrangement of mitochondrial genes in C. cohnii appears to be the result of homologous recombination within the central repeat between different gene-containing sequence contexts. Such recombining repeats are a characteristic feature of plant (angiosperm) mtDNA, but they have not previously been described in the mitochondrial genomes of protists. | en_US |
