Investigating Mitochondrial Biogenesis During Drosophila melanogaster Embryogenesis
Arnoldi, Ashley A.
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Mitochondria are essential organelles for most eukaryotic organisms, as they supply the majority of energy to the cell. Mitochondria are unique from the rest of the cell in that they contain their own genome and are inherited solely from the mother. During oogenesis, many proteins and RNAs, as well as mitochondria, accumulate in the cytoplasm of the egg to be used during initial development of the embryo. However, during embryogenesis, regulation of replication, transcription, and translation of the mitochondrial genome, mtDNA, remains unknown. The small circular mitochondrial genome encodes for only 13 polypeptides, while the remaining approximately 1500 mitochondrial proteins are nuclear encoded. Included among these are the proteins involved in replication, transcription, and translation of mtDNA. This dependence on nuclear proteins for mitochondrial biogenesis led to the first hypothesis that production of mitochondrial DNA, mRNA, and protein is coupled to changes in nuclear DNA levels during development. A second hypothesis takes into account the relationship between cell size and mitochondrial levels, with larger cells tending to require more energy and therefore mitochondrial activity. Without cell growth then, mitochondrial DNA, mRNA, and protein levels should remain constant. Analyses of mitochondrial DNA and mRNA were conducted using qPCR techniques while protein levels were analyzed with Western blotting of samples from Drosophila melanogaster embryos at different stages of development. Results indicate that nuclear DNA levels may influence mtDNA replication, while cell size may contribute to the regulation of mitochondrial DNA transcription and translation. Future work should confirm these findings and explore other possible factors involved in regulation of mitochondrial biogenesis.