Contribution to the study of mitochondrial metabolism and genome in Chlamydomonas reinhardtii

For the last decade, there has been growing concern about oil reserves depletion. Chlamydomonas reinhardtii, as well as other microalgae, has been investigated with a view to producing biofuel. But current production costs are still too high and impede the commercial implementation of the biofuel from microalgae strategy. Genetic improvement of C. reinhardtii is, thus, an area of immense interest in the worldwide scientific community.
During this work, we studied a mutant for the isocitrate lyase (ICL) enzyme. It is the key enzyme of the glyoxylate cycle, which allows Chlamydomonas to use acetate as a carbon source to grow and develop, especially when cultivated in the dark. Identification and characterization of effects of this mutation could, thus, be helpful to better understand the interplays between ICL and other metabolic pathways. This study of the icl mutant highlights modifications of several cellular functions such as respiration, amino acids biosynthesis and stress responses.
The second part of this work was devoted to the determination of mitochondrial transcription start site(s) in Chlamydomonas reinhardtii. Although mitochondrial genome transformation can be performed for several years, little is known about the mechanism of the mtDNA transcription in Chlamydomonas and especially about the promoter(s) used. In this work, we establish an almost functional protocol for transcription start site(s) identification and results suggest that multiple promoters might exist, which has never been observed before.