Abstract EN:

Mitochondrial genomes from various organisms differ in their structure, size and functional processes. Their complex expression is difficult to dissect. Diseases due to mutations in the mitochondrial DNA are widespread and mitochondrial genetics have a high agronomic relevance. There are thus strong needs to manipulate the mitochondrial genetic system in mammals and plants, but none of the attempted approaches has led to a mitochondrial transformation methodology in these organisms. The main problems to solve are the transfection of the organelles and the maintenance of the transfected DNA. Earlier experiments showed that isolated mitochondria can import DNA. Based on this mechanism, we have explored distinct strategies to achieve maintenance of exogenous DNA in human and plant organelles. In human mitochondria, recombination is a rare event. We have thus attempted to build and test constructs able to behave as autonomous replicons. In plants, homologous recombination is believed to shape the mitochondrial genome and we succeeded in integrating a reporter sequence into the organelle genomic DNA. The DNA import competence might be exploitable in vivo. We therefore used currently developed mitochondriotropic vesicles (DQAsomes, liposomes) to try and deliver our constructs to the vicinity of the mitochondria in human or plant cells. In a further, distinct strategy, our group showed that a passenger RNA associated with a tRNA mimic and expressed from a nuclear transgene is imported into the mitochondria of the transformed plant cells. We have tried to analyse the functionality of the passenger RNA in the mitochondria through in vitro, in organello and in vivo editing tests.