Chez les plantes, la dynamique structurelle et l'évolution concertée des génomes nucléaire et cytoplasmiques restent peu documentées. L'objectif de cette thèse était d'étudier la diversité structurelle et l'évolution des mitogénomes et des plastomes chez les Oleaceae à l'aide d'une approche de phylogénomique. Nous avons d'abord assemblé des mitogénomes à partir de données de séquençage de faible couverture, obtenues à partir de matériel frais et d'herbier. Une grande variation de structure du mitogénome a été observée chez l'olivier, et un gène chimérique potentiellement associé à un type de stérilité mâle a été identifié. Enfin, nous avons étudié l'évolution des plastomes et des gènes mitochondriaux chez les Oleaceae. Une accélération de l'évolution du plastome a été observée dans deux lignées indépendantes. Ce changement de trajectoire évolutive pourrait être la conséquence d'une transmission occasionnelle de plastes par le pollen, modifiant les pressions sélectives sur certains gènes. / In plants, the structural dynamics and concerted evolution of nuclear and cytoplasmic genomes are poorly understood. The objective of this thesis was to study the structural diversity and evolution of mitogenomes and plastomes in the family Oleaceae with a phylogenomic approach. First, we assembled mitogenomes from low-coverage sequencing data obtained from live and herbarium material. Considerable structural variation of mitogenomes was observed in the olive, and a chimeric gene potentially associated to a type of male sterility was detected. Finally, we studied the evolution of plastomes and mitochondrial genes in the Oleaceae. Accelerated evolution of plastomes was observed in two independent lineages. This change of evolutionary rate could be the consequence of an occasional transmission of plastids with pollen, modifying selective pressures on some genes.

Direct studies of speciation are possible in the superspecies complex of Drosophila paulistorum, which consists of six different semispecies undergoing incipient speciation. Strict maternal inheritance of mitochondria is the most common pattern of mitochondrial inheritance in animals. Here I show that paternal transmission of mitochondrial DNA occurs in the heteroplasmic Orinocan semispecies and is not limited to hybrid offspring. Inheritance of one mitotype is mainly maternal while the other is mainly paternal; a highly unusual pattern of mitochondrial inheritance. I used absolute quantification real-time PCR on DNA extracted from eggs and imagoes from the Amazonian and Orinocan semispecies, as well as hybrids between these two semispecies. In crosses performed between F1 hybrids with a combination of mitotypes not found in any of the parents, no F2 hybrids were acquired. One possible explanation for this is that differences in mitotypes and inheritance patterns of mitochondrial DNA may cause incompatibilities between the genomes of D. paulistorum. This may be one cause of hybrid inviability and genetic isolation between semispecies, a necessary part of the speciation process. This further complicates the story of the ongoing speciation process in the D. paulistorum superspecies complex, which offers much to learn about speciation, mitochondrial inheritance and interactions between multiple genomes in the same organism.

No description available.