• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 14
  • 6
  • 4
  • 2
  • 1
  • Tagged with
  • 40
  • 40
  • 11
  • 10
  • 10
  • 10
  • 8
  • 7
  • 6
  • 6
  • 6
  • 6
  • 6
  • 6
  • 5
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Consequences of the Domestication of Man’s Best Friend, The Dog

Björnerfeldt, Susanne January 2007 (has links)
The dog was the first animal to be domesticated and the process started at least 15 000 years ago. Today it is the most morphologically diverse mammal, with a huge variation in size and shape. Dogs have always been useful to humans in several ways, from being a food source, hunting companion, guard, social companion and lately also a model for scientific research. This thesis describes some of the changes that have occurred in the dog’s genome, both during the domestication process and later through breed creation. To give a more comprehensive view, three genetic systems were studied: maternally inherited mitochondrial DNA, paternally inherited Y chromosome and biparental autosomal chromosomes. I also sequenced complete mitochondrial genomes to view the effect new living conditions might have had on dogs’ genes after domestication. Finally, knowledge of the genetic structure in purebred dogs was used to test analytic methods usable in other species or in natural populations where little information is available. The domestication process appears to have caused a relaxation of the selective constraint in the mitochondrial genome, leading to a faster rate of accumulation of nonsynonymous changes in the mitochondrial genes. Later, the process of breed creation resulted in genetically separated breed groups. Breeds are a result from an unequal contribution of males and females with only a few popular sires contributing and a larger amount of dams. However, modern breeder preferences might lead to disruptive selective forces within breeds, which can result in additional fragmentation of breeds. The increase in linkage disequilibrium that this represents increases the value of purebred dogs as model organisms for the identification and mapping of diseases and traits. Purebred dogs’ potential for these kinds of studies will probably increase the more we know about the dog’s genome.
32

Secrets of the deep : the molecular genetics of cryptic beaked whales

Thompson, Kirsten Freja January 2017 (has links)
Beaked whales are comparatively unknown social mammals due to their deep-ocean distribution and elusive habits. The deep-ocean is the largest biome on Earth and the final frontier for human expansion. Since their first discovery, beaked whales have remained largely hidden from science. In this era of rapid technological advancement, genetic and genomic methods are key tools for population biologists and are particularly useful in describing rarely seen species. Using DNA-barcoding and nuclear markers, the publications in this thesis provide data on the distribution and external appearance of two species of beaked whale: the spade-toothed (Mesoplodon traversii) and Derinayagala’s whale (Mesoplodon hotaula). These whales were previously known from only a handful of tissue and bone specimens. Long-term efforts have facilitated the collection of samples of Gray’s beaked whale (Mesoplodon grayi) and we have used shot-gun sequencing to characterise the mitochondrial genome and isolate species-specific nuclear microsatellite loci. Using genetic species and sex identification, together with museum specimens and multivariate analyses, we provide clear evidence of sexual dimorphism in cranial dimensions and geographic variation in external morphology. No genetic differentiation was evident in Gray’s beaked whales across a large study area (~ 6,000 km). With a large female effective population size (Ne) and genetic homogeneity, we hypothesise that gene flow is facilitated by large-scale oceanographic features, such as the sub-tropical convergence. Genetic kinship analyses within Gray’s beaked whale groups suggest that the whales that strand together are not related. Both sexes disperse from their parents and these groups are not formed through the retention of kin. These results are consistent with a ‘fission-fusion’ social system that has been observed in some oceanic dolphin species. Taken together, these data provide the first insights into the population dynamics, dispersal and social organisation in Gray’s beaked whales. These publications highlight the value of using genetics alongside other techniques to describe inter- and intraspecific diversity. For beaked whales, the dead can tell us much about the living.
33

Molecular Evolution in non-bilaterian Metazoa with Emphasis on Phylum Porifera / Molekulare Evolution basaler Metazoa unter besonderer Berücksichtigung des Stammes Porifera

Voigt, Oliver 16 November 2008 (has links)
No description available.
34

Impact of mitochondrial genetic variation and immunity costs on life-history traits in Drosophila melanogaster

Bashir-Tanoli, Sumayia January 2014 (has links)
Immune activation is generally acknowledged to be costly. These costs are frequently assumed to result from trade-offs arising due to the reallocation of resources from other life-history traits to be invested in immunity. Here, I investigated the energetic basis of the costs associated with immune activation in Drosophila melanogaster. I found that immune activation significantly reduced fly fecundity (45%) and also caused a decline in metabolic rate (6%) but had no effect on body weight. To understand the factors behind reduced fecundity and metabolic rate I measured feeding and found that food intake was reduced by almost 31% in immune-challenged D. melanogaster. These findings suggest that fecundity costs of immune activation result not from the commonly accepted resource reallocation hypothesis but probably because resource acquisition is impaired during immune responses. The individuals of any animal population generally vary greatly in their ability to resist infectious disease. This variation arises due to both environmental heterogeneity and genetic diversity. Genetic variation in disease susceptibility has generally been considered to lie in the nuclear genome. Here, for the first time, I explored the influence of mitochondrial genetic (mtDNA) variation on disease susceptibility. I crossed 22 mitochondrial haplotypes onto a single nuclear genome and also studied epistasis interactions between mitochondrial and nuclear genomes (mitonuclear epistasis) by crossing five haplotypes onto five different genetic backgrounds. I found that fly susceptibility to Serratia marcescens was influenced significantly by mtDNA allelic variation. Furthermore, the effect of mitonuclear epistasis on fly susceptibility to S. marcescens was twice as great as the individual effects of either mitochondrial or nuclear genome. However, susceptibility to Beauveria bassiana was not affected by mtDNA allelic variation. These findings suggest the mitochondrial genome may play an important role in host-parasite coevolution. The Mother’s Curse hypothesis suggests that sex-specific selection due to maternal mitochondrial inheritance means that mitochondria are poorly adapted to function in males, resulting in impaired male fitness. Mother’s Curse effects have previously only been studied for two phenotypic traits (sperm-infertility and ageing) and their generality for broader life-history has not been explored. I investigated the impact of mtDNA allelic variation on 10 phenotypic traits and tested whether the patterns of phenotypic variation in males and females conformed to the expectations of the Mother’s Curse hypothesis. I found that seven of the 10 traits were significantly influenced by mtDNA allelic variation. However, there was no evidence that the effects of this variation differed between males and females. I therefore concluded that Mother’s Curse is unlikely to be a general phenomenon, nor to provide a general explanation for sexual dimorphism in life-history traits. Overall, this thesis explored the impacts of immunity costs, mitochondrial genetic variation, mitonuclear epistasis and sex-specific mitochondrial selection on D. melanogaster life-history.
35

Genome diversity and evolution in canine transmissible venereal tumour

Strakova, Andrea January 2018 (has links)
The canine transmissible venereal tumour (CTVT) is a contagious cancer that is naturally transmitted between dogs by the allogeneic transfer of living cancer cells during coitus. CTVT first arose several thousand years ago and has been reported in dog populations worldwide. The goals of this Thesis were (1) to gain further understanding of CTVT distribution patterns and prevalence around the world, (2) to use genetics to trace the historical spread of CTVT and (3) to map the genetic as well as phenotypic diversity of CTVT tumours around the world. To understand the distribution patterns of CTVT, I obtained information from 645 veterinarians and animal health workers in 109 countries, and generated a snapshot of the locations in which this disease is found. Additionally, as preparation for further genetic analysis, I collected samples from over one thousand CTVT cases from more than 50 countries, optimised methods for high-throughput DNA extraction and quantification and optimised a qPCR-based assay for CTVT diagnosis and host contamination detection. With the goal of tracing the historical spread of CTVT and learning about the genetic diversity of this disease, I sequenced complete mitochondrial genomes of 449 CTVT tumours and their matched hosts. The analysis of the CTVT mitochondrial diversity revealed that CTVT has captured mitochondrial DNA (mtDNA) through horizontal transfer events at least five times during the history of the lineage, delineating five tumour clades. CTVT appears to have spread rapidly around the world within the last 2,000 years, perhaps transported by dogs travelling along historic maritime trade routes. This work indicated that negative selection has operated to prevent accumulation of deleterious mutations in captured mtDNA, and that recombination has caused occasional mtDNA re-assortment. A histology-based screen of CTVT clades did not show any significant phenotypic differences between groups. In order to determine how the five mtDNA clades relate to each other, I analysed data from 539 CTVT exomes. This revealed that a single canine mtDNA haplogroup has recurrently and recently undergone multiple horizontal transfer events. Analysis of this haplotype highlighted a number of candidate genetic variants which may be conferring a selective advantage to this haplotype in CTVT, possibly by influencing mtDNA transcription or replication. Overall, genetic and phenotypic analysis of CTVT tumours from across the globe has broadened our understanding of CTVT diversity, and provided important insights into the biology of a unique transmissible cancer.
36

Inferring the phylogeny of problematic metazoan taxa using mitogenomic and phylogenomic data

Golombek, Anja 23 May 2019 (has links)
The evolutionary origin and the phylogeny of higher metazoan taxa is still under debate although considerable progress has been made in the past 20 years. Metazoa represents a monophyletic group of highly diverse animals including Bilateria, Cnidaria, Porifera, Ctenophores, and Placozoa. Bilateria comprises the majority of metazoans and consists of three major clades: Deuterostomia, Spiralia (= Lophotrochozoa sensu lato), and Ecdysozoa, whereas the sister group taxa Spiralia and Ecdyzozoa form the monophyletic clade Protostomia. Molecular data have profoundly changed the view of the bilaterian tree of life. One of the main questions concerning bilaterian phylogeny is the on-going debate about the evolution of complexity in Bilateria. It was assumed that the last common ancestor of Deuterostomia, Ecdysozoa and Spiralia had a segmented and coelomate body organization resembling that of an annelid. On the contrary, the traditional view is the evolution of Bilateria from a simple body organization towards more complex forms, assuming that the last common ancestor of Bilateria resembles a platyhelminth-like animal without coelomic cavities and segmentation. To resolve this question, it is necessary to unravel the phylogenetic relationships within Bilateria. By using mitogenomic and phylogenomic data, this thesis had a major contribution to clarify phylogenetic relationships within problematic metazoan taxa: (1) the phylogeny of Deuterostomia, (2) the questionable monophyly of Platyzoa, and first assumptions concerning the phylogeny of Gnathostomulida, Gastrotricha and Polycladida, (3) phylogenetic relationships within annelid taxa, especially Terebelliformia, Diurodrilidae, and Syllidae, with new insights into the evolution of mitochondrial gene order, and (4) new insights into the evolution of annelids, especially the interstitial ones, as well as the colonization of the interstitial realm.
37

Understanding natural expression of cytoplasmic male sterility in flowering plants using a wildflower <i>Lobelia siphilitica</i> L. (Campanulaceae)

Adhikari, Binaya 31 July 2018 (has links)
No description available.
38

Comparative mitochondrial genomics toward understanding genetics and evolution of arbuscular mycorrhizal fungi

Nadimi, Maryam 03 1900 (has links)
Les champignons mycorhiziens arbusculaires (CMA) sont très répandus dans le sol où ils forment des associations symbiotiques avec la majorité des plantes appelées mycorhizes arbusculaires. Le développement des CMA dépend fortement de la plante hôte, de telle sorte qu'ils ne peuvent vivre à l'état saprotrophique, par conséquent ils sont considérés comme des biotrophes obligatoires. Les CMA forment une lignée évolutive basale des champignons et ils appartiennent au phylum Glomeromycota. Leurs mycélia sont formés d’un réseau d’hyphes cénocytiques dans lesquelles les noyaux et les organites cellulaires peuvent se déplacer librement d’un compartiment à l’autre. Les CMA permettent à la plante hôte de bénéficier d'une meilleure nutrition minérale, grâce au réseau d'hyphes extraradiculaires, qui s'étend au-delà de la zone du sol explorée par les racines. Ces hyphes possèdent une grande capacité d'absorption d’éléments nutritifs qui vont être transportés par ceux-ci jusqu’aux racines. De ce fait, les CMA améliorent la croissance des plantes tout en les protégeant des stresses biotiques et abiotiques. Malgré l’importance des CMA, leurs génétique et évolution demeurent peu connues. Leurs études sont ardues à cause de leur mode de vie qui empêche leur culture en absence des plantes hôtes. En plus leur diversité génétique intra-isolat des génomes nucléaires, complique d’avantage ces études, en particulier le développement des marqueurs moléculaires pour des études biologiques, écologiques ainsi que les fonctions des CMA. C’est pour ces raisons que les génomes mitochondriaux offrent des opportunités et alternatives intéressantes pour étudier les CMA. En effet, les génomes mitochondriaux (mt) publiés à date, ne montrent pas de polymorphismes génétique intra-isolats. Cependant, des exceptions peuvent exister. Pour aller de l’avant avec la génomique mitochondriale, nous avons besoin de générer beaucoup de données de séquençages de l’ADN mitochondrial (ADNmt) afin d’étudier les méchanismes évolutifs, la génétique des population, l’écologie des communautés et la fonction des CMA. Dans ce contexte, l’objectif de mon projet de doctorat consiste à: 1) étudier l’évolution des génomes mt en utilisant l’approche de la génomique comparative au niveau des espèces proches, des isolats ainsi que des espèces phylogénétiquement éloignées chez les CMA; 2) étudier l’hérédité génétique des génomes mt au sein des isolats de l’espèce modèle Rhizophagus irregularis par le biais des anastomoses ; 3) étudier l’organisation des ADNmt et les gènes mt pour le développement des marqueurs moléculaires pour des études phylogénétiques. Nous avons utilisé l’approche dite ‘whole genome shotgun’ en pyroséquençage 454 et Illumina HiSeq pour séquencer plusieurs taxons de CMA sélectionnés selon leur importance et leur disponibilité. Les assemblages de novo, le séquençage conventionnel Sanger, l’annotation et la génomique comparative ont été réalisés pour caractériser des ADNmt complets. Nous avons découvert plusieurs mécanismes évolutifs intéressant chez l’espèce Gigaspora rosea dans laquelle le génome mt est complètement remanié en comparaison avec Rhizophagus irregularis isolat DAOM 197198. En plus nous avons mis en évidence que deux gènes cox1 et rns sont fragmentés en deux morceaux. Nous avons démontré que les ARN transcrits les deux fragments de cox1 se relient entre eux par épissage en trans ‘Trans-splicing’ à l’aide de l’ARN du gene nad5 I3 qui met ensemble les deux ARN cox1.1 et cox1.2 en formant un ARN complet et fonctionnel. Nous avons aussi trouvé une organisation de l’ADNmt très particulière chez l’espèce Rhizophagus sp. Isolat DAOM 213198 dont le génome mt est constitué par deux chromosomes circulaires. En plus nous avons trouvé une quantité considérable des séquences apparentées aux plasmides ‘plasmid-related sequences’ chez les Glomeraceae par rapport aux Gigasporaceae, contribuant ainsi à une évolution rapide des ADNmt chez les Glomeromycota. Nous avons aussi séquencé plusieurs isolats de l’espèces R. irregularis et Rhizophagus sp. pour décortiquer leur position phylogénéque et inférer des relations évolutives entre celles-ci. La comparaison génomique mt nous montré l’existence de plusieurs éléments mobiles comme : des cadres de lecture ‘open reading frames (mORFs)’, des séquences courtes inversées ‘short inverted repeats (SIRs)’, et des séquences apparentées aux plasimdes ‘plasmid-related sequences (dpo)’ qui impactent l’ordre des gènes mt et permettent le remaniement chromosomiques des ADNmt. Tous ces divers mécanismes évolutifs observés au niveau des isolats, nous permettent de développer des marqueurs moléculaires spécifiques à chaque isolat ou espèce de CMA. Les données générées dans mon projet de doctorat ont permis d’avancer les connaissances fondamentales des génomes mitochondriaux non seulement chez les Glomeromycètes, mais aussi de chez le règne des Fungi et les eucaryotes en général. Les trousses moléculaires développées dans ce projet peuvent servir à des études de la génétique des populations, des échanges génétiques et l’écologie des CMA ce qui va contribuer à la compréhension du rôle primorial des CMA en agriculture et environnement. / Arbuscular mycorrhizal fungi (AMF) are the most widespread eukaryotic symbionts, forming mutualistic associations known as Arbuscular Mycorrhizae with the majority of plantroots. AMF are obligate biotrophs belonging to an ancient fungal lineage of phylum Glomeromycota. Their mycelia are formed by a complex network made up of coenocytic hyphae, where nuclei and cell organelles can freely move from one compartment to another. AMF are commonly acknowledged to improve plant growth by enhancing mineral nutrient uptake, in particular phosphate and nitrate, and they confer tolerance to abiotic and biotic stressors for plants. Despite their significant roles in ecosystems, their genetics and evolution are not well understood. Studying AMF is challenging due to their obligate biotrophy, their slow growth, and their limited morphological criteria. In addition, intra-isolate genetic polymorphism of nuclear DNA brings another level of complexity to the investigation of the biology, ecology and function of AMF. Genetic polymorphism of nuclear DNA within a single isolate limits the development of efficient molecular markers mainly at lower taxonomic levels (i.e. the inter-isolate level). Instead, mitochondrial (mt) genomics have been used as an attractive alternative to study AMF. In AMF, mt genomes have been shown to be homogeneous, or at least much less polymorphic than nuclear DNA. However, by generating large mt sequence datasets we can investigate the efficiency and usefulness of developing molecular marker toolkits in order to study the dynamic and evolutionary mechanisms of AMF. This approach also elucidates the population genetics, community ecology and functions of Glomeromycota. Therefore, the objectives of my Ph.D. project were: 1) To investigate mitochondrial genome evolution using comparative mitogenomic analyses of closely related species and isolates as well as phylogenetically distant taxa of AMF; 2) To explore mt genome inheritance among compatible isolates of the model AMF Rhizophagus irregularis through anastomosis formation; and 3) To assess mtDNA and mt genes for marker development and phylogenetic analyses. We used whole genome shotgun, 454 pyrosequencing and HiSeq Illimina to sequence AMF taxa selected according to their importance and availability in our lab collections. De novo assemblies, Sanger sequencing, annotation and comparative genomics were then performed to characterize complete mtDNAs. We discovered interesting evolutionary mechanisms in Gigaspora rosea: 1) we found a fully reshuffled mt genome synteny compared to Rhizaphagus irregularis DAOM 197198; and 2) we discovered the presence of fragmented cox1 and rns genes. We demonstrated that two cox1 transcripts are joined by trans-splicing. We also reported an unusual mtDNA organization in Rhizophagus sp. DAOM 213198, whose mt genome consisted of two circular mtDNAs. In addition, we observed a considerably higher number of mt plasmidrelated sequences in Glomeraceae compared with Gigasporaceae, contributing a mechanism for faster evolution of mtDNA in Glomeromycota. We also sequenced other isolates of R. irregularis and Rhizophagus sp. in order to unravel their evolutionary relationships and to develop molecular toolkits for their discrimination. Comparative mitogenomic analyses of these mtDNAs revealed the occurrence of many mobile elements such as mobile open reading frames (mORFs), short inverted repeats (SIRs), and plasmid-related sequences (dpo) that impact mt genome synteny and mtDNA alteration. All together, these evolutionary mechanisms among closely related AMF isolates give us clues for designing reliable and efficient intra- and inter-specific markers to discriminate closely related AMF taxa and isolates. Data generated in my Ph.D. project advances our knowledge of mitochondrial genomes evolution not only in Glomeromycota, but also in the larger framework of the Fungal kingdom and Eukaryotes in general. Molecular toolkits developed in this project will offer new opportunities to study population genetics, genetic exchanges and ecology of AMF. In turn, this work will contribute to understanding the role of these fungi in nature, with potential applications in both agriculture and environmental protection.
39

La génomique évolutive mitochondriale révèle des échanges génétiques et la ségrégation chez les Gloméromycètes

Beaudet, Denis 06 1900 (has links)
Les champignons mycorhiziens à arbuscules (CMA) sont des organismes microscopiques du sol qui jouent un rôle crucial dans les écosystèmes naturels et que l’on retrouve dans tous les habitats de la planète. Ils vivent en relation symbiotique avec la vaste majorité des plantes terrestres. Ils sont des biotrophes obligatoires, c'est-à-dire qu'ils ne peuvent croître qu'en présence d'une plante hôte. Cette symbiose permet entre autres à la plante d'acquérir des nutriments supplémentaires, en particulier du phosphore et du nitrate. Malgré le fait que cette symbiose apporte des services importants aux écosystèmes, la richesse des espèces, la structure des communautés, ainsi que la diversité fonctionnelle des CMA sont mal connues et l'approfondissement des connaissances dans ces domaines dépend d’outils de diagnostic moléculaire. Cependant, la présence de polymorphisme nucléaire intra-isolat combiné à un manque de données génomiques dans différents groupes phylogénétique de ces champignons complique le développement de marqueurs moléculaires et la détermination de l'affiliation évolutive à hauts niveaux de résolution (c.a.d. entre espèces génétiquement similaires et/ou isolats de la même espèce). . Pour ces raisons, il semble une bonne alternative d’utiliser un système génétique différent en ciblant le génome mitochondrial, qui a été démontré homogène au sein d'un même isolat de CMA. Cependant, étant donné le mode de vie particulier de ces organismes, une meilleure compréhension des processus évolutifs mitochondriaux est nécessaire afin de valoriser l'utilisation de tels marqueurs dans des études de diversité et en génétique des populations. En ce sens, mon projet de doctorat consistait à investiguerétudier: i) les vecteurs de divergences inter-isolats et -espèces génétiquement rapprochéesphylogénétiquement apparentées, ii) la plasticité des génomes mitochondriaux, iii) l'héritabilité mitochondriale et les mécanismes potentiels de ségrégation, ainsi que iv) la diversité mitochondriale intra-isolat in situ. À l'aide de la génomique mitochondriale comparative, en utilisant le séquençage nouvelle génération, on a démontré la présence de variation génétique substantielle inter-isolats et -espèces, engendrées par l'invasion d'éléments mobiles dans les génomes mitochondriaux des CMA, donnant lieu à une évolution moléculaire rapide des régions intergéniques. Cette variation permettait de développer des marqueurs spécifiques à des isolats de la même espèce. Ensuite, à l'aide d'une approche analytique par réseaux de gènes sur des éléments mobiles, on a été en mesure de démontrer des évènements de recombinaisons homologues entre des haplotypes mitochondriaux distincts, menant à des réarrangements génomiques. Cela a permis d'ouvrir les perspectives sur la dynamique mitochondriale et l'hétéroplasmie dans un même isolatsuggère une coexistence de différents haplotypes mitochondriaux dans les populations naturelles et que les cultures monosporales pourraient induirent une sous-estimation de la diversité allélique mitochondriale. Cette apparente contradiction avec l'homogénéité mitochondriale intra-isolat généralement observée, a amené à investiguer étudier les échanges génétiques à l'aide de croisements d'isolats génétiquement distincts. Malgré l'observation de quelques spores filles hétéroplasmiques, l'homoplasmie était le statut par défaut dans toutes les cultures monosporales, avec un biais en faveur de l'un des haplotypes parentaux. Ces résultats suggèrent que la ségrégation opère durant la formation de la spore et/ou le développement de la coloniedu mycélium. De plus, ils supportent la présence d'une machinerie protéique de ségrégation mitochondriale chez les CMAAMF, où l'ensemble des gènes impliqués dans ce mécanisme ont été retrouvé et sont orthologues aux autres champignons. Finalement, on est revenue aux sources avecon a étudié le polymorphisme mitochondrial intra-isolat à l'aide d'une approche conventionnelle de PCR en utilisant une Taq polymérase de haute fidélité, suivie de clonage et de séquençage Sanger, sur deux isolats de R. irregularis. Cela a permis l'observation d'hétéroplasmie in situ, ainsi que la co-expression de variantes de variantes de protéines'ARNm dans une souche in vitro. Les résultats suggèrent que d'autres études basées sur le séquençage nouvelle génération aurait potentiellement ignorée cette variation, offrant ainsi plusieurs nouveaux arguments permettant de considérer les CMA comme des organismes possédant une population de génomes mitochondriaux et nucléaires distincts. / The association between arbuscular mycorrhizal fungi (AMF) and plant roots is one of the most widespread symbioses involving plants, and thus has an important role in terrestrial ecosystems. In exchange for carbohydrates, AMF improve plant fitness by enhancing mineral nutrient uptake, especially in particular phosphate and nitrate. Although this symbiosisDespite the fact that these symbioses contribute provides to important services toin ecosystems, the species richness, community structure and functional diversity of AMF is not well understood due to a lack of reliable molecular tools. The intra-isolate genetic polymorphism of nuclear DNA observed in AMF, combined with a lack of genomic data in a broad range of phylogenetic groups, has made it difficult to develop molecular markers and to determine evolutionary relatedness at high levels of resolution (i.e. between genetically-similar species and/or isolates). For these reasons, it seems a good alternative to use a different genetic system by targeting the mitochondrial genome, which have been shown to be homogeneous within AMF isolates. However, given the peculiar lifestyle of these organisms, a better understanding of the mitochondrial evolutionary processes and dynamics were is necessary in order to validate the usefulness of such markers in diversity and population genetics studies. In that regard, the objectives of my PhD project were to investigate: i) the divergence between closely related species and isolates, ii) mitochondrial genomes plasticity, iii) mitochondrial heritability and potential segregation mechanisms and iv) in situ mitochondrial intra-isolate allelic diversity. With Using comparative mitochondrial genomics using and next generation sequencing (NGS) sequencing, we found substantial sequence variation in intergenic regions caused by the invasion of mobile genetic elements. This variation gives risecontributes to rapid mitochondrial genome evolution among closely related isolates and species, which makes it possible to design reliable intra- and inter-specific markers. Also, an extensive gene similarity network-based approach allowed us to provide strong evidence of inter-haplotype recombination in AMF, leading to a reshuffled mitochondrial genome. These findings suggest the coexistence of distinct mtDNA haplotypes in natural populations and raise questions as to whether AMF single spore cultivations artificially underestimates mitochondrial genetic diversity in natural population.. This apparent contradiction with the intra-isolate mtDNA homogeneity usually observed in these fungi, led to the investigation of mitochondrial heritability in the spore progeny resulting from crossed-cultures. Although an heteroplasmic state was observed in some daughter spores, we found that homoplasmy was the dominant state in all monosporal cultures, with an apparent bias towards one of the parental haplotypes. These results strongly support the presence of a putative mitochondrial segregation proteic machinery in AMF, whose complete set of genes were orthologous with those found in other fungi. Our findings suggest that segregation takes place either during spore formation or colony mycelium development. Finally, we performed a conventional PCR based approach with a high fidelity Taq polymerase, followed by downstream cloning and Sanger sequencing using the model organism Rhizophagus irregularis. We found in situ heteroplasmy along with substantial intra-isolate allelic variation within the mtDNA that persists in the transcriptome. Our study also suggest that genetic variation in Glomeromycota is higher than meets the eye and might be critically underestimated in most NGS based-AMF studies both in nuclei and mitochondria.
40

Novel bioinformatics programs for taxonomical classification and functional analysis of the whole genome sequencing data of arbuscular mycorrhizal fungi

Kang, Jee Eun 10 1900 (has links)
No description available.

Page generated in 0.0781 seconds