Comparisons of flowering plant genomes reveal multiple rounds of ancient polyploidy characterized by large intragenomic syntenic blocks. Three such whole-genome duplication (WGD) events, designated as rho (rho), sigma (sigma), and tau (tau), have been identified in the genomes of cereal grasses. Precise dating of these WGD events is necessary to investigate how they have influenced diversification rates, evolutionary innovations, and genomic characteristics such as the GC profile of protein-coding sequences. The timing of these events has remained uncertain due to the paucity of monocot genome sequence data outside the grass family (Poaceae). Phylogenomic analysis of protein-coding genes from sequenced genomes and transcriptome assemblies from 35 species, including representatives of all families within the Poales, has resolved the timing of rho and sigma relative to speciation events and placed tau prior to divergence of Asparagales and the commelinids but after divergence with eudicots. Examination of gene family phylogenies indicates that rho occurred just prior to the diversification of Poaceae and sigma occurred before early diversification of Poales lineages but after the Poales-commelinid split. Additional lineage-specific WGD events were identified on the basis of the transcriptome data. Gene families exhibiting high GC content are underrepresented among those with duplicate genes that persisted following these genome duplications. However, genome duplications had little overall influence on lineage-specific changes in the GC content of coding genes. Improved resolution of the timing of WGD events in monocot history provides evidence for the influence of polyploidization on functional evolution and species diversification.

Motivation: The advent of clinical exome sequencing will require new tools to handlecoverage data and making it relevant to clinicians. That means genes over targets, smartsoftware over BED-files, and full stack, automated solutions from BAM-files to genetic testreport. Fresh ideas can also provide new insights into the factors that cause certain regionsof the exome to receive poor coverage.Results: A novel coverage analysis tool for analyzing clinical exome sequencing data has beendeveloped. Named Chanjo, it’s capable of converting between different elements such astargets and exons, supports custom annotations, and provides powerful statistics andplotting options. A coverage investigation using Chanjo linked both extreme GC content andlow sequence complexity to poor coverage. High bait density was shown to increasereliability of exome capture but not improve coverage of regions that had already proventricky. To improve coverage of especially very G+C rich regions, developing new ways toamplify rather than enrich DNA will likely make the biggest difference.

No description available.

Background: Mutator-like transposable elements, a class of DNA transposons, exist pervasively in both prokaryotic and eukaryotic genomes, with more than 10,000 copies identified in the rice genome. These elements can capture ectopic genomic sequences that lead to the formation of new gene structures. Here, based on whole-genome comparative analyses, we comprehensively investigated processes and mechanisms of the evolution of putative genes derived from Mutator-like transposable elements in ten Oryza species and the outgroup Leersia perieri, bridging similar to 20 million years of evolutionary history. Results: Our analysis identified thousands of putative genes in each of the Oryza species, a large proportion of which have evidence of expression and contain chimeric structures. Consistent with previous reports, we observe that the putative Mutator-like transposable element-derived genes are generally GC-rich and mainly derive from GC-rich parental sequences. Furthermore, we determine that Mutator-like transposable elements capture parental sequences preferentially from genomic regions with low methylation levels and high recombination rates. We explicitly show that methylation levels in the internal and terminated inverted repeat regions of these elements, which might be directed by the 24-nucleotide small RNA-mediated pathway, are different and change dynamically over evolutionary time. Lastly, we demonstrate that putative genes derived from Mutator-like transposable elements tend to be expressed in mature pollen, which have undergone de-methylation programming, thereby providing a permissive expression environment for newly formed/transposable element-derived genes. Conclusions: Our results suggest that DNA methylation may be a primary mechanism to facilitate the origination, survival, and regulation of genes derived from Mutator-like transposable elements, thus contributing to the evolution of gene innovation and novelty in plant genomes.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22356号 / 医博第4597号 / 新制||医||1042(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 萩原 正敏, 教授 岩田 想, 教授 齊藤 博英 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

No description available.

<p>Repetitive elements, including tandem repeats and transposable elements (TE), are genetic features of all plant and animal genomes. Despite their abundance and the phylogenetic breadth of host genomes, factors that control the genome-wide distribution of repetitive elements are not well understood. Here we have evaluated the correlation between various genomic predictor variables such as gene expression level, distance from genes, and GC content, with the presence of TEs and non-TE repeats in two kilobase windows of the complete genome sequence of the Western Clawed Frog (<em>Silurana tropicalis</em>). We found that the distributions of different classes of TEs and repeats have distinct correlations with these predictor variables, including a generally strong negative correlation with proximity to exons and GC content. We also found that DNA transposons, but not retrotransposons, are preferentially inserted or preferentially retained near germline-expressed genes. Retrotransposons and simple repeats are found more often in or near conserved regions than expected by chance. These results offer insights into various models that have been proposed to account for heterogeneity in the genomic distribution of repetitive elements, most notably for the “gene disruption model” which posits that TE insertion and repeat presence near or in genes imposes costs to host fitness. In general, multiple lines of evidence suggests that the nature of natural selection on TE and other repetitive element evolution in this frog appears to be similar to that acting on TE and other repetitive elements in the human genome. This is possibly related to the similar size and level of complexity of the genomes of both of these species.</p> / Master of Science (MSc)

La recombinaison méiotique joue un double rôle de moteur évolutif en participant à la création d'une diversité génétique soumise à la sélection naturelle et de contrôle dans la fabrication des gamètes lors de la méiose. De plus, en association avec certains mécanismes de réparation, la recombinaison, au travers de la conversion génique biaisée manipule les fréquences alléliques au sein des populations. Les connaissances sur le fonctionnement même de ce processus ont considérablement augmenté ces dernières années faisant découvrir un processus complexe, autant dans son fonctionnement que dans son évolution. Le thème général de la thèse est l'analyse, dans un contexte évolutif, des relations entre les différents rôles et caractéristiques fonctionnelles de la recombinaison. Un modèle de la recombinaison prenant en compte des contraintes liées au contrôle de la méiose et le phénomène d'interférence a permis une comparaison entre espèces au sein des vertébrés et des non-vertébrés de même qu'une comparaison entre sexes. Par ailleurs, nous avons montré l'impact de la localisation spécifique aux sexes des points chauds de recombinaison sur l'évolution du contenu en GC des génomes de plusieurs vertébrés. Finalement, nous proposons un modèle à l'échelle de la génétique des populations, permettant d'analyser l'impact de la recombinaison sur la fréquence de mutations délétères dans les populations humaines. Cette thèse, nous l'espérons, apportera sa pierre à l'étude interdisciplinaire de la recombinaison, à la fois au sein de la biologie et par ses relations au travers de la modélisation avec l'informatique et les mathématiques. / Meiotic recombination plays several critical roles in molecular evolution. First, recombination represents a key step in the production and transmission of gametes during meiosis. Second, recombination facilitates the impact of natural selection by shuffling genomic sequences. Furthermore, the action of certain repair mechanisms during recombination affects the frequencies of alleles in populations via biased gene conversion. Lately, the numerous advancements in the study of recombination have unraveled the complexity of this process regarding both its mechanisms and evolution. The main aim of this thesis is to analyze the relationships between the different causes, characteristics, and effects of recombination from an evolutionary perspective. First, we developed a model based on the control mechanisms of meiosis and inter-crossover interference. We further used this model to compare the recombination strategies in multiple vertebrates and invertebrates, as well as between sexes. Second, we studied the impact of the sex-specific localization of recombination hotspots on the evolution of the GC content for several vertebrates. Last, we built a population genetics model to analyze the impact of recombination on the frequency of deleterious mutation in the human population.

The study of bacterial evolution is fundamental for addressing current problems of antibiotic resistance and emerging infectious diseases and lays a solid foundation for successful and rational design in biotechnology and synthetic biology. The main aim of this thesis is to test evolutionary hypotheses, largely based on theoretical considerations and sequence analysis, by designing scenarios in a laboratory setting to obtain experimental data. Paper I examines how genomic GC-content can be reduced following a change in mutation rate and spectrum. Transcription-related biases in mutation location were found, but no replicative bias was detected. Paper II explores the distribution of fitness effects of random substitutions in two ribosomal protein genes using a highly sensitive fitness assay. The substitutions had a weakly deleterious effect, with low frequencies of both neutral and inactivating mutations. The surprising finding that synonymous and non-synonymous substitutions have very similar distribution of fitness effects suggests that, at least for these genes, fitness constraints are present mainly on the level of mRNA instead of protein. Paper III examines selective barriers to inter-species gene transfer by constructing mutants with a native gene replaced by an orthologue from another species. Results suggest that the fitness costs of these gene replacements are large enough to provide a barrier to this kind of horizontal gene transfer in nature. The paper also examines possible compensatory mechanisms that can reduce the cost of the poorly functioning alien genes and found that gene amplification acts as a first step to improve the selective contribution after transfer. Paper IV investigates the fitness constraints on horizontal gene transfer by inserting DNA from other species into the Salmonella chromosome. Results suggest that insertion of foreign DNA often is neutral and the manuscript provides new experimental data for theoretical analysis of interspecies genome variation and horizontal gene transfer between species.

The work deals with the fuzzy classification of DNA sequences. In the first part the theory summarized information about Fuzzy logic and methods of its use in the classification of biological sequence data. The second part is practically deal with the classification algorithm for assessing the similarity of sequences. Specifically, the dividing of coding and non-coding parts of the sequence and the use of fuzzy classification in DNA barcoding.