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Postglacial colonization and parallel evolution of metal tolerance in the polyploid Cerastium alpinum /Nyberg Berglund, Anna-Britt, January 2005 (has links) (PDF)
Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv. / Härtill 5 uppsatser.
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Polyploïdie et adaptation des plantes : caractérisation et variation de l'expression des gènes homoélogues chez le caféier Coffea arabica / Polyploidy and adaptation of plant : characterization and variation of expression homoeologous genes in Coffee tree Coffea arabicaCombes Gavalda, Marie-Christine 12 October 2015 (has links)
La plupart des espèces végétales sont des polyploïdes récents ou anciens. L’allopolyploïdisation qui résulte d’une hybridation interspécifique couplée à une duplication génomique joue un rôle fondamental dans l’évolution des plantes. Elle provoquerait des changements de l’organisation du génome et de la régulation de l’expression des gènes qui seraient à l’origine de nouvelles aptitudes de ces plantes. Dans ce contexte, l’étude des mécanismes de conciliation des réseaux parentaux de régulation des gènes semble essentielle pour définir leur rôle dans la variation de l’expression des gènes. Le genre Coffea, composé d’espèces diploïdes pouvant s’hybrider et d’une espèce allotétraploïde C. arabica, constitue un modèle approprié pour cette étude. L’allopolyploïde présente deux sous-génomes homéologues peu différenciés, provenant de l’hybridation de C. eugenioides et C. canephora. A l’inverse de ses espèces parentales qui se caractérisent par des écosystèmes différents et d’amplitude thermique faible, C. arabica se développe en tolérant des variations de température plus importantes. Ce travail a consisté à étudier chez C. arabica les conséquences de l’hybridation sur la variation de l’expression et de la régulation des gènes et à analyser la variation de l’expression des gènes homéologues et son implication dans les capacités adaptatives. L’expression et la régulation des gènes au sein d’hybrides F1 entre C. canephora et C. eugenioides ont été analysées en utilisant la technologie RNA-seq. L’étude de ces hybrides a montré que les espèces parentales se distinguent par une proportion importante de divergences de trans-régulation. Pour 77% des gènes différemment exprimés entre les espèces parentales et les hybrides, le niveau d’expression de l’hybride est comparable à celui de l’une des espèces parentales, c’est le phénomène de «level expression dominance». L’analyse de l’expression allélique spécifique a permis de caractériser la régulation de l’expression des gènes ; les deux allèles sont exprimés, avec exceptionnellement un biais en faveur d’un génome. L’expression des gènes est déterminée par des combinaisons complexes de divergences de cis-régulation des espèces parentales et des effets entrecroisés de leurs facteurs de trans-régulation. Le niveau d’expression des gènes dépend de la sur ou sous-régulation simultanée des deux allèles et en particulier, de l’asymétrie des effets des facteurs de trans-régulation qui semble être à l’origine du phénomène de «level expression dominance». Pour l’allopolyploïde, l’étude de l’expression relative des gènes homéologues à l’échelle du génome a révélé que les gènes homéologues des deux sous-génomes s’inter-régulent et contribuent au transcriptome. Le transcriptome de jeunes feuilles de C. arabica cultivés à deux conditions de températures, chacune convenant à l’une des espèces parentales a été analysé pour étudier la variation de l’expression des gènes homéologues chez C. arabica et son implication dans les capacités adaptatives. La contribution des sous-génomes au transcriptome est faiblement modifiée par les conditions de culture et n’apparait pas directement impliquée dans la capacité de C. arabica à tolérer des amplitudes thermiques plus élevées que les espèces parentales. Ces études ont permis de caractériser la réponse transcriptionnelle à un évènement d’hybridation récent et ancien. Elles mettent en évidence les bases génétiques de la variation de l’expression allélique suite à la fusion des réseaux divergents de régulation des gènes d’espèces parentales. Elles ont permis de proposer un modèle de la régulation de l’expression des gènes homéologues pour C. arabica.Mots clés : allopolyploïdie, hybridation, homéologue, expression allélique spécifique (ASE), cis- trans-régulation, transcriptome, RNA-seq, adaptation, caféier. / Polyploidy is a prominent mode of speciation and a recurrent process during plant evolution. Allopolyploidization, that involves inter-species hybridization and genome doubling, can induce an extensive array of genomic rearrangements and gene expression changes generating plants with new abilities to adaptation. The study of the merger of divergent gene expression regulatory networks seems fundamental to elucidate the role of conciliation processes in the gene expression variations.The genus Coffea that contains diploid species able to hybridize and C. arabica a recent allopolyploid between two low divergent diploid species C. eugenioides and C. canephora, represents an appropriate model for this study. Indeed C. arabica can be grown in regions with marked variations in thermal amplitude while the parental species are less adapted to temperature variations. The aims of the present work are, on one hand, the study of the effects of hybridization on the expression and regulation of genes and on the other hand, the analysis of homeologous gene expression variation in response to changing environment.To examine the immediate effects of hybridization, the expression and regulation of genes in F1 hybrids between C. canephora and C. eugenioides were analyzed by genome-wide RNA-seq technology. Parental species are distinguished by an important proportion of trans-regulatory divergences. In hybrids, among divergently expressed genes between parental species and hybrids, 77% are expressed like one parent (expression level dominance). Gene expression was shown to result from the expression of both alleles, with occasional bias toward one genome. The gene expression patterns appear determined by complex combinations of cis- and trans-regulatory divergences of parental species and by intertwined parental trans-regulatory factors. The gene expression level depends on the simultaneous up and down-regulation of both alleles and the observed biased expression level dominance seems to be derived from the asymmetric effects of trans-regulatory parental factors on regulation of alleles. In the allopolyploid, at the genomic scale, both homeologous genes are also inter-regulated and contribute to the transcriptome.The transcriptome of leaves from C. arabica cultivated at different growing temperatures suitable for one or the other parental species was examined to analyze the variation of homeologous gene expression in variable conditions. The relative subgenome contributions to the transcriptome appear to be only marginally altered by the growing conditions. C. arabica’s ability to tolerate a broader range of growing temperatures than its diploid parents does not result from differential use of homeologs. The transcriptional response after a recent or old hybridization event was characterized by these studies. The genetic bases of the variations in allelic expression after the merger of parental gene expression regulatory networks, were elucidated and a model of regulation of homeologous gene expression in C. arabica is proposed. Keywords : allopolyploidy, hybridization, homeolog, Allelic Specific Expression (ASE), cis- trans-regulation, transcriptome, RNA-seq, adaptation, coffee tree.
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Poliploidização induzida in vitro, como estratégia biotecnológica para a otimização da cultura de eucalipto / In vitro induced polyploidization as a biotechnology strategy for the optimization of eucalypt cultureRafaella Zanetti Dias 03 February 2017 (has links)
A poliploidia induzida é uma ferramenta valiosa para o melhoramento genético de plantas, resultando em genótipos com características superiores aos diploides correspondentes. Considerando a importância da cultura de eucalipto para o setor florestal e para a economia brasileira, o presente trabalho teve como objetivo estabelecer um protocolo de poliploidização in vitro para eucalipto, utilizando a espécie Eucalyptus urophylla ST Blake. Segmentos nodais contendo gemas laterais de plântulas desenvolvidas in vitro foram utilizados como explantes para os testes de indução. Os tratamentos avaliados consistiram na imersão e agitação dos explantes em soluções de colchicina nas concentrações: 0; 0,125% e 0,250% em tempos de exposição de 12 e 24 horas e posterior inoculação in vitro em meio de cultura para multiplicação. Após 60 dias, as brotações emitidas foram analisadas por citometria de fluxo e constatou-se indivíduos diploides, tetraploides e mixoploides. Estas foram micropropagadas para a obtenção de mudas clonais ao final do processo. As mudas obtidas foram avaliadas por meio de análises morfológicas organográficas e anatômicas para verificar possíveis alterações resultantes da poliploidização in vitro. Os tratamentos promoveram a indução de 16 poliploides, sendo 11 mixoploides, quatro tetraploides e um octaplóide. A eficência máxima de indução obtida foi de 28% de poliploides no tratamento com 0,125% de colchicina por 12 horas sob agitação, com a obtenção tanto de mixoploides como de tetraploides puros. O protocolo geral de micropropagação utilizado, apesar de algumas perdas durante as etapas, garantiu a obtenção de altos percentuais de mudas clonais inteiramente tetraploides, comprovando a eficiência da técnica no isolamento de setores poliploides. A análise morfo-anatômica das mudas mostrou diferenças significativas em relação às características estomáticas, apontando este tipo de análise como indicador de poliploidização na separação preliminar dos indivíduos. A estrutura anatômica das folhas, no entanto, não sofreu modificações significativas, com exceção da espessura e área foliar da epiderme adaxial. A análise de componentes principais realizada para algumas variáveis morfo-anatômicas demonstrou que, apesar da análise estatística não ter apontado diferenças significativas, existe uma tendência em agrupar os genótipos diploides e tetraploides, diferenciando-os principalmente em relação às características estomáticas, espessura foliar, área do mesofilo, parênquimas paliçádico e lacunoso e espaço intercelular. Os resultados obtidos neste trabalho instigam a continuidade do estudo em diversas possibilidades de abordagens, como o estudo do desenvolvimento das mudas em condições de campos, anatomia da madeira e avaliação do comportamento meiótico. / The induced polyploidy is a valuable tool for genetic improvement of plants, resulting in genotypes with superior characteristics to their corresponding diploid. Considering the Eucalyptus culture importance to the forest sector and Brazilian economy, the aim of this study was establish an in vitro polyploidy protocol for eucalyptus, using the species Eucalyptus urophylla ST Blake. Nodal segments containing lateral buds developed from in vitro seedlings were used as explants for induction tests. The treatments tested consisted of soak and shake the explants in colchicine solutions at the concentrations: 0; 0.125% and 0.250% in soaking by periods of 12 or 24 hours and subsequent in vitro inoculation in culture medium for multiplication. After 60 days, the emitted shoots were classified by flow cytometry in levels of ploidy (diploid, tetraploid and mixoploids) and were subsequently micropropagated to obtain clonal seedlings at the end of the process. The clonal seedlings were evaluated using morphological and anatomical analysis to check the possible changes resulting from the in vitro polyploidy. The treatments promoted the induction of sixteen polyploids, being eleven mixoploids, four tetraploid and one octaploid. The maximum induction efficiency was obtained in 28% of polyploidy in the treatment with 0.125% of colchicine by soaking period of 12 hours, having obtained both mixoploids and pure tetraploids. The general protocol of micropropagation used, although presenting some losses during the steps, guaranted the inducing of high percentages of enterelly tetraploid, proving the efficiency of micropropagation in the isolation of polyploid sectors. The morpho-anatomical analysis of the poliploidy seedlings showed significant differences in relation to stomatal characteristics, indicating this type of analysis as polyploidy indicator in the preliminary separation of individuals. The anatomical structure of the leaves, however, did not change significantly, except for the thickness and leaf area of the adaxial epidermis. The principal component analysis (PCA) performed for some morphological and anatomical variables demonstrated that despite the statistical analysis did not have pointed out significant differences, there is a tendency to group the diploid and tetraploid genotypes, differentiating them mainly in relation to stomatal characteristics, leaf thickness, mesophyll area, palisade and spongy parenchyma areas and intercellular space. The results of this work instigate to continue the study in several possibilities of approaches, such as the study of the development of seedlings in fields conditions, wood anatomy and study of meiotic behavior.
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Voies de formation des crossovers méiotiques chez une espèce allopolyploïde, le colza (Brassica napus) / Crossover Pathways of Brassica napus Allopolyploid MeiosisGonzalo, Adrian 25 October 2017 (has links)
La recombinaison méiotique est au cœur de l'hérédité Mendélienne, de l'évolution et de l'amélioration des plantes, car elle assure, grâce aux crossovers, une transmission fidèle des chromosomes et le brassage de l’information génétique au fil des générations. Deux voies de formation des crossovers coexistent chez les plantes. La voie principale (voie I) dépend de la protéine MSH4 (et de quelques autres). La voie secondaire ne produit que quelques crossovers (dits de voie II) au cours de la méiose d’une plante de type sauvage ; ils sont indépendants de MSH4 et leur nombre est limité par des protéines telles que FANCM. Si ces deux voies ont été bien décrites chez des espèces diploïdes, ce n’est pas le cas chez des plantes allopolyploïdes, pourtant très fréquentes parmi les plantes cultivées. Il s'agit là d'une lacune importante, car la présence de plusieurs jeux de chromosomes apparentés conduit à augmenter le nombre de partenaires susceptibles de former des crossovers et le nombre de copies de tous les gènes méiotiques, rendant la recombinaison méiotique plus complexe. Cette thèse vise à explorer l'interaction entre les voies de formation des crossovers et la polyploïdie en utilisant des mutants de colza (Brassica napus; AACC) et d’un de ces parents diploïdes (B. rapa; AA) pour deux gènes de la recombinaison méiotique.J'ai tout d'abord testé dans quelle mesure la formation de crossovers entre chromosomes homologues et entre homéologues (chromosomes A et C) est tributaire des voies I et II en évaluant l’effet d’une diminution du nombre de copies fonctionnelles de MSH4 sur le nombre de crossovers. J'ai montré que ce dernier n'est altéré que lorsque les deux copies MSH4 sont inactivées, toute autre combinaison de mutations conduisant au même nombre de crossovers inter-homologues que chez le sauvage. J'ai également montré que la proportion de crossovers de voie II chez des mutants msh4 de colza est bien supérieure à celles observées chez d’autres plantes mutantes pour msh4. Cette observation reste vraie chez des mutants msh4 de B. rapa, suggérant que la proportion accrue de crossovers de voie II n’est pas spécifique au colza, mais probablement une caractéristique des Brassicaceae. Chez des plantes allohaploïdes (AC) de colza, chez lesquelles les crossovers ne peuvent se former qu’entre homéologues, les copies MSH4 ne se compensent plus complétement ; le nombre de crossovers de voie I fluctue au contraire proportionnellement au dosage de MSH4, devenant presque nul lorsque toutes les copies sont inactivées. Mes résultats illustrent deux nouvelles propriétés spécifiques des crossovers entre homéologues: une plus grande sensibilité vis-à-vis du dosage MSH4 pour les crossovers de voie I et une plus faible efficacité des crossovers de voie II.Dans un second temps, j'ai caractérisé cytologiquement des mutants fancm de colza pour vérifier que l'augmentation des crossovers de voie II ne nuit pas à au bon déroulement de sa méiose. Cette question est restée en suspens, les mutants fancm de colza n’étant pas complètement nuls. Cet écueil m'a incité à développer une approche de TILLING par séquençage pour identifier de nouveaux mutants de recombinaison chez le colza. J'ai alors combiné les mutations fancm et msh4 chez B. rapa pour vérifier si les premières suffisent à corriger les défauts méiotiques induits par les secondes. J'ai montré que, conformément à ce qui avait été observé chez Arabidopsis thaliana, la mutation fancm augmente le nombre de crossovers à un point tel qu’elle restaure la formation de bivalents dans un mutant msh4. La fonction de FANCM est donc conservée chez B. rapa.Mes résultats ont fait progresser la compréhension des voies de formation des crossovers lors d’une méiose allopolyploïde. Ils indiquent que la transmission des chromosomes chez ces espèces implique principalement des crossovers de voie I, et qu’elle pourrait être assurée en limitant l’efficacité de cette voie (e.g. en diminuant le nombre de copies de gènes). / Meiotic recombination ensures, through the formation of crossovers (COs), both faithful chromosome transmission and allelic shuffling over generations; it is at the heart of Mendelian heredity, evolution and plant breeding. Two crossover pathways co-exist in plants. The main pathway (class I) is dependent on MSH4 (and additional proteins). The secondary pathway produces only a few MSH4-independent (class II) crossovers during wild-type meiosis that are limited in number by anti-crossover proteins such as FANCM. These pathways have been extensively described in diploid species, disregarding one of the most pervasive features of crop genomes: polyploidy. This is a major gap in our understanding because the presence of more than two related sets of chromosomes leads both to extra partners for crossover formation and additional copies for all meiotic genes, which make meiotic recombination more intricate. This thesis aims at exploring the interplay between meiotic recombination pathways and polyploidy using mutants for two recombination genes in allotetraploid Brassica napus (AACC; 2n=38) and its diploid progenitor, B. rapa (AA; 2n=20). I have first tested the extent to which class I and class II pathways contribute to inter-homolog and inter-homoeolog (between A and C chromosomes) crossover formation by analyzing how crossovers are affected as the number of functional MSH4 copies decreases. I showed that inter-homolog crossover formation is impaired only when the two MSH4 copies are lost, any other combination of msh4 mutations resulting in wild-type crossover numbers. I also observed that, when class I crossovers are completely abolished in B. napus, the highest frequency of class II crossover ever reported among plant msh4 mutants is observed. I reproduced this result using B. rapa msh4 mutants, thereby demonstrating that increased class II crossover frequencies is not specific to B.napus, but could instead be a general feature of the Brassicaceae. In B. napus allohaploids (AC), where crossovers are forced to occur between homeologs, MSH4 copies no longer complement each other perfectly; counter to the situation in euploids, the number of MSH4-dependent crossovers formed between homoeologs fluctuates with MSH4 dosage in these plants, and approximate zero when all MSH4 copies are depleted. Altogether, my results illustrate two novel specific properties of inter-homeolog crossovers: a greater sensitivity to MSH4 dosage for class I pathway and a lower efficiency for class II.Next, I characterized cytologically B. napus fancm mutants to confirm that boosting class II crossovers would not be detrimental to B. napus meiosis. However, a prudential interpretation of these results is demanded since the B. napus fancm alleles retained residual anti-crossover activity. This has prompted me to set up a TILLING-by-sequencing procedure in order to produce new recombination mutants in B. napus. I also combined the B. rapa fancm and msh4 mutations to test whether the former is sufficient to fix the meiotic defects resulting from the latter. I showed that, similarly to what had been observed in Arabidopsis thaliana, fancm mutation boost COs to such a point that it restores bivalent formation in B. rapa msh4 background. My results therefore confirmed that the function of FANCM is conserved in B. rapa. Overall, the findings and achievements of this thesis make a step forward dissection of CO pathways during allopolyploid meiosis. They indicate that meiotic adaptation to allopolyploidy mainly involve the class I crossover pathway and could be achieved by limiting its efficiency (e.g. by decreasing gene copy number).
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Fylogeneze a evoluční trendy v subtribu Hieraciinae (Asteraceae) / Phylogeny and evolutionary trends in subtribe Hieraciinae (Asteraceae)Zahradníček, Jaroslav January 2017 (has links)
No description available.
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The evolution of centrosome and chromosome number in newly formed tetraploid human cellsBaudoin, Nicolaas C. 22 June 2020 (has links)
Tetraploidy – the presence of four copies of the haploid chromosome complement – is common in cancer. There is evidence that ~40% of tumors pass through a tetraploid stage at some point during their development, and tetraploid cells injected in mice are more tumorigenic than their diploid counterparts. However, the reason for this increased tumorigenicity of tetraploid cells is not well established. Most routes by which cells may become tetraploid also confer cells with double the number of centrosomes, the small membraneless organelle that organizes the cell's microtubule cytoskeleton and mitotic spindle apparatus. Centrosome number homeostasis is crucial for health, and recent studies have shown inducing extra centrosomes in cells can induce tumor formation in mice. This has led some researchers to propose that the extra centrosomes that arise together with tetraploidy may be the reason that tetraploid cells are more tumorigenic. However, several anecdotal reports have found that tetraploid clones generated and grown in vitro appear to lose their extra centrosomes. Here, I investigate the population dynamics of the loss of extra centrosomes in newly formed tetraploid cells generated via cytokinesis failure. I uncover the mechanism driving the process and build a mathematical model that captures the experimentally observed dynamics. Next, I investigate karyotypic heterogeneity in newly formed tetraploid cells and their counterparts that are grown for 12 days under standard culture conditions and find that karyotypic heterogeneity has increased after 12 days of growth after tetraploidization. The day 12 'evolved' population with increased heterogeneity formed larger colonies in soft agar than newly formed tetraploid cells or diploid parental precursors and karyotype analysis of the largest soft agar colonies revealed recurrent aneuploidies shared by a subset of colonies. Finally, I investigate the effects of different culture conditions - meant to mimic various conditions in the tumor microenvironment - on the evolution of centrosome and chromosome number in newly formed tetraploid cells and identify a small subset of conditions that altered centrosome homeostasis or the fitness of tetraploid cells. / Doctor of Philosophy / The genetic information in cancer cells is often drastically altered compared to normal cells in the body. As one important example of this, the number and structure of chromosomes - the DNA structures that hold the genetic information - is often abnormal in cancer cells. Abnormal chromosome number is closely linked with cancer development, but the details of why this leads to more cancer are not clear. One important kind of chromosome number change is when a cell undergoes incomplete cell division, and the resulting cell acquires double the number of chromosomes compared to a normal cell (known as tetraploidy). Tetraploidy occurs in close to 40% of cancers and is linked with the most aggressive cases. The abnormal cell divisions that cause tetraploidy also lead to other cellular changes. One important change is that tetraploid cells also acquire double the number of the structures that organizes cell division (centrosomes). The centrosome organizes the mitotic spindle, the major apparatus that is responsible for equally distributing chromosomes to two daughter cells during the cell division process. Extra centrosomes in cells are closely linked with cancer and can lead to additionally chromosome number changes. Researchers have believed that the extra centrosomes that are acquired with doubled chromosome number may be the major reason that tetraploid cells are linked to more aggressive cancer. However, recent studies have suggested that tetraploid cells may lose their extra centrosomes, calling into question the details of the relationship between tetraploidy and tumor formation. Here, I use human cells grown in culture to understand how extra centrosomes are lost from tetraploid cells. I find that extra centrosomes in newly formed tetraploid cells promote abnormal 'multipolar' cell divisions, in which chromosomes are segregated unevenly to three or more partitions. Such divisions are often fatal to daughter cells. In some cases, the extra centrosomes can cluster to form bipolar spindles that segregate chromosomes into two equal partitions (as is normal). When forming bipolar spindles, extra centrosomes can cluster asymmetrically (three centrosomes at one pole, one at the other) or symmetrically (two centrosomes at each pole). Tetraploid cells with a normal number of centrosomes emerge when extra centrosomes cluster asymmetrically in a bipolar spindle, yielding one tetraploid daughter cell with a normal number of centrosomes. Such cells have a fitness advantage over cells with extra centrosomes, which over time are very likely to undergo fatal multipolar divisions. Thus, cells with a normal centrosome number 'take over' the population. Next, I investigate the cancer-like properties of tetraploid cells without their extra centrosomes and find that they display increased tumor-like behavior even in the absence of extra centrosomes. Finally, I investigate whether changing the conditions in which cells are grown (in ways meant to mimic different conditions that may be experienced in the body) affects whether tetraploid cells lose their extra centrosomes. We identify a small number of conditions that do influence loss of extra centrosomes. Together, these studies illuminate important details of the relationship between tetraploidy and tumor formation. This work lays the foundation to further explore and understand the relative roles of tetraploidy, extra centrosomes, and tissue environment in cancer.
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Cellular structure and sexual development of somatosensory cortexSigl-Glöckner, Johanna 16 March 2020 (has links)
Schaltkreise der Großhirnrinde von Säugetieren bestehen aus unterschiedlichen Zellarten, deren charakteristische Physiologie, Morphologie und Konnektivität die Verarbeitung eintreffender neuronaler Signale bestimmen. Im Rahmen dieser Doktorarbeit wurde die zelluläre Spezialisierung zweier kortikaler Schaltkreise untersucht: einerseits die der Eingangsschicht oder Schicht 4 (Kapitel 2 bis 4) und andererseits die der Ausgangsschicht oder Schicht 5 (Kapitel 5). Der erste Teil der Dissertation umfasst drei Publikationen, welche die Verarbeitung von genitalen Berührungen in der kortikalen Schicht 4 von Nagern als Forschungsgegenstand haben. Die Arbeiten konzentrieren sich auf strukturelle Veränderungen während der Pubertät, da sich die Bedeutung genitaler Berührungen in dieser Zeit stark verändert. Die Erforschung des „Barrel Cortex“ führte zu der Erkenntnis, dass der somatosensorische Kortex eine topographische Repräsentation der Körperoberfläche enthält. Diese wird kurz nach der Geburt gebildet und weist danach kaum Veränderungen auf. Erstaunlicherweise vergrößert sich während der Pubertät der Bereich dieser Körperkarte, der genitale Berührungen verarbeitet. Dieser Prozess kann durch frühe sexuelle Berührungen beschleunigt werden. Im zweiten Teil dieser Dissertation wurde die kortikale Ausgangsstruktur untersucht. Diese ist von verschiedenen Projektionsneuronen besiedelt. Angesichts der drastischen Größenunterschiede dieser Projektionsneurone haben wir deren Genomgröße untersucht. Unsere Ergebnisse legen nahe, dass einige außerordentlich große Projektionsneurone zusätzliche Kopien ihres gesamten Chromosomensatzes enthalten. Insgesamt wurden in dieser Dissertation zwei neue Formen zellulärer Spezialisierung in der Hirnrinde aufgezeigt: (i) Schicht 4 weist zelltypspezifische entwicklungs- und erfahrungsabhängige Veränderungen im Genitalfeld auf. (ii) Schicht 5 enthält Projektionsneurone, deren erstaunliche Zellgröße auf ein polyploides Genom zurückzuführen ist. / Functionally specialized circuits in the mammalian neocortex contain different neuronal cell-types, which process information depending on their physiology, morphology and synaptic connectivity. This doctoral thesis explores two functionally distinct cortical circuits, namely its input (Chapters 2 to 4) and output (Chapter 5) structures, layer 4 and layer 5 respectively. The first part of the thesis comprises three studies that examine the processing of genital touch in the cortical input layer, layer 4. We investigated how layer 4 and its inputs are structurally refined during puberty, a time when genital touch gains biological relevance. Earlier work from layer 4 of barrel cortex suggested that somatosensory cortex contains a topographic representation of the body surface. We find that the part of this body map that processes genital touch expands significantly during puberty and that this expansion could be advanced by the early experience of sexual touch. Our data further suggests that this expansion is not due to differences in the peripheral innervation of genitals. Finally, chronic imaging of excitatory neurons within layer 4 revealed cell-type specific functional and structural changes within genital cortex during puberty. The second part of this thesis focuses on the cellular specialization of the cortical output layer, layer 5, which contains different types of excitatory projection neurons. We investigated genomic differences as novel mechanism underlying projection neuron diversity. Our data suggests that some exceptionally large projection neurons may contain an increased DNA content, a phenomenon also referred to as polyploidy. Overall, this thesis highlights two novel instances of cellular specialization in the cortex: (i) Within the cortical input layer, we observed development and experience driven changes in the area which processes genital touch. (ii) Within the cortical output layer, we identified putatively polyploid projection neurons.
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Drought stress response of tetraploid hybrid aspen (Populus tremula L. x P. tremuloides Michx.) of protoplast fusion experiments)Hennig, Anne 08 July 2015 (has links)
Pappelsorten (Populus) für den Anbau in Kurzumtriebsplantagen sollten neben einer hohen Biomasseproduktion und der Vermehrbarkeit über Steckhölzer auch Trockentoleranz aufweisen. Trockenheit stellt einen wichtigen abiotischen Stressor dar, der das Wachstum der Pflanze, ihre Vitalität und ihre Produktivität negativ beeinflussen kann. Polyploide Sorten von Getreidepflanzen (Triticum), krautigen Pflanzen (Lonicera, Spathiphyllum und Nicotiana) aber auch Baumarten (Betula) zeigen eine höhere Toleranz gegenüber Stress, wie z.B. Trockenstress, im Vergleich zu Sorten mit niedrigerem Ploidiegrad. Hybridaspen Populus tremula (L.) x P. tremuloides (Michx.) der Sektion Populus können auch auf Grenzertragsböden ökonomische Zuwächse verzeichnen, auf denen andere Baumarten ausfallen. Den Hybridaspen fehlt allerdings die Vermehrbarkeit über Steckhölzer. Anderen Pappelarten der Sektionen Tacamahaca und Aigeiros wie beispielsweise P. nigra (L.) and P. trichocarpa (Torr. & Gray) x P. deltoides (Bartram ex Marsh) zeigen diese entscheidende Eigenschaft. Da Kreuzungen zwischen den Sektionen Populus und Tacamahaca oder Aigeiros auf natürlichem Weg schwierig sind, wurde die Methode der somatischen Hybridisierung eingesetzt. Der Klon P. tremula x P. tremuloides ('Münden 2') wurden als ein Fusionspartner und einer der Klone P. x canescens (INRA clone No. 717 1‑B4), P. nigra oder P. trichocarpa x P. deltoides (B19) als zweiter Fusionspartner in Hybridisierungsexperimenten verwendet. Blattmorphologisch und durch Mikrosatellitenanalysen konnten die erhaltenen Fusionsprodukte dem Ausgangsklon P. tremula x P. tremuloides ('Münden 2') zugeordnet werden, wiesen dabei aber einen tetraploiden Chromosomensatz auf.
In der vorliegenden Dissertation war das zentrale Ziel, Trockenstressreaktionen tetraploider Hybridaspenlinien (HAL) im Vergleich zur diploiden Ausgangslinie P. tremula x P. tremuloides ('Münden 2') zu untersuchen. Dazu wurden die folgenden Fragen aufgestellt. (i) Sind die tetraploiden HAL dem diploiden Ausgangsklon unter Trockenheit überlegen z.B. hinsichtlich des Wasserverbrauchs und des Verwelkungs- und Vertrocknungszeitpunktes der Blätter? (ii) Unterscheiden sich die tetraploiden HAL von dem diploiden Ausgangklon in morphologischen Ausprägungen wie beispielsweise der Stomatamorphologie, der Höhe, der Biomasse und der Gesamtblattfläche? (iii) Ist die höhere Trockentoleranz der tetraploiden HAL durch den erhöhten Ploidiegrad verursacht? (iv) Zeigen die tetraploiden HAL unter Trockenstress früh physiologische Veränderungen im Kohlenhydratgehalt, dem relativen Blattwassergehalt und der stomatären Leitfähigkeit? (v) Gibt es genetische Modifikationen abgesehen von der Tetraploidie wie z.B. Duplikationen und Deletionen, die eventuell Einfluss auf das Trockensressverhalten haben könnten?
In einem ersten Experiment wurden vier tetraploide HAL untersucht. Zwei HAL zeigten einen geringeren Wasserverbrauch und drei HAL eine spätere Verwelkung als der diploide Ausgangsklon. Außerdem entwickelten die tetraploiden HAL eine geringere Stomatadichte, größere Stomata und eine vergleichbare oder geringere Höhe, Biomasse und Gesamtblattfläche im Vergleich zum diploiden Ausgangsklon.
Das zweite Experiment wurde mit vier diploiden und 16 weiteren tetraploiden HAL durchgeführt. Auch die diploiden Linien stammten aus Protoplastenfusions-experimenten. Die tetraploiden HAL wiesen im Mittel eine höhere Überlebensrate als die diploiden HAL auf, entwickelten aber durchdschnittlich ein geringeres Höhenwachstum. Unter Berücksichtigung der Höhe verwelkten 11 tetraploide, aber keine diploide HAL später als der diploide Ausgangsklon.
In einem dritten Experiment wurden zwei Linien aus dem zweiten Experiment ausgewählt, die vergleichbares Höhenwachstum zeigten, aber später verwelkten als der diploide Ausgangklon. Es wurden physiologische Merkmale wie der Wasserverbrauch und der Verwelkungszeitpunkt der Blätter beobachtet und der relative Blattwassergehalt, die stomatäre Leitfähigkeit und der Kohlenhydratgehalt in einer Zeitreihe untersucht. Geringerer Wasserverbrauch im Vergleich zum diploiden Ausgangsklon konnte in beiden tetraploiden HAL gezeigt werden. Diese Beobachtung deckt sich mit dem höheren relativen Bodenwassergehalt der tetraploiden HAL im Vergleich zum diploiden Ausgangsklon. Insgesamt spricht das für geringeren Trockenstress in den tetraploiden HAL. Auf der anderen Seite sollte ein geringerer Wasserverbrauch auch eine geringere stomatäre Leitfähigkeit nach sich ziehen. Dies war in den tetraploiden HAL nicht durchgehend der Fall. Relativ zur Kontrolle konnten die tetraploiden Linien aber eine höhere stomatäre Leitfähigkeit bei Bodenwassergehalten aufrechterhalten, bei denen die diploide Ausgangslinie bereits ihre Stomata geschlossen hatte. Dies weist ebenfalls auf eine höhere Trockentoleranz der tetraploiden HAL hin.
Genetische Modifikationen wie beispielsweise Duplikationen und Deletionen wurden mit Hilfe von “copy number variation”(“Kopienzahlvariation”)-Analysen an drei tetraploiden HAL und der diploiden Ausgangslinie durchgeführt. Die drei tetraploiden Linien zeigten vergleichbares Höhenwachstum, aber spätere Verwelkung als die diploide Ausgangslinie. Bei dieser Analyse konnten nur drei Segmente detektiert werden, die bei allen drei tetraploiden HAL im Vergleich zum diploiden Ausgangsklon verändert vorlagen. Die putativen Gene der detektierten Segmente wiesen keine Annotation auf. Eine der drei tetraploiden HAL zeigte eine hohe Anzahl von 90 Segmenten, die hier aber weder in dem diploiden Ausgangsklon noch in den beiden anderen tetraploiden Linien erhöht vorlagen. Diese Linie zeigte zwar eine höhere Trockentoleranz als der diploide Ausgangsklon, aber nicht gegenüber der anderen untersuchten tetraploiden HAL (Experiment 3). Beide tetraploiden HAL waren bezüglich des Wasserverbrauchs, des Verwelkungszeitpunktes und der stomatären Leitfähigkeit ähnlich. Dies lässt vermuten, dass die Trockentoleranz durch die Tetraploidie und nicht durch weitere genetische Modifikationen bedingt ist. Trotzdem ist eine weiterführende funktionelle Untersuchung der drei Segmente, die in allen tetraploiden HAL verändert auftraten, sinnvoll, da auch hier ein trockenrelevantes Gen verändert sein könnte. Um eine Relevanz der putativen Gene bezüglich Trockenheit zu testen, könnte zukünftig das Verhalten von Knock-out-Mutanten, denen die entsprechende Sequenz fehlt, unter Trockenstress untersucht werden.
Abschließend ist zu bemerken, dass neben den hier untersuchten HAL mehrere hundert Fusionsprodukte in einem Verbundprojekt genetisch charakterisiert wurden. Die Heterofusionsfrequenz war äußerst gering und die Hybriden waren bereits in der in vitro Phase nicht überlebensfähig. Geringe Heterofusionsfrequenz wurde beteits in anderen Arten beobachtet (Cyclamen, Brassicaceae, Fabaceae, Poaceae, Solanaceae). Da in dieser Dissertation nur Homofusionslinien verwendet wurden, wurde die Vermehrbarkeit über Steckhölzer nicht getestet, sondern der Fokus auf das Trockenstressverhalten der tetraploiden Homofusionslinien gelegt.
Zusammenfassend zeigen die Ergebnisse, dass veränderte morphologische Ausprägungen und eine höhere Trockentoleranz in den HAL mit erhöhten Ploidiegrad auftraten. Dies prädestiniert die tetraploiden Linien für Standorte, an denen Wasser als limitierender Faktor auftritt und hohe Ausfallraten durch Dürre erwartet werden.
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Endemický taxon Krkonoš Campanula bohemica: zhodnocení rizika hybridizace s C. rotundifolia / Risk assessment of interspecific hybridization between endemic Campanula bohemica and widespread C. rotundifolia s.l.Hanušová, Kateřina January 2014 (has links)
The thesis deals with phenotypic, ploidy and genetic variation of two Campanula species occurring in the Krkonoše Mts., namely the endemic C. bohemica and widespread C. rotundifolia subsp. rotundifolia. For comparative purposes subspecies sudetica of the latter species was also included. The main aim was to get insight into population structure and assess the threat of interspecific hybridization to the survival of the endemic bluebell. Flow cytometry, distance-based morphometrics and molecular analysis were used to address these questions. Three distinct groups of fluorescence intensities were revealed by flow cytometry, corresponding to DNA diploids, tetraploids and pentaploids. While diploids morphologically matched the nominate subspecies of C. rotundifolia, tetraploids corresponded either to C. rotundifolia subsp. sudetica or C. bohemica. Most populations from the Krkonoše Mts. were uniform although a sympatric growth of diploids and tetraploids was encountered in 12 populations. Only two pentaploids individuals, most likely of hybrid origin, were found, which indicated that interspecific hybridization is much less common than previously assumed. The two tetraploid taxa were distinguished by molecular markers. A combination of flow cytometry and molecular analyses thus allowed reliable...
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Mikroevoluční procesy a meziploidní interakce v sympatrických populacích více cytotypů / Microevolutionary processes and inter-cytotype interactions in mixed-ploidy populationsTrávníček, Pavel January 2012 (has links)
[Abstract] This thesis is aimed at better understanding of cytotype co-existence in mixed- ploidy populations with an emphasis on a microevolutionary processes behind it. Our past knowledge was based on a few thoroughly investigated model taxa like Chamerion angustifolium and Heuchera grossulariifolia, but some generalizations seem to be premature in the light of new findings. A detailed research of other taxa included in the thesis showed that polyploid complexes can vary dramatically in their ability to cope with the co-existence of cytotypes in mixed-ploidy popu- lations. Whereas mixed-ploidy populations are virtually lacking in some species (an example being Vicia cracca, Paper III.), ploidy-heterogeneous populations are very common in others, maintained by free mating interactions and the absence of reproductive isolation among cytotypes (e.g. Pilosella echioides, Paper II.). The strenght and cumulative effect of various breeding barriers (both pre- or post- zygotic) govern the position of a particular multi-ploidy complex between these two extremes and co-determine the type of cytotype co-existence in its mixed- ploidy populations. Despite the fact that the number of studies revealing cytotype co-existence has been increasing rapidly, evolutionary background and consequences of such co-...
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