Dissertations / Theses on the topic 'Variegation'
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Hedrick, Amy L. "Characterization of a cluster of dominant suppressors of position effect variegation including effects on heterochromatic variegating rearrangements in Drosophila melanogaster." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27473.
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The mosiac, cell-autonomous expression of genes resulting from chromosomal rearrangement and relocation next to broken heterochromatin is termed position effect variegation (PEV). Since the gene is inactivated due to chromatin changes, this system allows the genetic study of chromatin structure and function using mutations which rescue the mosaic phenotype. These mutations called suppressors of variegation, Su(var)s, must influence chromatin structure. The genetic characterization of several groups of Su(var)s has been undertaken in this study using Drosophila melanogaster.
Variegation of the light gene, located in heterochromatin, is enhanced by several Su(var) mutations on chromosome two. This opposite effect suggests that products of these Su(var)s are essential for functioning heterochromatin and deleterious for euchromatic environments. Other Su(var)s have slight or no effects on the same variegating rearrangements, demonstrating functional differences, among the Su(var)s tested.
A group of Su(var)s located within 4 map units near the centromere of chromosome three was characterized using deficiency mapping, new compound autosome formation and inter se complementation based on newly established homozygous phenotypes. Two Su(var)s mapped to 87B on 3R, while one Su(var) maps to 3L according to compound mapping. Inter se complementation, in combination with mapping data, suggests that four seperate loci make up this group of Su(var)s.
Eight of nine Su(var)s are extremely sensitive to heterochromatic deletions as shown by their responses to loss of 2R heterochromatin, as well as the Y chromosome. In contrast, Su(var)A130 is insensitive to both forms of heterochromatic deficiencies. Su(var)s show complicated reactions to maternal verses paternal source effects. Six of nine Su(var)s show a female-specific temperature sensitive maternal effect. Some maternal and paternal effects are observed at 22 C. Su(var)A57 is maternal semi-lethal and suppressed at 29 C. This characterization has better defined these mutants, making them ammenable to molecular study.Science, Faculty of
Zoology, Department of
Graduate
2
Liu, Huiying. "The study of the mechanism of Arabidopsis immutans variegation." [Ames, Iowa : Iowa State University], 2010. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3403816.
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Blattes, Roxane. "BASES MOLECULAIRES DE LA VARIEGATION D'EFFETDE POSITION CHEZ DROSOPHILA MELANOGASTER." Phd thesis, Université Paul Sabatier - Toulouse III, 2006. http://tel.archives-ouvertes.fr/tel-00107128.
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Les séquences satellites III (SATIII) représentent la majeure partie de l'hétérochromatine duchromosome X de drosophile et jouent un rôle dans la variégation d'effet de position du gène
white dans l'inversion white-mottled. Leurs caractéristiques structurales dues à leur richesse en
dA•dT sont ciblées par des ligands synthétiques du petit sillon de l'ADN, outils qui ont permis de
caractériser la fonction des SATIII dans l'assemblage de l'hétérochromatine. Nous avons mis en
évidence un rôle de D1, qui reconnaît spécifiquement les SATIII, mais aussi de la topoïsomérase
II, dans l'initiation de l'assemblage de l'hétérochromatine. Nos résultats suggèrent que les
SATIII pourraient constituer un réservoir de protéines servant à la régulation de la transcription
du locus des gènes ribosomiques (rDNA) adjacent aux SATIII. Enfin, nous avons pu identifier un
élément frontière qui contrôle le cloisonnement de l'hétérochromatine et jouerait un rôle dans la régulation de l'expression du rDNA
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Sahasrabhojane, Pranoti. "Identification and characterization of the E(var)3-5 gene in Drosophila melanogaster." Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5853.
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Thesis (M.S.)--West Virginia University, 2008.Title from document title page. Document formatted into pages; contains vii, 96 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 84-96).
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Uribe, Lewis Santiago. "Regulation of transgene variegation by modifiers of chromatin structure in mice." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429040.
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Hiragami, Kyoko. "Studies into the stability of gene silencing in mammalian position effect variegation." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439517.
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Sabl, Joy F. "Effects of repetitiveness, pairing and linkage on position-effect variegation in Drosophila /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/5204.
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Fan, Ngo-yin, and 樊傲賢. "Functional study of suppressor of variegation 3-9 homolog 1 in hepatocellular carcinoma." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B49617928.
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Hepatocellular carcinoma (HCC) is the major type of primary liver cancer which is well-known for its high heterogenicity and metastatic potential. Despite of the current advancement in surgical resection and the availability of targeted therapy, HCC remains a barely curable and fatal disease. We previously demonstrated that deregulation of epigenetic regulators is a common event in human HCC. Herein, we identified the frequent up-regulation of the prototype of H3K9 tri-methyltransferase SUV39H1 in clinical HCCs. SUV39H1 over-expression was also significantly associated with increased Ki67 expression and the presence of venous invasion. By using both SUV39H1 over-expression and knockdown model, we consistently demonstrated that SUV39H1 contributed to HCC tumor growth and migration. Most importantly, SUV39H1 knockdown drastically suppressed in vivo tumorigenicity and extra-hepatic metastasis of HCC cells in nude mice model. These findings evidently demonstrated the oncogenic role of SUV39H1 in HCC and implied potential therapeutic targeting of SUV39H1 for HCC treatment.
Molecularly, SUV39H1 knockdown HCC cell underwent morphological changes and accompanied with increased lysosomal β-galactosidase activity and elevated p21 protein and γH2AX level. This data suggested senescence induction in SUV39H1 knockdown HCC cells. SUV39H1 has been implicated in telomere regulation and transcriptional control. However, neither telomere length nor expression of tumor suppressor genes was altered in SUV39H1 knockdown HCC cells. Interestingly, we demonstrated a novel observation that SUV39H1 may potentially methylate non-histone substrates that are yet to be identified, which may contribute to the pro-tumorigenic function of SUV39H1 in HCC.
We also investigated the upstream regulation of SUV39H1 and identified miR-125b as the negative post-transcriptional regulator of SUV39H1. Ectopic expression of miR-125b abolished SUV39H1 3’UTR-coupled luciferase activity and suppressed endogenous SUV39H1 at both mRNA and protein level. Clinically, miR-125b level was found inversely correlated with SUV39H1 expression. We have previously reported the frequent under-expression of miR-125b in HCC. Collectively, our data suggested that SUV39H1 up-regulation in HCC may be the sequential outcome of miR-125b down-regulation.
In conclusion, we demonstrated for the first time that SUV39H1 up-regulation contributed to HCC development and metastasis, potentially via senescence evasion. SUV39H1 elevation in HCC was attributed to the loss of its negative regulator, the tumor suppressive miR-125b.published_or_final_version
Pathology
Doctoral
Doctor of Philosophy
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Bruxner, Timothy James. "Characterisation of mutants influencing epigenetic gene silencing in the mouse." University of Sydney, 2008. http://hdl.handle.net/2123/2238.
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Doctor of Philosophy (PhD)The field of epigenetics emerged primarily from studies in Drosophila, and is now being studied intensively by mammalian biologists. In order to increase our knowledge of epigenetic gene control in the mouse, I have studied modifiers of epigenetic gene silencing. My main method of investigation involved the characterisation of mutants from a sensitised ENU mutagenesis screen performed previously in our laboratory. The screen was carried out in an FVB/NJ strain carrying a variegating GFP transgene expressed in erythrocytes. To date we have recovered 12 dominant (D) and seven recessive (R) mutant mouse lines from this screen that display altered transgene expression. We have named these Mommes (Modifiers of murine metastable epialleles). I investigated the phenotype and attempted to identify the underlying causative mutation of two of these Momme mutants. MommeD6 is a semi-dominant, homozygous lethal mutation that acts as a suppressor of variegation with respect to the GFP transgene. This mutation has a large effect on the level of expression of the transgene in expressing cells, but little effect on the percentage of cells expressing the transgene. MommeD6 is linked to a 2.5 Mbp interval on chromosome 14. MommeD9 is a semi-dominant, homozygous lethal mutation that acts as an enhancer of variegation with respect to the GFP transgene. Mutants have a tendency to become obese as they age, show abnormal haematology profiles, and females develop infertility. MommeD9 is linked to a 17.4 Mbp region on chromosome 7. I produced and studied a strain carrying the same GFP transgene but in a new strain background, C57BL/6J. This strain provided an opportunity to look for strain-specific modifiers of expression of the GFP transgene. Several regions were mapped to chromosomal locations. Further work will be needed to identify the genes involved. This mouse will be useful in future mutagenesis screens of this type.
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Festenstein, Richard. "Molecular analysis of the human CD2 Locus Control Region in transgenic mice." Thesis, Open University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321311.
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Bruxner, Timothy James. "Characterisation of mutants influencing epigenetic gene silencing in the mouse." Thesis, The University of Sydney, 2007. http://hdl.handle.net/2123/2238.
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The field of epigenetics emerged primarily from studies in Drosophila, and is now being studied intensively by mammalian biologists. In order to increase our knowledge of epigenetic gene control in the mouse, I have studied modifiers of epigenetic gene silencing. My main method of investigation involved the characterisation of mutants from a sensitised ENU mutagenesis screen performed previously in our laboratory. The screen was carried out in an FVB/NJ strain carrying a variegating GFP transgene expressed in erythrocytes. To date we have recovered 12 dominant (D) and seven recessive (R) mutant mouse lines from this screen that display altered transgene expression. We have named these Mommes (Modifiers of murine metastable epialleles). I investigated the phenotype and attempted to identify the underlying causative mutation of two of these Momme mutants. MommeD6 is a semi-dominant, homozygous lethal mutation that acts as a suppressor of variegation with respect to the GFP transgene. This mutation has a large effect on the level of expression of the transgene in expressing cells, but little effect on the percentage of cells expressing the transgene. MommeD6 is linked to a 2.5 Mbp interval on chromosome 14. MommeD9 is a semi-dominant, homozygous lethal mutation that acts as an enhancer of variegation with respect to the GFP transgene. Mutants have a tendency to become obese as they age, show abnormal haematology profiles, and females develop infertility. MommeD9 is linked to a 17.4 Mbp region on chromosome 7. I produced and studied a strain carrying the same GFP transgene but in a new strain background, C57BL/6J. This strain provided an opportunity to look for strain-specific modifiers of expression of the GFP transgene. Several regions were mapped to chromosomal locations. Further work will be needed to identify the genes involved. This mouse will be useful in future mutagenesis screens of this type.
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Grieger, Patrick. "Untersuchungen zur Züchtung variegater Pelargonium x zonale-Hybriden auf tetraploider Stufe." Doctoral thesis, Humboldt-Universität zu Berlin, Landwirtschaftlich-Gärtnerische Fakultät, 2007. http://dx.doi.org/10.18452/15673.
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Die vorliegende Arbeit befasst sich mit züchtungsmethodischen Untersuchungen zur Schaffung blattvariegater Pelargonium x zonale-Hybriden auf tetraploidem Leistungsstand. Basierend auf dem Wirkstoff Trifluralin konnte eine effektive Behandlungsvariante zur somatischen Polyploidisierung periklinalchimärischer Pelargonium x zonale-Klone etabliert werden. Unter Ausnutzung biparentaler Erbgänge wurden fünf ausgewählte Plasmotypen an das Leistungsniveau moderner Sortimente herangeführt. Daneben erbrachten Kreuzungen innerhalb der Sektion Ciconium hybridvariegate F1-Pflanzen. Die Möglichkeit der Ausnutzung von Kern-Plasma-Wechselwirkungen in der Pelargonienzüchtung wird diskutiert. Im Hinblick auf den Aufbau eines Protoplastenregenerationssystems konnten Zellsuspensionskulturen etabliert werden. Im Anschluss an enzymatische Verdauungen wurde die Regeneration von Kallus beobachtet. Variegate Pflanzen aus Mutationsversuchen mit NMH (Nitroso-Methyl-Harnstoff), einer weiteren experimentellen Variante, erwiesen sich als steril, so dass eine weiterführende Züchtungsarbeit auf diesem Weg bisher noch nicht möglich warThe study analyzes breeding schemes concerning the development of variegated tetraploid Pelargonium x zonale-hybrids (Pelargonium x hortorum). With a focus on practical relevance breeding methods for periclinal chimeric leaf patterns are discussed. Trifluralin-induced tetraploid Pelargonium x zonale-hybrids were successfully crossed with modern cultivars. Via biparental mode of inheritance five defined plasmotypes were transfered to the karyological background of current high-performance Pelargonium series. In a crossing-program within the section Ciconium hybrid-variegation was detected. The possibility of using nucleo-plasmatic interactions in developing new Pelargonium cultivars is discussed. First steps concerning a biotechnological approach to create variegated plants included the establishment of cell-suspension-cultures as the base for a protoplast regeneration system. Following the enzymatic digestion of Pelargonium-liquid cultures up to now, callus regeneration was achieved. Variegated plants resulting from mutagenic treatments with NMU (Nitroso-methylurea) proved to be sterile.
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Bui, Phuongngan Thi. "Investigating the Influence of CHD1 on Gene Expression in Drosophila Melanogaster Using Position Effect Variegation." Scholarship @ Claremont, 2015. http://scholarship.claremont.edu/scripps_theses/537.
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Position Effect Variegation (PEV) is the mosaic expression of a gene that has been moved out of its optimal environment and into a different area on the chromosome. Changing a gene’s environment may have profound effects on its eligibility for proper expression, which is a complicated process regulated by many factors. The PEV phenomenon is used as an assay to study gene expression as regulated by chromatin structure. In this study, the Drosophila melanogaster white gene was used as a reporter to study the various effects of CHD1, a chromatin regulating factor, on PEV gene expression. Inspired by preliminary data generated by the Armstrong Lab where overexpression of CHD1 resulted in suppression of gene silencing of the brown gene and loss of CHD1 resulted in enhancement of gene silencing, this study uses PEV as an assay to examine whether loss of function chd1 mutant alleles function dominantly to enhance silencing of the white gene when it is placed in a repressive chromatin environment. Surprisingly, I found that a chd1 loss of function mutant allele dominantly suppressed gene silencing (meaning I saw an increase in gene expression), suggesting that the CHD1 protein is normally required for effective silencing. The results demonstrated that CHD1 is a dominant modifier of PEV gene expression. CHD1 significantly modifies gene expression by suppressing silencing of the white gene inserted into pericentric heterochromatin on the second and fourth chromosomes and an insertion into the medial region of the fourth chromosome, while it shows no significant modification of the white gene inserted into telomeric heterochromatin of the fourth chromosome. Together, these intriguing results regarding varying gene expression at different chromosomal sites show that PEV is a dynamic phenomenon meriting further research and studying the effects of CHD1 as a modifier of PEV may be influential to understanding the mechanism and characteristics of gene expression.
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Toub, Omid. "Initial characterization and intracellular localization of two suppressors of position effect variegation in drosophila melanogaster, S2214 and puckered." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/16271.
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Emergence of the higher eukaryotic organisms from their prokaryotic ancestors has been closely associated with an increase of the genetic material. This progression has been dependant on machineries that can package the DNA to various extents, from the levels seen in the 30 nm fibers of interphase nuclei to that of metaphase chromosomes. These evolutionary changes in genome organization have correlated with advancements in regulation of gene expression during development. In eukaryotes, cellular differentiation is partly dependent on the mechanisms that would silence the correct genes in a particular tissue and maintain this silenced state throughout subsequent stages of development. To understand the factors involved in such mechanisms many labs, including ours, have used position effect variegation (PEV) to identify proteins that form or remodel the chromatin fiber. Genetic screens have identified S2214, and puckered as genes coding for putative modifiers of PEV. The aim of this thesis, is to characterize S2214, and puckered by addressing two main questions: i) do the mutations in each of these genes modify the phenotype observed in PEV? And ii) do their products localize to the nucleus, and if so to the chromatin? Results show that P element mutations in these genes cause dominant and strong suppression of PEV in wm⁴ and SbV. Moreover, the observed Su(var) activity is reverted upon mobilization of the P elements. I developed and purified an antibody for each gene. Puc, the product of puckered, localized to the nucleus of S2 and KC1cells (which are late embryonic Drosophila cell lines), as well as the nuclei of salivary gland cells of Drosophila melanogaster, but could not be detected on the polytene chromosomes. In addition, S2214, the product of S2214, was found in the nuclear fraction of S2 cells, and could be observed within the nuclei of S2 and KC1 cells as well as those of the salivary glands of Drosophila melanogaster. Furthermore, S2214 was found at several interbands of the polytene chromosomes of these salivary glands. It is our conclusion that gene products of both S2214 and puckered are involved in mechanisms that affect chromatin structure.
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Mau, Kianna. "Bifluorescent Analysis of ⍺-Synuclein Aggregation In Vivo." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40937.
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Parkinson’s disease is an incurable neurodegenerative disease characterized by motor deficits, owing to dopaminergic denervation in the nigrostriatal pathway. The abnormal formation of hallmark Lewy bodies underlies the disease process. The pre-synaptic protein alpha- synuclein (⍺-syn) has prion-like properties arising from its propensity to propagate, seed misfolding, and self-aggregate. Pathogenesis is postulated to arise in olfactory and enteric regions, exploiting connected neuronal pathways to ultimately propagate to the substantia nigra pars compacta. There is little known about the earliest stages of ⍺-syn aggregation and its prion-like propagation mechanisms. Bimolecular fluorescence complementation of ⍺-syn aggregates has allowed us to directly visualize aggregation in transgenic mice and mice transduced with an adeno-associated virus vector. Although our transgenic mice expressed BiSyn in a mosaic fashion that limited utility, we were successful in transducing neurons in the mouse striatum. This work has validated the AAV2/9-CMV-BiSyn approach as groundwork for future systematic studies.
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Drechsel, Oliver. "Untersuchungen zu Struktur und Expression des Plastidengenoms höherer Pflanzen." Phd thesis, Universität Potsdam, 2008. http://opus.kobv.de/ubp/volltexte/2009/3105/.
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Auf dem Weg der genetischen Information stellt die Translation der RNA in eine Aminosäuresequenz den letzten Schritt dar. In Chloroplasten, den grünen Organellen der Pflanzenzellen, findet ein Großteil der Regulation der Genexpression auf Ebene der Initiation dieses Schrittes statt. Eine Vielzahl von Eigenschaften der RNA und von Faktoren, die an die RNA binden, entfalten einen Einfluss auf diesen Schritt. Bisher unvollständig aufgeklärt ist die Rolle einer konservierten Nukleotidsequenz in der untranslatierten Region der RNA -- der Shine-Dalgarno-Sequenz. Diese stellt in Bakterien, wie z.B. E. coli als Ribosomenbindestelle sicher, dass Ribosomen den Anfang der zu translatierenden Sequenz zuverlässig erkennen. Im Rahmen dieser Arbeit wurden diverse DNA-Konstrukte in Plastiden von Tabak eingebracht. Hierzu zählten Konstrukte, die sowohl eine erhöhte Anzahl von Ribosomenbindestellen enthielten als auch vermehrte Startpunkte der Translation. Zusätzlich wurden Konstrukte hergestellt, die die Situation von mehreren zu translatierenden Regionen in der RNA nachstellten. Es konnte festgestellt werden, dass plastidäre Ribosomen die strangaufwärts gelegenen Translationsstartpunkte bevorzugen -- im Gegensatz zu E. coli, wo alle Startpunkte gleichmäßig genutzt wurden. Hierdurch zeigten die prokaryotischen Ribosomen aus Chloroplasten, die sich aus bakteriellen Systemen ableiten, Eigenschaften von eukaryotischen Ribosomen.
Ein zweites Teilprojekt dieser Arbeit beschäftigte sich mit der Inkompatibilität von Chloroplasten mit dem Kerngenom. In Kreuzungen von Arten der Gattung Pelargonium fielen Kombinationen auf, bei denen die Tochterpflanzen bleiche Blattbereiche bis hin zu vollständig weißen Pflanzen zeigten. Dieses Phänomen wird als Bastardbleichheit bezeichnet. In der Gattung Pelargonium werden Chloroplasten von beiden Elternteilen an die Tochterpflanzen vererbt. Da das Phänomen der Bastardbleichheit nur in einem der Plastiden vorkommt, nicht jedoch im anderen in der gleichen Pflanze, muss von einem Effekt ausgegangen werden, der von Plastiden ausgeht. Die Interaktionen zwischen Zellkern und Chloroplasten sind offensichtlich stark gestört. Zur detaillierten Untersuchung dieses Effekts wurde die Nukleotidsequenz von drei Chloroplastengenomen aufgeklärt. Es konnte eine Reihe von Sequenzunterschieden der Genome ermittelt werden. Aus diesen wurde eine Reihe von Unterschieden beobachtet, die einen solchen Effekt zur Folge haben können. Aus diesen Unterschieden wurde eine Reihe von potentiellen Kandidatengenen zusammengestellt, die in weiteren Arbeiten auf ihre Rolle in der Entstehung der Bastardbleichheit untersucht werden.Chloroplasts are the green organelles of plants with a evolutionary prokaryotic background. During evolution chloroplasts established translation initiation as the major step in regulation of gene expression. A vast number of factors, e.g. sequence elements, secondary structures or RNA binding proteins, influences the regulation of translation initiation. A conserved sequence – Shine-Dalgarno sequence – can be identified both in prokaryotes as well as chloroplasts. In prokaryotes this sequence provides a faithful means for positioning of the ribosome to the start codon. Due to lower conservation of Shine-Dalgarno sequences the role of this sequence in translation initiation is not completely understood. We designed a series of constructs that contain different arrangements of these sequences in the 5’ UTR resulting in an increased number of potential ribosome binding sites or translation initiation sites. Additionally we constructed a series of 5’ UTRs that resembled polycistronic transcripts. The results showed a dramatic effect of the different constructs on the translation efficiency of the reporter protein. It could be shown that numerous translation initiation sites increase translation efficiency, whereas increased numbers of ribosome binding sites do not. Additionally it could be shown, that plastidic ribosomes preferentially initiate on 5’ translations initiation sites in contrast to prokaryotic ribosomes that recognize initiation sites equally. This illustrates that plastidic ribosomes in contrast to prokaryotic ribosomes show a scanning like mechanism. Hence plastidic ribosomes gained some eukaryotic properties during evolution. A second project was dealing with hybrid variegation. This phenomenon is based on plastid-nuclear genome incompatibility. Due to biparental plastid inheritance in Pelargonium hybrids may show chimeric phenotypes with bleached (incompatible) and green (compatible) sectors. This points to the plastome as cause for the hybrid variegation. To this end the nucleotide sequence of three plastid genomes was determined and an array of candidate genes causing the incompatibility could be compiled.
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Rouinsard, Alexandre. "Étude du caractère de panachure et de sa stabilité lors de la micropropagation de plantes monocotylédones." Thesis, Rennes, Agrocampus Ouest, 2021. http://www.theses.fr/2021NSARC156.
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La micropropagation des variétés à feuillage panaché (plusieurs couleurs sur une même feuille) peut générer des plantes non conformes au phénotype d’origine, particulièrement dans le cadre de plantes monocotylédones acaules. Or, par leur caractère fortement ornemental, ces variétés présentent un fort potentiel commercial. L’objectif était de déterminer les potentialités de micropropagation des monocotylédones panachées dans un contexte industriel et commercial, de définir la stabilité de leurs phénotypes, et de comprendre l’apparition des plantes hors-type. Les observations de coupes foliaires au microscope confocal à balayage laser sur les quatre cultivars étudiés Yucca gloriosa ‘Variegata’ (YgVAR), Yucca flaccida ‘Golden Sword’ (YflGS), Phormium tenax ‘Jessie’ (PtJE) et Cordyline australis ‘Pink Passion’ (CaPP) ont révélé que tous les cultivars étaient des chimères périclines, soit une panachure liée à un méristème stratifié avec plusieurs génotypes différents. En micropropagation,YgVAR a présenté des taux de conformité élevés, PtJE des taux modérés et CaPP de faibles taux. Des analyses histologiques sur les vitroplants ont mis en évidence des différences majeures dans le développement et le comportement de multiplication in vitro de ces trois espèces de l’ordre des Asparagales : YgVAR n'a développé que des méristèmes axillaires (AxM), PtJE principalement des AxM et quelques méristèmes adventifs (AdM), et CaPP à la fois des AxM et des AdM. Alors que les méristèmes axillaires préformés maintiennent la structure chimérique, les méristèmes adventifs la maintiennent peu. Donc la stabilité de la panachure de ces variétés dépend de leur propension à se propager par méristèmes adventifs. Des essais pour abaisser la dominance apicale et stimuler les méristèmes axillaires ont été menés, ainsi qu’une analyse du transcriptome des différents tissus panachés chez YflGS. Des protocoles de production industrielle adaptés à chaque cultivar sont finalement proposésThe micropropagation of variegated cultivars (several colors on the same leaf) can generate off-type plants to the original phenotype, particularly in the case of monocotyledonous plants. However, because of their highly ornamental character, these cultivars have a strong commercial potential. The objective were to determine the micropropagation potential of variegated monocots in an industrial and commercial context, to define the stability of their phenotypes, and to understand the origin of off-types. Observations of leaf sections under a confocal laser scanning microscope on the four studied cultivars: Yucca gloriosa 'Variegata' (YgVAR), Yucca flaccida 'Golden Sword' (YflGS), Phormium tenax 'Jessie' (PtJE), and Cordyline australis 'Pink Passion' (CaPP) revealed that all cultivars were periclinal chimeras, i.e., a variegation bound to stratified meristem with several different genotypes.In micropropagation, YgVAR showed high compliance rates, PtJE moderate rates and CaPP low rates. Histological analyses on vitroplants revealed major differences in the development and in vitro propagation behavior of these three species of the order Asparagales: YgVAR developed only axillary meristems (AxM), PtJE mainly AxM and some adventitious meristems (AdM), and CaPP both AxM and AdM. While preformed axillary meristems maintain the chimeric structure, adventitious meristems maintain little. Thus, the variegation stability of these chimeras depends on their propensity to propagate by adventitious meristems. Trials to lower apical dominance and stimulate axillary meristems were conducted, as well as transcriptome analysis of different variegated tissues in YflGS. Industrial production protocols adapted to each cultivar are finally proposed
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Donaldson, Kathryn Marie. "Relationships between chromosome structure and long distance regulation of gene expression : a study of cis and trans modifiers of terminal deficiency-associated position effect variegation in a Drosophila melanogastor minichromosome /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p9987530.
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Jedrusik-Bode, Monika. "Molekulare Analyse der differentiellen Funktionen von Linkerhiston-Isoformen bei Caenorhabditis elegans." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=964334933.
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Blattes, Roxane. "Bases moléculaires de la variégation d'effet de position chez drosophila melanogaster." Toulouse 3, 2006. http://www.theses.fr/2006TOU30115.
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Les séquences satellites III (SATIII) représentent la majeure partie de l’hétérochromatine du chromosome X de drosophile et jouent un rôle dans la variégation d’effet de position du gène white dans l’inversion white-mottled. Leurs caractéristiques structurales dues à leur richesse en dA•dT sont ciblées par des ligands synthétiques du petit sillon de l’ADN, outils qui ont permis de caractériser la fonction des SATIII dans l’assemblage de l’hétérochromatine. Nous avons mis en évidence un rôle de D1, qui reconnaît spécifiquement les SATIII, mais aussi de la topoïsomérase II, dans l’initiation de l’assemblage de l’hétérochromatine. Nos résultats suggèrent que les SATIII pourraient constituer un réservoir de protéines servant à la régulation de la transcription du locus des gènes ribosomiques (rDNA) adjacent aux SATIII. Enfin, nous avons pu identifier un élément frontière qui contrôle le cloisonnement de l’hétérochromatine et jouerait un rôle dans la régulation de l’expression du rDNASatellite III sequences (SATIII) represent the bulk of drosophila X chromosome heterochromatin and play a key role in position effect variegation (PEV) of the white gene in the white-mottled strain. Their structural characteristics, based on their biased dA•dT rich nucleotidic composition, make them good targets for artificial DNA minor groove binders. Such new tools allowed us to improve the SATIII sequences’ function in heterochromatic structure formation. Our work allows us to shed light on the functional role of the D1 protein, which specifically binds SAT III sequences, as well as topoisomerase II, in the initiation of the heterochromatin assembly. Our results suggest that SATIII sequences represent a reservoir for proteins regulating ribosomal DNA arrays (rDNA) transcription located next to SATIII sequences. We also show involvement of a boundary element in heterochromatin partitioning, which plays a role in regulation of rDNA expression
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Susbielle, Guillaume. "Perturbation de la dynamique de l’hétérochromatine par des ligands synthétiques du petit sillon de l’ADN." Toulouse 3, 2006. http://www.theses.fr/2006TOU30109.
Full textAbstract:
Les séquences satellites III (SATIII) présentes dans les régions péricentriques du chromosome X sont les seules séquences satellites alphoïdes chez la drosophile, similaires à celles retrouvées autour du centromère chez les mammifères. Leurs caractéristiques structurales liées à leur composition nucléotidique A•T riche en font des cibles pour différentes classes de molécules artificielles. Nous proposons d’utiliser le modèle des SATIII de la drosophile pour améliorer notre compréhension du code des histones, de la fonction des régions péricentriques ainsi que pour l’évaluation du potentiel pharmacologique des diamidines. Nos travaux à l’aide de ligands du petit sillon nous ont permis de mettre en évidence un rôle de la topoïsomérase II, une cible thérapeutique majeure, dans l’assemblage de l’hétérochromatine et dans le mode d’action antiprolifératif des diamidinesThe satellite III sequences (SATIII) composing the pericentric regions of the X chromosome are the only alphoïd sequences found in Drosophila melanogaster. They are similar to those found near the centromeres of mammalian cells. Their structural characteristics, based on their biased, A•T rich, nucleotidic composition, make them good targets for different types of artificial and natural molecules. We propose to use the SAT III sequences as a model to study the histone code, the function of pericentric regions and as a tool to evaluate the pharmacological potential of diamidines. Our work with minor groove binding agents, allowed us to shed light on the functional role of topoisomerase II, a major target in anticancer and antiparasitic therapies, in the heterochromatin assembly process and in the antiproliferative mode of action of diamidines
22
Rodriguez, Ibanez David. "Musteranalysen an ausgewählten variegaten Formen der Araceae, Asteraceae, Ericaceae, Marantaceae und Rosaceae." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963516612.
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Ibanez, David Rodriguez. "Musteranalysen an ausgewählten variegaten Formen der Araceae, Asteraceae, Ericaceae, Marantaceae und Rosaceae." Doctoral thesis, Humboldt-Universität zu Berlin, Landwirtschaftlich-Gärtnerische Fakultät, 2001. http://dx.doi.org/10.18452/14667.
Full textAbstract:
Der Ursprung, die Entwicklung und die Formierung von Laubblatt-Mustern konnten bei ausgewählten variegaten Formen der Araceae, Asteraceae, Ericaceae, Maranthaceae und Rosaceae erklärt werden. Die Pflanzen wurden je nach Problematik untersucht und in drei verschiedene Gruppen verteilt: In der ersten Gruppe, Blattmuster mit unregelmäßiger makulater Musterung, Monstera deliciosa, Syngonium podophyllum und die Sorten 'Pirol' und 'Luyona' von Dendranthema grandiflorum zeigen ein unregelmäßiges Laubblattmuster und keine weiß-randigen bzw. weißkernigen Periklinalchimären. Mischzellen wurden durch direkte (mikroskopisch) und indirekte (In-vitro-Kultur und Selbstungen) Nach der Plastidenentmischung in den Schichten des Sprossmeristems wurde bei Syngonium, Monstera und den zwei Sorten von Dendranthema die GW-Form als einzige stabile Periklinalchimäre nachgewiesen. In der zweiten Gruppe, Immerspaltende Periklinalchimären, die chimärische Konstitution GA bei Spiraea bumalda 'Goldflame' konnte durch Wurzelaustriebe (BATESON-Test) und die Adventivsprossinduktion aus Kallus nachgewiesen werden. Darüber hinaus konnten mehrfach perikline Aufspaltungen der ersten Sprossscheitelschicht (Reduplikation von L1) nachgewiesen werden, die zur Entstehung der Panaschierung von 'Goldflame' zur Entmischung führten. Bei den Untersuchungen der In-vitro-Regenerate aus der Kalluskultur und der Wurzelaustriebe an S. bumalda 'Shirobana' wurde festgestellt, dass diese Pflanze keine Chimäre ist und das auftretende Muster der Blüten genetisch kontrolliert ist. In der dritten Gruppe, Hypoderm und Beeinflussung der Musterbildung: Die unmaskierten Binnenfelder bei Ctenanthe lubbersiana 'Variegata' und der Rhododendron-Hybride 'Goldflimmer' sind durch die Existenz eines Hypoderms zu erklären. Bei Ctenanthe lubbersiana 'Variegata' befindet sich ein Hypoderm an der Blattoberseite und der Blattunterseite. Bei 'Goldflimmer' liegt nur unter der oberen Epidermis ein einschichtiges Hypoderm vor. Infolgedessen fehlt an der Blattoberseite die Maskierung Das gelbe Binnenfeld des Blattmusters ist durch eine grüne Mesophyllschicht unterlagert.The origin, development and formation of foliage-leaf-patterns could be explained with selected variegaten forms of the Araceae, Asteraceae, Ericaceae, Marantaceae and Rosaceae. In order to prove this the plants were examined according to the problem and classified in three different groups: In the first group, leaf-patterns with irregular maculated patterns, Monstera deliciosa, Syngonium podophyllum and the sorts 'Pirol' and 'Luyona' of Dendranthema grandiflorum showed an irregular foliage-leaf-pattern, thought neither to show periclinal chimeras with white edges nor with green edges. Mixed cells were detected by direct (microscopic) and indirect (In vitro culture and self pollination) test. After the plastid sorting out in the layers of the meristems, the green over white Form was proven with Syngonium, Monstera and the two sorts of Dendranthema as a single stable periclinal chimera. In the second group, eversporting periclinal chimeras, the green over aurea chimeral constitution with Spiraea bumalda 'Goldflame' was proved by the regeneration of adventitious shoots from their roots (BATESON-Test) and also by the induction of adventitious bud from callus. Periclinal divisions of the first layer of meristems (reduplication of L1), which are responsible for the appearing of green pattern of the leafs was proved many times. Examination of the regenerated shoots from callus and from the adventitious shoots from roots of S. bumalda 'Shirobana' showed that this plant is not a chimera and that the appearing pattern of the blooms is genetically controlled. In the third group, hypoderm and influence of the pattern-formation, the unmasked inner-fields with Ctenanthe lubbersiana 'Variegata' and the Rhododendron-hybrid 'Goldflimmer' were explained through the existence of one layered hypoderm under the upper Epidermis as well as over the lower Epidermis of C. lubbersiana 'Variegata', thought in 'Goldflimmer' it is only found a one layer Hypoderm under the upper epidermis. Subsequently, the masking is missing at the upper-leaf side the yellow inner-field of the leaf-pattern is through a green Mesophyllslayer masked.
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Sutter, Nathaniel Barrett. "Suppression of stable and variegating position effects by the 5'HS2 and inducible 3MRE enhancers /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/5038.
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Yu, Fei. "The mechanism of var2 leaf variegation /." 2005.
Find full text
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Fu, Aigen. "The mechanism of Arabidopsis immutans variegation /." 2006.
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Chang, Fang-Chi, and 張芳綺. "Flowering, pollination, inheritance of foliar variegation and phylogeny analysis in Aglaonema." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/17887983990345979349.
Full textAbstract:
碩士國立臺灣大學
園藝學研究所
93
Aglaonemas are important interior plants. Breeding for cultivars with beautiful spotted leaves and bright color petiole has long been the prevailing goal. However, the perplex cultivar names, the unusual chromosome number resulted from interspecific hybridization, polyploid, timing of flowering, and pollen inactive during storage hinder the breeding. Moreover, the seed aborted due to pedicle rotten is another cause. The objectives of this study were to regulate the flowering and analyze inheritance of leaf variegation and genetic relationship as the reference of the aglaonemas breeding. The application of 250 ppm gibberellic acid (GA3) on leaves of Aglaonemas for continuous two years promoted flowering earlizer and centralize. The timing of application might not be the same for every cultivars or species. As for leaf variegation, three new alleles were proposed in this study. The description of each trait was one-third of the leaf width of silver-gray band in the middle of the leaf, white stripe cover on middle rib, and yellow-white spot dispersed on leaf surface. Thereafter, the three traits were designated as Vg, Vbr and Vcp respectively. In this study, pink petiole seedlings were obtained only in the combination of pink petiole x pink petiole and pink petiole x white petiole. All the combination using green petiole as one parents generated seedlings with green petiole. However, the inheritance of petiole color was not concluded due to the sample size was too small. The result of RAPD anaysis indicated that Aglaonema genotypes are highly diverged and can be clustered into seven groups. The incongruity between the first two groups (I and Ⅱ) and the last five groups（Ⅲ, Ⅳ, Ⅴ, Ⅵ and Ⅶ）are very high, except A. brevispathum （Engl.） Jervis f. immaculatum（Siamese Evergreen）(Ⅲ), A. simplex (Ⅴ) and A. rotundum × A. simplex（11）(Ⅴ) could be the parental parent as crosses to first three groups. Therefore, these cultivars might be the solution to confer the incongruity between the first and the last groups. The genetic background of A. pumilum(Ⅳ), A. rotundum（Ⅴ）and pictum(Ⅵ) were relatively simple as compared with other aglaonemas. A. costatum N.E. Br. var. costatum f. foxii （Engl.） Jervis ‘Foxii Grande’ and A. brevispathum clustered into group Ⅳ which was consistent with the hypothesis that A. costatum has two varieties, var. costatum and var. brevispathum（Ⅲ）, respectively .The IB group to divide into three subgroups. The common character of the ⅡC group, related to A. rotundum, was having red pigment. Individuals of this group would not produce viable pollen and could be the genetic resource of red pigment in any crosses. For the purpose to introuduce red color into other aglaonemas, A. rotundum × A. simplex（11）（Ⅴ）and A. rotundum × A. simplex x A. nitidum （Jack） Kunth. ‘Curtisii’ were suggested to be the paternal parents. In aglaonemas breeding, controling flowering time, pollination timing and technique, and humidity control of inflorescence were three critical factors to ensure the success of pollination. Regulate flowering time to be before June was also suggested to enhance the probability of obtaining matured seed due to provide fruit a warmer temperature while developing. Besides the consideration of the inheritance of foliar variegation and petiole color, genetic distant and incongruity among species were two other important factors while doing distant hybridization among Aglaonemas.
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Chen, Yun-Shiuan, and 陳運萱. "Mechanisms and ecophysiological implications of foliar variegation in seedlings of Blastus cochinchinensis." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/45762825754341354340.
Full textAbstract:
碩士國立中興大學
生命科學系所
103
Natural foliar variegation is common in the forest understory. Two main mechanisms of variegation, pigmental (chemical color) and structural (physical color), have been reported. Some plants maintain variegation throughout their lives, but some display this feature at the juvenile stage only. Blastus cochinchinensis (Melastomataceae) is a common understory shrub in Taiwan and East Asia, with two types of seedlings, variegated seedlings and normal green seedlings (non-variegated). The variegated leaves display novel and strong variegated patterns on their adaxial surfaces, consisting of series of white spots or chains on a normal green leaf. The aims of this study are to reveal the mechanism of this remarkable variegation and its effects on ecophysiology in seedlings of B. cochinchinensis, and with field surveys to gain understanding of its adaptive significance by correlating variegation and herbivore damage. In addition, Sonerila heterostemon, a plant collected from Singapore also with a strong variegation pattern before flowering, is studied to better understand the variegated mechanism of Melastomataceae. The results attribute the variegation of B. cochinchinensis and S. heterostemon to at least three combined mechanisms including epidermal type, intercellular air space type and partial chlorophyll type. The adaxial epidermal cells of the white area of a variegated leaves are flate, and the adaxial epidermal cells of the green area of a variegated leaves and the normal green leaves are apophysis. The white area of a variegated leaves are thicker and have intercellular spaces between the adaxial epidermal cells and the upper mesophyll; the the green area of a variegated leaves and the normal green leaves are in tight contant with adaxial epidermal cells. The chloroplasts were fewer and smaller in the upper mesophyll, but their sizes were significantly larger in the lower mesophyll of the white area than the green area. The chloroplast ultrastructure, showing dense thylakoid membranes, shows no differences between the white area, the green area of a variegated leaf and the normal green leaf. Raphide-form oxalate crystals, which may increase light reflection and scattering, were found only in the adaxial epidermal cells of the white area of the variegated leaf of Blastus. Thus, a total of four variegation mechanisms were detected in the variegated leaf of Blastus, but it is unknown if this mechanism also occurs in Sonerila. In addition, the stomatal density on the abaxial leaf surface of the white area of Blastus was significantly lower than those of the green area and the normal green leaf. The normal green leaf has highest stomatal density. The chlorophyll concentration of Blastus in the variegated leaves was lower than the green leaves. This may be related to the smaller size and lower number of chloroplasts in the upper mesophyll of the white area. The maximum quantum yield of PSII (Fv/Fm) of an area of variegated leaf covering both white and green areas was close to that of the green area alone. The maximum quantum yield of the green area was significantly higher than that of the normal green leaf. Under low light (300 μmol photons m-2 s-1), the PSII quantum yield and the electron transport rate (ETR) of the variegated leaf were lower than the normal green leaf, but the non-photochemical quenching (NPQ) of the variegated leaf was higher than the normal green leaf. The result implies that the variegated leaves of the variegated seedlings have photoprotection under the low light conditions where the seedlings of Blastus grow naturally in forests. At high light, the ETR of the variegated leaf was higher than the normal green leaf, but with lower NPQ and a similar PSII quantum yield to the normal green leaf. The net photosynthetic rate (Pn) of variegated leaves was significantly lower than that of green leaves. Through twice repeated field surveys of 10 transects in the Huisun Forest Area and Lianhuachi Research Center, the percentage of variegated seedlings was found to be around 50% or more. Normal green leaves appear on average at the 8th node of the variegated seedling. Three types of variegation patterns were delineated: punctate, chain-like and lump, which consisted 1.5-24.8% leaf area. Such variegation patterns are extremely distinctive when viewed with the animal-eye specific imaging system (AESIS) to mimic the vision of honey bees. Notably, the herbivore damage in the variegated leaves was significantly lower than in the green leaves. One large multicellular trichome is located in the center of the white area of the variegated leaf, which may deter herbivores from landing and feeding. In addition, the density of glandular trichomes on the abaxial surface of the white area was significantly higher than those on the green area and the normal green leaves. No significant difference in the content of C%, N% and C/N ratio was found between the variegated leaf and the normal green leaf. Taken together, the striking variegated pattern, trichomes and crystals might contribute to the reduction of herbivore damage on the variegated leaf. This is the first report of variegation caused by multiple combined mechanisms, with chemical, structural mechanisms and crystal effects. The micromorphological and structural differences of the variegated leaf lead to slightly weak the performance of photosynthesis of the variegated seedling, but it gains better photoprotection under low light, and significantly reduced herbivore damage. The variegated leaves appear only in the first seven pair leaves of the variegated seedling, showing an adaptive significance of heteroblasty. About half the seedlings of Blastus found in the forest edge of relatively open habitats are variegated, suggesting that this variegation trait is stabilized in Blastus and has evolutionary significance.
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Clegg, Nigel. "Suppressors of position-effect variegation and the cdc2Dm gene in Drosophila Melanogaster." Thesis, 1992. http://hdl.handle.net/2429/3200.
Full textAbstract:
Suppressor of Position-Effect-Variegation {Su(var)}
mutations in Drosophila melanogaster are believed to identify
genes that participate i n the establishment or maintenance of
heterochromatic domains. A cytogenetic analysis of region 31
of the Drosophila melanogaster polytene chromosome map was
undertaken to clarify the number and position of several
previously identified Su(var) mutations. Ten deficiencies were
used to divide the 31 region into 15 separate subintervals.
Results of this analysis suggest that there is a single
Su(var) locus (Suvar(2)1) in the 31A-B region. Two recessive
suppressors of position-effect variegation reside in the 31E-
32A region. A fourth locus, Su(var)216, was positioned in
region 3IE.
Additional mutations were sought throughout the 31
region. In total , one hundred and twenty-one new EMS, gamma-irradiation , and P element induced mutations were tested for
complementation and mapped using deficiencies. None of the
mutations had a Su(var) phenotype, but 8 alleles failed to
complement the lethal phenotype associated with the Su(var)216
chromosome.
A P element induced allele of Su(var)216 was cloned and
sequenced. The P is adjacent to cdc2Dm, the Drosophila
homologue of the fission yeast cdc2 gene. The kinase encoded
by cdc2 is required for proper progression through the cell
cycle. The lethal phenotype of Su(var)216 can be rescued by an ectopically placed cdc2Dm gene construct; however, the Su(var)
phenotypes are not rescued. Deficiency mapping of Su(var)216
with a cdc2Dm gene construct in the genetic background
suggests that the Su(var)216 and cdc2Dm mutations may be
tightly linked (<0.5 cM) but separable. [more abstract]
30
Carvalho, Anna-Bella. "Locating the chromatin modifying factor Suppressor of Variegation 3-8 in Drosophila melanogaster." Thesis, 2003. http://hdl.handle.net/2429/13941.
Full textAbstract:
This study is part of a project whose goal is to identify and then sequence the chromatin modifying gene Su(var)3-8. Chromatin structure is considered to play a significant role in gene expression. In order to better understand this role, we have undertaken a project to characterize one gene suspected of affecting chromatin structure, Su(var)3-8. The first approach taken was to tag the gene with a known sequence - the P element transposon. Mutations of Su(var)3-8 created by P element mutagenesis were tested to determine whether P elements were inserted in the gene. Remobilization of the P element by a cross that introduced transposase was used to detect reverted suppressors, under the supposition that precise excision of a mutation-causing P element would revert the gene to wild-type state. Southern blotting using radioactively labelled complete P element to probe digested genomic DNA was used to detect partial (immobile) remnants of P elements. Recessive lethal mutations containing P elements inserted in the region near Su(var)3-8 were tested for complementation to determine whether those P elements were inserted into the 3-8 locus. As no P-tagged alleles were discovered, Su(var)3-8 was then localized with the intention of delimiting the potential area to a few genes, allowing for direct testing of putative genes via plasmid rescue. Su(var)3-8 was localized genetically using recombination mapping with the genes cross-veinless and stubbloid, situated on the chromosomal arm 3R and near where previous studies placed Su(var)3-8 (53.5±0.9 ). 3-8 was localized cytologically by complementation to various recessive lethal chromosomal deficiencies also determined to be in the vicinity. It was not possible to localize the area sufficiently to allow for direct testing of open reading frames. 128 putative genes are located in the 1645Kb within which Su(var)3-8 appears to be located.
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Burr, Roderick H. L. "Functional characterization of mfs (2) 31 : a recessive supressor of position effect variegation." Thesis, 1995. http://hdl.handle.net/2429/3763.
Full textAbstract:
The Drosophila melanogaster gene, mfs(2)31, is a recessive
suppressor of position effect variegation (PEV) and has two open
reading frames (ORFs) putatively derived from a single
heterogeneous nuclear RNA (hnRNA). The coding region of
Intronic Centrosomal Protein (ICP) is located in the first
intron of the ubiquitin 80 amino acid fusion protein (DUb80)
transcript, and is known to be liberated as a 1.2 Kb
polyadenylated mRNA. Antibodies raised against the C-terminal
85 amino acids of ICP were used as a reagent for western
blotting and indirect immunofluorescent staining of Drosophila
embryos and HeLa cells. ICP was found to co-localize with p-
tubulin in a Triton X-100® resistant compartment of both the
Drosophila embryonic centrosome, and the HeLa cell centrosome.
ICP was also localized to small, discrete, Triton X-100®
resistant 'flecks' within HeLa cell nuclei in a pattern
suggestive of the nuclear scaffold. These data suggest that ICP
is involved in modulating nuclear and cytoplasmic microtubule
dynamics throughout the cell cycle.
32
Lin, Yi-Sian, and 林宜憲. "Comparative study of foliar variegation of Begonia formosana: leaf features, reproductive characters and herbivory." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/yer34m.
Full textAbstract:
碩士國立中興大學
生命科學系所
106
Natural foliar variegated plants are occasionally found in forest understoreys. Pigmental type (chemical color) and structural type (physical color) are two main mechanisms of foliar variegation, have been reported. Some plants keep variegation throughout their life history, some only show this feature at the juvenile stage, and still others display this feature before flowering time. Anti-herbivory and photoprotection are two main hypotheses of the ecological meaning of foliar variegation. Begonia formosana (Begoniaceae), a shade herb native to Taiwan, has variegated and green form in nature. The aims of this study are to: 1) describe morphological differences between green and variegated leaves; 2) elucidate the reproductive differences between variegated and green forms with a view to understanding fitness differences between the two forms; 3) clarify the interaction between variegation and visual herbivores. In this study, adult female grasshopper, Atractomorpha sinensis, is chosen to represent the visual herbivore for understanding the herbivore preference. The leaf morphological study shows the number of multiseriate unbranched hair, and there is no difference between the two forms. The polygonal-shaped adaxial epidermal cells significantly vary in size. The green area of a variegated leaf has the largest polygonal-shaped adaxial epidermal cells, and the following is the green leaf. The white area of a variegated leaf has the smallest one. There is no size difference between guard cells of different leaf areas, but the green area of a variegated leaf has the smallest subsidiary cells, and the white area of a variegated leaf has the lowest stomatal density. Few druse-form oxalate crystals were found only in the adaxial epidermal cells of the white area of a variegated leaf. The variegated form of Begonia formosana accounts for around 9% of total population in Qingshan Waterfall Trail area, but the herbivore damage in the variegated leaves is significantly fewer than in the green leaves. This observation support the anti-herbivory hypothesis. In the aspect of the reproductive organs, there is no significant difference in the number of male flowers, female flowers, fruits and seeds between variegated and green form. More detail characteristics, including the size of flower petals, 2D projected stigmata, fruits and the number of anthers also show the same pattern. However, the variegated form has significantly wider pollen grains and bigger seeds than the green form. This reproductive difference may reflect higher photosynthetic reserves in the variegated form potentially due to lower herbivory on the variegated plant, allowing it to produce larger pollen grains and seeds. The genome size between the variegated and green form showed no difference. The variegated form showed the leaf plasticity in the high and low light environment. Some variegated form individuals grew green leaves in the high and low light environment. The variegated and green form are different for the visual herbivores. The grasshoppers stayed significantly longer and caused larger damage area on the green form leaf than the variegated form. They showed the same preference at the beginning and the end of the experiment. These results strongly indicate the little fitness difference between the variegated and green form. Although the variegated form grow green leaves in the different light environment, they are not for photoprotection. The ecological meaning of foliar variegation in Begonia formosana should be anti-herbivory, providing the prevention of visual herbivores to whole population.
33
Mottus, Randall C. "A genetic and molecular analysis of histone deacetylase one in Drosophila melanogaster : specific missense mutations suppress position effect variegation." Thesis, 2003. http://hdl.handle.net/2429/14807.
Full textAbstract:
Essentially all higher organisms are made up of two or more types of
tissues. The specific identity of those tissues is dependent on the genes that are
expressed within the cells of the particular tissue type. The correct set of genes
must be expressed and genes, that are not part of the set specific to that tissue,
must be kept silenced. In addition, in most cells, the decision whether a gene
will be active or not is made early in development and therefore must be passed
on to daughter cells. The focus of this thesis is an investigation into the
mechanism or mechanisms employed by eukaryotes to silence genes and to
maintain that silenced state throughout development. The model system our
laboratory has been using to investigate silencing is position effect variegation
(PEV) in D. melanogaster. In PEV a gene is silenced in a certain proportion of the
cells of a tissue in which it is normally expressed due to its proximity to an
heterochromatic breakpoint. The decision whether a gene will be active or
inactive is made early in development and that decision is passed on to
daughter cells with reasonable fidelity. Thus PEV mimics normal development
in many ways. This has led our lab, and several others, to try to dissect the
mechanisms underlying PEV with the hope they will shed some light on the
more general silencing mechanisms that occur during normal development.
In Chapter 2 of this thesis I describe the cloning and characterization of a
gene identified in a screen for dominant suppressors of the variegation
associated with PEV [Su(var)s]. The gene encodes HDAC1 , an histone
deacetylase homologous to HDAC1 from mammals and Rpd3 from S. cerevisiae. Specific mis-sense mutations in HDAC1 cause strong dominant suppression of
PEV while null or hypomorphic mutations have no effect on the variegating
phenotype. I present a model proposing that the mis-sense mutations are
acting as anti-morphic mutations that "poison" the deacetylase complex.
The level of variegation of a gene subject to PEV is very sensitive to a
wide variety of factors, some, which may be acting directly and some, which
may be acting indirectly. HDAC1 localizes to a large number of sites on the
polytene chromosomes of D. melanogaster (Pile and Wasserman, 2000) and
therefore appears to regulate a large number of genes. Thus it is a possibility
that the Su(var) mutations in HDAC1 are affecting PEV indirectly. In Chapter 3
I present data from chromatin immuno-precipitation experiments (X-ChIP) that
provides compelling evidence that HDAC1 is acting directly on the
euchromatic region subject to silencing in PEV. I propose a model linking the
histone deacetylase activity of HDAC1 to the function of other proteins known
to be involved in the silencing associated with PEV.
34
Whitehead, Ian P. "The genetic and molecular analysis of the mfs(2)31 locus in Drosophila melanogaster : a novel suppressor of position-effect variegation." Thesis, 1993. http://hdl.handle.net/2429/2060.
Full textAbstract:
Position-effect variegation (PEV) is the variable inactivation of a euchromatic gene which has been moved, by way of a chromosomal rearrangement, into a heterochromatic environment. The transcriptional repression at the variegating locus is thought to be a consequence of inappropriate packaging of the euchromatin asheterochromatin. Second site mutations which modify the PEV phenotype (Su(var)s and E(var)s), identify loci which encode non-histone chromosomal proteins. Although the majority of mutations which modify PEV exhibit a dominant phenotype, rare recessives u(var) mutations have been reported. This study describes a locus which is identified by one such recessive mutation, mfs(2)31. A cytogenetic analysis of subdivisions 31D-E was undertaken to determine the precise location of the mfs(2)31 locus and to isolate additional alleles. Five new deficiencies and 123 new lethal mutations were induced, allowing for the partitioning of 31D-E intosix cytological subintervals. The mfs(2)31 gene was localized todistal 31E in an interval containing nine lethal complementation groups. Three new mfs(2)31 alleles were recovered, one of whichwas isolated in a screen for P element insertions. The new alleles of mfs(2)31 were used for a phenotypic analysis of the locus. Strong alleles that were lethal as homozygotes died in the larval phase, while weaker alleles exhibited the previously described bristle, sterility and su(var)phenotypes. Larval, pupal and adult functions were defined for the locus. Although no dominant phenotypes were observed, surviving heteroallelic combinations suppressed PEV in a variety of variegating backgrounds. When the weak, P-induced, allele was outcrossed in a dysgenic background, all the mfs(2)31 phenotypes, including suppression of PEV, were co-reverted. An in situhybridization to salivary gland polytene chromosomes revealed a P element in distal 31E of this strain. The P element, located in distal 31E, was cloned from thedysgenic mfs(2)31 allele. This element is responsible for the reduced transcription of a 1.2 kb message which is expressed throughout development. Wild-type levels of transcription are restored at this locus in revertants of the mfs(2)31 phenotype. The predicted amino acid sequence, as determined from a cDNA analysis, reveals similarities with a mouse microtubule-associated protein and mammalian histone H1.
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Paredes, Martinez Lida Silvana. "The Ribosomal DNA Genes Influence Genome-Wide Gene Expression in Drosophila melanogaster." Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-05-9108.
Full textAbstract:
Chromatin structure is a fundamental determinant of eukaryotic gene
expression and it is composed of two chromatin environments, euchromatin and
heterochromatin. Euchromatin provides an accessible platform for transcription
factors; hence it is permissive for gene expression. Heterochromatin on the
other hand is highly compacted and inaccessible, which in most cases leads to
transcriptional repression. A locus that is composed of both of these
environments is the ribosomal DNA (rDNA). In eukaryotes the rDNA is
composed of hundreds to thousands of tandemly repeated genes where
maintaining both silent and active copies is fundamental for the stability of the
genome. The aim of this research was to investigate the role of the rDNA in
gene expression in Drosophila melanogaster.
In D. melanogaster the rDNA loci are present on the X and Y
chromosomes. This research used the Y-linked rDNA array to investigate the
role of this locus on gene expression. A genetic and molecular strategy was
designed to create and quantify specific, graded and isogenic Y- linked rDNA deletions. Then the deletions were used to address the effect of rDNA deletions
on gene expression using reporter genes sensitive to Position Effect Variegation
(PEV). In addition, the effect of the deletions in nucleolus size and structure as
well as the effect of spontaneous rDNA deletions on gene expression were
tested in this study.
This research found that changes in rDNA size change the chromatin
balance, which resulted in increased expression of the reporter genes,
decreased nucleolus volume, and altered nucleolus structure. These findings
prompted a further research question on whether this effect on gene expression
occured globally in the genome. This was addressed by performing microarray
analysis where the results showed that rDNA deletions affect about half of the
genes on the genome. Presented in this dissertation is evidence that suggest a
novel role for the rDNA is a global modulator of gene expression and also is a
contributor to the gene expression variance observed in natural populations.
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Woo, Nicholas. "Characterization of a variegated purine biosynthesis mutant of Arabidopsis thaliana." Phd thesis, 2009. http://hdl.handle.net/1885/148264.
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Khairandish, Arash. "Global Position Effects on the Epigenetics of Variegated Lentiviral Vector Expression in Embryonic Stem Cells." Thesis, 2010. http://hdl.handle.net/1807/25726.
Full textAbstract:
Lentivirus efficiently transduce stem cells, however are notably silenced in embryonic stem cells (ESC). Provirus can be silent, expressing, or variegated when clonal single copy ESCs spawn daughters that revert expression despite containing identical integration sites (IS) indicating epigenetic regulation. In the silent state, variegated provirus are bound by H1 and MeCP2, where H1 compensates for MeCP2 binding in DNA methylation null ESCs, consistent with a model of heterochromatin formation dependent on concentrations of its constituent components. ESC Variegation was hypothesized to result from spreading of nearby heterochromatin. Global IS analysis indicates Variegated IS favour gene deserts, repeat clusters, and LINEs while Expressers prefer gene density with stable modest expression and SINEs. Chromatin data does not support a role for the spread of heterochromatin possibly a consequence of the dynamic/dispersed nature of ESC heterochromatin. Variegation thus may depend on stochastic chromatin regulation by pluripotency factors at proximal genome organizing repeats.
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Rodriguez, Ibanez David [Verfasser]. "Musteranalysen an ausgewählten variegaten Formen der Araceae, Asteraceae, Ericaceae, Marantaceae und Rosaceae / von David Rodriguez Ibanez." 2001. http://d-nb.info/963516612/34.
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