Dissertations / Theses on the topic 'Arabidopsis'
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1
Tasker, Adam. "Pectinesterase in Arabidopsis." Thesis, University of Nottingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.523497.
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Bano, Aziz Fatima. "Glucosinolates in Arabidopsis." Thesis, University of East Anglia, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262028.
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Pavangadkar, Kanchan Amol. "Role of ADA2b and GCN5 in COR gene expression during cold acclimation in Arabidopsis." Diss., Connect to online resource - MSU authorized users, 2008.
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4
Morris, Erin Rebecca. "FHA domain genes of Arabidopsis /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p3144443.
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Coker, Timothy L. R. "Infection-site-specific responses of Arabidopsis thaliana to the biotrophic oomycete Hyaloperonospora arabidopsidis." Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/90202/.
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Changes in gene expression form a crucial part of the plant response to infection, and whole-leaf expression profiling has been valuable in our understanding of the interactions between the model plant Arabidopsis thaliana and a diverse range of pathogens. However, when studying the interaction between Arabidopsis and the biotrophic oomycete Hyaloperonospora arabidopsidis (Hpa), whole-leaf profiling may fail to capture the complete Arabidopsis response. Highly localised expression changes that occur in infected cells may be diluted by the comparative abundance of non-infected cells, or local and systemic responses of a differing nature may become convoluted. The aim of this project was to spatially dissect the transcriptional response to Hpa, allowing differentiation of local and more systemic responses. Fluorescence Activated Cell Sorting (FACS), utilising an infection-site-specific fluorescent marker ProDMR6::GFP, was performed in order to isolate Hpa-proximal and Hpa-distal cells from infected seedling samples, and global gene expression measured in these FACS-sorted samples using microarrays. When compared with an uninfected control, 278 transcripts were identified as differentially expressed, the vast majority of which were differentially expressed specifically in Hpa-proximal cells. By comparing our data to previous, whole organ studies, we discovered many locally responding genes that were detected for the first time using our sensitive FACS technique. A portion of locally-responding genes were selected for further study. The promoters of a subset of highly locally induced genes were selected to drive expression of Green Fluorescent Protein (GFP) as a marker of Hpa-contacting cells for further FACS experiments, and to further validate their localised induction. Although some evidence of localised induction was seen in these lines, further investigation is required. We also hypothesised that a number of locally-induced genes would have a functional influence on infection, and tested this through the use of genetic knockouts. Knockouts in 7 of these genes showed altered disease resistance or susceptibility, and the mechanism behind two of these genes was investigated through the use of microarrays. Overall, the use of FACS to study the Arabidopsis response to Hpa on a spatial scale has allowed identification of new genes with a putative role in the Arabidopsis-Hpa interaction, and contributes to a systems-level understanding of plant-pathogen interactions.
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Dinneny, Jose R. "Patterning organs in Arabidopsis /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2005. http://wwwlib.umi.com/cr/ucsd/fullcit?p3190169.
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Strachan, Camille. "Phosphoproteomics of Arabidopsis thaliana." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011590.
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Usher, Sarah Louise. "Nucleosome positioning in Arabidopsis." Thesis, University of Warwick, 2009. http://wrap.warwick.ac.uk/3212/.
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The aim of this project was to test hypotheses relating to nucleosome positioning in Arabidopsis to provide a basis for better understanding of epigenetic transcriptional regulation in plants. Prior to this study, virtually no information existed regarding nucleosome positioning in plants. Eukaryote chromosomes consist of chromatin, composed of nucleosomes separated by linker DNA of variable lengths. Nucleosomes consist of 147 bp of DNA wrapped 1.7 times around a histone octamer. Whilst no consensus nucleosome positioning DNA sequence exists, sequence preferences influence positioning, and contribute to the complex epigenetic processes which act to control transcriptional activity. These details of the underlying mechanisms are known to differ between the plant and animal kingdoms. High-throughput sequencing technologies were utilised to generate large datasets of mono- and di-nucleosome sequences from wild-type Arabidopsis. These enabled genome-wide analysis and inference of plant-specific patterns of nucleosome positioning and sequence properties. Further data were generated from a methyltransferase antisense (MET1) which is depleted in methylated CG epigenetic marks. The internal distributions of dinucleotides within Arabidopsis nucleosomes were similar to those observed in non-plant eukaryotes. A unique periodicity in the distribution of linker lengths was detected in Arabidopsis wild type chromatin. In contrast, the MET1 antisense line displayed the expected periodicity, indicating systematic differences in chromatin organisation. There was a significant increase in nucleosome occupancy within exons compared with introns. However, this difference was less marked in the MET1 antisense. Specific patterns of nucleosome phasing were observed around transcription start sites. Linker lengths within rRNA gene clusters associated with nucleolar organiser regions (NORs) differed depending on chromosome of origin, suggesting differences in higher order chromatin structure between the NORs. Comparison of the nucleosome position and DNA methylation within the rRNA gene cluster revealed interesting differences between the two regions, which may reflect interactions affecting chromatin structure and transcriptional regulation.
9
Zhang, Yi. "Wound responses in arabidopsis." Thesis, University of East Anglia, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.502215.
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Environmental stresses, such as repeated injury by herbivory, stunt plant growth and reduce crop yield. A spectacular example of this effect is exemplified in ornamental bonsai plants. Wounding induces the synthesis of a plant hormone, jasmonates (JAs), which in turn activate non-specific defence against pests and pathogens. On the other hand, a most dramatic effect of the application of jasmonates to plant however is the inhibition of growth, and this raised the question of whether another function of endogenous jasmonates is to inhibit growth. The results presented in this thesis first demonstrated that a previous wounding primes plants to give an enhanced response to following wounds. Following this discovery, I have investigated the genetic and physiological basis of "bonsai effect" by repeatedly wounding leaves of the model plant Arabidopsis. Repeated wounding reduced the size of wild type plants by 50% and increased the endogenous content of jasmonate (JA) by seven-fold, but unexpectedly had no significant effect on the mutants unable to synthesise JA, or unable to respond to JA. This second discovery suggests another function of endogenous JA is to inhibit growth under stress.
10
Caryl, A. P. "Gene tagging in Arabidopsis." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597347.
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The work described in this thesis takes two approaches towards the identification of tagged genes in Arabidopsis thaliana. A family screening approach was used to isolate mutants from the T-DNA transformed Feldmann lines of Arabidopsis. Co-segregation analysis was used to determine whether these mutants were tagged. None of the mutants isolated showed co-segregation with the T-DNA so this approach was abandoned. Enhancer trap constructs are designed to report the activity of enhancers near a transgene insert. Typically they contain a reporter gene with an weak promoter in a transformation vector. The second approach used in this study was to investigate a collection of 123 independently transformed lines of Arabidopsis containing such constructs which were available in the laboratory. The construct introduced into these lines contained a β-Glucuronidase reporter gene under the control of an attenuated Cauliflower Mosaic Virus promoter. The number of independent active inserts, T-DNA copy number and GUS staining patterns of the lines were investigated. One of the lines, Δ31, showed GUS staining associated with meristematic tissue (with the exception of the primary root meristem). The expression of the GUS reporter gene was presumably being controlled by a plant enhancer adjacent to the insert. Presumably the enhancer would normally act to regulate the expression of an endongenous plant gene. Spectrophotometric assays were used to measure the response to auxin in root tissues. IPCR was used to amplify plant DNA flanking the insert in line Δ31. A clone of this DNA was used to isolate four large overlapping clones from a lambda genomic library of wild-type plants which would be likely to contain the tagged enhancer, and any endogenous gene regulated by this enhancer.
11
Rekarte, Cowie Iona. "Cold acclimation in Arabidopsis." Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246616.
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Brickell, Laura. "Wound signalling Arabidopsis thaliana." Thesis, University of York, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286054.
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Torney, Keri Rebecca. "Cytokinin Sensitivity in Arabidopsis." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624484.
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Lucas, Kerry A. "Valine Metabolism in Arabidopsis." Miami University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=miami1211214693.
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15
Clifton, Rachel. "The alternative oxidase gene family in arabidopsis : insights from a transcriptomic study /." Connect to this title, 2005. http://theses.library.uwa.edu.au/adt-WU2006.0004.
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Smith, Stephanie J. "Understanding genetic regulation of UV-B responses in Arabidopsis thaliana." View electronic thesis, 2008. http://dl.uncw.edu/etd/2008-1/r1/smiths/stephaniesmith.pdf.
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Petsch, Katherine Anne. "Characterisation of the arabidopsis broomhead phenotype /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19189.pdf.
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Nibbe, Matthias. "Molekulare Charakterisierung von Arabidopsis-Signaltransduktionsmutanten /." [S.l.] : [s.n.], 2002. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=14639.
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Müller, Frank. "Phosphatidylglycerophosphat-Synthasen aus Arabidopsis thaliana." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964559455.
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Para, Alessia. "Meristem Maintenance in Arabidopsis thaliana." Doctoral thesis, Uppsala universitet, Fysiologisk botanik, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4310.
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The shoot apical meristem (SAM) is the structure that shapes the aerial architecture of the plant, by producing lateral organs throughout development. In the model plant Arabidopsis thaliana, the SAM is always identifiable as a characteristic dome, whether it is found in the centre of a rosette of leaves or at the tip of an inflorescence. When senescence occurs and organogenesis ceases, the now inactive SAM still retains its characteristic appearance and it is never consumed into a terminal structure, such as a flower. Mutant plants that undergo termination represent a valuable tool to understand how the SAM structure and function are maintained during plant life. The aim of this work was to investigate the dynamics of meristem development through morphological and genetic studies of three Arabidopsis mutants that exhibit distinct modes of SAM termination: distorted architecture 1 (dar1), adenosine kinase 1 (adk1) and terminal flower 2 (tfl2). The dar1 mutation is characterised by a severely distorted cellular architecture within the SAM. We propose that dar1 affects the pattern of cell differentiation and/or cell proliferation within the SAM apical dome, resulting in termination by meristem consumption. Instead, the adk1 mutation affects the organogenic potential of the SAM, without altering its structure. The adk1 mutant has increased levels of cytokinins and, as a consequence of this, cell division is enhanced and cell differentiation is prevented in the apex, causing termination by meristem arrest. Finally, tfl2 is mutated in the conserved chromatin remodelling factor HP1, a transcriptional repressor with multiple roles during plant development. The tfl2 SAM terminates by conversion into a floral structure, due to de-repression of floral identity genes. Interestingly, tfl2 mutants also show an altered response to light, an indication that TFL2 might act as a repressor also in the context of light signalling.
21
Wang, Huachun. "Protein phosphorylation regulation in Arabidopsis." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/5896.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on July 18, 2008) Vita. Includes bibliographical references.
22
Gandorah, Batool. "Identifing Insulators in Arabidopsis thaliana." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23226.
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In transgenic research the precise control of transgene expression is crucial in order to obtain transformed organisms with expected desirable traits. A broad range of transgenic plants use the constitutive cauliflower mosaic virus (CaMV) 35S promoter to drive expression of selectable marker genes. Due to its strong enhancer function, this promoter can disturb the specificity of nearby eukaryotic promoters. When inserted immediately downstream of the 35S promoter in transformation vectors, special DNA sequences called insulators can prevent the influence of the CaMV35S promoter/enhancer on adjacent tissue-specific promoters for the transgene. Insulators occur naturally in organisms such as yeasts and animals but few insulators have been found in plants. Therefore, the goal of this study is to identify DNA sequences with insulator activity in Arabidopsis thaliana. A random oligonucleotide library was designed as an initial step to obtain potential insulators capable of blocking enhancer-promoter interactions in transgenic plants. Fragments from this library with insulator activity were identified and re-cloned into pB31, in order to confirm their activity. To date, one insulator sequence (CLO I-3) has been identified as likely possessing enhancer-blocking activity. Also, two other oligonucleotide sequences (CLO II-10 and CLO III-78) may possess insulator activity but more sampling is needed to confirm their activity. Further studies are needed to validate the function of plant insulator(s) and characterize their associated proteins.
23
Mirza, Bushra. "Gene activation in transgenic Arabidopsis." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243061.
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Chow, Cheung-ming. "Specialisation of Arabidopsis RabA GTPases." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437049.
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Rawlins, Marion Ruth. "Glutathion synthetase in Arabidopsis thaliana." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299174.
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Dunkley, Thomas Peter John. "Mapping the Arabidopsis organelle proteome." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598685.
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The work presented in this thesis involves the development of a proteomic method for protein localization that is not dependent on the preparation of pure organelles. This method has subsequently been named localization of organelle proteins by isotope tagging (LOPIT). Organelles are first partially separated using centrifugation through density gradients. Distributions of proteins within such gradients are then assessed by measuring the relative abundance of proteins between fractions along the length of the gradients. This is achieved using isotope-coded tags for protein quantitation by mass spectrometry. The subcellular localizations of proteins can then be determined by comparing their distributions to those of previously localized proteins, since proteins that belong to the same organelle will co-fractionate in the density gradients. Application of the LOPIT technique to the study of the Arabidopsis endomembrane system has resulted in the simultaneous assignment of 527 proteins to the endoplasmic reticulum, Golgi apparatus, vacuole, plasma membrane or to the mitochondria and plastids. These results demonstrate that proteomic analysis of the major endomembrane components can be performed in parallel, enabling protein steady state distribution between these organelles to be determined. Consequently, for the first time by proteomics, genuine residents of the endoplasmic reticulum, Golgi apparatus, vacuole and plasma membrane have been distinguished from contaminants and proteins that are in transit through the secretory pathway.
27
Jarsch, Iris. "Remorin proteins in Arabidopsis thaliana." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-181479.
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Die Plasmamembran lebender Zellen stellt die Hauptbarriere für alle Arten von
extrazellulären Signalen dar. Viele davon werden ins Innere der Zelle weitergeleitet, hier
lösen sie im Kern transkiptionelle Veränderungen und damit die Anpassung der Zelle auf
Proteinebene aus. Andere wiederum werden direkt erkannt und in unmittelbare molekulare
Antworten umgewandelt, wie zum Beispiel die Sekretion von gespeicherten Stoffen oder
Konformations-änderungen von Proteinen. Besonders in Pflanzen, welche durch ihre
sesshafte Lebensweise auf die rechtzeitige und spezifische Erkennung von
Umweltveränderungen angewiesen sind, hat sich ein höchst diverses Rezeptorsystem
entwickelt. In der Ackerschmalwand Arabidopsis thaliana, der in dieser Arbeit
verwendeten Modellpflanze, wurden 610 verschiedene Rezeptorproteine identifiziert,
welche wiederum von zahlreichen interagierenden, und bis jetzt weitestgehend
unerforschten Proteinen reguliert werden. Als entscheidendes Prinzip, dieses Aufgebot an
membran-gebundenen Komponenten von Signalkaskaden zu organisieren, gilt inzwischen
die zeitliche und lokale Kompartimentierung der Plasmamembran. Durch Akkumulation
relevanter Bestandteile von biologischen Prozessen in sogenannten Membrandomänen
werden kurze Reaktionszeiten und die unmittelbare Signalweiterleitung garantiert.
Besonders wichtig bei solchen Prozessen sind sogenannte Gerüstproteine, welche als
Adaptoren zwischen anderen Komponenten fungieren.
In dieser Arbeit wurden Remorine, eine Familie pflanzenspezifische Proteinen ohne bisher
definierte Funktion, aufgrund ihrer Eigenschaft Membrandomänen zu markieren und ihrer
mutmaßlichen Beteiligung an Pflanzen-Pathogen-Interaktionen, genauer untersucht.
Eine systematische Expression von Remorinen als Fluorophor-Fusionen mit anschließender
hochauflösender mikroskopischer und quantitativer Untersuchung offenbarte, dass die
meisten Remorine sich in deutlich unterschiedlichen Mustern an der Membran verteilen.
Untersucht wurden dabei Parameter wie die Größe der erkennbaren Domänen, die Form,
die Helligkeit, aus welcher auf die Proteinkonzentration rückgeschlossen werden kann,
sowie die Domänendichte an der Membran. Diese Ergebnisse wurden von
Kolokalisationsanalysen unterstützt, welche die Lokalisation in unterschiedlichen,
koexistierenden Membrankompartimenten erkennen ließen. Ferner wurden die
Eigenschaften der von Remorinen markierten Membrandomänen, wie zum Beispiel der
Austausch an Proteinen mit der umgebenden Membran, sowie lokale und zeitliche
Dynamik und Stabilität untersucht. Dabei konnte eine hohe Fluktuation einzelner Proteine
zwischen Domäne und umliegender Membran, jedoch eine klare laterale Immobilität der gesamten Domäne nachgewiesen werden. Zusätzlich zeichneten sich die untersuchten Domänen teilweise durch eine außerordentlich große zeitliche Stabilität aus, andere
wiederum scheinen abhängig von bestimmten Stimuli zu entstehen.
Weitergehende Arbeiten dienten der Identifizierung der Funktion einzelner Bereiche der
Proteine. Hierbei konnte die entscheidende Rolle des äußersten C-terminalen Bereichs, des
so- genannten RemCAs (Perraki et al., 2012; Konrad et al., 2014) als Membrananker
bestätigt werden. Zusätzlich wurden mit Hilfe eines Hefe-2-Hybrid Ansatzes zahlreiche
neue Interaktoren für eine Auswahl von Remorinen identifiziert. Dabei wurde ein
essentieller Rezeptor der basalen Immunantwort, BAK1 als Interaktor für Remorin 6.4
gefunden.
Zuletzt wurden einige wenige Remorine mit Hilfe von Mutantenlinien in einer genetischen
Studie phänotypischen Analysen bezüglich ihrer Funktion bei Pflanzen-Pathogen
Interaktionen unterzogen. Remorin 6.4 spielt hiernach eine Rolle bei der Immunantwort
nach Befall mit virulenten Bakterien.
Die grundlegende Erkenntnis, dass in lebenden Zellen zahlreiche klar unterscheidbare
Arten an Membrandomänen koexistieren, ist ein Meilenstein auf dem Weg zur
Anerkennung einer neuen Vorstellung vom Aufbau der Zytoplasmamembran. Diese wird häufig noch als undifferenzierte zweidimensionale Flüssigkeit beschrieben, in welcher
stellenweise sogenannte Lipidflöße, festere Strukturen aus Cholesterin und Sphingolipiden,
die auch bestimmte Proteine beherbergen können, auftreten. Anhand der in dieser Arbeit
gewonnen Ergebnisse, sowie ähnlicher Studien in Hefe lässt sich nun folgendes Bild
zeichnen: Es ist davon auszugehen, dass unterschiedliche Proteine, welche im selben
biologischen Prozess involviert sind, in unmittelbarer Nachbarschaft oder sogar im selben
Proteinkomplex in der Membran organisiert sind. Die Lipidzusammensetzung in der
unmittelbaren Umgebung wird von diesen Proteinen bestimmt, bietet jedoch auch die
Grundlage für die Bildung der Domäne, indem sie die Lokalisation der Komponenten in
diesem Bereich fördert. Die zahlreichen an der Zellmembran gleichzeitig ablaufenden,
unterschiedlichen Prozesse erfordern eine hochkomplexe, zeitlich und räumlich stark
regulierte Kompartimentierung der Membran. Es kann vermutet werden, dass Remorine
eine Rolle als Gerüstproteine bei der Ausbildung einer Auswahl dieser Domänen bilden. Im
Fall von Remorin 6.4 ist das Protein für den Prozess der Flagellin-Erkennung und die
unmittelbaren Abwehrantworten, welche nachweislich eine Präformierung der beteiligten
Proteinkomplexe voraussetzen, notwendig.
28
Bayer, Emmanuelle M. "Plasmodesmata in Arabidopsis suspension cells." Thesis, University of East Anglia, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423814.
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Evans-Roberts, Katherine Mary. "DNA gyrase of 'Arabidopsis thaliana'." Thesis, University of East Anglia, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443072.
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Orme, Wendy. "A plastid DnaJ in Arabidopsis." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270855.
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Saha, Kaushik. "Tetrapyrrole biosynthesis in Arabidopsis thaliana." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612435.
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Whyte, Jennifer. "Dissecting phosphate signalling in Arabidopsis." Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/11568.
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Plant phosphate starvation responses are initiated to reduce Pi demand, conserve Pi reserves and to increase Pi availability. Responses to Pi depravation range from alterations in growth and metabolism to the induction of Pi-inducible genes. Signalling pathways governing starvation responses are unknown, although individual responses have been found to be under the control of local phosphate availability, whilst other responses have been shown to be controlled by shoot-derived systemic signals. A comparison of the kinetics of different phosphate starvation responses, representing growth, physiology and gene expression, suggesting that changes in gene expression and physiology occurred prior to growth responses. The magnitude of all responses was found to be dependent on the duration of starvation and on previous Pi growth conditions, suggesting that internal Pi levels regulate the initiation of responses. Kinetic studies investigating gene expression after Pi re-supply found that down-regulation of expression is rapid and therefore possibly under local control. Enhanced Pi starvation responses were observed under increased sucrose availability, illustrating the importance of a balanced internal C:P ratio for plants. Split-root experiments revealed the systemic down-regulated of Pi-inducible genes and confirmed the existence of long-range signals governed by shoot Pi status in Arabidopsis. Experiments to determine the kinetics of down-regulation in split root plants discovered that the extent of down-regulation was dependent on internal Pi status and on the duration of split-root treatment. Complete down-regulation occurred only after several days. Split-root experiments were conducted with various mutants to further dissect signalling. Wild-type down-regulation was observed in the phosphate response mutant, phr1-1, the cytokinin receptor mutant, cre1and in Arabidopsis plants containing the Pi-inducible At4 gene under the control of the CaMV 35S promoter. Reduced systemic down-regulation was observed in the phosphate translocation mutant, pho1, confirming low shoot Pi status of this mutant.
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Garagounis, Constantine. "Microcompartmentation of aldolase in Arabidopsis." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:6a4e0671-ee0d-4303-9118-d1f34a7ce06c.
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Understanding the internal organization of cells from the molecular up to organelle level is a current challenge for biology if we are to better comprehend the mechanisms by which cellular processes occur. A prevailing view of the cell interior is that biochemical reactions and molecular movements are dominated by random diffusion. However, in addition to being compartmented into organelles, cells may well be organized at a finer level. Proteins may localise to specific areas within sub-cellular compartments, by associating with each other, the cytoskeleton and organelle membranes. Thus giving rise to distinct microcompartments. Considerable in vitro evidence exists for such interactions between enzymes and larger cellular components. This strengthens the idea that cells may be microcompartmented. However, little in vivo evidence supports this hypothesis, especially in plants. As a test-case for the concept of microcompartmentation this project investigated the sub-cellular distribution of the glycolytic enzyme fructose-bisphosphate aldolase in Arabidopsis thaliana; the ultimate aim being to establish whether it is microcompartmented in vivo and, further, to test the potential function(s) of such microcompartmentation.
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Hayton, Gemma. "Nitrogen-status sensing in Arabidopsis." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:41822013-c6db-464a-9413-686cad4952df.
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Plant nitrogen use efficiency (NUE) is important in agriculture because it significantly influences yield and fertiliser requirements. Many factors influence NUE; these include nitrogen availability, internal nitrogen-status, nitrogen uptake and assimilation rates as well as carbon status. Previous attempts to improve NUE by targeting the main nitrogen uptake or assimilation machinery (e.g. over-expression of nitrate reductase or glutamine synthetase) have had mixed results. This is because these enzymes are strictly controlled by multiple feedback mechanisms relating to internal and external nitrogen-status. Arguably, a better approach to manipulating NUE would be to identify and supress these feedback signals either alone, or in conjunction with over-expression of the uptake and assimilation machinery. This could enhance exploitation of nitrogen resources leading to increased growth. Internal nitrogen-status signalling is poorly understood. However, it is known that amino acids, when exogenously supplied, inhibit the uptake of nitrate. The mechanism for this inhibition has not been identified, but it is likely the result of sensing of internal nitrogen status, the amino acids representing a signal of nitrogen sufficiency, in turn leading to reduced expression and activity of the nitrogen uptake and assimilation machinery. In this thesis I conducted a reverse-genetic screen based on the response of candidate amino acid transporter knock-out mutants to exogenous alanine. In wild-type Arabidopsis, exogenous alanine caused inhibition of vegetative growth, which is accompanied by a reduction in nitrate uptake and transcripts encoding nitrate transporters. In the reverse-genetic growth screen, I identified four mutants with vegetative growth that was insensitive to exogenous alanine. Further characterisation of these mutants revealed that nitrogen uptake was not inhibited and this was accompanied by a lack of repression of nitrate transporter transcripts. Based on this evidence, I concluded that these amino acid transporter mutants were perturbed in nitrogen-status signalling. However, the origin of this signalling perturbation remains unclear. I formulated two hypotheses to explain how four amino acid transporter mutants could have the same signalling phenotype. The first suggested that the four alanine-insensitive transporters could form a functional complex, which is part of the nitrogen-status signalling pathway. The second suggested that the loss-of-function of the amino acid transporter perturbs metabolite levels, in a common way in each mutant, producing a metabolic signature which is sensed downstream of the transporter by an unknown mechanism. The latter hypothesis was tested by extensive metabolite profiling and I could find no evidence in support of the hypothesis. Preliminary investigations were made of the functional-complex hypothesis but technical problems prevented significant progress.
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Molojwane, Emang Tsametse Emi. "Engineering cyanide-tolerant Arabidopsis thaliana." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/19996.
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Cyanide is highly toxic as it inhibits respiration in aerobic organisms by binding to cytochrome c oxidase in the mitochondrial electron transport chain. Plants naturally produce cyanide from the hydrolysis of cyanogenic glycosides and as a by-product of ethylene biosynthesis. β-Cyanoalanine synthase prevents self-poisoning by combining endogenous cyanide with cysteine in the mitochondria to form β-cyanoalanine, which is further hydrolysed to asparagine, or aspartate and ammonia, by plant nitrilase 4 enzymes. β-Cyanoalanine synthase activity enables plants to detoxify limited concentrations of exogenous cyanide. However, phytotoxicity and death occur from exposure to relatively low concentrations of exogenous cyanide. In contrast, some microorganisms have a high capacity for cyanide detoxification due to a number of metabolic pathways including the degradation of cyanide to formate and ammonia; or formamide, by bacterial cyanidase (CynD) and fungal cyanide hydratase (CHT), respectively. Environmental contamination caused by failure to contain cyanide from anthropogenic sources is an important global problem. Hydrometallurgical gold mining utilises cyanide as a lixiviant due to the high affinity of cyanide for gold and the stability of the resulting cyanometallic complexes in aqueous solution, and thus is a significant source of cyanide contamination of soil and water. Biological treatment methods for cyanide, such as phytoremediation, could provide alternatives to the currently used chemical destruction techniques with their associated disadvantages. The use of phytoremediation would require plants to tolerate high concentrations of cyanide in soil. Two attempts have previously been made, with some success, to increase cyanide tolerance in Arabidopsis by genetic engineering: the first, by augmenting the β-cyanoalanine synthase pathway using a microbial nitrilase; and, the second, by introducing a microbial detoxification pathway targeted to the chloroplasts while overexpressing the endogenous enzyme which metabolises the product of the cyanide detoxification reaction. The aim of the current study was to determine whether Arabidopsis thaliana could co-opt the CynD and CHT genes from the cyanide-degrading Bacillus pumilus and Neurospora crassa to detoxify higher levels of cyanide using the encoded enzymes, and whether targeting CynD and CHT to the mitochondria would confer a greater enhancement of cyanide tolerance on plants compared to targeting to the cytoplasm.
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Granlund, Irene. "Proteomic analysis of Arabidopsis thaliana." Doctoral thesis, Umeå : Department of Chemistry, Umeå University, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1820.
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Schuhmann, Holger. "Deg Proteases in Arabidopsis thaliana." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:352-opus-64736.
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Melquist, Stacey Michelle. "DNA methylation signaling in Arabidopsis." Available to US Hopkins community, 2002. http://wwwlib.umi.com/dissertations/dlnow/3068188.
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Muños, Stéphane. "Reprogrammations génétiques induites en réponse à la déficience nutritionnelle en N chez Arabidopsis thaliana." Montpellier 2, 2002. http://www.theses.fr/2002MON20102.
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De, Bossoreille de Ribou Steve. "Etude fonctionnelle du gène REBELOTE chez Arabidopsis thaliana." Thesis, Lyon, École normale supérieure, 2011. http://www.theses.fr/2011ENSL0619.
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Ponts entre les séquences d'acides nucléiques et les protéines, les ribosomes sont des composants essentiels des cellules vivantes. Composé d'ARN et de protéines ribosomiques, ils sont transportés, durant leurs biogenèses, du nucléole au cytoplasme, où ils traduisent les ARN messagers (ARNm) en protéines. Ces dernières années, il a été montré que nombre de protéines ribosomiques étaient impliquées dans le développement d'Arabidopsis en intervenant sur la division et l'élongation cellulaire. L'impact d'un défaut de biogenèse des ribosomes sur le développement pourrait être expliqué par un effet dose, par une spécificité des ribosomes pour leur ARNm cibles ou par la multifonctionnalité de protéines ribosomiques. Les résultats obtenus montrent que REBELOTE (RBL), l'un des deux homologues chez Arabidopsis de la protéine NOC2p de levure, intervient probablement durant la biogenèse des ribosomes. Des mutations dans le gène RBL causent une gamme de phénotype de la létalité embryonnaire aux défauts de croissance (réduction de la taille de la plante, altération de la forme des feuilles...). Afin de mieux comprendre les processus contrôlés par RBL, la fonction ribosomique de RBL a été étudiée et ses interacteurs protéiques recherchés. Nous nous sommes ensuite focalisé sur les effets des mutations rbl sur la division et l'élongation cellulaire. Ce travail montre que les défauts observés aux niveaux moléculaire et cellulaire peuvent expliquer les retards de croissance des mutants rblBridges between nucleic acids sequences and proteins, ribosomes are central components and the “auletes” of living cells. Composed of ribosomal proteins and RNA, they move during their biogenesis from the nucleolus to the cytoplasm, where they translate RNA messengers into proteins. In the past years, some mutants of ribosomal-biogenesis-related proteins have shown the importance of these proteins during cell division and Arabidopsis development. The impact of ribosomal defects on development could be explained by dose effect (which could be important for cell fitness), specificity of ribosomes for some mRNA or multifunctional ribosomal proteins (Mary E. Byrne, 2009). Here I present our work on REBELOTE (RBL), one of the two Arabidopsis homologs of the yeast NOC2 protein, which act during the ribosomal 60S subunit biogenesis. Mutations in REBELOTE gene cause a range of phenotypes, from embryo lethality to growth defects (reduced plant size, altered leaf shape…). To have a better understanding of RBL-controlled processes, we first analyzed the ribosomal function of RBL, and searched for its protein partners. Our results shows that RBL act in two different nucleolar complexes supposed to regulate 60S ribosomal subunit biogenesis. Subsequently, we focused on the effects of rbl mutations on the cell division/elongation processes. Our work shows that defects observed at molecular and cellular levels could explain the slow down of cell divisions and growth delay in rbl mutants
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Vess, Christoph. "Identifizierung und Charakterisierung schwermetallregulierter Gene im Metallophyten Arabidopsis halleri (L.) und in Arabidopsis thaliana (L.)." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972493360.
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Passaia, Gisele. "Análise funcional dos genes de glutationa peroxidase em arroz (Oriza sativa) e Arabidopsis (Arabidopsis thaliana)." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2013. http://hdl.handle.net/10183/143442.
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As espécies reativas de oxigênio (ERO) afetam significativamente a homeostase redox celular. No entanto, o peróxido de hidrogênio (H2O2), uma das ERO mais estudadas, é considerado regulador chave em uma série de processos fisiológicos, dependendo de sua concentração na célula: em baixas concentrações atua como molécula sinalizadora envolvida na aclimatação da planta a estresses, desencadeando tolerância a estresses bióticos e abióticos; por outro lado, em altas concentrações o H2O2 pode levar à morte celular. Gradientes de ERO e fitohormônios têm influência nas respostas de crescimento local e consecutivamente afetam o estado redox celular. Diversos fitohormônios afetam a sinalização redox celular controlando processos de crescimento e defesa. Os níveis de H2O2 intracelulares são controlados pela ação de diversas enzimas da classe das peroxidases e catalases. Dentre as peroxidases, a família de proteínas GPX pode ser encontrada em praticamente todos os reinos e vem sendo cada vez mais estudada em plantas. Em arroz, essa família é composta de cinco genes, enquanto em Arabidopsis foram identificados oito genes. Este trabalho teve como objetivo caracterizar funcionalmente as GPX mitocondriais e cloroplastídica de arroz e sete dos oito genes de Arabidopsis thaliana. Mutantes knockout de Arabidopsis para os genes AtGPX1, AtGPX2, AtGPX3, AtGPX4, AtGPX6, AtGPX7 e AtGPX8 foram obtidos.Nesta espécie, pelo menos AtGPX2, AtGPX3 e AtGPX6 são necessárias para a correta formação da arquitetura da raiz dependente dos hormônios ABA, auxina e SL. O sileciamento por RNAi em arroz para os genes OsGPX1, OsGPX3 e OsGPX4 gerou plantas com crescimento deficiente de raiz, parte área e formação de panículas. A redução em 80% da expressão gênica da isoforma cloroplastídica (OsGPX4) foi letal para o desenvolvimento de plântulas regeneradas a partir de calos de arroz, enquanto que a redução da expressão de 40% e 95% de OsGPX1 (GPX1s) e OsGPX3 (GPX3s), respectivamente, não impediu a regeneração de plantas. No entanto, plantas GPX1s apresentaram menor tamanho, menor número de panículas e menor produção de sementes em comparação com as plantas NT (não transformadas). Adicionalmente, plantas GPX3s apresentaram redução do comprimento tanto da parte aérea quanto das raízes, além de acúmulo de H2O2 cerca de vinte vezes maior do que a planta NT. Neste trabalho, foi demonstrada a participação das enzimas GPX durante o desenvolvimento vegetativo e reprodutivo de plantas de arroz e o estabelecimento da arquitetura da raiz dependente de hormônios em Arabidopsis. O conjunto de dados obtidos contribuempara o entendimento do papel dessas enzimas na homeostase redox, como também na interação com fitohormônios nos processos de desenvolvimento e defesa vegetais.Reactive oxygen species (ROS) affect significantly cellular redox homeostasis. Hydrogen peroxide (H2O2), one of the most studied ROS, is considered a key regulator in a number of physiological processes dependent of its concentration in the cell: at low concentrations acts as a signaling molecule involved in plant acclimation to stress, triggering tolerance to biotic and abiotic stresses; on the other hand, at high concentrations can promote cell death. Gradients of ROS and phytohormones can influence the responses of local growth and consecutively can affect the cellular redox state. Several phytohormones affect redox signaling processes controlling cell growth and defense. The intracellular levels of H2O2 are controlled by the action of several enzymes like peroxidases and catalases. Among the peroxidases, the GPX family of proteins can be found in virtually all kingdoms and is being increasingly studied in plants. In rice, this family consists of five genes, while in Arabidopsis eight genes were identified. This study aimed to characterize functionally rice and Arabidopsis GPX genes. Arabidopsis thaliana nockout mutants for AtGPX1, AtGPX2, AtGPX3, AtGPX4, AtGPX6, and AtGPX7 AtGPX8 genes were obtained. In Arabidopsis, at least AtGPX2, AtGPX3 and AtGPX6 are necessary to hormone-dependent control of root achitecture formation. RNAi knockdown in rice of OsGPX1, and OsGPX3 OsGPX4 generated plants with shorter root and shoot lengths, and deficient panicle formation. An 80% gene expression reduction of the chloroplastic isoform (OsGPX4) was lethal, and impaired the regeneration of plants from rice calli, whereas the reduction of expression in 40% and 95% of OsGPX1 (GPX1s) and OsGPX3 (GPX3s), respectively, did not prevent plant regeneration. However, GPX1s plants were smaller and had fewer panicles and seed compared to NT (non-transformed) plants. Additionally, GPX3s plants showed reduced length of the shoot as roots and accumulation of H2O2 about twenty times greater than the plant NT. GPX participation during vegetative and reproductive development of rice plants and the hormone-dependent root arquitecture formation in Arabidopsis was demonstrated in this work. The data set obtained contributed to the understanding of the role of these enzymes in the redox homeostasis, as well as how the interaction with phytohormones in development processes and plant defense occurs.
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Garcia, Damien. "Etude des contrôles génétiques de la taille de la graine chez Arabidopsis Thaliana." Lyon, École normale supérieure (sciences), 2004. http://www.theses.fr/2004ENSL0274.
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Ahearn, Kelly Patricia. "Analysis of genes that regulate flowering and branch initiation in the shoot apex of Nicotiana tabacum and Arabidopsis /." view abstract or download file of text, 2000. http://wwwlib.umi.com/cr/uoregon/fullcit?p9963440.
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Thesis (Ph. D.)--University of Oregon, 2000.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 50-54). Also available for download via the World Wide Web; free to University of Oregon users. Address: http://wwwlib.umi.com/cr/uoregon/fullcit?p9963440.
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Teaster, Neal D. Chapman Kent Dean. "A regulatory role for N-acylethanolamine metabolism in Arabidopsis thaliana seeds and seedlings." [Denton, Tex.] : University of North Texas, 2009. http://digital.library.unt.edu/permalink/meta-dc-10978.
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Schubert, Maria. "The chloroplast lumen proteome of Arabidopsis thaliana /." Stockholm, 2006. http://diss.kib.ki.se/2006/91-7140-654-9/.
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Wu, Hui-Ju. "Contribution à l'étude du génome d'Arabidopsis thaliana dans la région du gène EM1." Perpignan, 1998. http://www.theses.fr/1998PERP0286.
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Dans le but d'acquerir des informations sur un locus du genome d'arabidopsis thaliana, le locus em1, differentes approches ont ete adoptees pour en etablir la structure et en etudier le contenu. Un premier travail a consiste a localiser sur la carte genetique de la plante et a montrer que em1 est situe sur le chromosome 3, a la position 68,5 centimorgans. La carte physique de cette region du genome a ete etablie par l'ordonnancement de clones yac representant un contig qui couvre environ 1,75 megabases. Ensuite, la sequence complete d'un contig de 32 kilobases autour du gene em1 a ete etablie et analysee. Hors em1, sept genes, jamais decrits jusqu'ici chez la plante, ont ete identifies et analyses. Deux de ces genes, en copie unique dans le genome, ont fait l'objet d'une etude plus approfondie. Une etude a d'abord ete consacree au gene atg5, dont la proteine s'est revelee tres similaire a la proteine sac1p de levure impliquee dans l'organisation du cytosquelette d'actine et la fonction secretoire de l'appareil de golgi. Ce gene presente la particularite de contenir un intron de type u12 et nous montrons que cet intron est conserve dans le gene homologue d'autres plantes. L'arnm atg5 n'est detecte qu'a tres faible niveau dans les differents tissus de la plante et il est absent des graines seches. L'apport d'aba exogene stimule l'accumulation de ce messager dans la plantule. Nous montrons que la proteine atg5p est capable de complementer un mutant sac1 de levure en restaurant le phenotype sauvage, par suppression de l'auxotrophie a l'inositol et de l'incapacite a croitre a basse temperature. L'analyse de plantes transgeniques ou le gene gus est sous le controle du promoteur atg5 indique que l'expression du gene est limitee a quelques tissus, et notamment a l'embryon precoce et au pollen en fin de maturation. Une seconde etude a ete effectuee sur le gene atg7 qui code une proteine kinase calcium-dependante. Une etude de l'expression du gene montre que les transcrits, presents dans la plupart des tissus, sont absents de la graine mature. Ces arnm codent une proteine de structure classique, avec quatre sites de fixation du calcium. Cependant, l'isolement d'un adnc ou seuls trois des sites sont conserves, suggere qu'il pourrait exister un epissage differentiel du transcrit primaire en reponse a une situation biologique specifique.
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Mantelin, Sophie. "Effet stimulateur d'une souche PGPR de Phyllobacterium sur la croissance d'arabidopsis thaliana : Caractérisation de la réponse morphogénétique du système racinaire et impact sur la nutrition azotée." Montpellier 2, 2004. http://www.theses.fr/2004MON20214.
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Surovtseva, Yulia V. "Telomere-associated proteins in Arabidopsis thaliana." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2656.
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Messerli, Gaëlle Liliane Yolande. "Starch degradation in Arabidopsis thaliana leaves /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17034.
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