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Xia, Qiong. "Molecular aspects of temperature regulation of sunflower seed dormancy." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066629/document.
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La graine est le produit de la reproduction sexuée chez les Angiospermes. Elle assure la survie et la dispersion de l'espèce. La germination des graines est la première étape de la croissance des plantes. La transition entre l'état de dormance des graines et leur germination est une étape clef dans le cycle de vie des plantes qui a des conséquences écologique et commerciale. Depuis plusieurs décennies, de nombreux facteurs de l'environnement ont été étudiés pour leurs implications et leurs conséquences dans le processus de dormance et de germination des graines. Les études sur la réponse des semences aux changements de température en liens avec le réchauffement climatique ont un intérêt primordial. Le but de ce travail a été d'étudier la régulation de la dormance et de la germination des graines de tournesol par la température. Une analyse protéomique et un profilage enzymatique ont été réalisés afin de mieux comprendre la régulation du métabolisme pendant la levée de dormance par la température. L'utilisation d'approches moléculaires et cytologiques, nous ont permis d'appréhender l'interaction entre la température et les phytohormones impliquées dans ce processus. Nos résultats ont révélé le rôle joué par la température comme facteur externe affectant la dormance et la germination des graines en agissant d'une part sur le métabolisme et d'autre part sur la quantité et la localisation cellulaire des principales hormones endogènes<br>A seed is the product of sexual reproduction and the means by which the new individual is dispersed by angiosperms. Seed germination being the first step of plant establishment, the ultimate role of the transition between seed dormancy and germination during plant lifecycle is an important ecological and commercial trait. Last several decades, several environment factors have been reviewed to strongly effect the process of seed dormancy and germination. However, studies about seed response to temperature change are acute with the global warming. The aim of this work was to investigate temperature regulation of dormancy and germination in sunflower seeds. Proteomic analysis and enzyme profiling have been used to study metabolism regulation during seed dormancy release by temperature. Moreover, using molecular and cytological approaches, we investigate the interaction between temperature and phytohormones involved in this process. Our results revealed that temperature as an external factor to effect seed dormancy and germination by affecting, in one hand, the metabolism, and in the other hand the level and localization of major endogenous hormones
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Xia, Qiong. "Molecular aspects of temperature regulation of sunflower seed dormancy." Electronic Thesis or Diss., Paris 6, 2016. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2016PA066629.pdf.
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La graine est le produit de la reproduction sexuée chez les Angiospermes. Elle assure la survie et la dispersion de l'espèce. La germination des graines est la première étape de la croissance des plantes. La transition entre l'état de dormance des graines et leur germination est une étape clef dans le cycle de vie des plantes qui a des conséquences écologique et commerciale. Depuis plusieurs décennies, de nombreux facteurs de l'environnement ont été étudiés pour leurs implications et leurs conséquences dans le processus de dormance et de germination des graines. Les études sur la réponse des semences aux changements de température en liens avec le réchauffement climatique ont un intérêt primordial. Le but de ce travail a été d'étudier la régulation de la dormance et de la germination des graines de tournesol par la température. Une analyse protéomique et un profilage enzymatique ont été réalisés afin de mieux comprendre la régulation du métabolisme pendant la levée de dormance par la température. L'utilisation d'approches moléculaires et cytologiques, nous ont permis d'appréhender l'interaction entre la température et les phytohormones impliquées dans ce processus. Nos résultats ont révélé le rôle joué par la température comme facteur externe affectant la dormance et la germination des graines en agissant d'une part sur le métabolisme et d'autre part sur la quantité et la localisation cellulaire des principales hormones endogènes<br>A seed is the product of sexual reproduction and the means by which the new individual is dispersed by angiosperms. Seed germination being the first step of plant establishment, the ultimate role of the transition between seed dormancy and germination during plant lifecycle is an important ecological and commercial trait. Last several decades, several environment factors have been reviewed to strongly effect the process of seed dormancy and germination. However, studies about seed response to temperature change are acute with the global warming. The aim of this work was to investigate temperature regulation of dormancy and germination in sunflower seeds. Proteomic analysis and enzyme profiling have been used to study metabolism regulation during seed dormancy release by temperature. Moreover, using molecular and cytological approaches, we investigate the interaction between temperature and phytohormones involved in this process. Our results revealed that temperature as an external factor to effect seed dormancy and germination by affecting, in one hand, the metabolism, and in the other hand the level and localization of major endogenous hormones
3
Li, L. "Enzymic changes during dormancy breakage." Thesis, University of Reading, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379772.
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Musselwhite, Sheri Ruth. "Overcoming Summer Dormancy of Boxwood." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/42177.
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The objective of this work was to determine if summer dormancy of boxwood could be removed either through nutritional or hormonal means. Buxus sempervirens L. â Suffruticosaâ , B. sempervirens â Vardar Valleyâ , and B sinica var. insularis (Nakai) â Justin Brouwersâ were used for these studies. In the nutrition study, experiments were conducted to examine the effects of various levels of Osmocote 15-9-12 and liquid 10-4-6 on growth of boxwood. Optimal shoot dry weight was achieved at applications of 12 to 16 g Osmocote and 100 â 150 ppm N liquid fertilizer. Leachate EC corresponding to optimal shoot dry weight ranged from 0.5 to 0.7 dS/m for Osmocote and from 0.7 to 1.5 dS/m for liquid fertilizer. While the fertilizer requirements for boxwood optimal dry weight accumulation were determined, additional flushes of growth subsequent to the initial spring flush did not occur for â Vardar Valleyâ and English boxwood. In the phytohormone study, experiments were conducted that examined the effects of pruning, Promalin (GA4+7 and BA), and defoliation on the growth of three boxwood species. While Promalin applied alone or in conjunction with pruning shows promise of increasing new shoot growth, its response was not consistent from experiment to experiment. In fact, when it was applied in conjunction with defoliation, it dramatically decreased number of new shoots and actually resulted in some shoot mortality. Pruning was also erratic in its promotion of new shoots. Defoliation increased new shoot number dramatically and shows the most promise in overcoming summer dormancy.<br>Master of Science
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Browning, Luke Wayne. "StCKP and potato tuber dormancy." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/275074.
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Nasiruddin, Khondoker Md. "Potato microtubers : their formation and dormancy." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284943.
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Basbouss-Serhal, Isabelle. "Role of mRNA post-transcriptional metabolism in the regulation of Arabidopsis thalian dormancy." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066147/document.
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Rôle du métabolisme post-transcriptionnel des ARNm dans la régulation de la dormance des semences d’Arabidopsis thaliana.Une étude physiologique nous a permis d'identifier l'influence de la température et de l'humidité relative (HR) lors du stockage des graines dormantes d’Arabidopsis. Après une levée de dormance atteinte en 7 semaines avec des cinétiques variables selon les conditions, on observe une induction de la dormance secondaire à faible HR et une perte progressive de la viabilité à forte HR. La levée et l’induction de la dormance sont associées à la régulation de gènes liés aux voies de l'acide abscissique et des gibbérellines. Nous avons étudié la dynamique d’association des ARNm aux polysomes et comparé la transcription et la traduction des graines dormantes et non dormantes au cours de l’imbibition. Nous montrons qu'il n'y a pas de corrélation entre transcriptome et traductome et que la régulation de la germination est principalement liée à la traduction. Ceci suppose un recrutement sélectif et dynamique des ARNm liés aux polysomes dans les graines dormantes et non dormantes. Certaines caractéristiques de la région 5'UTR des transcrits semble impliquées dans la sélection des ARNm traduits pendant la germination. Les phénotypes de mutants d’éléments du catabolisme des ARN montrent que la dormance est également associée à une dégradation sélective des ARNm. Les P-bodies (localisés dans des lignées YFP-DCP1) sont d’ailleurs en quantité plus importante dans les graines non-dormantes. La comparaison des transcriptomes des mutants vcs-8 et xrn4-5 a permis l'identification de plusieurs transcrits dégradés via VCS ou XRN4, dont le rôle sur la dormance a été confirmé par génétique inverse. Certains motifs spécifiques semblent être impliqués dans la sélection de transcrits pour leur dégradation<br>Role of mRNA post-transcriptional metabolism in the regulation of Arabidopsis thaliana dormancy.A physiological study allowed us to reveal the effect of temperature and relative humidity (RH) during Arabidopsis seed storage. Seven weeks of after ripening lead to alleviation of dormancy with different kinetics according to the conditions. Longer storage induced an induction of secondary dormancy at low RH and progressive loss of viability at high RH. Dormancy release and induction of secondary dormancy were associated with induction or repression of key genes related to abscissic acid and gibberellins pathways. We have studied the dynamics of mRNAs association with polysomes and compared transcriptome and translatome of dormant and non-dormant seeds. There was no correlation between transcriptome and translatome and germination regulation is largely translational, implying a selective and dynamic recruitment of mRNAs to polysomes in both dormant and non-dormant seeds. Some identified 5'UTR features could play a role in this selective. Dormancy is also associated with mRNA decay as demonstrated by phenotyping mutants altered in mRNA metabolism. Moreover we have shown that P-bodies were more abundant in non-dormant seeds that in dormant ones. Transcriptome analysis of xrn4-5 and vcs-8 mutants allowed us to identify several transcripts degraded via VCS ou XRN4 proteins, having a role in dormancy. This role was confirmed by reverse genetics for some of them. Some specific motifs were identified as involved in mRNA decay selection
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Lachabrouilli, Anne-Sophie. "Etude des mécanismes impliqués dans la mise en place et l'expression de la dormance des semences de tournesol." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS619.
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A la récolte, les semences de tournesol (Helianthus annuus L.) sont dormantes et germent difficilement. Les objectifs de ce travail étaient de caractériser l’influence des facteurs génétiques et environnementaux sur la dormance des akènes de tournesol, de sa mise en place pendant le développement à son élimination après la récolte, et d’identifier des marqueurs moléculaires de la dormance. Deux essais agronomiques, mis en place en 2016 et en 2017 avec 2 génotypes, ont permis de mettre en évidence le rôle des facteurs génétiques ainsi que l’effet majeur de la vitesse de déshydratation des semences sur la plante mère sur l’intensité de la dormance à la récolte. L’ensemble de ces données nous a permis de proposer un modèle prédictif de l’intensité de la dormance à la récolte en intégrant des données environnementales. En complément, le transcriptome et le traductome des semences issues des deux génotypes et dont l’intensité de dormance à la récolte était différente, ont été étudiés. Cette analyse a permis de souligner que la dormance est un phénomène actif au niveau moléculaire et que sa régulation serait liée à une sélection différentielle des transcrits à traduire. Ce travail a permis d’identifier des marqueurs moléculaires de la dormance. Après la récolte, la dormance s’élimine progressivement au cours du stockage. Nos résultats montrent que la vitesse d’élimination est fortement modulée par les conditions de stockage (température et humidité relative de l’atmosphère) et le niveau de dormance initial des semences. En revanche nous ne mettons pas en évidence une composante génétique dans ce phénomène, qui semble donc strictement dépendre des conditions environnementales<br>Freshly harvested sunflower seeds (Helianthus annuus L.) are dormant and poorly germinate. The aim of this study was to characterize the influence of genetic and environmental factors on the dormancy of sunflower achenes, from its establishment during seed development to its elimination after harvest, and eventually to identify molecular markers of dormancy. Two agronomic trials set up in 2016 and 2017 using two genotypes, highlighted the role of genetic factors and pointed towards a major effect of the seed dehydration rate, while they are still on the mother plant, on the degree of dormancy upon harvest. All these results allowed us to propose a predictive model of the dormancy intensity at harvest by integrating environmental data. In addition, the transcriptome and translatome of two genotypes displaying differences with the intensity of dormancy at harvest during the agronomic trials were further studied. Theses analyses show that dormancy is an active phenomenon at the molecular level and that is regulation should be linked to a differential selection of transcript for translation. These results lead to the identification of molecular markers of dormancy enabling the establishment of protocols designed to rapidly detect dormancy. Since dry storage is known to progressively alleviate dormancy, our results further showed that this process is strictly modulated by the storage conditions (temperature and relative humidity of the atmosphere) and the initial level of seed dormancy. On the other hand, there was no evidence suggesting that the genetic component, which seems to be strictly dependent on environmental conditions, could be involved in this phenomenon
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Tavakkol, Afshari Reza. "Variation in seed dormancy of tetraploid wheat." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ37916.pdf.
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Dilawari, Mridull. "Genetic Characterization of Dormancy in Durum Wheat." Diss., North Dakota State University, 2012. https://hdl.handle.net/10365/26476.
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Two populations derived by crossing LDN x LDN Dic-3A (Population I) and LDN x LDN Dic-3B (Population II) were genetically characterized for the seed dormancy present on chromosome 3A and 3B of durum wheat. The genes for seed dormancy in these two populations were contributed by the wild parent T. dicoccoides. Although the populations showed transgressive segregants for both dormant as well as nondormant parent, the populations were similar to the dormant parent at Langdon and Prosper 2006 field locations for Population I and at Langdon 2007 and Autumn greenhouse season for Population II. Genotypic and phenotypic analysis over the combined populations showed an environmental effect on expression of the trait. Different QTL were identified for both field and greenhouse season for the population derived from the cross between LDN x LDN Dic-3A. Five QTL for seed dormancy were identified on chromosome 3A for the QTL analysis performed over combined field locations. One QTL ranging between marker interval Xcfa2193 and Xcfd2a was consistently present for the 30 day period of seed germination and was also found to be linked to red grain color trait. The QTL analysis performed on the population derived from the cross between LDN x LDN Dic-3B identified only one major QTL on the long arm of chromosome 3B between the marker interval Xbarc84 and Xwmc291. This QTL was consistently present for all the field and spring greenhouse season for the seed germination period of 30 days. The QTL x E effect was also observed for this QTL, however it was very small.
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Keim, Rebecca. "Treatment-Induced Breast Cancer Dormancy and Relapse." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3500.
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When breast tumor cells encounter stress due to cancer therapies, they may enter a dormant state, escaping from treatment-induced apoptosis. Dormant cells may eventually regain proliferative capabilities and cause recurrent metastatic disease, which is the leading cause of mortality in breast cancer patients. We sought to determine if a high dose of radiation therapy (RT) or combined chemo-immunotherapy, with and without the blockade of autophagy by chloroquine (CQ), could overcome treatment-induced tumor dormancy or relapse. We found that autophagy contributes in part to treatment-induced tumor dormancy. We also found that three therapeutic strategies were successful in inhibiting or preventing tumor relapse. These include: 18Gy/day RT, chemotherapy combined with the blockade of autophagy, and combined chemo-immunotherapy. Follow-up studies are needed to determine the feasibility of preventing tumor relapse by prolonging tumor dormancy versus eliminating dormant tumor cells.
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Johnson, Catherine Lynn. "Dormancy in an eastern boundary current copepod /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2003. http://wwwlib.umi.com/cr/ucsd/fullcit?p3091321.
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Vert, Joshua Christopher. "Hypersaline Lake Environments Exhibit Reduced Microbial Dormancy." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/4050.
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From acid seeps and deep-sea thermal vents to glacial ice and hypersaline lakes, extreme environments contain relatively simplified communities consisting of extremophiles that have evolved to survive and thrive under adverse abiotic conditions. In more neutral environments, microorganisms use dormancy as a common life history strategy to weather temporal fluctuations of resources or stresses until more 'optimal' conditions are present. It is unclear if dormancy is an essential survival mechanism for microorganisms in extreme environments; however, recent studies suggest that extreme environments may create stable conditions for extremophiles to the extent that dormancy is of less ecological importance. Using lake salinity levels as measurements of "extreme," we evaluated the dormancy of bacterial and archaeal phyla and lake chemistry in five hypersaline and five freshwater lakes across the western United States. Dormancy was calculated using targeted metagenomics to analyze 16S rDNA and rRNA tag sequences. It was hypothesized that bacteria and archaea in hypersaline lake communities would exhibit lower levels dormancy than bacterial and archaeal communities in geologically similar freshwater lake controls. It was also hypothesized that microbial dormancy would decrease as the dominant extreme environmental variable increased in the lakes. As hypothesized, overall dormancy decreased at least 2-fold in hypersaline compared to freshwater lakes for both bacteria and archaea. Of the predominant phyla and subclasses, Firmicutes, Bacteroidetes, and Gammaproteobacteria each demonstrated at least a seven-fold decrease in dormancy in hypersaline lakes compared to freshwater lakes. Specifically, species within the genus Clostridium were responsible for 85% of the dormancy observed in the phylum Firmicutes. Also as hypothesized, microbial dormancy decreased as salinity increased in the lakes. Lower dormancy in hypersaline lakes correlated with increasing salinity while lower dormancy in freshwater lakes correlated with increasing total phosphorus levels. These results suggest that dormancy is a less common life history strategy for microorganisms in extreme environments; it is proposed that this is due to the relatively stable environment in hypersaline lakes and the reduced number of available microbial niches. These results also suggest that the dominant extreme stress (i.e., salinity) may override other driving factors in an environment to ultimately determine microbial community composition, diversity and richness.
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Nagy, Dóra. "Peptidergic control of dormancy in Drosophila melanogaster." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3426310.
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Organisms, especially those living in temperate zones, are constantly exposed to the cyclical changes of environmental factors due to the alternating seasons. In order to increase their chances of survival, they evolved different adaptive mechanisms to withstand the stress of harsh periods. Among insects, diapause is the most commonly used strategy to achieve seasonal synchronization.
Diapause is a neuro-hormonally regulated state of dormancy that enables insects to switch to an alternative developmental program when external conditions are not suitable for normal development. In the fruit fly, Drosophila melanogaster, diapause is characterized by the arrest of the ovarian development at previtellogenic stages. Insulin-like signaling has been identified as a key regulator of dormancy in many organisms. The insulin producing cells (IPCs), located in the Pars intercerebralis, are crucial neurosecretory cells that are neuroanatomically connected to the neuroendocrine center that governs hormonal regulation of diapause. They are responsible for the production and release of different insulin-like peptides that have been found to act as diapause-antagonist hormones. Here we found that two neuropeptides, pigment dispersing factor (PDF) and short neuropeptide F (sNPF), produced in a small subset of neurons (ventrolateral clock neurons, LNvs), modulate the diapause response of the flies, and this regulation is likely to exist via the IPCs. We discovered that an additional PDF-expressing neuron cluster in the tritocerebrum (PDF-Tri), previously shown to undergo apoptosis very early during adulthood, actually survives at cold temperatures and could be involved in cold-related functions. Interestingly, these PDF-Tri neurons were found to be synaptically connected to the IPCs in the cold.
Expression of genetically encoded sensors for the second messenger cAMP revealed that, IPCs respond to both synthetic neuropeptides PDF and sNPF. Surprisingly, they react with large cAMP increases to the co-application of the two peptides, raising the possibility of a synergistic effect between sNPF and PDF in controlling IPC activity. Since the detected cAMP responses are all abolished in PDF receptor mutant background, they seem to be regulated by PDFR. The study of two differently diapausing field lines highlighted marked differences between their PDF expression patterns, possibly related to diapause regulation.
When studying the general properties of D. melanogaster dormancy, we explored the relative relevance of some features of the experimental protocols used for diapause assays. While in the standard protocol flies are raised at temperatures in the range 23-25°C and exposed to diapause-inducing conditions starting from the adult stage, we investigated the effects of lower growing temperatures on diapause levels. We documented changes in diapause levels due to these altered settings, highlighting their importance in controlling dormancy. Additionally, adopting semi-natural light-dark profiles that better mimic outdoor conditions, strong photoperiodic diapause was observed, which was not detectable when simple rectangular light-dark regimes were used. Our findings should be considered in designing new protocols for diapause studies.<br>Gli organismi, soprattutto quelli che vivono in zone temperate, sono costantemente esposti a variazioni cicliche di fattori ambientali a causa dell’alternarsi delle stagioni. Si sono evoluti diversi meccanismi di adattamento che permettono di resistere e superare i periodi sfavorevoli. Tra gli insetti, la diapausa è la più comune strategia usata per raggiungere la sincronizzazione stagionale.
La diapausa è uno stato di dormienza, regolato a livello neurologico ed ormonale, che permette agli insetti di avviare un programma di sviluppo alternativo quando le condizioni ambientali non permettono un normale sviluppo. Nel moscerino della frutta Drosophila melanogaster, la diapausa si manifesta con l’arresto dello sviluppo delle ovaie nella frase previtellogenica. Segnali di tipo insulin-like sono stati identificati come regolatori chiave della dormienza in molti organismi. Le insulin-producing cells (IPCs) si trovano nella Pars intercerebralis, sono neuroanatomicamente connessi al centro neuroendocrino che controlla la regolazione ormonale della diapausa. Queste cellule sono responsabili della produzione e del rilascio di differenti insulin-like peptides che sono stati identificati come ormoni antagonisti della diapausa. Abbiamo scoperto che due neuropeptidi, pigment dispersing factor (PDF) e short neuropeptide F (sNPF), prodotti da un piccolo gruppo di neuroni chiamati ventrolateral clock neurons, regolano il processo della diapausa nei moscerini attraverso le IPCs.
Inoltre, abbiamo osservato che un altro gruppo di neuroni che producono PDF nel tritocerebrum (PDF-Tri) e che si ritenevano strutture rapidamente eliminate per apoptosi nell’adulto, in realtà sopravvivono e persistono nell’adulto a basse temperature, suggerendo quindi un loro coinvolgimento in funzioni correlate con la resistenza al freddo. L’espressione di sensori genetically-encoded per il secondo messaggero cAMP, ha rilevato che le IPCs reagiscono ad entrambi i neuropeptidi PDF e sNPF. Sorprendentemente reagiscono con grandi aumenti di cAMP alla somministrazione dei due peptidi, suggerendo un effetto sinergico tra sNPF e PDF nel controllo dell’attività delle IPCs. Dal momento che le risposte cAMP sono state abolite nel background mutante per il recettore PDF, sembrano essere regolate dallo stesso.
Lo studio di due diverse linee che manifestano differenze nel comportamento relativo alla diapausa ha evidenziato differenze marcate nell’espressione di PDF, potenzialmente collegata della regolazione della diapausa.
Studiando le proprietà generali della diapausa in D. melanogaster, abbiamo esplorato l’importanza relativa di alcuni aspetti dei protocolli sperimentali usati per i saggi di diapausa. Mentre nel protocollo originale i moscerini vengono fatti sviluppare a temperature comprese nel range 23-25oC e quindi esposti a condizioni che inducono la diapausa solo a partire dallo stadio adulto, noi abbiamo studiato gli effetti sui livelli di diapausa dello sviluppo a temperature inferiori. Abbiamo documentato cambiamenti nei livelli di diapausa indotti da queste modifiche, sottolineando la loro importanza nel controllo della dormienza. Inoltre, adottando profili di luce-buio seminaturali, che mimano meglio le condizioni esterne, è stata osservata una diapausa altamente regolata dal fotoperiodo. Una risposta fotoperiodica non era stata rilevata in studi precedenti nei quali venivano utilizzati regimi di luce-buio rettangolari. I nostri risultati suggeriscono l’opportunità di disegnare nuovi protocolli, più rappresentativi delle condizioni naturali, per lo studio delle basi genetiche e fisiologiche della diapausa.
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Al-Asadi, Mazin Gh. "Investigation of dormancy in acute myeloid leukaemia cells and the induction of dormancy in their response to genotoxic stress." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/43320/.
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Cancer cells can exist in a reversible state of dormancy (G0 phase of the cell cycle). Relapse of acute myeloid leukaemia (AML) is likely due to dormant cells escape frontline treatment. Dormant AML cells have been identified in the bone marrow (BM) endosteal region which is characterised by an excess of TGFβ1 and a shortage of nutrients. As the first step in this project, we developed an in vitro model of AML cell dormancy by exploiting these features. Following a preliminary investigation of four AML cell lines, the CD34+CD38- line TF1-a was selected for in-depth investigation. TF1-a showed significant inhibition of proliferation, with features of dormancy and stemness, in response to 72 hours of TGFB1+mTOR inhibitor treatment (mTOR pathway inhibition mimics major effects of nutrient scarcity) without affecting cell viability or inducing differentiation of these cells. Secondly, whole human genome gene expression profiling using Affymetrix microarray strips (HuGene2.1ST) was conducted to molecularly characterise the dormancy-induced TF1-a cells. As a result, we identified 240 genes which were significantly up-regulated by at least twofold, including genes involved in adhesion, stemness, chemoresistance, tumor suppression and genes involved in canonical cell cycle regulation. The most upregulated gene was osteopontin (17.1fold). Immunocytochemistry of BM biopsies from AML patients confirmed high levels of osteopontin in the cytoplasm of blasts near the paratrabecular BM. Osteopontin and other genes identified in this model, including well-characterised genes (e.g. CD44, CD47, CD123, ABCC3 and CDKN2B) as well as little-known ones (e.g. ITGB3, BTG2 and PTPRU), are potential therapeutic targets in AML. AML cells which are identified in the bone marrow (BM) endosteal region are likely to survive chemotherapy for several reasons including the low concentration of the drug delivered to this poorly perfused area of the BM. We hypothesised that these cells might induce dormancy features that help them escaping chemotherapy. Moreover, little is known regarding the molecular changes in those AML cells surviving genotoxic stress. The third aim of this study was to investigate the AML cells surviving genotoxic stress. Therefore, we developed and characterised an in vitro model of prolonged sub-lethal genotoxicity in AML cells by utilising the TF1-a cells treated with etoposide for 6 days. TF1-a cells survived this conditioning with significant inhibition of proliferation and limited damage and apoptosis. The molecular signature of these cells was characterized using GEP of the whole human genome and was compared to that of the dormancy-induced TF1-a cells in an aim to identify genes commonly up-regulated in both scenarios that might act as possible drivers of dormancy in AML cells residing in a sub-lethal genotoxic environment. In this context, 31 genes were significantly commonly upregulated in both scenarios including ITGB3, SLFN5, C15orf26 and GRAP2 which are candidates for in-depth investigation in AML. To sum up, in this study we developed and molecularly characterised in vitro models of dormancy and sub-lethal genotoxicity in AML cells with stemness characteristics through novel approaches that took bone marrow microenvironmental features into consideration. These features likely contribute to the resistance of the residual sub-population of AML cells that causing disease relapse. The current models helped to overcome the obstacles facing the in-depth studying of these rare AML cells due to the difficulty in obtaining them from clinical samples. Finally, the molecular findings of this study paved the way to potentially important future directions of research that could help to achieve the ultimate goal of eradicating AML cells and preventing relapse.
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Basbouss-Serhal, Isabelle. "Role of mRNA post-transcriptional metabolism in the regulation of Arabidopsis thalian dormancy." Electronic Thesis or Diss., Paris 6, 2015. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2015PA066147.pdf.
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Rôle du métabolisme post-transcriptionnel des ARNm dans la régulation de la dormance des semences d’Arabidopsis thaliana.Une étude physiologique nous a permis d'identifier l'influence de la température et de l'humidité relative (HR) lors du stockage des graines dormantes d’Arabidopsis. Après une levée de dormance atteinte en 7 semaines avec des cinétiques variables selon les conditions, on observe une induction de la dormance secondaire à faible HR et une perte progressive de la viabilité à forte HR. La levée et l’induction de la dormance sont associées à la régulation de gènes liés aux voies de l'acide abscissique et des gibbérellines. Nous avons étudié la dynamique d’association des ARNm aux polysomes et comparé la transcription et la traduction des graines dormantes et non dormantes au cours de l’imbibition. Nous montrons qu'il n'y a pas de corrélation entre transcriptome et traductome et que la régulation de la germination est principalement liée à la traduction. Ceci suppose un recrutement sélectif et dynamique des ARNm liés aux polysomes dans les graines dormantes et non dormantes. Certaines caractéristiques de la région 5'UTR des transcrits semble impliquées dans la sélection des ARNm traduits pendant la germination. Les phénotypes de mutants d’éléments du catabolisme des ARN montrent que la dormance est également associée à une dégradation sélective des ARNm. Les P-bodies (localisés dans des lignées YFP-DCP1) sont d’ailleurs en quantité plus importante dans les graines non-dormantes. La comparaison des transcriptomes des mutants vcs-8 et xrn4-5 a permis l'identification de plusieurs transcrits dégradés via VCS ou XRN4, dont le rôle sur la dormance a été confirmé par génétique inverse. Certains motifs spécifiques semblent être impliqués dans la sélection de transcrits pour leur dégradation<br>Role of mRNA post-transcriptional metabolism in the regulation of Arabidopsis thaliana dormancy.A physiological study allowed us to reveal the effect of temperature and relative humidity (RH) during Arabidopsis seed storage. Seven weeks of after ripening lead to alleviation of dormancy with different kinetics according to the conditions. Longer storage induced an induction of secondary dormancy at low RH and progressive loss of viability at high RH. Dormancy release and induction of secondary dormancy were associated with induction or repression of key genes related to abscissic acid and gibberellins pathways. We have studied the dynamics of mRNAs association with polysomes and compared transcriptome and translatome of dormant and non-dormant seeds. There was no correlation between transcriptome and translatome and germination regulation is largely translational, implying a selective and dynamic recruitment of mRNAs to polysomes in both dormant and non-dormant seeds. Some identified 5'UTR features could play a role in this selective. Dormancy is also associated with mRNA decay as demonstrated by phenotyping mutants altered in mRNA metabolism. Moreover we have shown that P-bodies were more abundant in non-dormant seeds that in dormant ones. Transcriptome analysis of xrn4-5 and vcs-8 mutants allowed us to identify several transcripts degraded via VCS ou XRN4 proteins, having a role in dormancy. This role was confirmed by reverse genetics for some of them. Some specific motifs were identified as involved in mRNA decay selection
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Jayasuriya, Kariyawasam Marthinna Gamage Gehan. "COMPARATIVE BIOLOGY OF SEED DORMANCY-BREAK AND GERMINATION IN CONVOLVULACEAE (ASTERIDS, SOLANALES)." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_diss/639.
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The biology of seed dormancy and germination of 46 species representing 11 of the 12 tribes in Convolvulaceae were compared in laboratory (mostly), field and greenhouse experiments. Seeds were tested for kind of dormancy and storage behavior; artificial or simulated natural treatments were applied to break physical dormancy (PY); the initial route of water entry (“water gap”) into seeds was identified; the morphoanatomy of the water gap was compared in seeds of 17 species; ontogenetical differences between water gap and seed coat away from the hilum were described in Ipomoea lacunosa seeds; cycling of sensitivity to dormancy break was elucidated in seeds of I. lacunosa, I. hederacea, Cuscuta australis and Jaquemontia ovalifolia; and mechanism of opening of the water gap was determined for seeds of I. lacunosa and of I hederacea.
Seeds of only three of the 46 species were nondormant. Two of these were recalcitrant (Maripa panamensis and Erycibe henryi), and the other one was orthodox (Bonamia menziesii). Seeds of the other 43 species were orthodox and had PY except those of Cuscuta europea, which also had physiological dormancy (PD) i.e. combinational dormancy (PY + PD). Two bulges adjacent to the micropyle were identified as the water gap in all seeds with PY except those of Cuscuta, in which the hilar fissure is the water gap. Anatomy of the bulges (water gap) adjacent to the micropyle differs from that of seed coat away from the bulges. A different sequence and phase of anticlinal and periclinal cell divisions during development created weak transitional zones between bulge - hilum and bulge - seed coat away from hilum. Water vapor pressure changes below the bulges caused formation of the opening(s) in water gap. Seeds of I. lacunosa I. hederacea, C. australis and J. ovalifolia cycle between sensitive and insensitive states to dormancy break, but not between PY and nondormancy. Seed dormancy and storage characteristics and anatomy and morphology of dormancy of seeds of Convolvulaceae closely follow the molecular phylogeny of the family. I suggest that PY in seeds of subfamily Convolvuloideae evolved from nondormant recalcitrant seeds of an ancestor closely related to Erycibeae.
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Zhang, Li. "Photoperiodic competency for dormancy induction in Populus balsamifera." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44685.
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Bud dormancy is an important overwintering mechanism for woody perennials and is induced in most species during late summer by short days (SD) and/or low temperature. Adaptively, however, it is important for new growth not to respond to similar photoperiods in early spring. To investigate this matter, two growth chamber experiments were conducted on four genotypes of balsam poplar (Populus balsamifera L.) originating from two latitudes. Rooted cuttings were moved into SD conditions at weekly intervals after flushing at either 15°C or 20°C. Plant heights were measured every other day. Plants were harvested weekly and total RNA was extracted for quantitative reverse transcription polymerase chain reaction (qRT-PCR) on genes known to be involved in dormancy induction, and for transcriptome sequencing followed by qRT-PCR validation to identify additional genes marking photoperiodic competency. Height growth cessation (HGC) data showed that before a certain age, no matter how soon plants were transferred to SD conditions, they continued to grow until they became competent to respond to photoperiod. The different genotypes became competent at different times (18-40 days since flush), indicating possible genetic variation in this trait. Once competency was attained, it took plants 7-20 days under 20°C to cease height growth under SD, depending on genotype, experiment and time since competency acquisition. Leaf number data revealed that competency acquisition and the transition from preformed leaf emergence to neoformed leaf production, are two independent processes. Temperature did not appear to influence the development of competency, though it increased the speed of height growth cessation. RT-qPCR results revealed three promising gene markers for competency: Potri.017G051100 (G6), Potri.001G222000 (G7) and CONSTANS 2. Increased expression for G6 and G7 was observed post-competency relative to pre-competency, and changes in expression varied between leaves and stem tissue. In contrast, CONSTANS 2 mRNA peaked 32 days after bud flush, coinciding with competency acquisition. This research offers new insight into the molecular mechanisms that underlie the acquisition of photoperiodic competency, which, in a warming climate, may cause phenological mismatch in deciduous boreal tree species, causing premature HGC and loss of productivity.
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Smith, Susan B. "An investigation into the mechanism of dormancy-breakage." Thesis, University of Reading, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.255418.
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Woods, S. L. "Analysis of plant hormones involved in potato dormancy." Thesis, University of Bristol, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384566.
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De, Cock Jasmine M. (Jasmine Morgan). "Inflammation triggers Zeb1-dependent escape from tumor dormancy." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104098.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2016.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (pages 167-181).<br>Metastasis-related mortality for breast cancer patients often occurs many years after treatment of the primary tumor. Inflammation, through the orchestra of immune cells and released inflammatory cytokines, can predispose certain tissues to cancer development and can create a favorable environment for metastatic outgrowth. I evaluated whether lipopolysaccharide (LPS) could induce an inflammatory response, leading to the activation of the cell-biological epithelial-mesenchymal transition (EMT) program in dormant disseminated cancer cells in vivo, and subsequent metastatic outgrowth. To model metastatic cellular dormancy, I used a dormant subpopulation of cells (D2A1-d) that were enriched for in vivo from the highly metastatic carcinoma cell line D2A1, that was derived from spontaneous murine mammary tumor. The ability of the EMT program to awaken dormant disseminated D2A1-d cells was directly assessed in vivo, which resulted in the formation of macro-metastases following a transient induction of either the EMT-transcription factor Snail or Zeb1. Furthermore, the transient induction of Zeb1 led to the generation of CD29+ CD24- metastasis-initiating cells. In mice bearing dormant disseminated D2A1-d cells, my findings demonstrated that LPS-treatment resulted in the awakening of D2A1-d cells and metastatic outgrowth in the lungs and bone. The awakening of dormant disseminated D2A1-d cells was dependent, albeit through unknown mechanism, on the presence of neutrophils. The LPS-mediated awakening of dormant disseminated cancer cells was also dependent upon the activation of the EMT-inducing transcription factor Zeb1 in the D2A1-d cells. In conclusion, my thesis work demonstrated that inflammation can trigger the escape of metastatic dormancy in vivo.<br>by Jasmine M. De Cock.<br>Ph. D.
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Jacobs, Johannes N. (Johannes Nicolaas). "Rootstock and dormancy studies in apple and pear." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52441.
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Thesis (MScAgric)--University of Stellenbosch, 2001.<br>ENGLISH ABSTRACT: Delayed foliation is commonly observed in apple and pear producing countries with
warm and/or short winter climates, resulting in less synchronised budburst, of fewer buds
and reduced yield. Applications of rest-breaking agents minimise the symptoms of
delayed foliation. According to chilling models used in fruit producing areas of the
world, the climate of South Africa is not suitable for deciduous fruit production, however
fruit has been successfully produced here for a long time. This study aimed to quantify
the effects of freezing temperatures, different chilling temperatures and the period of
chilling, to obtain a better knowledge of bud dormancy release on apple and pear shoots.
The chilling period was the most important factor influencing the progression of
dormancy. While in some cases the chilling temperature and the freeze treatment effects
were significant, the contribution to differences in the progression of dormancy was
negligible. Our findings indicate that currently used chilling models should emphasise the
time of exposure to low temperatures more than the difference in temperatures between I
to ro-c.
The South African apple and pear industry made good progress in moving towards high
density plantings, but large variation in soil types, non-optimum growing conditions,
replant situations and a lack experience with dwarfing rootstocks limited further
development. However, there is sti II an urgency to obtain higher early yields of good
quality fruit applying the most efficient production practices. We aimed to quantify the
field performance of locally available apple and pear rootstocks, in particular from data
outside of previously reported local trials, as well as early production of newly planted
trials.
Information obtained form the industry indicates that BPI and BP3 are the preferred pear
rootstocks. From production records of 'Packham's Triumph' pears, it appeared that BP3
and OHxF97 produced the best yields compared to the other rootstocks. Production of
'Doyenne du Cornice' was the best on QA and BP3. In newly planted 'Rosemarie',
'Flamingo', and 'Forelle' trials, different rootstocks were evaluated. 'Rosemarie' showed
indications 01 incompatibility with QA and QC5 I, but on BPI and QA with a 'Beurre Hardy' interstock produced good initial yields although BPI induced slightly larger trees.
'Flamingo' on QA and QC51 produced the best yields. 'Forelle' on BPI, BP3, and QA
produced similar yields up to the 4th leaf.
For apples M793 seems to be the preferred rootstock in the South African industry. From
production records of 'Golden Delicious' and 'Granny Smith' apples, it appeared that
M793 and MM 106 produced the best yields when compared to Seedling rootstock. In a
'Cripps' Pink' trial, MMI09, M793 and M25 were more vigorous than M7, MMlll and
MMI06. MMI06 was cumulatively, over four years from planting, the most yield
efficient, although no consistent trend regarding fruit quality was observed between the
rootstocks evaluated.<br>AFRIKAANSE OPSOMMING: Vertraagde bot word algemeen opgemerk in appel en peer produserende lande met n'
warm enlof kort winter klimaat, wat veroorsaak dat bot van minder knoppe, meer
ongelyk plaasvind en gevolglik lei tot swakker opbrengste. Toediening van rus-breek
middels beperk die simptome van vertraagde bot. Volgens koue modelle wat in vrugte
produserende areas in die wereld gebruik word, is Suid Afrika se klimaat nie geskik vir
die verbouing van sagtevrugte nie alhoewel sagtevrugte al vir n lang tyd met groot sukses
hier verbou word. Hierdie studie is daarop gemik om die effek van vries temperature,
verskillende koue temperature en die periode van koue op die vrystelling van dormansie
op knoppe van appel en peer lote te kwantifiseer.
Die peri ode van koue was die mees belangrikste faktor wat die ontwikkeling van
dormansie beinvloed het. In sommige gevalle was die effek van die koue temperature
betekenisvol, maar die bydrae tot die verskille in die ontwikkeling van dormansie was
weglaatbaar klein. Ons bevindinge dui aan dat die huidige koue modelle wat gebruik
word, meer klem moet le op die periode van blootstelling aan koue as aan die effek van
verski llende temperature tussen 1 en 10°e. Die Suid Afrikaanse appel en peer bedryf het goeie vordering in die beweging na hoe
digtheid aanplantings gemaak, maar groot verskille in grond tipes, sub-optimale groei
toestande, herplant probleme en n' tekort aan ondervinding met dwergende onderstamme
het verdere ontwikkeling beperk. Ten spyte hiervan is daar steeds n' dringendheid om
hcer produksies, van goeie kwaliteit vrugte so vroeg as moontlik te kry deur die
toepassing van die mees effektiewe produksie praktyke. Ons het gepoog om die prestasie
van plaaslik beskikbare appel en peer onderstamme te kwantifiseer, in besonder deur data
wat nog nie van tevore oor verslag gedoen is nie en ook deur te meld van vroee
produksies op nuut aangeplante proewe.
lnformasie uit die bedryf het aangedui dat BP 1 en BP3 die voorkeur peer onderstamme
is. Deur na die produksie geskiedenis van 'Packham's Truimph' pere te kyk kom dit voor
of BP3 en OHxF97 die beste produksies in vergelyking met die ander onderstamme
gelewer het. Die produksie van 'Doyenne du Com ice' was die beste op QA en BP3. In
nuut geplante 'Rosemarie', 'Flamingo', en 'Forelle' pro ev e was verskillende onderstammc
gecvalueer. 'Rosemarie' het tekens van onverenigbaarheid getoon met QA en Q 51, maar
op BP 1 en QA met n 'Beurre Hardy' tussenstam het 'Rosemarie' goeie aanvanklike
opbrengste gel ewer, al was bome op BP 1 effens grater. 'Flamingo' op QA en QCS 1 het
die beste opbrengste gelewer. 'Forelle' op BP 1, BP3, en QA het ongeveer ewe veel tot
die 4dc blad geproduseer.
By appels is M793 die voorkeur onderstam van die Suid-Afrikaanse appel bedryf. M793
en MM 106 gee beter opbrengste as Saailing onderstam wanner die produksie geskiedenis
van 'Golden Delicious' en 'Granny Smith' appels evalueer word. In n' 'Cripps' Pink'
proefwas MMI09, M793 en M2S meer groeikragtig as M7, MMlil en MMI06.
MM I 06 het kumulatief meer geproduseer en was ook meer produsie doeltreffend tot en
met die 4de blad na plant. Daar was egter geen konstante neiging rakende vrug kwaliteit
tussen die verskillende onderstamme wat getoets is nie.
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Bromley, Jennifer Rachael. "Cytokinin interconversion by StCKP1 controls potato tuber dormancy." Thesis, University of Cambridge, 2009. https://www.repository.cam.ac.uk/handle/1810/270232.
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Worldwide production of potatoes is in excess of 350 million metric tonnes per annum, of which 60% is intended for human consumption. Since the period of tuber dormancy before tuber buds sprout is usually shorter than the optimal market storage period, control of sprouting is essential. To prolong dormancy, tubers are either stored at low temperatures and/or are treated with chemical sprout inhibitors, the use of which subject to increasing scrutiny in the European Union due to their impact upon the environment. Cytokinins, a group of plant growth regulators, are known to play a central role in tuber bud sprouting and tuber initiation from stolon tips in Solanum tuberosum L. although it is unclear when and how cytokinins act to regulate dormancy. The interconversion of cytokinins is incompletely understood. Enzymes identified to date have higher affinities for aminopurines than their cytokinin equivalents. A novel cytokinin binding protein Solanum tuberosum Cytokinin Phosphorylase 1 (StCKP1), has been identified in tuberising stolon tips which shares regions of homology with members of the nucleosidase and phosphoribosyl transferase family. The composition of cytokinin N9 conjugates in tuber bud and surrounding tissue is known to change on transition from a dormant state, with an increase in base and riboside types observed. Analysis of transcripts indicates an increase in abundance of StCKP1 on tuberisation of stolon tips, and high abundance in the periderm of dormant tubers. Analysis of protein abundance by immunoblotting echoes this finding and indicates StCKP1 begins to accumulate in stolon tips shortly before tuberisation, matching binding activity. Transgenic analysis of the cytological reporter gene uidA under the control of two identified promoter regions indicates StCKP1 is expressed predominantly in tuber tissue. Analysis of StCKP1 activity by HPLC and LC-MS-MS shows that StCKP1 catalyses the interconversion of free base and riboside. KMs determined for cytokinin and aminopurine substrates indicate that StCKP1 has a higher affinity for cytokinin substrates and, of these cytokinins, displays a higher affinity for the free base catalysing ribosylation of the N9 to form the corresponding riboside. Desiree cultivars over-expressing StCKP1 under the CaMV 35S promoter exhibited an increased rate of tuberisation of stolon tips and an increase in the length of the dormant period following lifting. Over-expression of StCKP1 was found in particular to increase the chill sensitive period of dormancy, confirming results of StCKP1 knock-down by RNAi. Transcript abundance of StCKP1 at tuberisation in other cultivars including King Edward and Maris Peer was found to correlate with the dormancy characteristics prescribed by the European Cultivated Potato Database and the British potato variety database.
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Docherty, Freyja. "Identifying and characterising dormancy in prostate cancer cells." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/8110/.
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Prostate cancer is the second leading cause of cancer death in men in the UK. Around 30% of patients with apparently localized disease at diagnosis and who receive radical surgery to remove the primary tumour, will present with skeletal metastasis, in many cases >5 years after initial treatment. This suggests that prostate cancer cells can persist in a dormant or indolent state, undetected in patients for many years. To investigate states of dormancy in prostate cancer cells, the growth of human prostate cancer cell lines in vitro was examined to test the hypothesis that there are sub-populations of dormant cells present even within widely used, rapidly proliferating cell lines. My studies successfully identified these cells, which were then extensively characterised. Parallel studies in our laboratory indicated that these cells had greater potency than other cells in the initiation of metastatic lesions in xenograft models. To identify dormant cells in three prostate cancer cell lines: PC-3NW1, LNCaP and C42B4, were stained with the lipophilic membrane dye Vybrant DiD. The retention of this dye was used as a marker of dormant or slow-cycling cells. Flow cytometry analysis and fluorescent microscopy identified a dormant cell sub-population in all three prostate cancer cell lines at a frequency of <2% after 14 days in culture. Dormancy was not an intrinsic characteristic of this sub-population, as this phenotype could re-emerge in cultures of separated re-cultured non-dormant cells. The frequency of dormant cells in cultures could be altered by changes in culture conditions and when isolated these cells could be released from dormancy to form colonies. Gene expression profiles for the non-dormant and dormant sub-population were compared by RT-qPCR and a set of differentially expressed, dormancy specific genes identified. Immunofluorescence microscopy was used to assess whether the observed differences in gene expression between populations were reflected in altered specific protein levels. The presence of a specific marker of dormancy, CXCR4, identified by these experiments, was then evaluated in 75 primary patient samples by immunohistochemistry. Elevated CXCR4, as measure by immunohistochemistry, in patient samples correlated to other indicators of poor prognosis but did not independently predict the presence of metastases.
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Ausland, Hayden Willis. "Vadose zone denitrification enhancement by poplars during dormancy." Thesis, University of Iowa, 2014. https://ir.uiowa.edu/etd/4566.
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Andreatta, Gabriele. "Dormancy awakened: aminergic control of diapause in Drosophila." Doctoral thesis, Università degli studi di Padova, 2015. http://hdl.handle.net/11577/3424143.
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Coping with adverse environmental conditions is one of the most crucial challenges for all living beings. The coupling between external cues and hormonal signaling is key to allow survivorship of individuals and insects in particular have been intensively studied to better understand this connection. Although the hormonal cascade that promotes insect development and reproduction is well known (insulin signaling - juvenile hormone – 20-Ecdysone), how this neuroendocrine axis is modulated by environmental stimuli remains still largely elusive. To deepen the molecular features of IIS-JH-20E axis regulation, we focused our attention on one of the best examples of physiological strategies triggered by environmental stimuli, diapause. Diapause is an inducible developmental arrest, which characterizes the life cycle of several species, from Caenorhabditis elegans to mammals. Our results shed new light on the regulation of key neuroendocrine pathways for growth and development, and suggest how organisms couple environmental conditions with inner hormonal physiology.<br>Sopravvivere a drastici cambiamenti climatici rappresenta una delle sfide principali per gli esseri viventi. Gli insetti non solo forniscono esempi straordinari di adattamenti morfologici e fisiologici a climi sfavorevoli, ma sono anche molto studiati per comprendere quali sono i meccanismi molecolari responsabili di questi adattamenti. Negli insetti, i principali processi ormonali che promuovono lo sviluppo e la riproduzione sono ben noti e comprendono tre attori principali, il segnale insulinico (IIS), l’ormone giovanile (JH) e l’idrossi-ecdisone (20E). Nonostante questo importante asse neuroendocrino (IIS-JH-20E) sia ben studiato, poco si conosce riguardo i meccanismi molecolari che trasducono le informazioni ambientali ai componenti fondamentali del sistema endocrino, modulandone l’attività regolatoria. Per questo abbiamo rivolto la nostra attenzione ad uno degli esempi più interessanti di strategie fisiologiche evocate dagli stimoli esterni, la diapausa, un arresto dello sviluppo inducibile che rappresenta un evento estremamente diffuso nel regno animale. I nostri risultati forniscono un contributo alla comprensione degli aspetti regolativi dei meccanismi neuroendocrini fondamentali per la crescita, lo sviluppo e la riproduzione, e suggeriscono alcune modalità con le quali gli insetti accoppiano la percezione delle condizioni ambientali con la loro fisiologia ormonale.
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Habib, Ahsan. "Microtuberization and dormancy breaking in potato (Solanum tuberosum L.)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ50781.pdf.
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Wherley, Benjamin George. "Nitrogen Relations in Bermudagrass During Growth and Dormancy Cycles." NCSU, 2007. http://www.lib.ncsu.edu/theses/available/etd-12142007-163215/.
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Use of recycled water for turfgrass irrigation is increasing in the southeastern U.S. because of population growth and interest in protecting water quality. Turfgrass systems are perceived to be well suited for effluent dispersal due to their proximity to waste treatment facilities, in-ground irrigation systems, and ability to efficiently absorb (i.e. filter) nutrient contaminants when actively growing. However, effluent generation is continuous and bermudagrass growth is seasonal in the southeastern U.S. Clearly, there is a need to more thoroughly understand the capacity of bermudagrass, the turfgrass most often involved with effluent dispersal, for receiving effluent irrigation. This series of experiments was designed with the overall intent of examining the capacity of a bermudagrass turf/soil system for handling effluent applications. Experiments involved 1) characterizing seasonal changes in nitrate assimilation efficiency of the system, 2) determining the effects of prolonged soil saturation on nitrate uptake efficiency, and 3) characterizing internal nitrogen relations during the spring emergence period. While it is difficult to extend the results of these experiments, quantitatively, to situations where effluent is being applied in the field, the evidence does support a few basic observations. Bermudagrass appears to be capable of assimilating large amounts of N when growing, an ability that may well extend into transition months when little vertical shoot growth is occurring. Furthermore, although reduction in quality occurred, shoot growth and nitrate uptake efficiency of bermudagrass and centipedgrass was relatively unaffected by prolonged saturated soil conditions, a condition that may be likely with effluent irrigated sites.
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Rossouw, Jan Adriaan. "Effect of cytokinin and gibberellin on potato tuber dormancy." Diss., Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-07302008-164519.
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Field, Rachel. "Dormancy and germination in seeds of Corylus avellana L." Thesis, University of Sheffield, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343516.
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Dzomeku, Israel K. "Modelling seed dormancy, germination and emergence of Striga hermonthica." Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252261.
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Stutchbury, P. A. "The regulation of seed dormancy in the genus Acer." Thesis, University of Bristol, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379534.
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Lopes, Bastos Bruno. "A possible IDO1-TSP1 role in breast cancer dormancy." Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/105066/.
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Disseminated breast cancer cells have been found in the perivascular niche of lung, brain and bone marrow. Research has suggested that thrombospondin 1 (TSP1), an antiangiogenic protein secreted by endothelial cells, is involved in cancer dormancy. My research aims to clarify the role of TSP1 in cancer dormancy. On the other hand, breast tumours overexpress indoleamine 2,3-dioxygenase (IDO1) which degrades intracellular tryptophan, a key amino acid of TSP1. I aim to investigate whether cancer cells induce endothelial IDO1 expression and therefore limit TSP1 synthesis. I hypothesize that the decrease of TSP1 might enable cancer cell proliferation and angiogenesis. To evaluate whether endothelial cells can induce cancer dormancy, MDA-MB-231 cells were cultured on the top of an endothelial monolayer or treated with endothelial conditioned medium. Ki67, p21 and cell cycle analysis showed that endothelial cells induce cell cycle arrest in MDA-MB-231 cells but not senescence. ki67 was also decreased when MDA-MB-231 cells were cultured with TSP1. MDA-MB-231 revealed to be more resistant to docetaxel, a breast cancer drug, when pre-cultured with TSP1. Conditioned medium experiments showed that MDA-MB-231 cells are capable of inducing endothelial IDO1 expression and it also increased tryptophan degradation, which was prevented by siRNA IDO1 knockdown. Interestingly, endothelial TSP1 secretion was revealed to be decreased under low tryptophan concentration. Immunohistochemistry of breast cancer tissue showed that there was a negative correlation between vascular IDO1 and stromal TSP1. IFNγ, a potent inducer of IDO1, showed to be able to induce endothelial IDO1 and a decrease in endothelial TSP1. Taken together, the data presented here suggests that endothelial cells induce breast cancer dormancy and drug resistance via TSP1. My research also suggests that an IFNγ/IDO1 pathway might decrease TSP1 synthesis leading to cancer cell proliferation and angiogenesis.
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Barros, Galvão Thiago. "Regulation of seed dormancy and germination in Arabidopsis thaliana." Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/15593/.
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Seed germination is one of the most important developmental steps in the life cycle of a higher plant. Because of this, seed producing plants have evolved mechanisms, such as dormancy, that time germination based on environmental cues. The present study uses Arabidopsis thaliana as a model to address questions about seed dormancy and germination. Three different lines of investigation were followed. The first involved an investigation of how light quality regulates phytohormones in order to control germination. This identified a light-dependent mechanism that differentially regulates expression of the ALLENE OXIDE SYNTHASE and OXOPHYTODIENOATE-REDUCTASE 3 genes resulting in accumulation of cis-12-oxo-phytodienoic acid (cis-OPDA) and repression of seed germination under FR conditions. The second line of investigation involved a re- examination of the role of the ABSCISIC ACID INSENSITIVE (ABI) 5 and ABI4 transcription factors in regulating seed germination and oil mobilization respectively. The study found that abscisic acid (ABA) is able to block testa rupture in nicked seeds and this involves the ABI5, but not the ABI4, transcription factor. Furthermore, it was found that ABI4 is involved in the repression of ABA and cis-OPDA biosynthesis in a light- dependent manner, but has only a minor role in regulating oil mobilization in seeds. The third line of investigation focused on the regulation of dormancy during after-ripening and found that changes in phytohormone levels over an extended period can account for changes in dormancy state.
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Cheema, M. U. A. "Dormancy and sprout control in root and tuber crops." Thesis, University of Greenwich, 2010. http://gala.gre.ac.uk/6890/.
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Research objectives were to study dormancy/sprout control in potato and sweetpotato, and to identify novel sprout control strategies. Consistent with sprout stimulation by gibberellins (GAs) in potato, 10 mM GA3 enhanced sprout length and number in sweetpotato roots and sprout growth was decreased by 20 ml/L piccolo (GA synthesis inhibitor). Continuous application of 10 ppm ethylene or greater prevented sprouting in sweetpotato roots over 4 weeks storage at 25° C. Sprout growth was also inhibited by 1000 ppm aminoethoxyvinylglycine (AVG) (ethylene synthesis inhibitor) or 625 ppb 1-methylcyclopropene (1-MCP) (ethylene antagonist). Continuous ethylene treatment or single 1-MCP treatment could be a practical sprout control method for sweetpotatoes stored at >15° C. 5 ppm or greater ethylene increased root respiration rates, but this effect was reduced by 1-MCP or AVG. Sugar content in ethylene treated roots +/- 1-MCP or AVG were lower than untreated roots, with lowest levels in roots treated with ethylene alone. Hormonal control of dormancy/sprout growth was studied in excised buds from potato tubers transformed to over-express a bacteria gene encoding 1-deoxy-D-xylulose 5 phosphate synthase (DXS), which exhibit arrested buds, Five weeks post-harvest over-expressing lines, DXS1 and DXS2, showed greater sprout growth compared to wild type when treated with 1 mM GA3 or tZR in 2009, whereas DXS1 showed less sprout growth 4 weeks post-harvest in 2007. There was no difference in DXS1 and DXS2 behaviour 4 months after harvest in 2007. The different behaviour of DXS1 over seasons and with time from harvest underlines how tuber state can change with maturity. No consistent differences were found in chemical profile of peel among potato tubers of accessions with a range of dormancy characteristics. Although 1, 4-Dimethylnaphthalene has been identified as a natural sprout suppressant, it could not be detected in any accession even though measurements were sensitive to below 100 ppb.
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Rukuni, Dzingai. "Dormancy in pre-variety germplasm of native Coreopsis species." [Gainesville, Fla.] : University of Florida, 2008. http://purl.fcla.edu/fcla/etd/UFE0023750.
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Fabbroni, Cristina <1979>. "Kiwifruit bud release from dormancy: effect of exogenous cytokinins." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1966/1/Fabbroni_Cristina.pdf.
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A new formulate containing citokinins, that is commercialized as Cytokin, has been introduced as dormancy breaking agents. During a three-years study, Cytokin was applied at different concentrations and application times in two producing areas of the Emilia-Romagna region to verify its efficacy as a DBA. Cytokin application increased the bud break and showed a lateral flower thinning effect. Moreover, treated vines showed an earlier and more uniform flowering as compared to control ones. Results obtained on the productive performance revealed a constant positive effect in the fruit fresh weight at harvest. Moreover, Cytokin did not cause any phytotoxicity even at the highest concentrations. Starting from the field observation, which suggested the involvement of cytokinins in kiwifruit bud release from dormancy, 6-BA was applied in open field condition and molecular and histological analyses were carried out in kiwifruit buds collected starting from the endo dormant period up to complete bud break to compare the natural occurring situation to the one induced by exogenous cytokinin application. In details, molecular analyses were set up on to verify the expression of genes involved in the reactivation of cell cycle: cyclin D3, histone H4, cyclin-dependent kinase B, as well as of others which are known to be up regulated during bud release in other species, i.e.isopenteniltransferases (IPTs), which catalyze the first step in the CK biosynthesis, and sucrose synthase 1 and A, which are involved in the sugar supplied. Moreover, histological analyses of the cell division rate in kiwifruit bud apical meristems were performed. These analyses showed a reactivation of the cell divisions during bud release and changes in the expression level of the investigated genes.
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Fabbroni, Cristina <1979>. "Kiwifruit bud release from dormancy: effect of exogenous cytokinins." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1966/.
Full textAbstract:
A new formulate containing citokinins, that is commercialized as Cytokin, has been introduced as dormancy breaking agents. During a three-years study, Cytokin was applied at different concentrations and application times in two producing areas of the Emilia-Romagna region to verify its efficacy as a DBA. Cytokin application increased the bud break and showed a lateral flower thinning effect. Moreover, treated vines showed an earlier and more uniform flowering as compared to control ones. Results obtained on the productive performance revealed a constant positive effect in the fruit fresh weight at harvest. Moreover, Cytokin did not cause any phytotoxicity even at the highest concentrations. Starting from the field observation, which suggested the involvement of cytokinins in kiwifruit bud release from dormancy, 6-BA was applied in open field condition and molecular and histological analyses were carried out in kiwifruit buds collected starting from the endo dormant period up to complete bud break to compare the natural occurring situation to the one induced by exogenous cytokinin application. In details, molecular analyses were set up on to verify the expression of genes involved in the reactivation of cell cycle: cyclin D3, histone H4, cyclin-dependent kinase B, as well as of others which are known to be up regulated during bud release in other species, i.e.isopenteniltransferases (IPTs), which catalyze the first step in the CK biosynthesis, and sucrose synthase 1 and A, which are involved in the sugar supplied. Moreover, histological analyses of the cell division rate in kiwifruit bud apical meristems were performed. These analyses showed a reactivation of the cell divisions during bud release and changes in the expression level of the investigated genes.
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Wickman, Marise. "The practical application of two dormancy induction trials on douglas-fir and western hemlock container seedlings." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/24429.
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Two dormancy induction trials were conducted in a private container nursery in Saanichton, British Columbia. The first study examined the effects of photoperiod induced dormancy on morphology, root growth and field performance of fall planted western hemlock (Tsuga heterophyl_1ji (Raf.)Sarg.) and Douglas-fir (Pseudotsuga menzi_esv[ (Mirb.) Franco) seedlings. Various periods of eight hour days, ranging from two to eight weeks, were applied throughout July and August 1983. Outplanting was done in late September. Survival and growth were assessed one year later.
The second project investigated the effectiveness of short days, varying levels of moisture stress and a combination of both as dormancy induction techniques for Douglas-fir seedlings. The short day treatment was four weeks of eight hour days. Four levels of predawn moisture stress were: -5, -10, -15 and -25 bars. These classes respectively corresponded to control, light, medium and severe moisture stress levels. Short days and moisture stress were also combined whereby the four week period of short days followed the moisture stress treatments. These induction treatments were applied in July and August 1984. All seedlings were lifted in January 1985 and placed into cold storage for five weeks until March 1985. Morphology, root growth capacity, frost hardiness and dormancy intensity were assessed in January. Root growth capacity and dormancy intensity were again measured in March.
In Study I, short days quickly initiated homogeneous budset in both species in approximately three weeks. The average height increment after treatment initiation was 3.7 cm in Douglas-fir and 4.2 cm in western hemlock. Short days reduced shoot dry weight and height. Caliper and root dry weight were unaffected. In September a surge in root growth occurred in hemlock seedlings treated with six or eight weeks of short days. The importance of early budset to allow increased root growth prior to a fall lift was demonstrated. Root growth capacity was similar among all treatments for both species.
The planting survival of western hemlock seedlings increased with increasing weeks of short days. Control plants had 76% survival while the eight week regime had 91%. Survival was similar for all treated Douglas-fir seedlings. It ranged from 89% in the two week interval to 98% in the four week regime. One year height increment was significantly greater in the six and eight week short day treatments for both species. For hemlock, it ranged from 6.1 cm in the control plants to 10.4 cm in the six week trees. Douglas-fir height increment ranged from 6.4 cm for the control interval to 8.6 cm in the eight week regime.
The six and eight week photoregimes produced the best quality hemlock seedlings for this study. Four weeks of short days appeared adequate for Douglas-fir.
In Study II short days effectively initiated and maintained budset in Douglas-fir seedlings in four weeks. After six weeks from treatment initiation, a light to severe moisture stress was as effective in controlling height growth. A natural photoperiod with no moisture stress was least effective. In a comparison of all treatment combinations, only the control plants under a natural photoperiod were significantly larger in all morphological properties. Short days, moisture stress or a combination of both had similar effects on reducing height, caliper, shoot dry weight and root dry weight.
Unstressed seedlings in a natural daylength had the highest value of root growth capacity. All other treatment combinations had significantly lower root growth capacity. Only the severe stress under a natural photoperiod significantly reduced root growth capacity compared to any other
treatment. Short days accelerated bud burst in the January and March dormancy intensity tests. Frost hardiness was similar among all treatments.
Selection of a regime which controlled height growth while maintaining seedling quality was not clearcut. A short photoperiod with no moisture stress was most effective in initiating budset. However, few morphological and physiological differences were evident between short day plants and light and medium stressed seedlings.<br>Forestry, Faculty of<br>Graduate
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Larner, Victoria Susan. "Characterisation of the COMATOSE locus that regulates germination potential in Arabidopsis thaliana." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369795.
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Cuesta, Borràs Estefania. "Role of DPPA3 in hypoxia and tumour dormancy in cancer." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/668282.
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Colorectal cancer (CRC) is a leading cause of death worldwide and tumour recurrence is a frequent complication that arises from minimal residual disease and shows up after a period of clinical dormancy. Slow-cycling cancer cells (SCCC), also called dormant tumour cells, have been shown to be responsible for tumour relapse due to their enhanced chemoresistance and tumour-initiating capacity. Although the recent efforts invested in the characterization of SCCC, our knowledge about the mechanisms underlying tumour dormancy is still limited. Thanks to the identification, isolation and molecular characterization of SCCC in our laboratory, we identified a set of pluripotency factors overexpressed in these cells, among them, DPPA3. In the present work, we characterized for the first time the role of DPPA3 in the biology of tumour dormancy. DPPA3 is an epigenetic factor essential for early development and predominantly expressed in embryonic stem cells (ESCs) and primordial germ cells (PGCs). Its function is linked to the protection of imprinted loci and transposable elements in the genome from active demethylation processes. Besides maintaining a repressive state in specific loci, DPPA3 is also related to the passive demethylation phenomenon observed in cells at these developmental stages. By the use of genetically modified CRC cell lines we revealed a central role of DPPA3 promoting cell dormancy. We unmasked its capacity controlling the response to hypoxia as a key mechanism to govern cancer cell phenotype. DPPA3 overexpression stimulated the hypoxia program by increasing hypoxia inducible factor 1 subunit alpha (HIF1α) protein levels and enhancing its transcriptional activity. Besides, overexpression of DPPA3 alone was sufficient to induce a G2/M-phase cell cycle arrest and reduce tumour growth. Interestingly, DPPA3 enhanced chemoresistance to CRC standard of care adjuvant chemotherapies. Finally, a cohort of CRC patients with high expression of DPPA3 or enriched in a DPPA3 signature showed a shorter disease-free survival. Altogether, these results pioneer the importance of DPPA3 in cancer and contribute to the understanding of tumour malignancy associated to hypoxia, chemoresistance and dormancy, the unravelling of which is of foremost importance to progress in the battle against the disease.<br>El càncer colorectal (CRC) presenta una elevada mortalitat arreu del món i la recurrència és una complicació freqüent que sorgeix com a conseqüència de la malaltia mínima residual que es presenta després d'un període de latència clínica. Diversos estudis han descrit la presència de cèl·lules canceroses amb una baixa taxa proliferativa (slow-cycling cancer cells, SCCC) responsables de la recaiguda del pacient a causa de la seva elevada quimioresistència i capacitat regenerativa de tumors. Tot i l'esforç invertit en la caracterització de les SCCC, anomenades també cèl·lules dorments, el nostre coneixement sobre els mecanismes moleculars subjacents a la seva latència és encara limitat. Gràcies a la identificació, aïllament i caracterització molecular de les SCCC feta al nostre laboratori, vam poder identificar un conjunt de factors de pluripotència sobreexpressats en aquestes cèl·lules, entre ells, DPPA3. DPPA3 és un factor epigenètic essencial per al desenvolupament embrionari i expressat en cèl·lules mare embrionàries (ESCs) i cèl·lules germinals primordials (PGCs). La seva funció està relacionada amb la protecció en loci improntats i elements transposables del genoma de processos de desmetilació activa. A part de mantenir un estat repressiu en regions concretes del genoma, DPPA3 també està relacionat amb processos de desmetilació passiva durant el desenvolupament embrionari. Amb l’ús de línies de CRC modificades genèticament per sobreexpressar exògenament o reduir els nivells endògens de DPPA3, vam poder esbrinar el rol que exerceix aquest factor en els programes d’hipòxia i latència tumoral. La sobreexpressió de DPPA3 en línies de CRC va induir el programa d’hipòxia augmentant els nivells de proteïna i activitat transcripcional de HIF1α. A més, també va ser suficient per generar una parada del cicle cel·lular en la fase G2/M in vitro i un retard del creixement tumoral i major quimioresistència a tractaments d’adjuvància estàndards en CRC in vivo. Finalment, vam observar que una elevada expressió de DPPA3 en pacients de CRC està associada amb una major quimioresistència. El conjunt d’aquests resultats contribueixen a la comprensió de la rellevància de DPPA3 en càncer i la malignitat tumoral associada a hipòxia, quimioresistència i latència tumoral.
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Holmberg, Kyle B. "SELECTION FOR REDUCED SEED DORMANCY IN SEVEN NATIVE GRASS SPECIES." MSSTATE, 2008. http://sun.library.msstate.edu/ETD-db/theses/available/etd-11052007-220827/.
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Lowland switchgrass (Panicum virgatum), big bluestem (Andropogon gerardii), indiangrass (Sorghastrum nutans), upland switchgrass (Panicum virgatum), little bluestem (Schizachyrium scoparium), beaked panicum (Panicum capillare), and purpletop (Tridens flavus) all show strong signs of seed dormancy which contributes to extremely poor field establishment. The objective of this work was to reduce seed dormancy by selecting individuals that exhibited reduced pre-stratification dormancy in laboratory tests. The classical breeding method of phenotypic recurrent selection was used to enhance germination. Of the three tall-stature species, lowland switchgrass made the greatest improvement in pre-stratification germination, followed by indiangrass and big bluestem. The four short stature species have shown various results after one cycle of selection at Starkville. A field emergence trial was also conducted to evaluate three cycles of breeding seed with five commercially available cultivars in which Cycle 3 seed produced more plants per hectare than any of the other cultivars or germplasm.
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Vasquez, Castillo Wilson Arturo. "Seed production, dormancy and commercialisation of Solanum phureja in Ecuador." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415897.
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Wood, Laura Anne. "RELATIONSHIP BETWEEN ETHYLENE AND SEED DORMANCY RELEASE IN ECHINACEA SPECIES." UKnowledge, 2007. http://uknowledge.uky.edu/gradschool_theses/465.
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Inconsistent seed germination poses a problem for efficient seedling production of Echinacea species. Evidence suggests that ethylene can be effective for improving germination in Echinacea species. The objectives of this research were: to develop an ethylene pre-germination treatment that enhances germination in Echinacea species that is retained following drying and storage, and to determine if the ethylene effect on enhanced germination was an important mode of action for dormancy release. Four species of Echinacea (E. purpurea, E. tennesseensis, E. angustifolia and E. simulata) treated with 1-aminocyclopropane-1-carboxylic acid (ACC) or ethephon resulted in faster and generally higher germination. Pre-treatment of seeds with ACC or ethephon followed by drying was as effective as chilling stratification for enhancing germination depending on the species. While ethylene pretreatments did increase germination to some extent depending on species, it was concluded that 60-day stratification alone was a more commercially-viable treatment. Ethylene production or perception was not necessary for germination in untreated or stratified seeds as shown by aminoethoxyvinylglycine (AVG), silver thiosulfate (STS), and 1-methylcyclopropene (MCP) treatments. Both stratification and ACC treatment reduced Echinacea seed sensitivity to ABA and could be a common mechanism for enhanced germination. However, it does not appear that the increased germination seen after stratification was mediated through ethylene production because final germination percentages were generally unchanged following inhibition of ethylene production or action. In contrast, inhibition of ethylene production and perception reduced early 3-day germination suggesting that ethylene was more involved in seed vigor than final germination. It was determined that there is no physiological significance of ethylene for dormancy release in these Echinacea species.
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Ross, Benjamin James. "Responses to Chemical Exposure by Foraminifera: Distinguishing Dormancy From Mortality." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4397.
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The Deepwater Horizon blowout in 2010 released an estimated 4.9 million barrels of crude oil into the Gulf of Mexico in the 83 days between the initial explosion and the capping of the well. Response included extensive use of Corexit© oil dispersant. Although South Florida was spared exposure by currents, this event highlights the need for effective bioassay organisms for coral reefs. Amphistegina spp. are benthic foraminifers that host diatom symbionts in a relationship similar to that of coral and their zooxanthellae. Amphistegina spp. occur abundantly in reef communities nearly worldwide, are easily collected and maintained in culture, and are a key component of the FoRAM Index, a indicator of water and sediment quality in coastal waters. The major goals of this project were to develop protocols to test the acute and chronic responses of A. gibbosa to potentially toxic organic chemicals.
Initial objectives were to determine lethal concentrations and effects ranges, as defined by the US Environmental Protection Agency, of two components of the Corexit© dispersants. Preliminary experiments indicated that many specimens exposed to propylene glycol (v/v) at concentrations of 2% or higher appeared to be dead following 48-hour exposure, resulting in apparent LC50 of 3% and an initial effects range of 2-4%. When placed in filtered seawater, after 72-hours the observed LC50 was 6%. All parameters assessed, including sub-lethal chronic effects (differences in growth and visible responses after 40 days), revealed an effects range of 0.5% to 12%, above which there was 100% mortality. For 2-butoxyethanol, the apparent LC50 after 48-hour exposure was 0.2%; after 72-hour recovery the LC50 was 1%. In all experiments, a 72-hour recovery period was sufficient to determine acute effects. A key discovery was the observation of inactivity during exposure to toxic substances, followed by recovery when placed in filtered seawater. This observation indicates the potential for dormancy in adult foraminifers exposed to toxic substances that has not previously been reported.
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Fraser, Gillian Anne. "An analysis of dormancy and chilling of Ribes nigrum L." Thesis, University of Reading, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427807.
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Leida, Carmen Alice. "Molecular aspects of dormancy in peach (Prunus persica [L.] Batsch.)." Doctoral thesis, Universitat Politècnica de València, 2012. http://hdl.handle.net/10251/15864.
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Dormancy is one of the most important adaptive mechanisms developed by perennial plants, in order to survive the low temperatures of autumn and winter in temperate climates. The study of the genes regulated during dormancy release is crucial to understand the process, with the final objective of the development of new varieties with a better adaptation to certain environments; in particular in the Mediterranean area. The general aim of this work is to understand the molecular and physiological mechanisms underlying the maintenance and release of seasonal dormancy in peach. The first part of this work is focused on the identification of peach genes related to dormancy release by suppression subtractive hybridization (SSH) and microarray hybridization. A significant number of genes identified in this work were homologous to ABA and drought related genes from other species. Our data contribute to highlight a prominent role of ABA in dormancy processes and also uncover elements of the ABA and drought regulatory response in peach, as an ABA-INSENSITIVE5 (ABI5) binding protein (AFP)-like, a dehydration-responsive element (DRE)-binding protein (DREB2C)-like, a calcium-binding annexin, and several genes regulated by stress signalling pathways. Other identified genes were also evaluated to assess the chilling requirement of cultivars by analysis of expression showing a very good correlation between the expression pattern of DAM5, together with other transcripts (BD396, DB247, SB280 and PpB63) and the chilling requirements values of five different varieties ('Big Top', 'Catherina', 'Fergold', 'Maruja' and 'Springlady') measured following Utah and Dynamic models. Furthermore, a study of chromatin modifications associated to dormancy release in the DAM6 gene is presented. A ChIP analysis of DAM6 promoter and structural gene revealed chromatin modification events similar to those observed in vernalization of Arabidopsis and cereals.<br>Leida, CA. (2012). Molecular aspects of dormancy in peach (Prunus persica [L.] Batsch.) [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/15864<br>Palancia
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Butler, Savannah E. "TUMOR-INTRINSIC INFLAMMATORY PATHWAYS ASSOCIATED WITH TUMOR DORMANCY AND RECURRENCE." VCU Scholars Compass, 2017. http://scholarscompass.vcu.edu/etd/4753.
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The successful treatment of breast cancer is limited due to a fraction of tumor cells escaping drug-treatment by entering a dormant state, only to relapse years or decades later at distant sites. Host-driven chronic inflammatory cells such as M2 macrophages play an important role in tumorigenesis, but the role of tumor-intrinsic inflammatory signaling involved in tumor dormancy and recurrence is unknown. We sought to determine the role of tumor-intrinsic inflammatory pathways in mouse mammary carcinoma cells (MMC) treated with Adriamycin (ADR), a clinically relevant chemotherapeutic drug. We found that ADR-induced dormant tumor cells autonomously produced pro-inflammatory cytokines, in vitro. MMC treated with Chloroquine (CQ) prior to ADR treatment displayed a delay in relapse, or prolonging of dormancy, when compared to ADR-treated MMC. Additional gene array data showed predicated activation of NF-κB p65 in ADR-treated dormant MMC that eventually relapsed. These data suggest that the anti-inflammatory function of CQ led to prolonged dormancy. To test this, we investigated the role of inflammatory signaling pathways directly by shRNA-mediated knockdown and CRISPR-Cas9-mediated knockout of NF-κB p65 in MMC. We found that knockdown of NF-κB p65 resulted in fewer dormant cells after ADR treatment and reduced rate of relapse, in vitro. NF-κB p65 was also found to reduce the immunomodulatory effects of ADR, with shNF-κB p65 showing increased upregulation of neu upon ADR treatment. Additionally, we found NF-κB p65 to be associated with a higher infiltration of CD8+ T cells and anti-tumor T cell responses. Our findings suggest a dual role of tumor-intrinsic NF-κB p65 pathway, allowing for escape from drug treatment through dormancy which leads to relapse, but also for proper lymphocyte infiltration and subsequent anti-tumor activity.
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Kendall, Sarah. "Temperature regulation of seed dormancy and germination in Arabidopsis thaliana." Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/3109/.
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The environmental regulation of seed dormancy and germination by temperature is an important process which allows the environmental conditions experienced by plants in the following generation to be controlled. Coping with temperature effects during seed maturation is essential for the consistent production of high quality seeds, but currently temperature signalling pathways in seeds are poorly understood. Previous work has shown that temperature during seed maturation regulates the levels of dormancy which are induced in the seed, although a mechanism for this pathway is currently unknown. Low temperature during imbibition promotes germination and although this is known to involve alterations to GA metabolism, again a mechanism is missing. Therefore, the aim of this study was to identify components of the mechanisms which regulate the temperature control of dormancy and germination in the model plant Arabidopsis thaliana. Cool and warm seed maturation temperatures induce high and low levels of dormancy respectively in Arabidopsis. These changes to dormancy levels are coupled with altered ABA and GA levels and gene expression controlling hormone synthesis and breakdown. Changes in maturation temperature do not appear to be linked to altered seed coat morphology or embryo development. During testing of cold-response mutants for dormancy phenotypes the expression of CBFs, a group of transcription factors which were characterised through the study of cold acclimation, was found to be necessary for dormancy. CBF RNAi and mutant seeds display reduced dormancy when matured at low temperature. However, the expression of CBFs is not promoted by exposure to low temperature in seeds, suggesting that this is not an important mechanism for the temperature control of dormancy. More strikingly, the E3 ligase HOS1 is absolutely required for high dormancy levels in response to low maturation temperature. hos1 mutants show a complete loss of dormancy when matured at any temperature and this phenotype is maternally inherited. The germination of hos1 seeds in the presence of PAC or ABA does not differ from wild-type, thus suggesting that sensitivity to GA and ABA is not altered in these seeds. However, levels of GA are increased in hos1 mutant seeds, which could be important for the reduced dormancy phenotype. The expression of TT genes, which are responsible for the accumulation of anthocyanidins in the seed coat, is downregulated in hos1 mutants and so could be involved in the regulation of dormancy by HOS1. Therefore; HOS1 defines a novel essential maternal pathway that regulates dormancy levels which involves the regulation of GA metabolism. A forward genetic screen identified a number of cold stratification insensitive (cosi) mutants. A thorough characterisation of these mutants revealed interesting phenotypes, but phenotypic variation and a lack of robust segregation data meant that the cosi mutants were not mapped.
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Just, Michael. "Seed morphology, dormancy and germination of South-West Australian Ericaceae." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2018. https://ro.ecu.edu.au/theses/2051.
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The Ericaceae in South West Australia contains species with difficult to germinate seeds, including many species with deep intractable dormancy. A better understanding of seed biology and species specific dormancy, and germination mechanisms is required to overcome these difficulties. Land clearing, salinity and disease has resulted in over 125 species within 15 genera being listed as rare, highly restricted, threatened and endangered (Western Australian Herbarium 1998–). The present study examined the seed biology of eight species of Ericaceae native to Western Australia, exploring fruit and seed morphology, dormancy and germination. Cold and warm stratification was used in combination with gibberellic acid to classify dormancy. Among the two distinct fruit types that occur within the Ericaceae separate patterns of dormancy were found. Seeds held within a dehiscent capsule were found to possess non-deep and intermediate physiological dormancy whilst those within an indehiscent drupe possessed physiological and morphophysiological dormancy. Oxygen and nitric oxide enriched atmospheres, removal of seeds from endocarps and propagation from cuttings provided potential avenues for the propagation of study species.