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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Level and structure of SNP and indel variation between individuals on large (North America and Sweden) and small (within Sweden) geographic scale of Phlebiopsis gigantea

Cao, Weilan January 2014 (has links)
No description available.
2

The evolution of small GTP binding proteins in cellular organisms. Studies of RAS GTPases in arabidopsis thaliana and the Ral GTPase from Drosophila melanogaster

Winge, Per January 2002 (has links)
Small GTP binding proteins function as molecular switches which cycles between GTP-bound ON and GDP-bound OFF states, and regulate a wide variety of cellular processes as biological timers. The first characterized member of the small GTPase family, the mutated oncogene p21 src, later known as Harvey-Ras, was identified in the early 1980s (Shih, T. Y. et al. 1980). In the following years small Ras-lik GTPases were found in several organisms and it was soon discovered that they took part in processes, such as signal transduction, gene expression, cytoskeleton reorganisation, microtubule organisation, and vesicular and nuclear transport. The first Rho (Ras homology) gene was cloned in 1985 from the sea slug Aplysia (Madaule, P. et al. 1985) and because of their homology to Ras it was first suspected that they could act as oncogenes. Later studies have shown that even though they participate in processes such as cell migration and motility they are not mutated in cancers. The first indications that Rho was a signaling protein regulating the actin cytoskeleton, came from experiments where activated forms of human RhoA was microinjected into 3T3 cells (Paterson, H. F. et al. 1990). Another Rho-like GTPase Rac1 (named after Ras-related C3 botulinum toxin substrate) was later shown to regulate actin cytoskeletal dynamics as well, suggesting that Rho-family members cooperate in controlling these processes (Ridley, A. J. et al. 1992). The Rac GTPase was also implicated in regulating the phagocytic NADPH oxidase, which produce superoxide for killing phagocytized microorganisms (Abo, A. et al. 1991). Thus, it soon became clear that Rac/Rho and the related GTPase Cdc42 (cell division cycle 42) had central functions in many important cellular processes. There are at least three types of regulators for Rho-like proteins. The GDP/GTP exchange factors (GEFs) which stimulates conversion from the GDPbound form to the GTP-bound form. GDP dissociation inhibitors (GDIs) decrease the nucleotide dissociation from the GTPase and retrieve them from membranes to the cytosol. GTPase activating proteins (GAPs) stimulates the intrinsic GTPase activity and GTP hydrolysis. In addition there are probably regulators that dissociate GDI from the GTPase leaving it open for activation by the RhoGEFs. Ras and Rho-family proteins participate in a coordinated regulation of cellular processes such as cell motility, cell growth and division. The Ral GTPase is closely related to Ras and recent studies have shown that this GTPase is involved in crosstalk between both Ras and Rho proteins (Feig, L. A. et al. 1996; Oshiro, T. et al. 2002). Ral proteins are not found in plants and they appear to be restricted to animalia and probably yeast. During a screen for small GTPases in Drosophila melanogaster I discovered in 1993 several new members of the Ras-family, such as Drosophila Ral (DRal), Ric1 and Rap2. The functions of Ral GTPases in Drosophila have until recently been poorly known, but in paper 2 we present some of the new findings. Rho-like GTPases have been identified in several eukaryotic organisms such as, yeast (Bender, A. et al. 1989), Dictyostelium discoideum (Bush, J. et al. 1993), plants (Yang, Z. et al. 1993), Entamoeba histolytica (Lohia, A. et al. 1993) and Trypanosoma cruzi (Nepomuceno-Silva, J. L. et al. 2001). In our first publication, (Winge, P. et al. 1997), we describe the cloning of cDNAs from RAC-like GTPases in Arabidopsis thaliana and show mRNA expressions pattern for five of the genes. The five genes analyzed were expressed in most plant tissues with the exception of AtRAC2 (named Arac2 in the paper), which has an expression restricted to vascular tissues. We also discuss the evolution and development of RAC genes in plants. The third publication, (Winge, P. et al. 2000), describe the genetic structure and the genomic sequence of 11 RAC genes from Arabidopsis thaliana. As most genomic sequences of the AtRACs we analyzed came from the Landsberg erecta ecotype and the Arabidopsis thaliana genome was sequenced from the Columbia ecotype, it was possible to compare the sequences and identify new polymorphisms. The genomic location of the AtRAC genes plus the revelation of large genomic duplications provided additional information regarding the evolution of the gene family in plants. A summary and discussion of these new findings are presented together with a general study of small Ras-like GTPases and their evolution in cellular organisms. This study suggests that the small GTPases in eukaryots evolved from two bacterial ancestors, a Rab-like and a MglA/Arp-like (Arf-like) protein. The MglA proteins (after the mgl locus in Myxococcus xanthus) are required for gliding motility, which is a type of movement that take place without help of flagella. The second publication describes experiments done with the Drosophila melanogaster DRal gene and its effects on cell shape and development. Ectopic expression of dominant negative forms of DRal reveals developmental defects in eye facets and hairs, while constitutive activated forms affects dorsal closure, leaving embryos with an open dorsal phenotype. Results presented in this publication suggest that DRal act through the Jun N-terminal kinase (JNK) pathway to regulate dorsal closure, but recent findings may point to additional explanations as well. The results also indicate a close association between processes regulated by Rac/Rho and Ral proteins in Drosophila.
3

The evolution of small GTP binding proteins in cellular organisms. Studies of RAS GTPases in arabidopsis thaliana and the Ral GTPase from Drosophila melanogaster

Winge, Per January 2002 (has links)
<p>Small GTP binding proteins function as molecular switches which cycles between GTP-bound ON and GDP-bound OFF states, and regulate a wide variety of cellular processes as biological timers. The first characterized member of the small GTPase family, the mutated oncogene p21 src, later known as Harvey-Ras, was identified in the early 1980s (Shih, T. Y. et al. 1980). In the following years small Ras-lik GTPases were found in several organisms and it was soon discovered that they took part in processes, such as signal transduction, gene expression, cytoskeleton reorganisation, microtubule organisation, and vesicular and nuclear transport. The first <i>Rho</i> (Ras homology) gene was cloned in 1985 from the sea slug Aplysia (Madaule, P. et al. 1985) and because of their homology to <i>Ras</i> it was first suspected that they could act as oncogenes. Later studies have shown that even though they participate in processes such as cell migration and motility they are not mutated in cancers.</p><p>The first indications that Rho was a signaling protein regulating the actin cytoskeleton, came from experiments where activated forms of human RhoA was microinjected into 3T3 cells (Paterson, H. F. et al. 1990). Another Rho-like GTPase Rac1 (named after Ras-related C3 botulinum toxin substrate) was later shown to regulate actin cytoskeletal dynamics as well, suggesting that Rho-family members cooperate in controlling these processes (Ridley, A. J. et al. 1992). The Rac GTPase was also implicated in regulating the phagocytic NADPH oxidase, which produce superoxide for killing phagocytized microorganisms (Abo, A. et al. 1991). Thus, it soon became clear that Rac/Rho and the related GTPase Cdc42 (cell division cycle 42) had central functions in many important cellular processes.</p><p>There are at least three types of regulators for Rho-like proteins. The GDP/GTP exchange factors (GEFs) which stimulates conversion from the GDPbound form to the GTP-bound form. GDP dissociation inhibitors (GDIs) decrease the nucleotide dissociation from the GTPase and retrieve them from membranes to the cytosol. GTPase activating proteins (GAPs) stimulates the intrinsic GTPase activity and GTP hydrolysis. In addition there are probably regulators that dissociate GDI from the GTPase leaving it open for activation by the RhoGEFs.</p><p>Ras and Rho-family proteins participate in a coordinated regulation of cellular processes such as cell motility, cell growth and division. The Ral GTPase is closely related to Ras and recent studies have shown that this GTPase is involved in crosstalk between both Ras and Rho proteins (Feig, L. A. et al. 1996; Oshiro, T. et al. 2002). Ral proteins are not found in plants and they appear to be restricted to animalia and probably yeast. During a screen for small GTPases in <i>Drosophila</i> <i>melanogaster</i> I discovered in 1993 several new members of the Ras-family, such as Drosophila Ral (DRal), Ric1 and Rap2. The functions of Ral GTPases in <i>Drosophila</i> have until recently been poorly known, but in paper 2 we present some of the new findings.</p><p>Rho-like GTPases have been identified in several eukaryotic organisms such as, yeast (Bender, A. et al. 1989), <i>Dictyostelium discoideum</i> (Bush, J. et al. 1993), plants (Yang, Z. et al. 1993), <i>Entamoeba histolytica</i> (Lohia, A. et al. 1993) and <i>Trypanosoma cruzi</i> (Nepomuceno-Silva, J. L. et al. 2001). In our first publication, (Winge, P. et al. 1997), we describe the cloning of cDNAs from<i> RAC</i>-like GTPases in <i>Arabidopsis thaliana</i> and show mRNA expressions pattern for five of the genes. The five genes analyzed were expressed in most plant tissues with the exception of <i>AtRAC2</i> (named <i>Arac2</i> in the paper), which has an expression restricted to vascular tissues. We also discuss the evolution and development of RAC genes in plants. The third publication, (Winge, P. et al. 2000), describe the genetic structure and the genomic sequence of 11 RAC genes from <i>Arabidopsis</i> <i>thaliana</i>. As most genomic sequences of the AtRACs we analyzed came from the <i>Landsberg erecta</i> ecotype and the <i>Arabidopsis thaliana</i> genome was sequenced from the Columbia ecotype, it was possible to compare the sequences and identify new polymorphisms. The genomic location of the AtRAC genes plus the revelation of large genomic duplications provided additional information regarding the evolution of the gene family in plants. A summary and discussion of these new findings are presented together with a general study of small Ras-like GTPases and their evolution in cellular organisms. This study suggests that the small GTPases in eukaryots evolved from two bacterial ancestors, a Rab-like and a MglA/Arp-like (Arf-like) protein. The MglA proteins (after the <i>mgl</i> locus in <i>Myxococcus</i> <i>xanthus</i>) are required for gliding motility, which is a type of movement that take place without help of flagella.</p><p>The second publication describes experiments done with the <i>Drosophila melanogaster</i> DRal gene and its effects on cell shape and development. Ectopic expression of dominant negative forms of DRal reveals developmental defects in eye facets and hairs, while constitutive activated forms affects dorsal closure, leaving embryos with an open dorsal phenotype. Results presented in this publication suggest that DRal act through the Jun N-terminal kinase (JNK) pathway to regulate dorsal closure, but recent findings may point to additional explanations as well. The results also indicate a close association between processes regulated by Rac/Rho and Ral proteins in <i>Drosophila</i>.</p>
4

Effects of climatic change on the growth of dominating tree species along major environmental gradients.

Solberg, Bård Øyvind January 2002 (has links)
This thesis deals with effects of climate on tree growth of the dominating conifer species, Picea abies (L) Karst. (Norway spruce) and Pinus sylvestris L (Scots pine), in central Norway and Fennoscandia. Both species are sampled along major environmental gradients, i.e. altitude and oceanicity, and growth responses to climate, i.e. temperature and precipitation, are examined along these gradients. Additionally, time is considered as an environmental gradient and temporal responses are carefully deciphered. Special attention is given to large-scale climate oscillation and their effect on tree growth. In the individual papers the specific aims have been to: 1. identify climate variables (all seasons) with significant influence on radial tree growth of P. abies and P. sylvestris along major environmental gradients (Paper I-IV) 2. identify if and how the growth response to climate has changed through time along these gradients (Paper I-IV) 3. make interregional comparisons of P. sylvestris growth pattern across Fennoscandia from oceanic western Norway to continental eastern Finland (Paper III) 4. analyse to what degree large-scale circulation patterns of air masses are registered in regional tree growth of both P. abies and P. sylvestris (Paper I, III and IV) 5. discuss possible effects on radial tree growth of a predicted warmer climate (Paper I, III and IV)
5

Cultivation of Herbs and Medicinal Plants in Norway - Essential Oil Production and Quality Control

Rohloff, Jens January 2003 (has links)
Essential oils (EO) are plant secondary metabolites that are known for their fragrance and food flavour properties. They consist of a complex mixture of mono- and sesquiterpenes, phenyl propanoids and oxygenated compounds. EOs can be present in different plant organs and materials, and their storage is related to specialised secretory structures. The yield of EOs from plant raw materials by distillation or pressing may on average vary from 0.1 – 1%, thus restricting the major EO production to the plant group of aromatic plants. Due to their function as signalling compounds between different types of organisms and diverse biological systems, their general antimicrobial and antioxidative effects and medicinal activity, EOs offer a promising potential for future applications within the fields of agriculture, medicine, pharmaceutical industry and biotechnology. Changed consumer demands and raised interest in natural product compounds, especially essential oils, have formed the basis for initiating the research project “Norwegian Herb Production (Norsk Urteproduksjon NUP)” to encourage the cultivation, processing, marketing and distribution of aromatic and medicinal plants. The production, composition and quality characteristics of EOs (yield and terpene composition) from chamomile, lemon balm, oregano, peppermint, sachalinmint, thyme and yarrow have been investigated in the project period between 1994-1998. Much focus has been put on the application of solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) for the analysis of EO volatiles from various aromatic and medicinal plants. SPME is a fast, solvent-free and non- destructive sample preparation technique where the analytes are extracted from fluid or solid matrices by headspace (HS) or direct immersion sampling (DI). Apart from EO isolation by common distillation, the applicability and sensitivity of the SPME fibre has made it feasible to carry out qualitative and semi-quantitative HS analyses of aromatic plants with regard to changes of EO metabolism during ontogenesis and plant development. Based on NUP-results from field trials in the period between 1995-1996, the mint species peppermint (Mentha × piperita L.) and sachalinmint (Mentha sachalinensis (Briq.) Kudô) have been studied in detail (Papers B, D and E). Comparative analyses by applying distillation sampling and SPME have been carried out in order to study the advantages and disadvantages of both techniques (Papers B and E). It could be shown, that SPME offers a fast and reliable method for detecting quality-impact compounds from the p-menthane group (menthol, menthone, neomenthol, isomenthone and menthyl acetate). A distinct increase in the menthol/menthone ratio in the basipetal direction could be detected for peppermint and sachalinmint by applying SPME, thus revealing within-plant quality differences according to pharmacopeial requirements. Taking the increase of EO production from the vegetative to the generative growth stage into account, the harvest of mint plants in bloom will result in better EO yield and quality with regard to higher amounts of menthol. When applying HS-SPME on complex EO volatile matrices such as known for yarrow (Achillea millefolium L.; Paper C), one might deal with fibre-partitioning effects of the different mono- and sesquiterpenes due to their physical and chemical properties. Despite these disadvantages, HS-SPME appears to be a sensitive extraction method for the screening of EO volatiles from complex sample matrices. Comparative analyses of volatiles from rose root rhizomes (Rhodiola rosea L.) have been carried out in order to characterize the rose-like odour compounds (Paper F). A total of 75 and 59 compounds have been identified by distillation sampling and HS-SPME, respectively, thus underscoring the excellent extraction properties and applicability of the SPME fibre. Paper A gives a brief overview of EO biosynthesis and chemical structures, plant sources and methods of EO production. Before leading over to the main topic of HS-SPME applications by referring to numerous examples from the research work at The Plant Biocenter in the past 5 years, an introduction of solid-phase microextraction with regard to devices, procedures and extraction parameters is given. The advantages and disadvantages of distillation vs. SPME are outlined on the background of comparative analyses of peppermint, chamomile, basil and dill. Furthermore, the utilization of HS-SPME for quantitative studies with regard to extraction time and analyte concentration is being highlighted. Examples for the screening of chemotypes (hops −Humulus lupulus L.) and cultivars (dill – Anethum graveolens L.) and ontogenetic studies are given (Mentha species; arnica −Arnica montana L.). Finally, the applicability of HS-SPME for the quality assessment of processed herbs (sweet basil −Ocimum basilicum L.) and phytomedicinal preparations (red coneflower – Echinacea purpurea L.) is being discussed. The advantages of HS-SPME over classical distillation and headspace applications are impressive due to drastically reduced analysis time and will introduce new frontiers in plant volatile research with regard to secondary metabolism, plant-insect interactions and in vivo studies. The user-friendliness of operating SPME will initiate the development of future applications and equipment for the monitoring of volatiles for plant biological and environmental studies, extraction automation, on-site sampling and on-fibre storage of analytes. / Paper VI reprinted with kind permission of Elsevier, Sciencedirect, www.sciencedirect.com
6

Behavioural effects on environmental pollution in threespine stickleback Gasterosteus aculeatus L

Espmark, Åsa Maria January 2003 (has links)
The aims of this study were to investigate the effects of known environmental contaminants on defined behavioural variables in fish, and to discuss properties of these behavioural traits that make them useful as potential indicators of pollution. In studying the effects of pollution, the resulting biochemical and physiological alterations are more commonly measured. However, effects of pollution can manifest itself at all levels of biological organisation, including behaviour. In this respect, behaviour can be considered a valid biomarker of pollution in that it is expected to be both susceptible to pollution and of high ecological significance, as it influences the fitness of the affected individuals. This thesis is based on four individual studies, in which the threespine stickleback Gasterosteus aculeatus was used as a model species. Results from these studies show that antipredator behaviour, feeding behaviour, shoaling behaviour, bottom-dwelling behaviour and reproductive behaviour are all sensitive to exposure to sublethal concentrations of defined environmentally relevant chemicals. The results showed that antipredator behaviour and fright response in threespine stickleback were impaired following exposure to sublethal concentrations of bis(tributyltin)oxide (TBTO). However, for some of the tested antipredator variables the effects were reversed after the ending of exposure. Further, it was shown that feeding motivation in fish exposed to butyl benzyl phthalate (BBP) and/or 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene (DDE) was increased in that exposed fish initiated feeding more often than the controls. Exposure to BBP also caused sticklebacks to aggregate into tight shoals and to spend more time at the bottom of the aquarium compared to the control fish. The reported significant differences between the controls and BBPexposed fish with respect to feeding and shoaling behaviour were shown even though the levels of BBP were below the analytical detection limit. Different suggested explanations, for example, too high detection limit, or degradation to its BBP metabolites are given to this result. 17β-Oestradiol (E2) exposed male sticklebacks started nest building later than non-exposed males, but there were no differences between exposed and control males with respect to the number of males that built nests. Further, the exposed males spent less time displaying paternal care compared to the control males, although there were no differences between the two groups in the number of performed courtship displays. Because of the significant effect upon some but not all reproductive behavioural traits, it was suggested that the different variables might vary in sensitivity, implying that a variety of variables should be studied in order to obtain a more reliable evaluation of the effects of pollution. Chemicals can cause deleterious effects at one or more levels of biological organisation, from biochemical, physiological, individual, population and through to the ecosystem levels. In contrast to the established hypothesis that a pollutant affects the different biological levels in an escalating timedependent pattern, starting at the biochemical level, it is here suggested that biomarkers at the biochemical, physiological and behavioural levels often will respond early and simultaneously in the same individual. Whereas some biochemical responses are specifically related to one class of exposure agents and thus may act as specific indicators of pollution, most behavioural traits may be altered in response to a variety of chemicals. One exception may be alterations in reproductive behaviour caused by endocrine disrupting chemicals, due to effects of the chemicals on hormones that result in immediate reproductive behavioural effects. In spite of the specific action of some biochemical biomarkers, they are often considered to be of little ecological relevance since many of them are not related to individual fitness. In this thesis, it is argued that behavioural variables can be employed as useful and reliable biomarkers of environmental contamination. It is also important to focus on behaviour to map and quantify the resposes. However, to reliably evaluate the effects of pollution, behavioural variables should be used in association with biochemical and physiological traits. Moreover, optimal combination of results from laboratory and field experiments would enhance the ecological relevance of the study. / All papers reprinted with kind permission of Elsevier, sciencedirect.com
7

Control of Pistil Development in Arabidopsis thaliana by a Novel Class of Regulatory Genes

Kuusk, Sandra January 2003 (has links)
The pistil, or the gynoecium, is the female reproductive organ of the angiosperm flower and its ontogeny has been studied in the model plant Arabidopsis thaliana. The mature Arabidopsis gynoecium consists of a basal ovary that contains the ovules, a short style and an apical stigma that serves as the site of pollen adherence and germination. This thesis describes the identification and functional characterisation of genes with roles in the regulation of Arabidopsis gynoecium development. Mutant analyses and sequence similarity database searches led to the identification of a small Arabidopsis gene family, denoted the SHI gene family, the ten members of which encode proteins with zinc finger-like motifs. This class of genes is novel and appears to be unique to plants. Double, triple and quadruple mutant analyses revealed that at least six of the SHI-related genes, STY1, STY2, SHI, SRS4, SRS5, and LRP1, redundantly contribute to the formation of stylar and stigmatic tissues in developing gynoecia. Several of the genes appear also to influence carpel fusion and vascular patterning in the gynoecium. Gynoecia of transgenic plants that express STY1 or STY2 constitutively develop ectopic style cells, confirming a role for the genes in the promotion of style formation. STY1, STY2, SHI and SRS5 are expressed in the apical parts of the developing gynoecium and, hence, likely act cell autonomously. As judged from mutant and overexpression analyses, the SHI-related genes appear also to regulate leaf development. Possibly, SHI family members act in concert with the plant growth hormones gibberellin and auxin.
8

Mitochondrial Evolution : Turning Bugs into Features

Karlberg, Olof January 2004 (has links)
The bacterial origin of mitochondria from an ancient endosymbiosis is now widely accepted and the mitochondrial ancestor is generally believed to belong to the bacterial subdivision α-proteobacteria. The high fraction of mitochondrial proteins encoded in the nucleus has commonly been explained with a massive transfer of genes from the genome of the ancestral mitochondrion. The aim of this work was to get a better understanding of the mitochondrial origin and evolution by comparative genomics and phylogenetic analyses on mitochondria and α-proteobacteria. To this end, we sequenced the genomes of the intracellular parasites Bartonella henselae and Bartonella quintana, the causative agents of cat-scratch disease and trench fever, and compared them with other α-proteobacteria as well as mitochondrial eukaryotes. Our results suggest that the adaptation to an intracellular life-style is coupled to an increased rate of genome degradation and a reduced ability to accommodate environmental changes. Reconstruction of the α-proteobacterial ancestor and phylogenetic analyses of the mitochondrial proteome in yeast revealed that only a small fraction of the proteins used for mitochondrial functions could be traced to the α-proteobacteria. Furthermore, a substantial fraction of the mitochondrial proteins was of eukaryotic origin and while most of the genes of the α-proteobacterial ancestor have been lost, many of those that have been transferred to the nuclear genome seem to encode non-mitochondrial proteins.
9

Coastal heath vegetation in central Norway; recent past, present state and future possibilities

Nilsen, Liv Sigrid January 2004 (has links)
No description available.
10

Functional characterisation of olfactory receptor neurone types in heliothine moths : Identification of molecular receptive ranges by the use of single cell recordings linked to gas chromatography and mass spectrometry

Røstelien, Tonette January 2005 (has links)
When the study of this thesis was initiated, hardly any work had been carried out on how plant odour information was encoded by the olfactory RNs in heliothine moths. The method of gas chromatography linked to single cell recordings (GC-SCR) was employed and improved for identifying naturally occurring plant odorants that are detected by single RNs and can be considered as biologically relevant. Three species of the subfamily Heliothinae were included in this work, the two polyphagous H. virescens and H. armigera and the oligophagous H. assulta. The American H. virescens is geographically separated from the other two species. H. armigera and H. assulta are partly sympatric in Asia and Australia. The aims of the thesis elucidated in Papers I-IV were as follows: 1. To identify plant produced volatiles detected by antennal RNs in the three species of the subfamily Heliothinae. 2. To elucidate whether the single RNs can be classified into distinct types according to their specificity. 3. To characterise the plant odour RN types by their molecular receptive ranges, sensitivity and specificity. 4. To compare the specificity of plant odour RN types across the three related species of Heliothinae, with the aim to reveal any differences in the peripheral olfactory system that may have evolved through evolution.

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