| 42311. |
- Kunsmann, Lisa, et al.
(författare)
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Virulence from vesicles : Novel mechanisms of host cell injury by Escherichia coli O104:H4 outbreak strain
- 2015
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- The highly virulent Escherichia coli O104:H4 that caused the large 2011 outbreak of diarrhoea and haemolytic uraemic syndrome secretes blended virulence factors of enterohaemorrhagic and enteroaggregative E. coli, but their secretion pathways are unknown. We demonstrate that the outbreak strain releases a cocktail of virulence factors via outer membrane vesicles (OMVs) shed during growth. The OMVs contain Shiga toxin (Stx) 2a, the major virulence factor of the strain, Shigella enterotoxin 1, H4 flagellin, and O104 lipopolysaccharide. The OMVs bind to and are internalised by human intestinal epithelial cells via dynamin-dependent and Stx2a-independent endocytosis, deliver the OMV-associated virulence factors intracellularly and induce caspase-9-mediated apoptosis and interleukin-8 secretion. Stx2a is the key OMV component responsible for the cytotoxicity, whereas flagellin and lipopolysaccharide are the major interleukin-8 inducers. The OMVs represent novel ways for the E. coli O104: H4 outbreak strain to deliver pathogenic cargoes and injure host cells.
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| 42312. |
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| 42313. |
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| 42314. |
- Kunz, Sabine, et al.
(författare)
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Functional Dissection of Sugar Signals Affecting Gene Expression in Arabidopsis thaliana
- 2014
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:6, s. e100312-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Sugars modulate expression of hundreds of genes in plants. Previous studies on sugar signaling, using intact plants or plant tissues, were hampered by tissue heterogeneity, uneven sugar transport and/or inter-conversions of the applied sugars. This, in turn, could obscure the identity of a specific sugar that acts as a signal affecting expression of given gene in a given tissue or cell-type. Methodology/Principal Findings: To bypass those biases, we have developed a novel biological system, based on stem-cell-like Arabidopsis suspension culture. The cells were grown in a hormone-free medium and were sustained on xylose as the only carbon source. Using functional genomics we have identified 290 sugar responsive genes, responding rapidly (within 1 h) and specifically to low concentration (1 mM) of glucose, fructose and/or sucrose. For selected genes, the true nature of the signaling sugar molecules and sites of sugar perception were further clarified using non-metabolizable sugar analogues. Using both transgenic and wild-type A. thaliana seedlings, it was shown that the expression of selected sugar-responsive genes was not restricted to a specific tissue or cell type and responded to photoperiod-related changes in sugar availability. This suggested that sugar-responsiveness of genes identified in the cell culture system was not biased toward heterotrophic background and resembled that in whole plants. Conclusions: Altogether, our research strategy, using a combination of cell culture and whole plants, has provided an unequivocal evidence for the identity of sugar-responsive genes and the identity of the sugar signaling molecules, independently from their inter-conversions or use for energy metabolism.
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| 42315. |
- Kunz, Sabine, et al.
(författare)
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Hexokinase 1 is required for glucose-induced repression of bZIP63, At5g22920, and BT2 in Arabidopsis
- 2015
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Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Simple sugars, like glucose (Glc) and sucrose (Suc), act as signals to modulate the expression of hundreds of genes in plants. Frequently, however, it remains unclear whether this regulation is induced by the sugars themselves or by their derivatives generated in the course of carbohydrate (CH) metabolism. In the present study, we tested the relevance of different CH metabolism and allocation pathways affecting expression patterns of five selected sugar-responsive genes (bZIP63, At5g22920, BT2, MGD2, and TPS9) in Arabidopsis thaliana. In general, the expression followed diurnal changes in the overall sugar availability. However, under steady growth conditions, this response was hardly impaired in the mutants for CH metabolizing/transporting proteins (adg1, sex1, sus1-4, sus5/6, and tpt2), including also hexokinase1 (HXK1) loss- and gain-of-function plants—gin2.1 and oe3.2, respectively. In addition, transgenic plants carrying pbZIP63::GUS showed no changes in reporter-gene-expression when grown on sugar under steady-state conditions. In contrast, short-term treatments of agar-grown seedlings with 1% Glc or Suc induced pbZIP63::GUS repression, which became even more apparent in seedlings grown in liquid media. Subsequent analyses of liquid-grown gin2.1 and oe3.2 seedlings revealed that Glc -dependent regulation of the five selected genes was not affected in gin2.1, whereas it was enhanced in oe3.2 plants for bZIP63, At5g22920, and BT2. The sugar treatments had no effect on ATP/ADP ratio, suggesting that changes in gene expression were not linked to cellular energy status. Overall, the data suggest that HXK1 does not act as Glc sensor controlling bZIP63, At5g22920, and BT2 expression, but it is nevertheless required for the production of a downstream metabolic signal regulating their expression.
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| 42316. |
- Kunz, Sabine, et al.
(författare)
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Monitoring the role of distinct sugars on cell division in Arabidopsis plant cells and seedlings
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Within the last decades, research on sugar-dependent plant growth provided evidence for a directregulation of cell division by sugars. Recently we showed, in A. thaliana cell suspension cultures, thatdistinct sugars differentially regulate a rapid transcriptional response of genes, some of which functionduring the cell cycle progression. In order to assess the relationship between sugar species and celldivision, we developed a new methodology for long-term real-time live-cell imaging on dividing A.thaliana cell suspension cultures. This technique, using cells grown in hormone-free media, allowed toestimate the cell cycle synchronicity and efficiency of an entire cell population and to monitor thedynamics and geometry of cell division in single cells in response to a given sugars. A marker cell lineconstitutively expressing TUA::GFP, a protein that labels microtubule-based structures hallmarkingprogression of the mitotic division, was used to measure the sugar-dependent efficiency andsynchronicity of the cell cycle progression. Altogether, we were able to confirm the distinct relationshipsof specific sugar molecules on the cell cycle progression at a single cell level. Cell division efficiencyand synchronicity were altered when grown on the different sugars sucrose, glucose and xylose.Interestingly, the progression of the mitotic division appeared unaffected by the sugar species supplied,indicating that length of the interphase is likely to control the cell division rate. In contrast, treatment ofA. thaliana cell cultures and seedlings with the Glc-analogue 2-deoxy-glucose (2dog) led to growtharrest and to cell death during long exposure. The growth resulting from 2dog removal in cell culturesand seedlings showed the unique feature of plants to induce new active zones of cell division.
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| 42317. |
- Kunz, Sabine, 1981-
(författare)
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Sugar-modulated gene expression and cell division in cell culture and seedlings of A. thaliana
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Throughout their life cycle, plants adjust growth in response to their developmental and environmental situation within the limits of their energetic capacities. This capacity is defined by the local sugar availability, which is constantly modulated through synthesis, transport and consumption of sugar. The monitoring of sugar presence is carried out by a complex signalling network in which simple sugars (e.g. glucose, fructose and sucrose) act as metabolic signals for the modulation of physiological processes. However, often it remains unclear whether the regulation is induced by the simple sugars themselves or by their derivatives generated during sugar metabolism. This thesis focuses on the dissection of distinct sugar signals, their generation, perception and impact on the modulation of gene expression and cell division both in cell culture and young seedlings.Based on a stem-cell-like A. thaliana cell culture, which could be sustained in a hormone-free media, a new biological system, supplied with Xyl as the only carbon source was developed. The performance of a variety of sugar and sugar analogue treatments in this novel system allowed for the identification of sugar-responsive candidate genes, which were specifically regulated by glucose, fructose and sucrose. For several genes (e.g. bZIP63, AT5g22920, TPS9, MGD2 and BT2), this regulation required both sugar transport into the cytosol and metabolisation for the generation of the signal. Furthermore, gene expression analyses in young A. thaliana seedlings indicated the requirement for the catalytic activity of hexokinase 1 in the regulation of bZIP63, Atg22920 and BT2 under conditions of a perturbed carbohydrate balance. These findings have been combined in a proposed model for the transcriptional regulation of bZIP63, AT5g22920, TPS9, MGD2 and BT2, which further proposes a function of those genes in the regulation of cell division.The optimisation of a protocol for long-term real-time live-cell imaging provided a valuable tool to show that, similar to gene expression, the progression of cell division depended on a sugar-type-specific regulation at the single-cell level; this regulation was most likely caused by prolongation of the interphase. Together with the observation of cell death and growth arrest of the primary root in intact seedlings in response to the glucose analogue 2dog, this led to the conclusion that sugar signals themselves were sufficient to induce cell division. However, the continuation of cell cycle progression and consequently organ growth over long-time required the availability of the energy contained in the sugar.
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| 42318. |
- Kunz, T. J., et al.
(författare)
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Phytoplankton, light and nutrients along a gradient of mixing depth : a field test of producer-resource theory
- 2003
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Ingår i: Freshwater Biology. ; 48:6, s. 1050-1063
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Tidskriftsartikel (refereegranskat)abstract
- 1. Variation in depth of the mixed surface layer of temperate lakes should affect phytoplankton dynamics because, with increasing mixing depth, average light intensity in and specific sedimentation losses out of the mixed layer both decrease. 2. Our aim was to test a recent dynamic model which relates phytoplankton biomass and the availability of production-limiting resources (light and dissolved mineral nutrients) to mixing depth and nutrient supply from external sources. 3. During summer stratification we sampled the mixed layers of 30 dimictic, phosphorus-limited, oligo- to mesotrophic, mostly non-humic lakes north of the Alps. 4. The results agree well qualitatively with model expectations. Algal concentration in the mixed layer was negatively related to mixing depth or its surrogate log-transformed lake area. Light intensity at the bottom of the mixed layer decreased whereas the concentration of available, inorganic phosphorus increased with increasing mixing depth. Across all depths, higher total phosphorus content was accompanied by higher phytoplankton biomass, lower light availability, and higher inorganic phosphorus concentration. 5. Our data match the predicted shift with increasing mixing depth from predominantly nutrient limitation towards increased light limitation of algal biomass.
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| 42319. |
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| 42320. |
- Künzli, Nino, et al.
(författare)
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Comparison of oxidative properties, light absorbance, total and elemental mass concentration of ambient PM2.5 collected at 20 European sites.
- 2006
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Ingår i: Environ Health Perspect. - 0091-6765. ; 114:5, s. 684-90
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Body mass, as well as distribution of body fat, are predictors of both diabetes and cardiovascular disease. In Northern Sweden, despite a marked increase in average body mass, prevalence of diabetes was stagnant and myocardial infarctions decreased. A more favourable distribution of body fat is a possible contributing factor.This study investigates the relative importance of individual food items for time trends in waist circumference (WC) and hip circumference (HC) on a population level. METHODS: Independent cross-sectional surveys conducted in 1986, 1990, 1994 and 1999 in the two northernmost counties of Sweden with a common population of 250,000. Randomly selected age stratified samples, altogether 2982 men and 3087 women aged 25-64 years. Questionnaires were completed and anthropometric measurements taken. For each food item, associations between frequency of consumption and waist and hip circumferences were estimated. Partial regression coefficients for every level of reported intake were multiplied with differences in proportion of the population reporting the corresponding levels of intake in 1986 and 1999. The sum of these product terms for every food item was the respective estimated impact on mean circumference. RESULTS: Time trends in reported food consumption associated with the more favourable gynoid distribution of adipose tissue were increased use of vegetable oil, pasta and 1.5% fat milk. Trends associated with abdominal obesity were increased consumption of beer in men and higher intake of hamburgers and French fried potatoes in women. CONCLUSION: Food trends as markers of time trends in body fat distribution have been identified. The method is a complement to conventional approaches to establish associations between food intake and disease risk on a population level.
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