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31.
Friedrich Oehlkers und Ute Ebell 《Molecular & general genetics : MGG》1958,89(4):559-586
Ohne ZusammenfassungMit 5 Textabbildungen 相似文献
32.
Liverworts are well supported as the sister group to all other land plants (embryophytes) by molecular data. Observations
strongly supporting this earliest dichotomy in embryophyte evolution are the strikingly different introns occurring in the
mitochondrial DNAs of liverworts versus non-liverwort embryophytes (NLE), including the mosses. A final conclusion on the
most basal lineages of mosses, for which genera such as Sphagnum and Takakia are the most likely candidates, is lacking. We have now investigated cox1i624, a mitochondrial group I intron conserved between
the moss Physcomitrella patens and the liverwort Marchantia polymorpha. Focusing on a sampling of liverwort and moss genera, which had previously been identified as early branching taxa in their
respective clades, we find that group I intron cox1i624 is universally conserved in all 33 mosses and 11 liverworts investigated.
The group I intron core secondary structure is well conserved between the two ancient land plant clades. However, whereas
dramatic size reductions are seen in the moss phylogeny, exactly the opposite is observed for liverworts. The cox1i624g1 locus
was used for phylogenetic tree reconstruction also in combination with data sets of nad5i753g1 as well as chloroplast loci
rbcL and rps4. The phylogenetic analyses revealed (i) very good support for the Treubiopsida as sister clade to all other liverworts,
(ii) a sister group relationship of the nematodontous Tetraphidopsida and Polytrichopsida and (iii) two rivalling hypotheses
about the basal-most moss genus with mitochondrial loci suggesting an isolated Takakia as sister to all other mosses and chloroplast loci indicating a Takakia–Sphagnum clade. 相似文献
33.
Studying global change through investigation of the plastic responses of xylem anatomy in tree rings 总被引:1,自引:0,他引:1
Patrick Fonti Georg von Arx Ignacio García-González Britta Eilmann Ute Sass-Klaassen Holger Gärtner Dieter Eckstein 《The New phytologist》2010,185(1):42-53
Variability in xylem anatomy is of interest to plant scientists because of the role water transport plays in plant performance and survival. Insights into plant adjustments to changing environmental conditions have mainly been obtained through structural and functional comparative studies between taxa or within taxa on contrasting sites or along environmental gradients. Yet, a gap exists regarding the study of hydraulic adjustments in response to environmental changes over the lifetimes of plants. In trees, dated tree-ring series are often exploited to reconstruct dynamics in ecological conditions, and recent work in which wood-anatomical variables have been used in dendrochronology has produced promising results. Environmental signals identified in water-conducting cells carry novel information reflecting changes in regional conditions and are mostly related to short, sub-annual intervals. Although the idea of investigating environmental signals through wood anatomical time series goes back to the 1960s, it is only recently that low-cost computerized image-analysis systems have enabled increased scientific output in this field. We believe that the study of tree-ring anatomy is emerging as a promising approach in tree biology and climate change research, particularly if complemented by physiological and ecological studies. This contribution presents the rationale, the potential, and the methodological challenges of this innovative approach. 相似文献
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35.
Resonance Raman experiments were performed on different green bacteria. With blue excitation, i.e. under Soret resonance or preresonance conditions, resonance Raman contributions were essentially arising from the chlorosome pigments. By comparing these spectra and those of isolated chlorosomes, it is possible to evaluate how the latter retain their native structure during the isolation procedures. The structure of bacteriochlorophyll oligomers in chlorosomes was interspecifically compared, in bacteriochlorophyllc- and bacteriochlorophylle- synthesising bacteria. It appears that interactions assumed by the 9-keto carbonyl group are identical inChlorobium limicola, Chlorobium tepidum, andChlorobium phaeobacteroides. In the latter strain, the 3-formyl carbonyl group of bacteriochlorophylle is kept free from intermolecular interactions. By contrast, resonance Raman spectra unambiguously indicate that the structure of bacteriochlorophyll oligomers is slightly different in chlorosomes fromChloroflexus auranticus, either isolated or in the whole bacteria. 相似文献
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38.
Colocalization but differential regulation of neuronal NO synthase and nicotinic acetylcholine receptor in C2C12 myotubes 总被引:1,自引:0,他引:1
Ebert JG Zelenka M Gath I Gödtel-Armbrust U Förstermann U 《American journal of physiology. Cell physiology》2003,284(4):C1065-C1072
In mammalian skeletal muscle,neuronal-type nitric oxide synthase (nNOS) is found to be enriched atneuromuscular endplates. Here we demonstrate the colocalization of thenicotinic acetylcholine receptor (nAChR, stained with -bungarotoxin)and nNOS (stained with a specific antibody) in murineC2C12 myotubes. However, coimmunoprecipitation experiments demonstrated no evidence for a direct protein-protein association between the nAChR and nNOS in C2C12myotubes. An antibody to the 1-subunit of the nAChR didnot coprecipitate nNOS, and an nNOS-specific antibody did notprecipitate the 1-subunit of the nAChR. Treatment ofmice with bacterial LPS downregulated the expression of nNOS inskeletal muscle, and treatment of C2C12 cellswith bacterial LPS and interferon- markedly decreased nNOS mRNA andprotein expression. In contrast, mRNA and protein of the nAChR (-,-, and -subunits) remained unchanged at the mRNA and proteinlevels. These data demonstrate that nNOS and the nAChR are colocalizedin murine skeletal muscle and C2C12 cells but differ in their expressional regulation. 相似文献
39.
U Hofmann S Michaelis T Winckler J Wegener KH Feller 《Biosensors & bioelectronics》2013,39(1):156-162
This study presents the time-resolved detection of chemically induced stress upon intracellular signaling cascades by using genetically modified sensor cells based on the human keratinocyte cell line HaCaT. The cells were stably transfected with a HSP72-GFP reporter gene construct to create an optical sensor cell line expressing a stress-inducible reporter protein. The time- and dose-dependent performance of the sensor cells is demonstrated and discussed in comparison to a label-free impedimetric monitoring approach (electric cell-substrate impedance sensing, ECIS). Moreover, a microfluidic platform was established based on μSlidesI(0,4)Luer to allow for a convenient, sterile and incubator-independent time-lapse microscopic observation of the sensor cells. Cell growth was successfully achieved in this microfluidic setup and the cellular response to a cytotoxic substance could be followed in real-time and in a non-invasive, sensitive manner. This study paves the way for the development of micro-total analysis systems that combine optical and impedimetric readouts to enable an overall quantitative characterization of changes in cell metabolism and morphology as a response to toxin exposure. By recording multiple parameters, a detailed discrimination between competing stress- or growth-related mechanisms is possible, thereby presenting an entirely new in vitro alternative to skin irritation tests. 相似文献
40.
Susanne Schmitt Peter Tsai James Bell Jane Fromont Micha Ilan Niels Lindquist Thierry Perez Allen Rodrigo Peter J Schupp Jean Vacelet Nicole Webster Ute Hentschel Michael W Taylor 《The ISME journal》2012,6(3):564-576
Marine sponges are well known for their associations with highly diverse, yet very specific and often highly similar microbiota. The aim of this study was to identify potential bacterial sub-populations in relation to sponge phylogeny and sampling sites and to define the core bacterial community. 16S ribosomal RNA gene amplicon pyrosequencing was applied to 32 sponge species from eight locations around the world''s oceans, thereby generating 2567 operational taxonomic units (OTUs at the 97% sequence similarity level) in total and up to 364 different OTUs per sponge species. The taxonomic richness detected in this study comprised 25 bacterial phyla with Proteobacteria, Chloroflexi and Poribacteria being most diverse in sponges. Among these phyla were nine candidate phyla, six of them found for the first time in sponges. Similarity comparison of bacterial communities revealed no correlation with host phylogeny but a tropical sub-population in that tropical sponges have more similar bacterial communities to each other than to subtropical sponges. A minimal core bacterial community consisting of very few OTUs (97%, 95% and 90%) was found. These microbes have a global distribution and are probably acquired via environmental transmission. In contrast, a large species-specific bacterial community was detected, which is represented by OTUs present in only a single sponge species. The species-specific bacterial community is probably mainly vertically transmitted. It is proposed that different sponges contain different bacterial species, however, these bacteria are still closely related to each other explaining the observed similarity of bacterial communities in sponges in this and previous studies. This global analysis represents the most comprehensive study of bacterial symbionts in sponges to date and provides novel insights into the complex structure of these unique associations. 相似文献