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61.
UGT73C6 and UGT78D1, glycosyltransferases involved in flavonol glycoside biosynthesis in Arabidopsis thaliana 总被引:1,自引:0,他引:1
Jones P Messner B Nakajima J Schäffner AR Saito K 《The Journal of biological chemistry》2003,278(45):43910-43918
Flavonol glycosides constitute one of the most prominent plant natural product classes that accumulate in the model plant Arabidopsis thaliana. To date there are no reports of functionally characterized flavonoid glycosyltransferases in Arabidopsis, despite intensive research efforts aimed at both flavonoids and Arabidopsis. In this study, flavonol glycosyltransferases were considered in a functional genomics approach aimed at revealing genes involved in determining the flavonol-glycoside profile. Candidate glycosyltransferase-encoding genes were selected based on homology to other known flavonoid glycosyltransferases and two T-DNA knockout lines lacking flavonol-3-O-rhamnoside-7-O-rhamnosides (ugt78D1) and quercetin-3-O-rhamnoside-7-O-glucoside (ugt73C6 and ugt78D1) were identified. To confirm the in planta results, cDNAs encoding both UGT78D1 and UGT73C6 were expressed in vitro and analyzed for their qualitative substrate specificity. UGT78D1 catalyzed the transfer of rhamnose from UDP-rhamnose to the 3-OH position of quercetin and kaempferol, whereas UGT73C6 catalyzed the transfer of glucose from UDP-glucose to the 7-OH position of kaempferol-3-O-rhamnoside and quercetin-3-O-rhamnoside, respectively. The present results suggest that UGT78D1 and UGT73C6 should be classified as UDP-rhamnose:flavonol-3-Orhamnosyltransferase and UDP-glucose:flavonol-3-O-glycoside-7-O-glucosyltransferase, respectively. 相似文献
62.
Junt T Nakano H Dumrese T Kakiuchi T Odermatt B Zinkernagel RM Hengartner H Ludewig B 《Journal of immunology (Baltimore, Md. : 1950)》2002,168(12):6032-6040
The paucity of lymph node (LN) T cells (plt) mutation in mice results in strongly reduced T cell numbers in LNs and homing defects of both dendritic cells (DCs) and naive T cells. In this study, we investigated the functional significance of the plt phenotype for the generation of antiviral immune responses against cytopathic and noncytopathic viruses. We found that DC-CD8(+) T cell contacts and the initial priming of virus-specific T cells in plt/plt mice occurred mainly in the marginal zone of the spleen and in the superficial cortex of LNs. The magnitude of the initial response and the maintenance of protective memory responses in plt/plt mice was only slightly reduced compared with plt/+ controls. Furthermore, plt/plt mice mounted rapid neutralizing antiviral B cell responses and displayed normal Ig class switch. Our data indicate that the defective homing of DCs and naive T cells resulting from the plt/plt mutation results in a small, but not significant, effect on the induction of protective antiviral T and B cell immunity. Overall, we conclude that the spatial organization of secondary lymphoid T cell zones via the CCR7-CC chemokine ligand 19/CC chemokine ligand 21 pathway is not an absolute requirement for the initial priming and the maintenance of protective antiviral T and B cell responses. 相似文献
63.
Functional characteristics of corticolous lichens in the understory of a tropical lowland rain forest 总被引:1,自引:0,他引:1
In tropical lowland forests, corticolous crustose green algal lichens are abundant and highly diverse. This may be related to adaptation to prevailing microenvironmental conditions including, for example, high precipitation and low light intensities. In the understory of a tropical lowland rain forest in French Guiana, we studied the morphology of crustose green algal lichens and measured gas exchange and chlorophyll a fluorescence. We found that (i) periods of thallus suprasaturation with water were reduced by the presence of water-repelling surface structures of mycobiont hyphae at the thallus surface and the medulla; (ii) photosynthesis was adapted to the low light intensities present in the understory; and (iii) photosynthesis was rapidly activated in fluctuating light. The combination of these three mechanisms enables corticolous lichens to implement specific morphological and physiological strategies, which may favour growth in the limiting understory habitat of tropical lowland rain forests. 相似文献
64.
65.
Allan T. Green Mark Schlensog Leopoldo G. Sancho Barbro J. Winkler Fraser D. Broom Burkhard Schroeter 《Oecologia》2002,130(2):191-198
Photosystem activity status of the green algal (Pseudocyphellaria lividofusca) and cyanobacterial (P. knightii) components of a photosymbiodeme were continuously monitored in the field over a period of 35 days. The photosymbiodeme grew on a Nothofagus menziesii tree at Lake Waikaremoana, Urewera National Park, North Island, New Zealand. Two Mini-PAM fluorometers were placed so that the chlorophyll a fluorescence, temperature and PPFD (photosynthetically active photon flux density) could be recorded every 30 min for green algal and cyanobacterial parts of the thallus. Microclimate conditions were also recorded with a datalogger. The study confirmed the already known ability of green algal lichens to reactivate from high humidity alone whilst cyanobacterial species need liquid water, here obtained from rainfall. The photosystems of P. lividofusca were activated on every day and positive ETR (relative electron transport rate) occurred on all but 3 days. Activation level depended on the overnight relative humidity. P. knightii was activated and had positive ETR on only 13 days when rainfall had occurred. Both species were mostly inactive above 12°C but differed at low temperatures. P. knightii showed no activation at very low temperatures, -2 to 0°C, since these only occurred on clear, rain-free nights. PPFD was always very low, mostly below 80 µmol m-2 s-1, and both species were inactive at higher PPFD. The three-dimensional structure of the thallus seemed to contribute to the hydration. The cyanobacterial sectors were more appressed to the trunk and needed substantial rainfall to rewet whereas the green algal lobes were more distant from the trunk and this probably caused more rapid desiccation as well as lower temperatures. It is suggested that the longer active periods for photosynthesis by P. lividofusca are balanced by several factors: first, depressed net photosynthesis at high thallus water contents after rainfall, a feature not shown by P. knightii; second, possible lower maximal net photosynthetic rates; and third, the possibility of greater respiratory rates when thalli have been hydrated by high relative humidity. There is little evidence for high PPFD differently affecting the photosymbiodeme components since sustained, high PPFD did not occur. It has been reported that the photosystems of cyanobacterial species from photosymbiodemes can reactivate at high relative humidity but the results obtained here suggest that it is not ecologically significant. 相似文献
66.
Petteri Vihervaara Timo Kumpula Ari Tanskanen Benjamin Burkhard 《Ecological Complexity》2010,7(3):410-420
The concept of ecosystem services (ESs) is a relatively new scientific methodology, offering a possible approach to the prevention of ecological problems caused by human action and to the resolution of conflicts arising from land-use questions. Since ESs were launched as a major conceptual tool in the Millennium Ecosystem Assessment (MA, 2005), interest in them has been increasing. Despite the scientific as well as economic and political enthusiasm for the ES approach, only few case studies have as yet been published. We studied the interface between ESs and landscape planning in Forest Lapland, in northern Finland. In the article, we present a methodology and various databases which can be used in applied research on ESs. We classify the ESs offered by various biotopes of the study area, and examine the effects of different land-use forms on the provision of ESs. On the basis of our results, we suggest possible uses of the European CORINE land cover database in case studies. 相似文献
67.
Clonal descent and microevolution of Neisseria meningitidis during 30 years of epidemic spread 总被引:3,自引:0,他引:3
Giovanna Morelli Burkhard Malorny Kerstin Müller rea Seiler Jian-Fu Wang Jesus del Valle & Mark Achtman 《Molecular microbiology》1997,25(6):1047-1064
Serogroup A meningococci of subgroups III, IV-1 and IV-2 are probably descended from a common ancestor that existed in the nineteenth century. The 10.5 kb sequences spanning five distinct chromosomal loci, encoding cell-surface antigens, a secreted protease or housekeeping genes and intergenic regions, were almost identical in strains of those subgroups isolated in 1966, 1966 and 1917 respectively. During the subsequent two to three decades, all of these loci varied as a result of mutation, translocation or import of DNA from unrelated neisseriae. Thus, microevolution occurs frequently in naturally transformable bacteria. Many variants were isolated only once or within a single geographical location and disappeared thereafter. Other variants achieved genetic fixation within months or a few years. The speed with which sequence variation is either eliminated or fixed may reflect sequential bottlenecks associated with epidemic spread and contrasts with the results of phylogenetic analyses from bacteria that do not cause epidemics. 相似文献
68.
Burkhard Scherer Wolfgang Siess Peter C. Weber 《Prostaglandins & other lipid mediators》1977,13(6):1127-1139
The estimation of prostaglandin (PG) E2 and of PGF2α by radioimmunoassay is described in detail. PGE2 was measured after conversion to either PGB2 or PGF2α and the results compared to bioassay. The methods were used to follow the excretion of PGE2 and PGF2α after salt loading in rabbits. A marked reduction of PGE2 levels was observed at high NaCl intake, while PGF2α excretion remained unchanged. 相似文献
69.
Daniela Russo Maria Grazia Ortore Francesco Spinozzi Paolo Mariani Camille Loupiac Burkhard Annighofer Alessandro Paciaroni 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013
Methods
Combining small-angle X-ray and neutron scattering measurements with inelastic neutron scattering experiments, we investigated the impact of high hydrostatic pressure on the structure and dynamics of β-lactoglobulin (βLG) in aqueous solution.Background
βLG is a relatively small protein, which is predominantly dimeric in physiological conditions, but dissociates to monomer below about pH 3.Results
High-pressure structural results show that the dimer–monomer equilibrium, as well as the protein–protein interactions, are only slightly perturbed by pressure, and βLG unfolding is observed above a threshold value of 3000 bar. In the same range of pressure, dynamical results put in evidence a slowing down of the protein dynamics in the picosecond timescale and a loss of rigidity of the βLG structure. This dynamical behavior can be related to the onset of unfolding processes, probably promoted from water penetration in the hydrophobic cavity.General significance
Results suggest that density and compressibility of water molecules in contact with the protein are key parameters to regulate the protein flexibility. 相似文献70.
Degradation kinetics of biochar from pyrolysis and hydrothermal carbonization in temperate soils 总被引:2,自引:0,他引:2
Mo Bai Burkhard Wilske Franz Buegger Jürgen Esperschütz Claudia Irene Kammann Christian Eckhardt Martin Koestler Philipp Kraft Martin Bach Hans-Georg Frede Lutz Breuer 《Plant and Soil》2013,372(1-2):375-387