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1.
The effects brought about by growing Allochromatium (Alc.) minutissimum in the presence of different concentrations of the carotenoid (Car) biosynthetic inhibitor diphenylamine (DPA) have been investigated. A decrease of Car content (from approximately 70% to >5%) in the membranes was accompanied by an increase of the percentage of (immature) Cars with reduced numbers of conjugated C=C bonds (from neurosporene to phytoene). Based on the obtained results and the analysis of literature data, the conclusion is reached that accumulation of phytoene during inhibition did not occur. Surprisingly, DPA inhibited phytoene synthase instead of phytoene desaturase as generally assumed. The distribution of Cars in peripheral antenna (LH2) complexes and their effect on the stability of LH2 has been investigated using absorption spectroscopy and HPLC analysis. Heterogeneity of Car composition and contents in the LH2 pool is revealed. The Car contents in LH2 varied widely from control levels to complete absence. According to common view, the assembly of LH2 occurs only in the presence of Cars. Here, we show that the LH2 can be assembled without any Cars. The presence of Cars, however, is important for structural stability of LH2 complexes. 相似文献
2.
‘Phytoantibodies’: a general vector for the expression of immunoglobulin domains in transgenic plants 总被引:6,自引:0,他引:6
Eugenio Benvenuto Ricardo J. Ordàs Raffaela Tavazza Giorgio Ancora Silvia Biocca Antonino Cattaneo Patrizia Galeffi 《Plant molecular biology》1991,17(4):865-874
Sequences encoding the immunoglobulin heavy-chain variable (VH) domains were engineered in a new general purpose vector to transform plants via Agrobacterium. The expression of an isolated VH domain (IVD) after introduction into the plant genome has been monitored by northern, western and immuno-histochemical analysis. Immunoblotting showed that the polypeptide was stably expressed and accounted for up to 1% of the soluble protein fraction. It is therefore proposed that single immunoglobulin domains of suitable specificity expressed in plants may constitute an effective system to inhibit the activity of molecules involved in plant pathology or plant development. 相似文献
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Epidemic transmission is one of the critical density-dependent mechanisms that affect species viability and dynamics. In a
predator-prey system, epidemic transmission can strongly affect the success probability of hunting, especially for social
animals. Predators, therefore, will suffer from the positive density-dependence, i.e., Allee effect, due to epidemic transmission
in the population. The rate of species contacting the epidemic, especially for those endangered or invasive, has largely increased
due to the habitat destruction caused by anthropogenic disturbance. Using ordinary differential equations and cellular automata,
we here explored the epidemic transmission in a predator-prey system. Results show that a moderate Allee effect will destabilize
the dynamics, but it is not true for the extreme Allee effect (weak or strong). The predator-prey dynamics amazingly stabilize
by the extreme Allee effect. Predators suffer the most from the epidemic disease at moderate transmission probability. Counter-intuitively,
habitat destruction will benefit the control of the epidemic disease. The demographic stochasticity dramatically influences
the spatial distribution of the system. The spatial distribution changes from oil-bubble-like (due to local interaction) to
aggregated spatially scattered points (due to local interaction and demographic stochasticity). It indicates the possibility
of using human disturbance in habitat as a potential epidemic-control method in conservation. 相似文献
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Shiringani AL Friedt W 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2011,123(6):999-1011
Compared to maize and temperate grasses, sorghum has received less attention in terms of improving cell wall components. The
objectives of this study were to identify quantitative trait loci (QTL) with main effects, epistatic and pleiotropic effects
along with QTL × environment (QE) interactions controlling fibre-related traits in sorghum. Neutral detergent fibre (NDF),
acid detergent fibre (ADF), acid detergent lignin (ADL), cellulose, hemicellulose, fresh leaf mass, stripped stalk mass, dry
stalk mass, fresh biomass and dry biomass were analysed from a population of 188 grain × sweet sorghum recombinant inbred
lines. A genetic map consisting of 157 DNA markers was constructed, and QTL were detected using composite interval mapping
(CIM). CIM detected more than 5 additive QTL per trait explaining 7.1–24.7% of the phenotypic variation. Abundant co-localization
of these QTL was observed across all chromosomes, and the highest cluster was identified on chromosome 6. Searching for candidate
genes using the confidence interval of our QTL clusters reveals that these clusters might comprise a set of genes that are
tightly linked. Some QTL showed multiple effects; however, the allele for each trait was favouring the parent with the increasing
effect. QE interactions were observed for QTL showing multiple effects. Additive × additive interaction was observed for 7
out of 10 traits, indicating the importance of epistatic analysis. However, the phenotypic variation explained by digenic
interactions was lower compared to the individual QTL. Our results indicate that various genetic components contribute to
fibre-related traits and should be considered during the enhancement of sorghum for lignocellulosic biomass. 相似文献
7.
Biophysical consequences of remodeling the neutral side chains of rhamnogalacturonan I in tubers of transgenic potatoes 总被引:1,自引:0,他引:1
Ulvskov P Wium H Bruce D Jørgensen B Qvist KB Skjøt M Hepworth D Borkhardt B Sørensen SO 《Planta》2005,220(4):609-620
Two lines of transgenic potato (Solanum tuberosum L.) plants modified in their cell wall structure were characterized and compared to wild type with regard to biomechanical properties in order to assign functional roles to the particular cell wall polysaccharides that were targeted by the genetic changes. The targeted polymer was rhamnogalacturonan I (RG-I), a complex pectic polysaccharide comprised of mainly neutral oligosaccharide side chains attached to a backbone of alternating rhamnosyl and galacturonosyl units. Tuber rhamnogalacturonan I molecules from the two transformed lines are reduced in linear galactans and branched arabinans, respectively. The transformed tuber tissues were found to be more brittle when subjected to uniaxial compression and the side-chain truncation was found to be correlated with the physical properties of the tissue. Interpretation of the force–deflection curves was aided by a mathematical model that describes the contribution of the cellulose microfibrils, and the results lead to the proposition that the pectic matrix plays a role in transmitting stresses to the load-bearing cellulose microfibrils and that even small changes to the rheological properties of the matrix have consequences for the biophysical properties of the wall. 相似文献
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Klaus Pfeifer Werner Kofler Walter Oberhuber 《Vegetation History and Archaeobotany》2005,14(3):211-220
Distinct radial growth reductions in Cembran pine (Pinus cembra L.) were studied at the timberline on Mt. Patscherkofel (2246 m a.s.l., Tyrol, Austria), which is situated in the inner-Alpine dry region of the Central Austrian Alps. Six timberline stands with different aspects were sampled and ring-width chronologies developed based on dendroecological techniques. Growth-climate relationships between residual chronologies and climate variables were explored using Pearson product-moment correlation coefficients. P. cembra growth at the timberline appears to be limited by cool summer (June-August) and previous autumn (September-October) temperatures and low precipitation in late winter (March). Timberline stands show concurrent growth depressions lasting ≥ 5 yr during the periods 1815–1823, 1851–1858 and 1913–1920, indicating growth depressions were steadily decreasing. Although evaluation of climate data revealed that these growth depressions can mainly be explained by occurrence of cold growing seasons and therefore the influence of recent climate warming on tree growth is plausible, an effect of tree ageing on climate sensitivity may also be involved. On the other hand, climate extremes do not inevitably induce growth responses as would be expected from growth-climate relationships. This is explained by the occurrence of synergistic and/or compensating effects of growth limiting climate variables and preconditioning of tree growth in previous years. Comparison of growth reductions with two published P. cembra timberline chronologies from inner-Alpine dry locations in the Eastern Alps revealed that investigated stands show the highest climate sensitivity during the last 200 yr. This difference in growth response to climate variability is most probably related to the special climate situation at Mt. Patscherkofel, which is exceptionally windy throughout the year and frequently exposed to warm dry winds (Föhn). 相似文献
10.
We conduct a mathematical study of a cellular automata model of the spread of the HIV virus in a lymph node. The model was
proposed by Zorzenon dos Santos and Coutinho and captures the unique time scale of the viral spread. We give some rigorous
mathematical results about the time scales and other dynamical aspects of the model as well as discuss parameter and model
changes and their consequences. 相似文献
11.
Hitomi Inagaki Satoshi Tsuzuki Takashi Iino Kazuo Inoue Tohru Fushiki 《Cytotechnology》2008,57(2):145-150
It has well been known that human and rodents exhibit a preference for fats. This suggests the existence of an orosensory
system responsible for the detection of dietary fats. A plasma membrane glycoprotein CD36, besides the role in the uptake
of long-chain fatty acids (LCFAs) as well as oxidized low-density lipoprotein (OxLDL) in a variety of cells, has been postulated
to be a candidate fat taste receptor on the tongue. Therefore, molecules that bind with CD36 to cause intracellular signaling
but have fewer calories could be substitutes for dietary fats. In the present study, we developed an in vitro system for the
screening of CD36 ligands using Chinese hamster ovary-K1 cells (CHO-K1) stably transfected with human or mouse CD36. When
incubated with OxLDL labeled with fluorescence dye, the fluorescence was much higher in the transfected CHO-K1 cells than
in non-transfected CHO-K1 cells. Incubation of the transfected cells with OxLDL caused a rapid phosphorylation of extracellular
signal regulated kinase, and the degree was significantly higher compared with that in non-transfected CHO-K1 cells. The expression
system using CHO-K1 cells could be a convenient tool to screen the novel ligands of CD36. 相似文献
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The geometry and dynamics of plasma?dust structures in a longitudinal magnetic field is studied experimentally. The structures are formed in a glow-discharge trap created in the double electric layer produced as a result of discharge narrowing by means of a dielectric insert introduced in the discharge tube. Studies of structures formed in the new type of glow-discharge trap are of interest from the standpoint of future experiments with complex plasmas in superstrong magnetic fields in which the dust component is magnetized. Different types of dielectric inserts were used: conical and plane ones with symmetric and asymmetric apertures. Conditions for the existence of stable dust structures are determined for dust grains of different density and different dispersity. According to the experimental results, the angular velocity of dust rotation is ≥10 s–1, which is the fastest type of dust motion for all types of discharges in a magnetic field. The rotation is interpreted by analyzing the dynamics of individual dust grains. 相似文献
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Fluctuating light intensity had a more significant impact on growth of gametophytes of transgenic Laminaria japonica in a 2500 ml bubble-column bioreactor than constant light intensity. A fluctuating light intensity between 10 and 110 μE m−2 s−1, with a photoperiod of 14 h:10 h light:dark, was the best regime for growth giving 1430 mg biomass l−1. 相似文献
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Arbuscular mycorrhizal infection changes the bacterial 16 S rDNA community composition in the rhizosphere of maize 总被引:4,自引:0,他引:4
Mycorrhizal and non-mycorrhizal (NM) maize plants were grown for 4 or 7 weeks in an autoclaved quartz sand-soil mix. Half of the NM plants were supplied with soluble P (NM-HP) while the other half (NM-LP), like the mycorrhizal plants, received poorly soluble Fe and Al phosphate. The mycorrhizal plants were inoculated with Glomus mosseae or G. intraradices. Soil bacteria and those associated with the mycorrhizal inoculum were reintroduced by adding a filtrate of a low P soil and of the inocula. At 4 and 7 weeks, plants were harvested and root samples were taken from the root tip (0-1 cm), the subapical zone (1-2 cm) and the mature root zone at the site of lateral root emergence. DNA was extracted from the roots with adhering soil. At both harvests, the NM-HP plants had higher shoot dry weight than the plants grown on poorly soluble P. Mycorrhizal infection of both fungi ranged between 78% and 93% and had no effect on shoot growth or shoot P content. Eubacterial community compositions were examined by polymerase chain reaction-denaturing gradient gel electrophoresis of 16 S rDNA, digitisation of the band patterns and multivariate analysis. The community composition changed with time and was root zone specific. The differences in bacterial community composition in the rhizosphere between the NM plants and the mycorrhizal plants were greater at 7 than at 4 weeks. The two fungi had similar bacterial communities after 4 weeks, but these differed after 7 weeks. The observed differences are probably due to changes in substrate composition and amount in the rhizosphere. 相似文献
17.
The acid-sensing ion channels (ASICs) are members of the DEG/ENaC superfamily of Na+ channels. Acid-gated cation currents have been detected in neurons from multiple regions of the brain including the cerebellum, but little is known about their molecular identity and function. Recently, one of ASICs (ASIC1a) was implicated in synaptic plasticity. In this study we examined the subcellular distribution of ASIC2a in rat cerebellum by immunostaining and confocal microscopy. Monoclonal antibodies for labeling of defined brain structures, for example, astroglia, Purkinje cell dendrites, nuclei, and presynaptic terminals were used for colocalization analyses. In the gray matter, the anti-ASIC2a antibody intensively stained dendrite branches of Purkinje cells evenly distributed throughout the entire molecular layer (ML). In the granule cell layer (GL), anti-ASIC2a antibody stained synaptic glomeruli. Neuronal localization of ASIC2a was confirmed by lack of co-staining with glial fibrillary acidic protein. Anti-ASIC2a staining in the ML colocalized with metabotropic glutamate receptor 1alpha (mGluR1alpha) in Purkinje cell dendrites and dendritic spines. Both proteins, mGluR1alpha and ASIC2a, were enriched in a crude synaptic membrane fraction prepared from cerebellum, suggesting synaptic expression of these proteins. Dual staining with anti-syntaxin 1A and anti-ASIC2a antibodies demonstrates characteristic complementary distribution of two proteins in both ML and GL. Because syntaxin 1A localized in presynaptic membranes and synaptic vesicles, complementary distribution with ASIC2a suggests postsynaptic localization of ASIC2a in these structures. This study shows specific localization of ASIC2a in both Purkinje and granule cell dendrites of the cerebellum and enrichment of ASIC2a in a crude cerebellar synaptic membrane fraction. The study is the first report of synaptic localization of ASIC2a in the CNS. The synaptic localization of ASIC2a in the cerebellum makes this channel a candidate for a role in motor coordination and learning. 相似文献
18.
Daria Maria Monti Fulvio Guglielmi Maria Monti Flora Cozzolino Silvia Torrassa Annalisa Relini Piero Pucci Angela Arciello Renata Piccoli 《European biophysics journal : EBJ》2010,39(9):1289-1299
In amyloidosis associated with apolipoprotein A-I (ApoA-I), heart amyloid deposits are mainly constituted by the 93-residue
ApoA-I N-terminal region. A recombinant form of the amyloidogenic polypeptide, named [1-93]ApoA-I, shares conformational properties
and aggregation propensity with its natural counterpart. The polypeptide, predominantly in a random coil state at pH 8.0,
following acidification to pH 4.0 adopts a helical/molten globule transient state, which leads to formation of aggregates.
Here we provide evidence that fibrillogenesis occurs also in physiologic-like conditions. At pH 6.4, [1-93]ApoA-I was found
to assume predominantly an α-helical state, which undergoes aggregation at 37°C over time at a lower rate than at pH 4.0.
After 7 days at pH 6.4, protofibrils were observed by atomic force microscopy (AFM). Using a multidisciplinary approach, including
circular dichroism (CD), fluorescence, electrophoretic, and AFM analyses, we investigated the effects of a lipid environment
on the conformational state and aggregation propensity of [1-93]ApoA-I. Following addition of the lipid-mimicking detergent
Triton X-100, the polypeptide was found to be in a helical state at both pH 8.0 and 6.4, with no conformational transition
occurring upon acidification. These helical conformers are stable and do not generate aggregated species, as observed by AFM
after 21 days. Similarly, analyses of the effects of cholesterol demonstrated that this natural ApoA-I ligand induces formation
of α-helix at physiological concentrations at both pH 8.0 and 6.4. Zwitterionic, positively charged, and negatively charged
liposomes were found to affect [1-93]ApoA-I conformation, inducing helical species. Our data support the idea that lipids
play a key role in [1-93]ApoA-I aggregation in vivo. 相似文献
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