Root system development of Lotus corniculatus L. in calcareous sands with embedded finer-textured fragments in an initial soil

Background and aims

In post mining landscapes as in the Lusatian region (Brandenburg, Germany), Pleistocene coarse-textured, sandy sediments are used for soil rehabilitation and land reclamation. The homogeneously-appearing initial soils are characterized by finer-textured soil clumps (fragments) of different sizes that are embedded in a sandy matrix. These soils with typical local-scale heterogeneity may serve as a model for studying how spatially-distributed soil fragments may be utilized by pioneering plant species. The aim of this study was to gain insight into the physical and chemical properties of sandy matrix and fragments that could possibly explain why embedded fragment may act as hot spots for root growth.

Methods

In 2009, three soil monoliths of dimension 50 cm?×?50 cm?×?50 cm that were exclusively vegetated by Lotus corniculatus L. planted in 2008 were studied. Each layer of 10 cm was sampled successively using a cubic metal frame with 10 cm edge length (25 samples per layer each with a volume of 1 l). The samples were analyzed for root biomass, root lengths and diameter, and for chemical and physical properties of sandy matrix and fragments.

Results

Bulk density, water contents, total carbon, total nitrogen, and plant available calcium contents were higher for the fragments compared to the sandy matrix. The roots of L. corniculatus were heterogeneously distributed in the monoliths. The root density distributions for the 1 L samples indicated a positive influence of fragments on directed root growth. Fragments embedded in the sandy matrix were found to be strongly penetrated by roots despite their relatively high bulk density. The presence of fragments also led to an increased root biomass in the sandy matrix in the direct vicinity of fragments. Such direct effects on root development were accompanied by more indirect effects by locally-elevated moisture and nutrient contents.

Conclusion

The results suggest that finer-textured fragments embedded in coarser-textured sediments, can have favorable effect on plant and root development during the initial stages of establishment of vegetation cover. The fragments can act as water and nutrient hot spots to improve supply of pioneering plants especially in coarse-textured soil. The existence of small-scale heterogeneities owing to incomplete sediment mixing e.g., in soil reclamation, could be generally important for controlling the speed and direction of early plants-establishment, for instance, in the succession of post-mining areas.     

Expression of PSACH-associated mutant COMP in tendon fibroblasts leads to increased apoptotic cell death irrespective of the secretory characteristics of mutant COMP.

OBJECTIVE: Pseudoachondroplasia (PSACH) is a dominantly inherited chondrodysplasia associated with mutations of cartilage oligomeric matrix protein (COMP), characterized clinically by disproportionate dwarfism and laxity of joints and ligaments. Studies in chondrocytes and cartilage biopsies suggest that the cartilage disease is caused by retention of mutant COMP in the endoplasmic reticulum of chondrocytes and by disruption of the collagen network of the extracellular matrix. The pathogenesis of the tendon disease remains unclear in the absence of a cell culture model, with available tendon biopsies leading to conflicting results with respect to the intracellular retention of mutant COMP. METHODS: We established a cell culture model using adenoviral gene transfer in tendon fibroblast cultures. We compared the effect of expression of three PSACH-associated COMP mutants and the wildtype protein on COMP secretion, matrix composition and cellular viability. RESULTS: Our results show that mutants D475N and D469Delta are retained within the endoplasmic reticulum of tendon cells similar to what is known from chondrocytes, whereas mutant H587R is secreted like wildtype COMP. In spite of this difference, the collagen I matrix formed in culture appears disturbed for all three mutants. All COMP-mutants induce apoptotic cell death irrespective of their differing secretion patterns. CONCLUSION: Pathogenic pathways leading to tendon disease in humans appear to be heterogeneous between different COMP mutants.     

In vitro cell growth of marine archaeal-bacterial consortia during anaerobic oxidation of methane with sulfate

Anoxic sediment from a methane hydrate area (Hydrate Ridge, north-east Pacific; water depth 780 m) was incubated in a long-term laboratory experiment with semi-continuous supply of pressurized [1.4 MPa (14 atm)] methane and sulfate to attempt in vitro propagation of the indigenous consortia of archaea (ANME-2) and bacteria (DSS, Desulfosarcina/Desulfococcus cluster) to which anaerobic oxidation of methane (AOM) with sulfate has been attributed. During 24 months of incubation, the rate of AOM (measured as methane-dependent sulfide formation) increased from 20 to 230 micromol day(-1) (g sediment dry weight)(-1) and the number of aggregates (determined by microscopic counts) from 0.5 x 10(8) to 5.7 x 10(8) (g sediment dry weight)(-1). Fluorescence in situ hybridization targeting 16S rRNA of both partners showed that the newly grown consortia contained central archaeal clusters and peripheral bacterial layers, both with the same morphology and phylogenetic affiliation as in the original sediment. The development of the AOM rate and the total consortia biovolume over time indicated that the consortia grew with a doubling time of approximately 7 months (growth rate 0.003 day(-1)) under the given conditions. The molar growth yield of AOM was approximately 0.6 g cell dry weight (mol CH(4) oxidized)(-1); according to this, only 1% of the consumed methane is channelled into synthesis of consortia biomass. Concentrations of biomarker lipids previously attributed to ANME-2 archaea (e.g. sn-2-hydroxyarchaeol, archaeol, crocetane, pentamethylicosatriene) and Desulfosarcina-like bacteria [e.g. hexadecenoic-11 acid (16:1omega5c), 11,12-methylene-hexadecanoic acid (cy17:0omega5,6)] strongly increased over time (some of them over-proportionally to consortia biovolume), suggesting that they are useful biomarkers to detect active anaerobic methanotrophic consortia in sediments.     

New nitrogen mustards structurally related to (L)-carnitine

Enantiopure nitrogen mustards which mimic (L)-carnitine framework are prepared by a multi-step synthesis from the (R)-di-tert-butyl malate and their antitumor properties evaluated.     

Conformational states of the Rapana thomasiana hemocyanin and its substructures studied by dynamic light scattering and time-resolved fluorescence spectroscopy

Hemocyanins are dioxygen-transporting proteins freely dissolved in the hemolymph of mollusks and arthropods. Dynamic light scattering and time-resolved fluorescence measurements show that the oxygenated and apo-forms of the Rapana thomasiana hemocyanin, its structural subunits RtH1 and RtH2, and those of the functional unit RtH2e, exist in different conformations. The oxygenated respiratory proteins are less compact and more asymmetric than the respective apo-forms. Different conformational states were also observed for the R. thomasiana hemocyanin in the absence and presence of an allosteric regulator. The results are in agreement with a molecular mechanism for cooperative dioxygen binding in molluscan hemocyanins including transfer of conformational changes from one functional unit to another.     

Sequence-variant repeats of MUC1 show higher conformational flexibility, are less densely O-glycosylated and induce differential B lymphocyte responses

The human epithelial cancer mucin MUC1 is able to break tolerance and to induce humoral immune responses in healthy subjects and in cancer patients. We recently showed that clusters of sequence-variant repeats are interspersed in the repeat domain of MUC1 at high frequency, which should contribute to the structural and immunological features of the mucin. Here we elucidated the potential effects exerted by sequence-variant repeats on their O-glycosylation. Evidence from in vitro glycosylation with polypeptide N-acetylgalactosaminyltransferases GalNAc-T1 and GalNAc-T2 in concert with mass spectrometric analyses of in vivo glycosylated MUC1 probes from transiently transfected HEK293 cells indicated reduced glycosylation densities of repeats with three concerted replacements: AHGVTSAPESRPAPGSTAPA. The Pro to Ala replacement in STAPA exerts not only proximal effects on the ppGalNAc-T2 preferred site at -3 and -4, but also more distant effects on the ppGalNAc-T1 preferred site at -15 (TSAPESRPAPGSTAPA). We also examined the conformational changes of MUC1 glycopeptides induced by the concerted DT to ES replacements and revealed a higher conformational flexibility of ES/P peptides compared to DT/P peptides. Differences in conformational flexibilities and in O-glycosylation densities could underlie the observed differential humoral responses in humans. We were able to show that the natural immunoglobulin G (IgG) responses to the repeat domain of MUC1 in sera from nonmalignant control subjects are preferentially directed to variant repeat clusters. In contrast, the IgG response in patients with adenocarcinoma shifted to higher frequencies of preferential DTR peptide binding.     

Pathways of chaperone-mediated protein folding in the cytosol

Cells are faced with the task of folding thousands of different polypeptides into a wide range of conformations. For many proteins, the folding process requires the action of molecular chaperones. In the cytosol of prokaryotic and eukaryotic cells, molecular chaperones of different structural classes form a network of pathways that can handle substrate polypeptides from the point of initial synthesis on ribosomes to the final stages of folding.     

Rapid microtubule bundling and stabilization by the Streptococcus pneumoniae neurotoxin pneumolysin in a cholesterol-dependent, non-lytic and Src-kinase dependent manner inhibits intracellular trafficking

Streptococcus pneumoniae is the most frequent cause of bacterial meningitis, leading to permanent neurological damage in 30% and lethal outcome in 25% of patients. The cholesterol-dependent cytolysin pneumolysin is a major virulence factor of S. pneumoniae . It produces rapid cell lysis at higher concentrations or apoptosis at lower concentrations. Here, we show that sublytic amounts of pneumolysin produce rapid bundling and increased acetylation of microtubules (signs of excessive microtubule stabilization) in various types of cells – neuroblastoma cells, fibroblasts and primary astrocytes. The bundling started perinuclearly and extended peripherally towards the membrane. The effect was not connected to pneumolysin's capacity to mediate calcium influx, macropore formation, apoptosis, or RhoA and Rac1 activation. Cellular cholesterol depletion and neutralization of the toxin by pre-incubation with cholesterol completely inhibited the microtubule phenotype. Pharmacological inhibition of Src-family kinases diminished microtubule bundling, suggesting their involvement in the process. The relevance of microtubule stabilization to meningitis was confirmed in an experimental pneumococcal meningitis animal model, where increased acetylation was observed. Live imaging experiments demonstrated a decrease in organelle motility after toxin challenge in a manner comparable to the microtubule-stabilizing agent taxol, thus proposing a possible pathogenic mechanism that might contribute to the CNS damage in pneumococcal meningitis.