Refine
Has Fulltext
- no (158)
Year of publication
- 2011 (158) (remove)
Document Type
- Article (158) (remove)
Is part of the Bibliography
- yes (158)
Keywords
- Photosynthesis (4)
- Arabidopsis thaliana (3)
- climate change (3)
- AFLP (2)
- Biodiversity exploratories (2)
- Chlamydomonas acidophila (2)
- Cytosolic heteroglycans (2)
- Grazing (2)
- Habitat fragmentation (2)
- Mowing (2)
- Phosphorus limitation (2)
- Population genetics (2)
- Sexual selection (2)
- Species richness (2)
- Starch metabolism (2)
- functional traits (2)
- gene expression (2)
- latitude (2)
- local adaptation (2)
- metabolomics (2)
- plant population and community dynamics (2)
- potassium channel (2)
- 2D gel electrophoresis (1)
- 3D structure (1)
- 4-Fluoroaniline (1)
- Above-belowground interactions (1)
- Acacia erioloba (1)
- Acidification (1)
- Acidophilic algae (1)
- Acrocephalus paludicola (1)
- Activation of dendritic cells (1)
- Aggression (1)
- Agrocybe aegerita peroxygenase (1)
- Algebraic geometry (1)
- Alien species (1)
- Allee effects (1)
- Allometry (1)
- Aniline (1)
- Aniline biosensor (1)
- Anser albifrons (1)
- Arabidopsis (1)
- Arabidopsis lyrata (1)
- Asparagales (1)
- Au nanoparticles (1)
- Auditory cortex (1)
- Bait lamina (1)
- Bengal tiger (1)
- Bifurcation parameters (1)
- Biodiversity ecosystem function research (1)
- Bioelectrocatalysis (1)
- Biogeography (1)
- Bioinorganic chemistry (1)
- Biomass (1)
- Biomaterial (1)
- Biosensors (1)
- Body mass-abundance (1)
- Body size (1)
- Boolean algebra (1)
- Boosted regression tree (1)
- Boraginaceae (1)
- Bottom-up effect (1)
- Branta canadensis (1)
- Breeding system (1)
- Bromus hordeaceus (1)
- Browsing damage (1)
- Browsing pressure (1)
- C-reactive protein (1)
- C3 photosynthesis (1)
- CART (1)
- CD spectroscopy (1)
- CO(2) (1)
- Calcareous grassland (1)
- Calvin cycle (1)
- Canada goose (1)
- Carbohydrate binding proteins (1)
- Carbohydrate-binding agents (1)
- Carbon concentrating mechanism (1)
- Carollia perspicillata (1)
- Caspian Sea (1)
- Catechol (1)
- Cellular P quota (1)
- Centrosome (1)
- Character evolution (1)
- Character mapping (1)
- Cherry (1)
- Chlamydomonas (1)
- Chlorophyceae (1)
- Chlorophyll fluorescence (1)
- Chlorophyll metabolism (1)
- Chronotopy (1)
- Climate warming (1)
- Clonal growth (1)
- Co-existence (1)
- Coexistence (1)
- Colimitation (1)
- Collection date (1)
- Communication networks (1)
- Comparative ecology (1)
- Complexity (1)
- Composite (1)
- Conductivity (1)
- Connectance (1)
- Conservation (1)
- Correlation networks (1)
- Cytochrome c (1)
- Cytochrome oxidase I (1)
- Cytosolic glucosyl transferases (1)
- DTOF (1)
- Daphnia (1)
- Dark-induced senescence (1)
- DdCP224 (1)
- Decomposition (1)
- Desiccation (1)
- Diatoms (1)
- Dictyostelium (1)
- Dielectrophoresis (1)
- Direct electron transfer (1)
- Disease (1)
- Dispersal (1)
- Disposable (1)
- Distribution (1)
- Disturbance (1)
- Djoudj National Park (1)
- Dry grasslands (1)
- Dynamic modeling (1)
- Dynamical global vegetation model (1)
- Echolocation (1)
- Effective pathlength (1)
- Electrochemical switch (1)
- Elevation (1)
- Enzyme models (1)
- Establishment (1)
- European rabbit (1)
- Eutrophication (1)
- Expression profiling (1)
- External structural measures (1)
- Extinction cascades (1)
- Extinction risk (1)
- FRET (1)
- FTIR spectroscopy (1)
- Faecal pellet group count (1)
- Fallow deer (1)
- Fatty acid composition (1)
- Female choice (1)
- Fertilization (1)
- Fitness components (1)
- Floristics (1)
- Fluid streaming (1)
- Food quality (1)
- Food web robustness (1)
- Forest management (1)
- Fruit maturity (1)
- Functional ecology (1)
- Gelatin (1)
- Gene function prediction (1)
- Gene tree-species tree reconciliation (1)
- Generality (1)
- Genetic drift (1)
- Genetic variability (1)
- Genotype by environment (1)
- Geothermobarometric P-T (1)
- Glucose (1)
- Goldenrod (1)
- Gondwana (1)
- Grewia flava (1)
- Gustafson-Kessel (1)
- HIV (1)
- Hawaii (1)
- Heliconiaceae (1)
- Heterotrophic tissues (1)
- Hierarchical partitioning of variance (1)
- Hill exponent (1)
- Historical ecology (1)
- Home-site advantage (1)
- Human carrying capacity (1)
- Human impact (1)
- Human mesenchymal stem cells (1)
- Hydrogel (1)
- Hydroxyapatite (1)
- In vitro expression (1)
- In vitro immunization (1)
- Indium tin oxide (1)
- Individual-based model (1)
- Induction of antibody responses (1)
- Infection (1)
- Injection-molding (1)
- Interaction of T and B cells with antigen-presenting cells (1)
- Interference (1)
- Interspecific interaction (1)
- Intraspecific functional variability (1)
- Invasive plant species (1)
- Iron toxicity (1)
- Isolation by distance (1)
- Kernel estimation (1)
- Keystone species (1)
- LEA protein (1)
- Lake Naivasha (1)
- Lake sediments (1)
- Lambert-Beer (1)
- Land use (1)
- Large ungulates (1)
- Leishmania (1)
- Light reactions (1)
- Long-term change (1)
- Macarorchestia remyi (1)
- Maltose metabolism (1)
- Mate choice copying (1)
- Mate preferences (1)
- Mathematical model (1)
- Maximum population (1)
- Metabolite profiles (1)
- Micro-algae (1)
- Microarray (1)
- Microbicide (1)
- Microperoxidase-11 (1)
- Microsatellites (1)
- Microtubules (1)
- Mixotrophy (1)
- Molybdenum (1)
- Monazite growth (1)
- Moving window (1)
- Multi-grain sampling (1)
- Multistationarity (1)
- NAC transcription factor (1)
- NIR (1)
- NMR (1)
- Nanobead (1)
- Nanoparticles (1)
- Natural selection (1)
- Neckbanding (1)
- Nest predation (1)
- Nitrogen (1)
- Non-independent mate choice (1)
- Non-invasive (1)
- Non-photochemical quenching of chlorophyll fluorescence (1)
- Noninnocence (1)
- Nonphotochemical quenching of chlorophyll fluorescence (1)
- Nutrient limitation (1)
- Oceanic distribution (1)
- Ochromonas spp. (1)
- Optical device (1)
- Oryctolagus cuniculus (1)
- Oxytricha spp. (1)
- PLS (1)
- PSI (plastic sphere of influence) (1)
- Palaeozoic metamorphism New Zealand (1)
- Peru (1)
- Phenotypic plasticity (1)
- Phosphorus (1)
- Photoautotrophic tissues (1)
- Photooxidation (1)
- Photoprotection (1)
- Phylogenetics (1)
- Phytoplankton (1)
- Pigments (1)
- Plant diversity (1)
- Plant functional groups (1)
- Plant functional hairs (1)
- Plant functional types (1)
- Plant interactions (1)
- Plant invasions (1)
- Plant traits (1)
- Plastics (1)
- Poecilia mexicana (1)
- Point density (1)
- Pollen-ovule ratio (1)
- Pollination experiment (1)
- Pollination syndromes (1)
- Potential natural vegetation (1)
- Pre-existing bias (1)
- Printhead (1)
- Productivity (1)
- Protein expression (1)
- Protein purification (1)
- Protein secondary structure (1)
- Protein-membrane interactions (1)
- Pteronotus parnellii (1)
- RNA (1)
- Random Forests (1)
- Reciprocal transplant (1)
- Red deer (1)
- Regreening (1)
- Regression tree analysis (1)
- Ripeness (1)
- Rodents (1)
- Rotifera (1)
- Rubisco (1)
- ScHxk2 (1)
- Scale-dependence (1)
- Scattering (1)
- Schmettau map (1)
- Seasonality (1)
- Secondary extinctions (1)
- Seed dormancy (1)
- Seed longevity (1)
- Sensor fusion (1)
- Shrews (1)
- Size structure (1)
- Small mammals (1)
- Social environment (1)
- Soil fauna (1)
- Solanum lycopersicum (1)
- Somateria mollissima (1)
- South Africa (1)
- South African Cape Floristic Region (1)
- Space use (1)
- Spatial association (1)
- Spatial autocorrelation (1)
- Spatial distribution (1)
- Spatial scale (1)
- Spatially explicit model (1)
- Species density (1)
- Species loss (1)
- Specific leaf area (1)
- Spectroscopy (1)
- Sperm competition (1)
- Stability (1)
- Succession (1)
- Synergy (1)
- TACC (1)
- TIRF (1)
- Talitridae (1)
- Tenofovir (1)
- Terai Arc (1)
- Time-resolved spectroscopy (1)
- Top-down effect (1)
- Toponymy (1)
- Transcription factor (1)
- Transductive learning (1)
- Trophic interactions (1)
- U87 glioma cells (1)
- Unconscious selection (1)
- Uniform sampling (1)
- Vegetation map (1)
- Vegetative regeneration (1)
- Veronica (1)
- Virus (1)
- Vis (1)
- Voles (1)
- Vulnerability (1)
- White-fronted goose (1)
- Wiegand-Moloney O-ring statistics (1)
- Wild geese (1)
- Winter (1)
- Winter biology (1)
- Within-species variability (1)
- Woody plant (1)
- X-ray absorption spectroscopy (1)
- XMAP215 (1)
- Zea mays (1)
- acidophily (1)
- adaptation (1)
- adaptation of conservation strategies (1)
- adaptive management (1)
- age-dependent dispersal (1)
- airborne (1)
- algae (1)
- allelic variants (1)
- allopatric speciation (1)
- ancient forest (1)
- animal personality (1)
- attitude (1)
- backbone conformation (1)
- bioelectrochemistry (1)
- biotic interactions (1)
- biotin (1)
- blood (1)
- body composition (1)
- calcium sensor (1)
- catalytic antibody (1)
- cellulose (1)
- channel gating (1)
- ciliates (1)
- clinical diagnostics (1)
- clonality (1)
- cluster analysis (1)
- clustering (1)
- colimitation (1)
- colonization capacity (1)
- common garden experiment (1)
- comparative co-expression analysis (1)
- comparative genomics (1)
- comparative proteomics (1)
- compensatory dynamics (1)
- competition (1)
- competition intensity (1)
- competitive performance (1)
- conservation planning (1)
- conservation targets (1)
- crustacean (1)
- cytochrome c (1)
- data integration (1)
- density-dependent dispersal (1)
- development (1)
- device (1)
- dimorphism (1)
- dispersal of cryptogams (1)
- diversity (1)
- drafted genomes (1)
- dynamic light scattering (1)
- ecological stoichiometry (1)
- eider duck (1)
- elderly (1)
- electrode (1)
- enemy release (1)
- energy limiting condition (1)
- energy metabolism (1)
- entropic enzymes (1)
- environmental forcing (1)
- epilimnic methane peak (1)
- epizoochory (1)
- essential resources (1)
- everything is everywhere (1)
- female choice (1)
- fitness (1)
- flagellates (1)
- fleshy fruit ripening (1)
- fluorescein (1)
- food quality (1)
- forest herbs (1)
- forest understorey (1)
- freshwater microbes (1)
- functional diversity (1)
- fuzzy c-means (1)
- g3p (1)
- geitonogamy (1)
- gene duplication (1)
- gene flow (1)
- gene regulatory network (1)
- gene tree parsimony (1)
- genetic variability (1)
- genome partitioning (1)
- glycobiology (1)
- grazing (1)
- growth (1)
- habitat fragmentation (1)
- habitat loss (1)
- habitat-species interaction (1)
- handgrip strength (1)
- haplotype (1)
- heterosis (1)
- hierarchical framework (1)
- histidin (1)
- hummingbird pollination (1)
- hydrogen peroxide (1)
- imbalanced diet (1)
- immunoassay (1)
- indirect fitness (1)
- indium tin oxide ITO (1)
- intraspecific brood parasitism (1)
- invasive species (1)
- landscape structure (1)
- leaf area (1)
- leaf senescence (1)
- life history attributes (1)
- life-history traits (1)
- lipoxygenase (1)
- luminescence lifetime (1)
- machine learning (1)
- management (1)
- mass accuracy (1)
- mesoporous materials (1)
- meta-analysis (1)
- metabolic regulation (1)
- metapopulation dynamics (1)
- methanogens (1)
- microarray (1)
- microsatellites (1)
- modeling (1)
- modularity (1)
- morphological plasticity (1)
- mtDNA haplotype (1)
- native range (1)
- naturalized species (1)
- new species (1)
- non-independent mate choice (1)
- nuclear proteins (1)
- nucleus (1)
- nutrient analogues (1)
- nutrient limitation (1)
- nutrient stoichiometry (1)
- nutritional ecology (1)
- open-top chambers (1)
- opening strength (1)
- oxidoreductase (1)
- p-Aminophenol (1)
- paleoecology (1)
- phagemid display (1)
- phenotype (1)
- phenotypic plasticity (1)
- phenotyping (1)
- phloem reloading (1)
- phylogenomics (1)
- phytoplankton (1)
- plant density (1)
- plant invasions (1)
- plant phylogeny (1)
- plant-soil feedbacks (1)
- plant-water relations (1)
- plasma (1)
- pollen limitation (1)
- pollination experiment (1)
- population dynamics (1)
- population genetic structure (1)
- population history (1)
- positive selection (1)
- posttranslational regulation (1)
- pot experiment (1)
- potato tuber (1)
- predator recognition (1)
- prediction (1)
- process-based models (1)
- protease inhibitor (1)
- protein design (1)
- protein engineering (1)
- protein isoforms (1)
- protein kinase (1)
- proteomics (1)
- quantitative RT-PCR (1)
- quantum dots (1)
- radio telemetry (1)
- rain forest understory (1)
- random matrix theory (1)
- relatedness (1)
- resazurin (1)
- resorufin (1)
- school children (1)
- scramble competition (1)
- secondary cell wall (1)
- secondary succession (1)
- seed nitrogen (1)
- seed predation (1)
- seed provisioning (1)
- selection (1)
- serotinous Proteaceae (1)
- sexual reproduction (1)
- shoot fragments (1)
- signal transduction (1)
- skeletal robustness (1)
- soil inoculation (1)
- soil sterilization (1)
- spatial scales (1)
- stability (1)
- stable isotopes (1)
- streptavidin (1)
- structure prediction (1)
- subcellular localization (1)
- support vector machine (1)
- synchrony (1)
- taxonomy (1)
- temporal dynamics (1)
- terbium (1)
- threats to biological diversity (1)
- threshold behavior (1)
- torque (1)
- transcription factor (1)
- transition intermediate (1)
- transsaharan migrant (1)
- trnS-G spacer (1)
- urban forest (1)
- vegetation structure (1)
- vegetative reproduction (1)
- well-being (1)
- wilderness (1)
- wing polyphenism (1)
- wood anemone (1)
- zone-of-influence model (1)
- zooplankton (1)
Institute
- Institut für Biochemie und Biologie (158) (remove)
Ten square-based pyramidal molybdenum complexes with different sulfur donor ligands, that is, a variety of dithiolenes and sulfides, were prepared, which mimic coordination motifs of the molybdenum cofactors of molybdenum-dependent oxidoreductases. The model compounds were investigated by Mo K-edge X-ray absorption spectroscopy (XAS) and (with one exception) their molecular structures were analyzed by X-ray diffraction to derive detailed information on bond lengths and geometries of the first coordination shell of molybdenum. Only small variations in Mo=O and Mo-S bond lengths and their respective coordination angles were observed for all complexes including those containing Mo(CO)(2) or Mo(mu-S)(2)Mo motifs. XAS analysis (edge energy) revealed higher relative oxidation levels in the molybdenum ion in compounds with innocent sulfur-based ligands relative to those in dithiolene complexes, which are known to exhibit noninnocence, that is, donation of substantial electron density from ligand to metal. In addition, longer average Mo-S and Mo=O bonds and consequently lower.(Mo=O) stretching frequencies in the IR spectra were observed for complexes with dithiolene-derived ligands. The results emphasize that the noninnocent character of the dithiolene ligand influences the electronic structure of the model compounds, but does not significantly affect their metal coordination geometry, which is largely determined by the Mo(IV) or (V) ion itself. The latter conclusion also holds for the molybdenum site geometries in the oxidized Mo-VI cofactor of DMSO reductase and the reduced Mo-IV cofactor of arsenite oxidase. The innocent behavior of the dithiolene molybdopterin ligands observed in the enzymes is likely to be related to cofactor-protein interactions.
Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase; EC 4.1.1.39), the most abundant protein in nature, catalyzes the assimilation of CO(2) (worldwide about 10(11) t each year) by carboxylation of ribulose-1,5-bisphosphate. It is a hexadecamer consisting of eight large and eight small subunits. Although the Rubisco large subunit (rbcL) is encoded by a single gene on the multicopy chloroplast genome, the Rubisco small subunits (rbcS) are encoded by a family of nuclear genes. In Arabidopsis thaliana, the rbcS gene family comprises four members, that is, rbcS-1a, rbcS-1b, rbcS-2b, and rbcS-3b. We sequenced all Rubisco genes in 26 worldwide distributed A. thaliana accessions. In three of these accessions, we detected a gene duplication/loss event, where rbcS-1b was lost and substituted by a duplicate of rbcS-2b (called rbcS-2b*). By screening 74 additional accessions using a specific polymerase chain reaction assay, we detected five additional accessions with this duplication/loss event. In summary, we found the gene duplication/loss in 8 of 100 A. thaliana accessions, namely, Bch, Bu, Bur, Cvi, Fei, Lm, Sha, and Sorbo. We sequenced an about 1-kb promoter region for all Rubisco genes as well. This analysis revealed that the gene duplication/loss event was associated with promoter alterations (two insertions of 450 and 850 bp, one deletion of 730 bp) in rbcS-2b and a promoter deletion (2.3 kb) in rbcS-2b* in all eight affected accessions. The substitution of rbcS-1b by a duplicate of rbcS-2b (i.e., rbcS-2b*) might be caused by gene conversion. All four Rubisco genes evolve under purifying selection, as expected for central genes of the highly conserved photosystem of green plants. We inferred a single positive selected site, a tyrosine to aspartic acid substitution at position 72 in rbcS-1b. Exactly the same substitution compromises carboxylase activity in the cyanobacterium Anacystis nidulans. In A. thaliana, this substitution is associated with an inferred recombination. Functional implications of the substitution remain to be evaluated.
Our goal was to reconstruct the late eighteenth century forest vegetation of the Prignitz region (NE Germany) at a scale of 1:50,000. We also wanted to relate the historical forest vegetation to the actual and potential natural vegetation. For these purposes, we selected 15 woody species and transferred relevant data found in historical records from various sources together with the recent localities of (very) old individuals belonging to these woody species into ArcView GIS. Following multi-step data processing including the generation of a point density layer using a moving window with kernel estimation and derivation of vegetation units applying Boolean algebra rules together with information on site conditions, we derived 17 forest communities corresponding to the potential natural vegetation. We were able to reconstruct the historical forest vegetation for 90% of the forest area ca. 1780. Only two of the 17 forest communities covered large parts of the forested area. The oak forest with Agrostis capillaris covered about 44% of the total forest area, and alder forests on fenland made up about 37%. Oak-hornbeam forests with Stellaria holostea comprised slightly less than 6% of the forest area, while all other forest communities comprised less than 1%. The historical forest vegetation is more similar to the potential forest vegetation and quite different from the actual forest vegetation because coniferous tree species currently cover approximately two-thirds of the actual forest area. The most beneficial result of this study is the map of high-resolution historical vegetation units that may serve as the basis for various further studies, e.g., modelling long-term changes in biodiversity at the landscape scale.
To gain a deeper understanding of the mechanisms behind biomass accumulation, it is important to study plant growth behavior. Manually phenotyping large sets of plants requires important human resources and expertise and is typically not feasible for detection of weak growth phenotypes. Here, we established an automated growth phenotyping pipeline for Arabidopsis thaliana to aid researchers in comparing growth behaviors of different genotypes.
The analysis pipeline includes automated image analysis of two-dimensional digital plant images and evaluation of manually annotated information of growth stages. It employs linear mixed-effects models to quantify genotype effects on total rosette area and relative leaf growth rate (RLGR) and ANOVAs to quantify effects on developmental times.
Using the system, a single researcher can phenotype up to 7000 plants d(-1). Technical variance is very low (typically < 2%). We show quantitative results for the growth-impaired starch-excessmutant sex4-3 and the growth-enhancedmutant grf9.
We show that recordings of environmental and developmental variables reduce noise levels in the phenotyping datasets significantly and that careful examination of predictor variables (such as d after sowing or germination) is crucial to avoid exaggerations of recorded phenotypes and thus biased conclusions.
The nutrient concentration in seeds determines many aspects of potential success of the sexual reproductive phase of plants, including the seed predation probability, efficiency of seed dispersal and seedling performance. Despite considerable research interest in latitudinal gradients of foliar nutrients, a similar gradient for seeds remains unexplored. We investigated a potential latitudinal gradient in seed nutrient concentrations within the widespread European understorey forest herb Anemone nemorosa L. We sampled seeds of A. nemorosa in 15 populations along a 1900-km long latitudinal gradient at three to seven seed collection dates post-anthesis and investigated the relative effects of growing degree-hours > 5 degrees C, soil characteristics and latitude on seed nutrient concentrations. Seed nitrogen, nitrogen:phosphorus ratio and calcium concentration decreased towards northern latitudes, while carbon:nitrogen ratios increased. When taking differences in growing degree-hours and measured soil characteristics into account and only considering the most mature seeds, the latitudinal decline remained particularly significant for seed nitrogen concentration. We argue that the decline in seed nitrogen concentration can be attributed to northward decreasing seed provisioning due to lower soil nitrogen availability or greater investment in clonal reproduction. This pattern may have large implications for the reproductive performance of this forest herb as the degree of seed provisioning ultimately co-determines seedling survival and reproductive success.
Under natural conditions, plants are exposed to rapidly changing light intensities. To acclimate to such fluctuations, plants have evolved adaptive mechanisms that optimally exploit available light energy and simultaneously minimise damage of the photosynthetic apparatus through excess light. An important mechanism is the dissipation of excess excitation energy as heat which can be measured as nonphotochemical quenching of chlorophyll fluorescence (NPQ). In this paper, we present a highly simplified mathematical model that captures essential experimentally observed features of the short term adaptive quenching dynamics. We investigate the stationary and dynamic behaviour of the model and systematically analyse the dependence of characteristic system properties on key parameters such as rate constants and pool sizes. Comparing simulations with experimental data allows to derive conclusions about the validity of the simplifying assumptions and we further propose hypotheses regarding the role of the xanthophyll cycle in NPQ. We envisage that the presented theoretical description of the light reactions in conjunction with short term adaptive processes serves as a basis for the development of more detailed mechanistic models by which the molecular mechanisms of NPQ can be theoretically studied.
The preparation of porous, i.e., high surface area electrodes from transparent conducting oxides, is a valuable goal in materials chemistry as such electrodes can enable further development of optoelectronic, electrocatalytic, or bioelectronic devices. In this work the first tin-rich mesoporous indium tin oxide is prepared using the molecular heterobimetallic single-source precursor, indium tin tris-tert-butoxide, together with an appropriate structure-directing template, yielding materials with high surface areas and tailorable pore size. The resulting mesoporous tin-rich ITO films show a high and durable electrical conductivity and transparency, making them interesting materials for hosting electroactive biomolecules such as proteins. In fact, its unique performance in bioelectronic applications has been demonstrated by immobilization of high amounts of cytochrome c into the mesoporous film which undergo redox processes directly with the conductive electrode material.
Nostoc punctiforme is a filamentous cyanobacterium capable of forming symbiotic associations with a wide range of plants. The strain exhibits extensive phenotypic characteristics and can differentiate three mutually exclusive cell types: nitrogen-fixing heterocysts, motile hormogonia and spore-like akinetes. Here, we provide evidence for a crucial role of an extracellular metabolite in balancing cellular differentiation. Insertional mutagenesis of a gene of the polyketide synthase gene cluster pks2 led to the accumulation of short filaments carrying mostly terminal heterocysts under diazotrophic conditions. The mutant has a strong tendency to form biofilms on solid surfaces as well as in liquid culture. The pks2-strain keeps forming hormogonia over the entire growth curve and shows an early onset of akinete formation. We could isolate two fractions of the wildtype supernatant that could restore the capability to form long filaments with intercalary heterocysts. Growth of the mutant cells in the neighbourhood of wild-type cells on plates led to a reciprocal influence and a partial reconstruction of wild-type and mutant phenotype respectively. We postulate that extracellular metabolites of Nostoc punctiforme act as life cycle governing factors (LCGFs) and that the ratio between distinct factors may guide the differentiation into different life stages.
Active transport of NaCl across thick ascending limb (TAL) epithelium is accomplished by Na+, K+,2Cl(-) cotransporter (NKCC2). The activity of NKCC2 is determined by vasopressin (AVP) or intracellular chloride concentration and includes its amino-terminal phosphorylation. Co-expressed Tamm-Horsfall protein (THP) has been proposed to interact with NKCC2. We hypothesized that THP modulates NKCC2 activity in TAL. THP-deficient mice (THP-/-) showed an increased abundance of intracellular NKCC2 located in subapical vesicles (+47% compared with wild type (WT) mice), whereas base-line phosphorylation of NKCC2 was significantly decreased (-49% compared with WT mice), suggesting reduced activity of the transporter in the absence of THP. Cultured TAL cells with low endogenous THP levels and low base-line phosphorylation of NKCC2 displayed sharp increases in NKCC2 phosphorylation (+38%) along with a significant change of intracellular chloride concentration upon transfection with THP. In NKCC2-expressing frog oocytes, co-injection with THP cRNA significantly enhanced the activation of NKCC2 under low chloride hypotonic stress (+112% versus +235%). Short term (30 min) stimulation of the vasopressin V2 receptor pathway by V2 receptor agonist (deamino-cis-D-Arg vasopressin) resulted in enhanced NKCC2 phosphorylation in WT mice and cultured TAL cells transfected with THP, whereas in the absence of THP, NKCC2 phosphorylation upon deamino-cis-D-Arg vasopressin was blunted in both systems. Attenuated effects of furosemide along with functional and structural adaptation of the distal convoluted tubule in THP-/- mice supported the notion that NaCl reabsorption was impaired in TAL lacking THP. In summary, these results are compatible with a permissive role for THP in the modulation of NKCC2-dependent TAL salt reabsorptive function.
Intraspecific brood parasitism (IBP) is a remarkable phenomenon by which parasitic females can increase their reproductive output by laying eggs in conspecific females' nests in addition to incubating eggs in their own nest. Kin selection could explain the tolerance, or even the selective advantage, of IBP, but different models of IBP based on game theory yield contradicting predictions. Our analyses of seven polymorphic autosomal microsatellites in two eider duck colonies indicate that relatedness between host and parasitizing females is significantly higher than the background relatedness within the colony. This result is unlikely to be a by-product of relatives nesting in close vicinity, as nest distance and genetic identity are not correlated. For eider females that had been ring-marked during the decades prior to our study, our analyses indicate that (i) the average age of parasitized females is higher than the age of nonparasitized females, (ii) the percentage of nests with alien eggs increases with the age of nesting females, (iii) the level of IBP increases with the host females' age, and (iv) the number of own eggs in the nest of parasitized females significantly decreases with age. IBP may allow those older females unable to produce as many eggs as they can incubate to gain indirect fitness without impairing their direct fitness: genetically related females specialize in their energy allocation, with young females producing more eggs than they can incubate and entrusting these to their older relatives. Intraspecific brood parasitism in ducks may constitute cooperation among generations of closely related females.