Showing papers by "Swedish University of Agricultural Sciences published in 1999"
Imperial College London1, University of Zurich2, University of Bayreuth3, Technical University of Lisbon4, University of the Aegean5, University College Cork6, Swedish University of Agricultural Sciences7, University of Basel8, École Normale Supérieure9, University of Sheffield10, Max Planck Society11
TL;DR: Niche complementarity and positive species interactions appear to play a role in generating diversity-productivity relationships within sites in addition to sampling from the species pool.
Abstract: At eight European field sites, the impact of loss of plant diversity on primary productivity was simulated by synthesizing grassland communities with different numbers of plant species. Results differed in detail at each location, but there was an overall log-linear reduction of average aboveground biomass with loss of species. For a given number of species, communities with fewer functional groups were less productive. These diversity effects occurred along with differences associated with species composition and geographic location. Niche complementarity and positive species interactions appear to play a role in generating diversity-productivity relationships within sites in addition to sampling from the species pool.
1,870 citations
TL;DR: Plants possess a mechanism to communicate excess excitation energy systemically, allowing them to mount a defense against further episodes of such stress, and systemic redox changes in the proximity of photosystem II, hydrogen peroxide, and the induction of antioxidant defenses are key determinants of this mechanism of systemic acquired acclimation.
Abstract: Land plants are sessile and have developed sophisticated mechanisms that allow for both immediate and acclimatory responses to changing environments. Partial exposure of low light-adapted Arabidopsis plants to excess light results in a systemic acclimation to excess excitation energy and consequent photooxidative stress in unexposed leaves. Thus, plants possess a mechanism to communicate excess excitation energy systemically, allowing them to mount a defense against further episodes of such stress. Systemic redox changes in the proximity of photosystem II, hydrogen peroxide, and the induction of antioxidant defenses are key determinants of this mechanism of systemic acquired acclimation.
910 citations
TL;DR: The x-ray structure of the FimC-FimH chaperone-adhesin complex from uropathogenic Escherichia coli at 2.5 angstrom resolution reveals the basis for carbohydrate recognition and for pilus assembly.
Abstract: Type 1 pili—adhesive fibers expressed in most members of the Enterobacteriaceae family—mediate binding to mannose receptors on host cells through the FimH adhesin. Pilus biogenesis proceeds by way of the chaperone/usher pathway. The x-ray structure of the FimC-FimH chaperone-adhesin complex from uropathogenic Escherichia coli at 2.5 angstrom resolution reveals the basis for carbohydrate recognition and for pilus assembly. The carboxyl-terminal pilin domain of FimH has an immunoglobulin-like fold, except that the seventh strand is missing, leaving part of the hydrophobic core exposed. A donor strand complementation mechanism in which the chaperone donates a strand to complete the pilin domain explains the basis for both chaperone function and pilus biogenesis.
615 citations
TL;DR: This paper addresses changes in plant gene expression induced by inoculation with plant-growth-promoting rhizobacteria (PGPR), suggesting that genes and/or gene classes associated with plant defenses against abiotic and biotic stress may be co-regulated.
Abstract: This paper addresses changes in plant gene expression induced by inoculation with plant-growth-promoting rhizobacteria (PGPR). A gnotobiotic system was established with Arabidopsis thaliana as model plant, and isolates of Paenibacillus polymyxa as PGPR. Subsequent challenge by either the pathogen Erwinia carotovora (biotic stress) or induction of drought (abiotic stress) indicated that inoculated plants were more resistant than control plants. With RNA differential display on parallel RNA preparations from P. polymyxa-treated or untreated plants, changes in gene expression were investigated. From a small number of candidate sequences obtained by this approach, one mRNA segment showed a strong inoculation-dependent increase in abundance. The corresponding gene was identified as ERD15, previously identified to be drought stress responsive. Quantification of mRNA levels of several stress-responsive genes indicated that P. polymyxa induced mild biotic stress. This suggests that genes and/or gene classes associated with plant defenses against abiotic and biotic stress may be co-regulated. Implications of the effects of PGPR on the induction of plant defense pathways are discussed.
546 citations
TL;DR: The results indicate that one site of physiological action for heparin could be inside connective-tissue-type mast cells, where its absence results in severe defects in the secretory granules.
Abstract: Heparin is a sulphated polysaccharide, synthesized exclusively by connective-tissue-type mast cells1 and stored in the secretory granules in complex with histamine and various mast-cell proteases2. Although heparin has long been used as an antithrombotic drug, endogenous heparin is not present in the blood, so it cannot have a physiological role in regulating blood coagulation. The biosynthesis of heparin involves a series of enzymatic reactions, including sulphation at various positions1,3. The initial modification step, catalysed by the enzyme glucosaminyl N -deacetylase/N -sulphotransferase-2, NDST-2 (4–7), is essential for the subsequent reactions. Here we report that mice carrying a targeted disruption of the gene encoding NDST-2 are unable to synthesize sulphated heparin. These NDST-2-deficient mice are viable and fertile but have fewer connective-tissue-type mast cells; these cells have an altered morphology and contain severely reduced amounts of histamine and mast-cell proteases. Our results indicate that one site of physiological action for heparin could be inside connective-tissue-type mast cells, where its absence results in severe defects in the secretory granules.
479 citations
TL;DR: It was concluded that the current model is adequate to model photosynthesis in elevated [CO2], and the underlying biochemistry of photosynthesis was affected, as shown by a down-regulation of the parameters Jmax and Vcmax of the order of 10%.
Abstract: The effects of elevated atmospheric CO2 concentration on growth of forest tree species are difficult to predict because practical limitations restrict experiments to much shorter than the average life-span of a tree. Long-term, processbased computer models must be used to extrapolate from shorter-term experiments. A key problem is to ensure a strong flow of information between experiments and models. In this study, meta-analysis techniques were used to summarize a suite of photosynthetic model parameters obtained from 15 field-based elevated [CO2] experiments on European forest tree species. The parameters studied are commonly used in modelling photosynthesis, and include observed light-saturated photosynthetic rates (Amax), the potential electron transport rate (Jmax), the maximum Rubisco activity (Vcmax) and leaf nitrogen concentration on mass (Nm) and area (Na) bases. Across all experiments, light-saturated photosynthesis was strongly stimulated by growth in elevated [CO2]. However, significant down-regulation of photosynthesis was also observed; when measured at the same CO2 concentration, photosynthesis was reduced by 10‐20%. The underlying biochemistry of photosynthesis was affected, as shown by a down-regulation of the parameters Jmax and Vcmax of the order of 10%. This reduction in Jmax and Vcmax was linked to the effects of elevated [CO2] on leaf nitrogen concentration. It was concluded that the current model is adequate to model photosynthesis in elevated [CO2]. Tables of model parameter values for different European forest species are given.
462 citations
TL;DR: Using consensus regions in gene sequences encoding the two forms of nitrite reductase (Nir), a key enzyme in the denitrification pathway, two sets of PCR primers to amplifycd1- and Cu-nir were designed and conserved.
Abstract: Using consensus regions in gene sequences encoding the two forms of nitrite reductase (Nir), a key enzyme in the denitrification pathway, we designed two sets of PCR primers to amplify cd1- and Cu-nir. The primers were evaluated by screening defined denitrifying strains, denitrifying isolates from wastewater treatment plants, and extracts from activated sludge. Sequence relationships of nir genes were also established. The cd1 primers were designed to amplify a 778 to 799-bp region of cd1-nir in the six published sequences. Likewise, the Cu primers amplified a 473-bp region in seven of the eight published Cu-nir sequences. Together, the two sets of PCR primers amplified nir genes in nine species within four genera, as well as in four of the seven sludge isolates. The primers did not amplify genes of nondenitrifying strains. The Cu primers amplified the expected fragment in all 13 sludge samples, but cd1-nir fragments were only obtained in five samples. PCR products of the expected sizes were verified as nir genes after hybridization to DNA probes, except in one case. The sequenced nir fragments were related to other nir sequences, demonstrating that the primers amplified the correct gene. The selected primer sites for Cu-nir were conserved, while broad-range primers targeting conserved regions of cd1-nir seem to be difficult to find. We also report on the existence of Cu-nir in Paracoccus denitrificans Pd1222.
426 citations
TL;DR: In this paper, the authors suggest that quality is the number of enzymatic steps required to release as carbon dioxide a carbon atom from an organic compound, and that the larger the steps the lower the quality of the carbon atom.
Abstract: Soil organic matter quality in the sense of how easily carbon in the soil organic matter can be mineralised is a major determinant of soil carbon storage and rate of mineralisation of nutrients. Its origin has so far remained elusive and a number of indices, such as C-to-N-ratio, lignin concentration and other combinations of chemical constituents have been used as substitutes for quality. We suggest here that quality is the number of enzymatic steps required to release as carbon dioxide a carbon atom from an organic compound . The larger the number of steps the lower is the quality of the carbon atom. Such a measure connects quality to thermodynamics. It also explains the rapid decrease in decomposition rate with decreasing quality suggested in the q-theory of organic matter dynamics and shows that the decomposition rate of low quality substrates has a stronger temperature dependence than that of high quality substrates.
415 citations
TL;DR: A paternally expressed QTL affecting skeletal and cardiac muscle mass in pigs maps to the IGF2 locus in a manner similar to that seen in humans.
Abstract: A paternally expressed QTL affecting skeletal and cardiac muscle mass in pigs maps to the IGF2 locus
361 citations
TL;DR: In this paper, two yield optimisation experiments in young stands of Norway spruce in northern and south-eastern Sweden are presented after 10 and 9 years' treatment, respectively.
347 citations
TL;DR: Iso-pentenyladenine (iP) was identified in the two defined media used for the cultivation of P. polymyxa, and small amounts of iP appeared in all three media, and iPR had disappeared from the yeast-containing medium, which indicates that the bacterium can metabolize cytokinins.
Abstract: The production of hormones has been suggested to be one of the mechanisms by which plant growth-promoting rhizobacteria (PGPR) stimulate plant growth. To evaluate whether the free-living soil bacterium, Paenibacillus polymyxa, releases the hormone group cytokinins and, if so, their identity, the content of cytokinins in the growth media, before and after cultivation of this bacterium, was determined by immunoaffinity chromatography (IAC). This method allows the isolation of almost all known cytokinins and their metabolites. Separation and characterization were done by high performance liquid chromatography (HPLC) with on-line ultraviolet (UV) detection, and final identification was by gas chromatography-mass spectrometry. Iso-pentenyladenine (iP) was identified in the two defined media used for the cultivation of P. polymyxa, but not earlier than at its late stationary growth. A third medium, supplemented with yeast extract, contained iso-pentenyladenine riboside (iPR) and some additional cytokinin-like substances before inoculation. When the same medium was sampled after the cultivation of P. polymyxa up to its logarithmic growth phase, the cytokinin concentration had decreased. After prolonged cultivation of P. polymyxa, small amounts of iP appeared in all three media, and iPR had disappeared from the yeast-containing medium, which indicates that the bacterium can metabolize cytokinins.
Journal Article•
TL;DR: A new function of DNA-anti-DNA Ab complexes, IFN-alpha induction, that might be important in the pathogenesis of SLE is identified.
Abstract: Anti-double-stranded DNA antibodies and immunostimulatory plasmid DNA in combination mimic the endogenous IFN-alpha inducer in systemic lupus erythematosus
TL;DR: In this paper, a two-coordinate binding environment with one oxygen atom and one sulfur atom at distances of 2.02 and 2.38 was found in the first coordination shell of Hg(II) complexed by humic acid.
Abstract: Analysis of Hg(II) complexed by a soil humic acid (HA) using synchrotron-based X-ray absorption spectroscopy (XAS) revealed the importance of reduces sulfur functional groups (thiol (R-SH) and disulfide (R-SS-R)/disulfane (R-SSH)) in humic substances in the complexation of Hg(II). A two-coordinate binding environment with one oxygen atom and one sulfur atom at distances of 2.02 and 2.38 {angstrom}, respectively, was found in the first coordination shell of Hg(II) complexed by humic acid. Model calculations show that a second coordination sphere could contain one carbon atom and a second sulfur atom at 2.78 and 2.93 {angstrom}, respectively. This suggests that in addition to thiol S, disulfide/disulfane S may be involved with the complexation of Hg(II) in soil organic matter. The appearance of carbon atom in the second coordination shell suggests that one O-containing ligand such as carboxyl and phenol ligands rather than H{sub 2}O molecule is bound to the Hg(II). The involvement of oxygen ligand in addition to the reduced S ligands in the complexation of Hg(II) is due to the low density of reduced S ligands in humic substances. The XAS results from this experiment provided direct molecular level evidence for the preference of reduced S functional groups over oxygen ligandsmore » by Hg(II) in the complexation with humic substances.« less
TL;DR: The reaction pathway for the formation of methane from acetate was investigated in sludge from 13 different biogas reactors and it was shown that methane formation by syntrophic acetate oxidation was the dominating mechanism for acetotrophic methanogenesis inSludge containing high levels of salts, mainly ammonium, and volatile acids.
Journal Article•
TL;DR: The present review deals with the mechanism of uptake and transport of metals in the olfactory system, and it is considered that the occupational neurotoxicity of inhaled manganese may be related to an uptake of the metal into the brain via the Olfactory pathways.
Abstract: In the olfactory epithelium the dendrites of the primary olfactory neurons are in contact with the nasal lumen, and via the axons these neurons are also connected to the olfactory bulbs of the brain. Materials which come into contact with the olfactory epithelium can be taken up in the primary olfactory neurons and be transported to the olfactory bulbs and even further into other areas of the brain. The present review deals with the mechanism of uptake and transport of metals in the olfactory system. Metals discussed are mainly manganese, cadmium, nickel and mercury. Among the metals so far examined, manganese has been found to have a unique capacity to be taken up via the olfactory pathways and pass transneuronally to other parts of the brain. It is considered that the occupational neurotoxicity of inhaled manganese may be related to an uptake of the metal into the brain via the olfactory pathways. Studies with nickel indicate that this metal, following a transport to the terminal parts of the primary olfactory neurons in the glomeruli of the bulbs, slowly passes to secondary and tertiary olfactory neurons. Cadmium and mercury are transported along the primary olfactory neurons to their terminations in the olfactory bulbs, but these metals appear unable to continue along secondary olfactory neurons. Occupational inhalation of nickel or cadmium can be toxic to the olfactory sense. It is not yet known whether mercury is toxic to the olfactory system in mammals, but this metal is known to alter olfaction and olfactory-related behaviour in fish. Data in the literature dealing with a potential olfactory-related neurotoxicity of aluminum are also discussed in the paper.
TL;DR: It is found that patients with active SLE patients and their sera frequently induced production of IFN‐α in cultures of peripheral blood mononuclear cells from healthy blood donors, especially when the PBMC were costimulated with the cytokines IFn‐α2b and granulocyte‐macrophage colony‐stimulating factor (GM‐CSF).
Abstract: Patients with systemic lupus erythematosus (SLE) have a circulating inducer of interferon-alpha (IFN-alpha) production acting on leucocytes resembling immature dendritic cells
TL;DR: This study suggests that during the early stages of succession the microbial community cannot incorporate all the added substrate into its biomass, but rapidly increases its respiration, and the later-stage microbial community remains in an “energy-saving state,” accumulating C to its biomass.
Abstract: We studied microbial community composition in a primary successional chronosequence on the forefront of Lyman Glacier, Washington, United States. We sampled microbial communities in soil from nonvegetated areas and under the canopies of mycorrhizal and nonmycorrhizal plants from 20- to 80-year-old zones along the successional gradient. Three independent measures of microbial biomass were used: substrate-induced respiration (SIR), phospholipid fatty acid (PLFA) analysis, and direct microscopic counts. All methods indicated that biomass increased over successional time in the nonvegetated soil. PLFA analysis indicated that the microbial biomass was greater under the plant canopies than in the nonvegetated soils; the microbial community composition was clearly different between these two types of soils. Over the successional gradient, the microbial community shifted from bacterial-dominated to fungal-dominated. Microbial respiration increased while specific activity (respiration per unit biomass) decreased in nonvegetated soils over the successional gradient. We proposed and evaluated new parameters for estimating the C use efficiency of the soil microbial community: “Max” indicates the maximal respiration rate and “Acc” the total C released from the sample after a standard amount of substrate is added. These, as well as the corresponding specific activities (calculated as Max and Acc per unit biomass), decreased sharply over the successional gradient. Our study suggests that during the early stages of succession the microbial community cannot incorporate all the added substrate into its biomass, but rapidly increases its respiration. The later-stage microbial community cannot reach as high a rate of respiration per unit biomass but remains in an “energy-saving state,” accumulating C to its biomass.
TL;DR: The number of severe feather pecks received was significantly related with feather damage at all ages; however, no relation with gentle feather peck received was found.
Abstract: The aim of this experiment was to describe and examine the relationship between pecks received by individual birds and the feather and skin damage of those birds at different ages. The effect of group size was also studied. Laying hens were raised in floor pens in group sizes of 15, 30, 60 and 120 birds, each with 4 replicates. Behavioural observations were performed at the ages of 22, 27, 32 and 37 weeks. Detailed feather scoring was carried out at the ages of 18, 23, 28 and 33 weeks. Behavioural observations focused on the number of feather pecks (gentle and severe) and aggressive pecks received, and on the part of the body that was pecked. Scoring of feather and skin damage focused on the same 11 parts of the body. Increasing numbers of aggressive pecks received were associated with decreased body weight and increased feather damage at the ages of 27 and 32 weeks. The number of severe feather pecks received was significantly related with feather damage at all ages; however, no relation with gentle feather pecks received was found. Group size had a significant effect on feather condition, with large group sizes having most feather damage.
TL;DR: Life-history traits of Rana temporaria were studied in an alpine French population and in the literature, and mean adult body length was greater in females than in males.
Abstract: Life-history traits of Rana temporaria were studied in an alpine French population and in the literature. In the living frogs, mean adult body length was greater in females than in males. Sexual dimorphism in body length was 0.109 using Lovich & Gibbon's (1992) formula, but tended to decrease with age. Age of adult frogs was assessed by skeletochronology, and age distribution was not significantly different between the sexes (range 4–15 years in males, 5–12 in females). Adult survival rate was about 0.80 in both sexes. Once maturity was reached, the total expected longevity was 6.1 years in males and 5.5 years in females. Age and body length were positively correlated in both sexes. The growth coefficient (K) was 0.47 in males, and 0.55 in females, mainly reflected as faster female growth between metamorphosis and maturation. Growth rate generally decreased before sexual maturity was reached. On average, females matured 1 year later than males. Newly metamorphosed froglets averaged 16.1 mm. When combined with published data from 12 European populations of R. temporaria, the following general patterns emerge. Mean adult body length is significantly greater in females than in males, and mean body length at maturity shows the same trend. Variation in mean age at maturity and in longevity are considerable among populations, but there is no consistent trend of difference between the sexes. Body length and age are correlated between males and females, i.e. populations with long and old males also have long and old females. Mean adult body length, mean body length at maturity, age at maturity, and longevity all increase with decreasing activity period. Adults exposed to a short activity period grow slower but attain a greater final length. Sexual dimorphism in body length generally increases as activity period gets shorter. Polygons describing norms of reaction for maturation in an age–body length space are similarly oriented in both sexes, but with a wider range in age for females. This is due to an older age at maturity for females in populations with a short activity season. Mean age and length at maturity are significantly correlated in females, but not in males, partly supporting the hypothesis that this species has a flexible pattern of development. Observed patterns are compared with predictions from life-history theory, paying attention to all life stages and environmental variation.
TL;DR: Species richness was not affected by fire, whereas the evenness of species distributions of mycorrhizas was lower in the burned stands, suggesting that EM fungal communities show a high degree of continuity following low‐intensity wildfires.
Abstract: This study was conducted to evaluate the effects of wildfires on ectomycorrhizal (EM) fungal communities in Scots pine (Pinus sylvestris) stands. Below- and above-ground communities were analysed in terms of species richness and evenness by examining mycorrhizas and sporocarps in a chronosequence of burned stands in comparison with adjacent unburned late-successional stands. The internal transcribed spacer (ITS)-region (rDNA) of mycobionts from single mycorrhizas was digested with three restriction enzymes and compared with an ITS–restriction fragment length polymorphism (RFLP) reference database of EM sporocarps. Spatial variation seemed to be more prominent than the effects of fire on the EM fungal species composition. Most of the common species tended to be found in all sites, suggesting that EM fungal communities show a high degree of continuity following low-intensity wildfires. Species richness was not affected by fire, whereas the evenness of species distributions of mycorrhizas was lower in the burned stands. The diversity of EM fungi was relatively high considering that there were only three EM tree species present in the stands. In total, 135 EM taxa were identified on the basis of their RFLP patterns; 66 species were recorded as sporocarps, but only 11 of these were also recorded as mycorrhizas. The species composition of the below-ground community of EM fungi did not reflect that of the sporocarps produced. EM fungal species present in our ITS–RFLP reference database accounted for 54–99% of the total sporocarp production in the stands, but only 0–32% of the mycorrhizal abundance.
TL;DR: The principles and properties of the available tests, which are discussed in relation to different applications, are reviewed.
TL;DR: In this article, the authors used analyses of lead concentrations and stable lead isotopes (206Pb/207Pb ratios) of annually laminated sediments from four lakes in northern Sweden (∼65° N) to provide a decadal record of atmospheric lead pollution for the last 3000 years.
Abstract: There is great concern for contamination of sensitive ecosystems in high latitudes by long-range transport of heavy metals and other pollutants derived from industrial areas in lower latitudes. Atmospheric pollution of heavy metals has a very long history, and since metals accumulate in the environment, understanding of present-day pollution conditions requires knowledge of past atmospheric deposition. We use analyses of lead concentrations and stable lead isotopes (206Pb/207Pb ratios) of annually laminated sediments from four lakes in northern Sweden (∼65° N) to provide a decadal record of atmospheric lead pollution for the last 3000 years. There is a clear signal in the sediments of airborne pollution from Greek and Roman cultures 2000 years ago, followed by a period of “clean” conditions 400−900 A.D. From 900 A.D. there was a conspicuous, permanent increase in atmospheric lead pollution fallout. The sediments reveal peaks in atmospheric lead pollution at 1200 and 1530 A.D. comparable to present-day lev...
TL;DR: Phylogenetic analyses based on these four sequences gave consistent results and strongly supported the monophyly hypothesis for the genus Pinus and its two recognized subgenera.
Abstract: The sequence divergence of chloroplast rbcL, matK, trnV intron, and rpl20-rps18 spacer regions was analyzed among 32 Pinus species and representatives of six other genera in Pinaceae. The total aligned sequence length is 3570 bp. Of the four sequences examined, matK evolved much faster than rbcL in Pinus and in other Pinaceae genera. The two noncoding regions did not show more divergence than the two coding regions, especially within each Pinus subgenus. Phylogenetic analyses based on these four sequences gave consistent results and strongly supported the monophyly hypothesis for the genus Pinus and its two recognized subgenera. Pinus krempfii,the two-flat-needle pine endemic to Vietnam, was placed in subgen. Strobus and showed closer affinity to subsect. Gerardianae. The ancient character of sect. Parrya is further confirmed. However, monophyly of the sect. Parrya is not supported by our data. Among the Eurasian pines of subgen. Pinus, Mediterranean pines formed one clade and the Asian members of subsect. Sylvestres formed another. The Himalayan P. roxburghii showed considerable divergence from all the other hard pines from both regions. Pinus merkusii was distinctly separated from all the Asian members of subsect. Sylvestres. The implications of our results for Pinus classification are discussed.
TL;DR: In this article, the effect of soil thawing and soil temperature on postwinter recovery of photosynthetic capacity was studied, during late spring and early summer, in Norway spruce stands in northern Sweden.
Abstract: The effect of soil thawing and soil temperature on postwinter recovery of photosynthetic capacity was studied, during late spring and early summer, in Norway spruce stands in northern Sweden. Soil temperature was manipulated by means of buried heating cables. The warming treatment was applied to stands with low (natural) and high (fertilized) availability of nutrients. Soil thawing, expressed as water availability, was followed by means of sapflow in stems, and shoot water potentials. The recovery of photosynthetic capacity was assessed by measuring the rate of light-saturated photosynthesis (Amax), and maximum photochemical efficiency of photosystem II in detached shoots, and chlorophyll a fluorescence. Accumulation of starch reserves in the needles was followed as an independent indicator of photosynthetic performance in situ. Snowmelt and soil thawing occurred more than one month earlier in heated than in unheated plots. This was expressed both as sapflow and as differences in shoot water potential between treatments. During May, the rates of Amax were significantly higher on heated than on control plots. The effect of soil warming on Amax was, however, not reflected in chlorophyll fluorescence or needle starch content. The time course of the recovery of photosynthetic capacity was mainly controlled by mean air temperature and by the frequency of severe night frosts, and to a lesser extent by earlier soil thawing and higher soil temperatures.
TL;DR: It is found that the activation level of AKIN immunocomplexes is higher in the prl1 mutant, suggesting that PRL1 is a negative regulator of Arabidopsis SNF1 homologs, and the observation that PR l1 is an inhibitor of AKin10 and AKIN11 in vitro is supported.
Abstract: Mutation of the PRL1 gene, encoding a regulatory WD protein, results in glucose hypersensitivity and derepression of glucose-regulated genes in Arabidopsis. The yeast SNF1 protein kinase, a key regulator of glucose signaling, and Arabidopsis SNF1 homologs AKIN10 and AKIN11, which can complement the Δsnf1 mutation, were found to interact with an N-terminal domain of the PRL1 protein in the two-hybrid system and in vitro. AKIN10 and AKIN11 suppress the yeast Δsnf4 mutation and interact with the SNF4p-activating subunit of SNF1. PRL1 and SNF4 bind independently to adjacent C-terminal domains of AKIN10 and AKIN11, and these protein interactions are negatively regulated by glucose in yeast. AKIN10 and AKIN11, purified in fusion with glutathione S-transferase, undergo autophosphorylation and phosphorylate a peptide of sucrose phosphate synthase in vitro. The sucrose phosphate synthase-peptide kinase activity of AKIN complexes detected by immunoprecipitation is stimulated by sucrose in light-grown Arabidopsis plants. In comparison with wild type, the activation level of AKIN immunocomplexes is higher in the prl1 mutant, suggesting that PRL1 is a negative regulator of Arabidopsis SNF1 homologs. This conclusion is supported by the observation that PRL1 is an inhibitor of AKIN10 and AKIN11 in vitro.
TL;DR: Estimates ofSexual selection gradients on male secondary sexual plumage characters resulting from extrapair paternity in the collared flycatcher Ficedula albicollis are reported, and the importance of this form of sexual selection with that resulting from variation in mate fecundity is compared.
TL;DR: Support that soil was the major contamination source was found by comparison of genetic fingerprints by random amplified polymorphic DNA polymerase chain reaction of isolates of B. cereus from soil and milk and by teat cleansing experiments, which resulted in reduced contamination levels in milk.
TL;DR: Natural variations in stable carbon isotope ratios (delta(13)C) is used as an approach to distinguish between fungal decomposers and symbiotic mycorrhizal fungal species in the rich sporocarp flora of temperate forests.
Abstract: Fungi play crucial roles in the biogeochemistry of terrestrial ecosystems, most notably as saprophytes decomposing organic matter and as mycorrhizal fungi enhancing plant nutrient uptake. However, a recurrent problem in fungal ecology is to establish the trophic status of species in the field. Our interpretations and conclusions are too often based on extrapolations from laboratory microcosm experiments or on anecdotal field evidence. Here, we used natural variations in stable carbon isotope ratios (δ13C) as an approach to distinguish between fungal decomposers and symbiotic mycorrhizal fungal species in the rich sporocarp flora (our sample contains 135 species) of temperate forests. We also demonstrated that host-specific mycorrhizal fungi that receive C from overstorey or understorey tree species differ in their δ13C. The many promiscuous mycorrhizal fungi, associated with and connecting several tree hosts, were calculated to receive 57–100% of their C from overstorey trees. Thus, overstorey trees also support, partly or wholly, the nutrient-absorbing mycelia of their alleged competitors, the understorey trees.
TL;DR: Reducing insect populations resulted in greater evenness of relative plant species abundances and revealed a strong positive relationship between plant species richness and above-ground biomass, suggesting that insects can alter relationships between plant diversity and ecosystem processes through all three mechanisms.
Abstract: This study examined whether insects can alter relationships between plant species diversity and ecosystem function in grassland communities, by (i) altering biomass across a plant diversity gradient, (ii) altering relative abundances of plant species, or (iii) altering ecosystem function directly. We measured herbivore damage on seminatural grassland plots planted with 1, 2, 4, 8, or 12 plant species, and compared plant biomass in a subset of these plots with replicates in which insect levels were reduced. Plant biomass and herbivore damage increased with species richness. Reducing insect populations resulted in greater evenness of relative plant species abundances and revealed a strong positive relationship between plant species richness and above-ground biomass. Reducing insects also changed the relationship between plant species richness and decomposition. Plant species mixtures and their relative abundances partially explained plant biomass results, but not decomposition results. These results suggest that insects can alter relationships between plant diversity and ecosystem processes through all three mechanisms.
TL;DR: Although it was not significant, early access to litter had a non-significant tendency to reduce the prevalence of feather pecking, and no other factor had a significant effect in these models.
Abstract: 1. Effects of rearing conditions on behavioural problems were investigated in a cohort study of commercial flocks of laying hens housed in 2 different loose housing systems. The sample population was 120 385 laying hens from 59 flocks of various hybrids at 21 different farms. 2. Logistic regression modelling was used to test the effects of selected factors on floor eggs, cloacal cannibalism and feather pecking. In addition to early access to perches or litter, models included hybrid, stocking density, group size, housing system, age at delivery, identical housing system at the rearing farm and at the production farm and, in models for floor eggs and cloacal cannibalism, nest area per hen. Odds ratios were calculated from the results of the models to allow risk assessment. 3. No significant correlations were found between the prevalence of floor eggs, cloacal cannibalism and feather pecking. 4. Access to perches from not later than the 4th week of age decreased the prevalence of floor eggs during the period from start-of-lay until 35 weeks of age, odds ratio 0-30 (P<0-001). Furthermore, early access to perches decreased the prevalence of cloacal cannibalism during the production period, odds ratio 0-46 (P=0.03). 5. No other factor had a significant effect in these models. Although it was not significant, early access to litter had a non-significant tendency to reduce the prevalence of feather pecking.