Showing papers by "University of Hohenheim published in 2009"

IntCal13 and Marine13 radiocarbon age calibration curves 0-50,000 years cal BP

Abstract: Additional co-authors: TJ Heaton, AG Hogg, KA Hughen, KF Kaiser, B Kromer, SW Manning, RW Reimer, DA Richards, JR Southon, S Talamo, CSM Turney, J van der Plicht, CE Weyhenmeyer

Genome sequence and analysis of the Irish potato famine pathogen Phytophthora infestans.

Abstract: Phytophthora infestans is the most destructive pathogen of potato and a model organism for the oomycetes, a distinct lineage of fungus-like eukaryotes that are related to organisms such as brown algae and diatoms. As the agent of the Irish potato famine in the mid-nineteenth century, P. infestans has had a tremendous effect on human history, resulting in famine and population displacement(1). To this day, it affects world agriculture by causing the most destructive disease of potato, the fourth largest food crop and a critical alternative to the major cereal crops for feeding the world's population(1). Current annual worldwide potato crop losses due to late blight are conservatively estimated at $6.7 billion(2). Management of this devastating pathogen is challenged by its remarkable speed of adaptation to control strategies such as genetically resistant cultivars(3,4). Here we report the sequence of the P. infestans genome, which at similar to 240 megabases (Mb) is by far the largest and most complex genome sequenced so far in the chromalveolates. Its expansion results from a proliferation of repetitive DNA accounting for similar to 74% of the genome. Comparison with two other Phytophthora genomes showed rapid turnover and extensive expansion of specific families of secreted disease effector proteins, including many genes that are induced during infection or are predicted to have activities that alter host physiology. These fast-evolving effector genes are localized to highly dynamic and expanded regions of the P. infestans genome. This probably plays a crucial part in the rapid adaptability of the pathogen to host plants and underpins its evolutionary potential.

Black carbon decomposition and incorporation into soil microbial biomass estimated by 14C labeling

Abstract: Incomplete combustion of organics such as vegetation or fossil fuel led to accumulation of charred products in the upper soil horizon. Such charred products, frequently called pyrogenic carbon or black carbon (BC). may act as an important long-term carbon (C) sink because its microbial decomposition and chemical transformation is probably very slow. Direct estimations of BC decomposition rates are absent because the BC content changes are too small for any relevant experimental period. Estimations based on CO(2) efflux are also unsuitable because the contribution of BC to CO(2) is too small compared to soil organic matter (SOM) and other sources. We produced BC by charring (14)C labeled residues of perennial ryegrass (Latium perenne). We then incubated this (14)C labeled BC in Ah of a Haplic Luvisol soil originated from loess or in loess for 3.2 years. The decomposition rates of BC were estimated based on (14)CO(2) sampled 44 times during the 3.2 years incubation period (1181 days). Additionally we introduced five repeated treatments with either 1) addition of glucose as an energy source for microorganisms to initiate cometabolic BC decomposition or 2) intensive mixing of the soil to check the effect of mechanical disturbance of aggregates on BC decomposition. Black carbon addition amounting to 20% of C(org) of the soil or 200% of C(org) of loess did not change total CO(2) efflux from the soil and slightly decreased it from the loess. This shows a very low BC contribution to recent CO(2) fluxes. The decomposition rates of BC calculated based on 14C in CO(2) were similar in soil and in loess and amounted to 1.36 10-5 d(-1) (=1.36 10-3% d(-1)). This corresponds to a decomposition of about 0.5% BC per year under optimal conditions. Considering about 10 times slower decomposition of BC under natural conditions, the mean residence time (MRT) of BC is about 2000 years, and the half-life is about 1400 years. Considering the short duration of the incubation and the typical decreasing decomposition rates with time, we conclude that the MRT of BC in soils is in the range of millennia. The strong increase in BC decomposition rates (up to 6 times) after adding glucose and the decrease of this stimulation after 2 weeks in the soil (and after 3 months in loess) allowed us to conclude cometabolic BC decomposition. This was supported by higher stimulation of BC decomposition by glucose addition compared to mechanical disturbance as well as higher glucose effects in loess compared to the soil. The effect of mechanical disturbance was over within 2 weeks. The incorporation of BC into microorganisms (fumigation/extraction) after 624 days of incubation amounted to 2.6 and 1.5% of (14)C input into soil and loess, respectively. The amount of BC in dissolved organic carbon (DOC) was below the detection limit (<0.01%) showing no BC decomposition products in water leached from the soil. We conclude that applying (14)C labeled BC opens new ways for very sensitive tracing of BC transformation products in released CO(2), microbial biomass, DOC, and SOM pools with various properties. (C) 2008 Elsevier Ltd. All rights reserved.

Plant-rhizobacteria interactions alleviate abiotic stress conditions.

Abstract: Root-colonizing non-pathogenic bacteria can increase plant resistance to biotic and abiotic stress factors. Bacterial inoculates have been applied as biofertilizers and can increase the effectiveness of phytoremediation. Inoculating plants with non-pathogenic bacteria can provide 'bioprotection' against biotic stresses, and some root-colonizing bacteria increase tolerance against abiotic stresses such as drought, salinity and metal toxicity. Systematic identification of bacterial strains providing cross-protection against multiple stressors would be highly valuable for agricultural production in changing environmental conditions. For bacterial cross-protection to be an effective tool, a better understanding of the underlying morphological, physiological and molecular mechanisms of bacterially mediated stress tolerance, and the phenomenon of cross-protection is critical. Beneficial bacteria-mediated plant gene expression studies under non-stress conditions or during pathogenic rhizobacteria-plant interactions are plentiful, but only few molecular studies on beneficial interactions under abiotic stress situations have been reported. Thus, here we attempt an overview of current knowledge on physiological impacts and modes of action of bacterial mitigation of abiotic stress symptoms in plants. Where available, molecular data will be provided to support physiological or morphological observations. We indicate further research avenues to enable better use of cross-protection capacities of root-colonizing non-pathogenic bacteria in agricultural production systems affected by a changing climate.

The Influence of Sustainability Orientation on Entrepreneurial Intentions - Investigating the Role of Business Experience

Abstract: Do individuals who are concerned by issues of sustainability also exhibit strong entrepreneurial intentions? Given that existing imperfections in the market create numerous opportunities for entrepreneurship connected with sustainable development, adding individual sustainability orientation to models of entrepreneurial intention could increase their explanatory power. Based on survey data collected from students and alumni of a German technical university, we provide evidence that entering sustainability orientation into the equation is actually meaningful. However, our findings suggest that the positive impact of sustainability orientation vanishes with business experience. Consequently, we suggest measures to nourish an evidently existing potential for sustainable entrepreneurship.

Jatropha curcas, a promising crop for the generation of biodiesel and value-added coproducts

Abstract: The review highlights the specific features of the Jatropha curcas plant and its potential for the production of biofuel, protein concentrates as livestock feed and value-added products that could enhance the economic viability of Jatropha seed oil-based biodiesel production. The roles of the plant in carbon capture, enhancing socio-economic conditions, food production in the tropical regions, and influencing microclimate, vegetation and soil quality are discussed. The paper also gives a comparative account of the toxic and non-toxic genotypes of J. curcas from the point of view of their physical and chemical properties and their potential for biodiesel and livestock feed production. Future areas of research are also presented.

Effect of surfactant surface coverage on formation of solid lipid nanoparticles (SLN).

Abstract: The effect of surfactant surface coverage on formation and stability of Tween 20 stabilized tripalmitin solid lipid nanoparticles (SLN) was investigated. A lipid phase (10% w/w tripalmitin) and an aqueous phase (2% w/w Tween 20, 10 mM phosphate buffer, pH 7) were heated to 75 degrees C and then homogenized using a microfluidizer. The resulting oil-in-water emulsion was kept at a temperature (37 degrees C) above the crystallization temperature of the tripalmitin to prevent solidification of emulsion droplets, and additional surfactant at various concentrations (0-5% w/w Tween 20) was added. Droplets were then cooled to 5 degrees C to initiate crystallization and stored at 20 degrees C for 24 h. Particle size and/or aggregation were examined visually and by light scattering, and crystallization behavior was examined by differential scanning calorimetry (DSC). Excess Tween 20 concentration remaining in the aqueous phase was measured by surface tensiometry. Emulsion droplets after homogenization had a mean particle diameter of 134.1+/-2.0 nm and a polydispersity index of 0.08+/-0.01. After cooling to 5 degrees C at low Tween 20 concentrations, SLN dispersions rapidly gelled due to aggregation of particles driven by hydrophobic attraction between insufficiently covered lipid crystal surfaces. Upon addition of 1-5% w/w Tween 20, SLN dispersions became increasingly stable. At low added Tween 20 concentration ( 1% w/w). The Tween 20 concentration in the aqueous phase decreased after tripalmitin crystallization suggesting additional surfactant adsorption onto solid surfaces. At higher Tween 20 concentrations, SLN had increasingly complex crystal structures as evidenced by the appearance of additional thermal transition peaks in the DSC. The results suggest that surfactant coverage at the interface may influence crystal structure and stability of solid lipid nanoparticles via surface-mediated crystal growth.

Ridge Regression and Extensions for Genomewide Selection in Maize

Abstract: This paper reviews properties of ridge regres- sion for genomewide (genomic) selection and establishes close relationships with other meth- ods to model genetic correlation among rela- tives, including use of a kinship matrix and the simple matching coeffi cient as computed from marker data. A number of alternative models are then proposed exploiting ties between genetic correlation based on marker data and geostatis- tical concepts. A simple method for automatic marker selection is proposed. The methods are exemplifi ed using a series of experiments with test-cross hybrids of maize (Zea mays L.) con- ducted in fi ve environments. Results underline the need to appropriately model genotype- environment interaction and to employ an inde- pendent estimate of error. It is also shown that accounting for genetic effects not captured by markers may be important.

Effects of elevated CO2 on grain yield and quality of wheat: results from a 3-year free-air CO2 enrichment experiment

Abstract: Spring wheat (Triticum aestivum L. cv. TRISO) was grown for three consecutive seasons in a free-air carbon dioxide (CO(2)) enrichment (FACE) field experiment in order to examine the effects on crop yield and grain quality. CO(2) enrichment promoted aboveground biomass (+11.8%) and grain yield (+10.4%). However, adverse effects were predominantly observed on wholegrain quality characteristics. Although the thousand-grain weight remained unchanged, size distribution was significantly shifted towards smaller grains, which may directly relate to lower market value. Total grain protein concentration decreased significantly by 7.4% under elevated CO(2), and protein and amino acid composition were altered. Corresponding to the decline in grain protein concentration, CO(2) enrichment resulted in an overall decrease in amino acid concentrations, with greater reductions in non-essential than essential amino acids. Minerals such as potassium, molybdenum and lead increased, while manganese, iron, cadmium and silicon decreased, suggesting that adjustments of agricultural practices may be required to retain current grain quality standards. The concentration of fructose and fructan, as well as amounts per area of total and individual non-structural carbohydrates, except for starch, significantly increased in the grain. The same holds true for the amount of lipids. With regard to mixing and rheological properties of the flour, a significant increase in gluten resistance under elevated CO(2) was observed. CO(2) enrichment obviously affected grain quality characteristics that are important for consumer nutrition and health, and for industrial processing and marketing, which have to date received little attention.

Corporate Taxation and the Choice of Patent Location within Multinational Firms

Abstract: Corporate patents are perceived to be the key profit-drivers in many multinational enterprises (MNEs). Moreover, as the transfer pricing process for royalty payments is often highly intransparent, they also constitute a major source of profit shifting opportunities between multinational entities. For both reasons, MNEs have an incentive to locate their patents at affiliates with a relatively small corporate tax rate. Our paper empirically tests for this relationship by exploiting a unique dataset which links information on patent applications to micro panel data for European MNEs. Our results suggest that the corporate tax rate (differential to other group members) indeed exerts a negative effect on the number of patents filed by a subsidiary. The effect is quantitatively large and robust against controlling for affiliate size. The findings prevail if we additionally account for royalty withholding taxes. Moreover, binding `Controlled Foreign Company' rules tend to decrease the number of patent applications.

Ageing, Health and Life Satisfaction of the Oldest Old: An Analysis for Germany

Abstract: This analysis uses data from the German Socio-Economic Panel (GSOEP) and the Survey on Health, Ageing and Retirement in Europe (SHARE) to assess the effect of ageing and health on the life satisfaction of the oldest old (defined as 75 and older). We observe a U-shaped relationship between age and levels of life satisfaction for individuals aged between 16 and approximately 65. Thereafter, life satisfaction declines rapidly and the lowest absolute levels of life satisfaction are recorded for the oldest old. This decline is primarily attributable to low levels of perceived health. Once cohort effects are also controlled for, life satisfaction remains relatively constant across the lifespan.

Physiological and pathophysiological functions of intestinal mast cells

Abstract: The normal gastrointestinal (GI) mucosa is equipped with mast cells that account for 2-3% of lamina propria cells under normal conditions. Mast cells are generally associated with allergic disease, and indeed, food allergy that manifests in the GI tract is usually mast cell dependent. On the other hand, mast cells have a number of physiological functions in the GI tract, namely regulatory functions such as control of blood flow and coagulation, smooth muscle contraction and peristalsis, and secretion of acid, electrolytes, and mucus by epithelial cells. One of the most intriguing functions of intestinal mast cells is their role in host defense against microbes like bacteria, viruses, or parasites. Mast cells recognize microbes by antibody-dependent mechanisms and through pattern-recognition receptors. They direct the subsequent immune response by attracting both granulocytes and lymphocytes to the site of challenge via paracrine cytokine release. Moreover, mast cells initiate, by releasing proinflammatory mediators, innate defense mechanisms such as enhanced epithelial secretion, peristalsis, and alarm programs of the enteric nervous This initiation can occur in response to a primary contact to the microbe or other danger signals, but becomes much more effective if the triggering antigen reappears and antibodies of the IgE or IgG type have been generated in the meantime by the specific immune system. Thus, mast cells operate at the interface between innate and adaptive immune responses to enhance the defense against pathogens and, most likely, the commensal flora. In this respect, it is important to note that mast cells are directly involved in controlling the function of the intestinal barrier that turned out to be a crucial site for the development of infectious and immune-mediated diseases. Hence, intestinal mast cells perform regulatory functions to maintain tissue homeostasis, they are involved in host defense mechanisms against pathogens, and they can induce allergy once they are sensitized against foreign antigens. The broad spectrum of functions makes mast cells a fascinating target for future pharmacological or nutritional interventions.

Revealing the genetic architecture of FHB resistance in hexaploid wheat (Triticum aestivum L.) by QTL meta-analysis.

Abstract: Fusarium head blight (FHB) in wheat results in reduced yield and quality and in accumulation of mycotoxins. The objective of this study was to identify genomic regions in wheat involved in the control of FHB resistance applying a QTL meta-analysis approach by combining QTL of 30 mapping populations to propose independent meta-QTL (MQTL). A consensus map was created on which initial QTL were projected. Nineteen MQTL comprising 2–13 initial QTL with widely varying confidence intervals were found on 12 chromosomes. Some of them coincided with genomic regions previously identified (e.g. chromosomes 3BS, 6B), however, some MQTL were newly detected by this study. Separate analysis of populations with the same resistant parent showed a rather high consistency for the Chinese spring wheat donor ‘Sumai 3’, but little consistency for the Chinese donor ‘Wangshuibai’ and the Swiss donor ‘Arina’. According to our results breeders can in future (1) choose parents for crossing not comprising the same resistance loci or QTL intervals, (2) exploit new MQTL, and (3) select markers of some of these MQTL to be used in marker-assisted selection.

Ten things to know about oomycete effectors

Abstract: Long considered intractable organisms by fungal genetic research standards, the oomycetes have recently moved to the centre stage of research on plant-microbe interactions. Recent work on oomycete effector evolution, trafficking and function has led to major conceptual advances in the science of plant pathology. In this review, we provide a historical perspective on oomycete genetic research and summarize the state of the art in effector biology of plant pathogenic oomycetes by describing what we consider to be the 10 most important concepts about oomycete effectors.

Stimulation of microbial extracellular enzyme activities by elevated CO2 depends on soil aggregate size

Abstract: Increased belowground carbon (C) transfer by plant roots at elevated CO 2 may change properties of the microbial community in the rhizosphere. Previous investigations that focused on total soil organic C or total microbial C showed contrasting results: small increase, small decrease or no changes. We evaluated the effect of 5 years of elevated CO 2 (550 ppm) on four extracellular enzymes: β-glucosidase, chitinase, phosphatase, and sulfatase. We expected microorganisms to be differently localized in aggregates of various sizes and, therefore analyzed microbial biomass (C mic by SIR) and enzyme activities in three aggregate-size classes: large macro- (> 2 mm), small macro- (0.25-2 mm), and microaggregates (< 0.25 mm). To estimate the potential enzyme production, we activated microorganisms by substrate (glucose and nutrients) amendment. Although C total and C mic as well as the activities of β-glucosidase, phosphatase, and sulfatase were unaffected in bulk soil and in aggregate-size classes by elevated CO 2 , significant changes were observed in potential enzyme production after substrate amendment. After adding glucose, enzyme activities under elevated CO 2 were 1.2-1.9-fold higher than under ambient CO 2 . This indicates the increased activity of microorganisms, which leads to accelerated C turnover in soil under elevated CO 2 . Significantly higher chitinase activity in bulk soil and in large macroaggregates under elevated CO 2 revealed an increased contribution of fungi to turnover processes. At the same time, less chitinase activity in microaggregates underlined microaggregate stability and the difficulties for fungal hyphae penetrating them. We conclude that quantitative and qualitative changes of C input by plants into the soil at elevated CO 2 affect microbial community functioning, but not its total content. Future studies should therefore focus more on the changes of functions and activities, but less on the pools.

Strategies and methods for studying the rhizosphere—the plant science toolbox

Abstract: This review summarizes and discusses methodological approaches for studies on the impact of plant roots on the surrounding rhizosphere and for elucidation of the related mechanisms, covering a range from simple model experiments up to the field scale. A section on rhizosphere sampling describes tools and culture systems employed for analysis of root growth, root morphology, vitality testing and for monitoring of root activity with respect to nutrient uptake, water, ion and carbon flows in the rhizosphere. The second section on rhizosphere probing covers techniques to detect physicochemical changes in the rhizosphere as a consequence of root activity. This comprises compartment systems to obtain rhizosphere samples, visualisation techniques, reporter gene approaches and remote sensing technologies for monitoring the conditions in the rhizosphere. Approaches for the experimental manipulation of the rhizosphere by use of molecular and genetic methods as tools to study rhizosphere processes are discussed in a third section. Finally it is concluded that in spite of a wide array of methodological approaches developed in the recent past for studying processes and interactions in the rhizosphere mainly under simplified conditions in model experiments, there is still an obvious lack of methods to test the relevance of these findings under real field conditions or even on the scale of ecosystems. This also limits reliable data input and validation in current rhizosphere modelling approaches. Possible interactions between different environmental factors or plant-microbial interactions (e.g. mycorrhizae) are frequently not considered in model experiments. Moreover, most of the available knowledge arises from investigations with a very limited number of plant species, mainly crops and studies considering also intraspecific genotypic differences or the variability within wild plant species are just emerging.

Role of serotonin in intestinal inflammation: knockout of serotonin reuptake transporter exacerbates 2,4,6-trinitrobenzene sulfonic acid colitis in mice

Abstract: Serotonin (5-HT) regulates peristaltic and secretory reflexes in the gut. The serotonin reuptake transporter (SERT; SLC6A4), which inactivates 5-HT, is expressed in the intestinal mucosa and the enteric nervous system. Stool water content is increased and colonic motility is irregular in mice with a targeted deletion of SERT. We tested the hypotheses that 5-HT plays a role in regulating intestinal inflammation and that the potentiation of serotonergic signaling that results from SERT deletion is proinflammatory. Rectal installation of 2,4,6-trinitrobenzene sulfonic acid (TNBS) was used to induce an immune-mediated colitis, which was compared in SERT knockout mice and littermate controls. Intestinal myeloperoxidase and histamine levels were significantly increased, whereas the survival rate and state of health were significantly decreased in TNBS-treated mice that lacked SERT. Deletion of SERT thus increases the severity of TNBS colitis. These data suggest that 5-HT and its SERT-mediated termination play roles in intestinal immune/inflammatory responses in mice.

Cell Movements at Hensen’s Node Establish Left/Right Asymmetric Gene Expression in the Chick

Abstract: In vertebrates, the readily apparent left/right (L/R) anatomical asymmetries of the internal organs can be traced to molecular events initiated at or near the time of gastrulation However, the earliest steps of this process do not seem to be universally conserved In particular, how this axis is first defined in chicks has remained problematic Here we show that asymmetric cell rearrangements take place within chick embryos, creating a leftward movement of cells around the node It is the relative displacement of cells expressing sonic hedgehog (Shh) and fibroblast growth factor 8 (Fgf8) that is responsible for establishing their asymmetric expression patterns The creation of asymmetric expression domains as a passive effect of cell movements represents an alternative strategy for breaking L/R symmetry in gene activity

The Ethical Rational of Business for the Poor – Integrating the Concepts Bottom of the Pyramid, Sustainable Development and Corporate Citizenship

Abstract: The first United Nations Millennium Development Goal calls for a distinct reduction of worldwide poverty. It is now widely accepted that the private sector is a crucial partner in achieving this ambitious target. Building on this insight, the ‘Bottom of the Pyramid’ concept provides a framework that highlights the untapped opportunities with the ‘poorest of the poor,’ while at the same time acknowledging the abilities and resources of private enterprises for poverty alleviation.This paper connects the idea of business with the poor to sustainable development and especially to the notions of inter- and intragenerational justice. These principles of justice can be linked with the ‘Bottom of the Pyramid’ approach directly through the Rawlsian principles to foster holistic thinking. On this basis, the paper offers a normative-ethical reasoning of corporations’ possible responsibilities for the poorest of the poor. Today’s state of worldwide inequalities is likely to generate future tensions between the privileged western world and the uncounted mass of poor (let alone the ethical dubiousness of this status). However, it is at the same time problematic if not even impossible to improve the situation of the poor by simply copying the resource intensive western way of living to the ‘Bottom of the Pyramid’ due to the limited carrying capacity of the earth. After highlighting possible moral dilemmas which may occur through such a potential trade off, this paper concludes with an outlook on how the concepts ‘Bottom of the Pyramid’ and sustainable development could be combined.

Stimulation of microbial extracellular enzyme activities by elevated CO2 depends on soil aggregate size

Abstract: Increased belowground carbon (C) transfer by plant roots at elevated CO 2 may change properties of the microbial community in the rhizosphere. Previous investigations that focused on total soil organic C or total microbial C showed contrasting results: small increase, small decrease or no changes. We evaluated the effect of 5 years of elevated CO 2 (550 ppm) on four extracellular enzymes: β-glucosidase, chitinase, phosphatase, and sulfatase. We expected microorganisms to be differently localized in aggregates of various sizes and, therefore analyzed microbial biomass (C mic by SIR) and enzyme activities in three aggregate-size classes: large macro- (> 2 mm), small macro- (0.25-2 mm), and microaggregates (< 0.25 mm). To estimate the potential enzyme production, we activated microorganisms by substrate (glucose and nutrients) amendment. Although C total and C mic as well as the activities of β-glucosidase, phosphatase, and sulfatase were unaffected in bulk soil and in aggregate-size classes by elevated CO 2 , significant changes were observed in potential enzyme production after substrate amendment. After adding glucose, enzyme activities under elevated CO 2 were 1.2-1.9-fold higher than under ambient CO 2 . This indicates the increased activity of microorganisms, which leads to accelerated C turnover in soil under elevated CO 2 . Significantly higher chitinase activity in bulk soil and in large macroaggregates under elevated CO 2 revealed an increased contribution of fungi to turnover processes. At the same time, less chitinase activity in microaggregates underlined microaggregate stability and the difficulties for fungal hyphae penetrating them. We conclude that quantitative and qualitative changes of C input by plants into the soil at elevated CO 2 affect microbial community functioning, but not its total content. Future studies should therefore focus more on the changes of functions and activities, but less on the pools.