Organotin and especially butyltin compounds are used for a variety of applications, e.g. as biocides, stabilizers, catalysts and intermediates in chemical syntheses. Tributyltin (TBT) compounds exhibit the greatest toxicity of all organotins and have even been characterized as one of the most toxic groups of xenobiotics ever produced and deliberately introduced into the environment. TBT is not only used as an active biocidal compound in antifouling paints, which are designed to prevent marine and freshwater biota from settlement on ship hulls, harbour and offshore installations, but also as a biocide in wood preservatives, textiles, dispersion paints and agricultural pesticides. Additionally, it occurs as a by-product of mono- (MBT) and dibutyltin (DBT) compounds, which are used as UV stabilizer in many plastics and for other applications. Triphenyltin (TPT) compounds are also used as the active biocide in antifouling paints outside Europe and furthermore as an agricultural fungicide since the early 1960s to combat a range of fungal diseases in various crops, particularly potato blight, leaf spot and powdery mildew on sugar beet, peanuts and celery, other fungi on hop, brown rust on beans, grey moulds on onions, rice blast and coffee leaf rust. Although the use of TBT and TPT was regulated in many countries world-wide from restrictions for certain applications to a total ban, these compounds are still present in the environment. In the early 1970s the impact of TBT on nontarget organisms became apparent. Among the broad variety of malformations caused by TBT in aquatic animals, molluscs have been found to be an extremely sensitive group of invertebrates and no other pathological condition produced by TBT at relative low concentrations rivals that of the imposex phenomenon in prosobranch gastropods speaking in terms of sensitivity. TBT induces imposex in marine prosobranchs at concentrations as low as 0,5 ng TBT-Sn/L. Since 1993, for the littorinid snail Littorina littorea a second virilisation phenomenon, termed intersex, is known. In female specimens affected by intersex the pallial oviduct is transformed of towards a male morphology with a final supplanting of female organs by the corresponding male formations. Imposex and intersex are morphological alterations caused by a chronic exposure to ultra-trace concentrations of TBT. A biological effect monitoring offers the possibility to determine the degree of contamination with organotin compounds in the aquatic environment and especially in coastal waters without using any expensive analytical methods. Furthermore, the biological effect monitoring allows an assessment of the existing TBT pollution on the basis of biological effects. Such results are normally more relevant for the ecosystem than pure analytical data. usw.
Comprehension of belowground competition between plant species is a central part in understanding the complex interactions in intercropped agricultural systems, between crops and weeds as well as in natural ecosystems. So far, no simple and rapid method for species discrimination of roots in the soil exists. We will be developing a method for root discrimination of various species based on Fourier Transform Infrared (FTIR)-Attenuated Total Reflexion (ATR) Spectroscopy and expanding its application to the field. The absorbance patterns of FTIR-ATR spectra represent the chemical sample composition like an individual fingerprint. By means of multivariate methods, spectra will be grouped according to spectral and chemical similarity in order to achieve species discrimination. We will investigate pea and oat roots as well as maize and barnyard grass roots using various cultivars/proveniences grown in the greenhouse. Pea and oat are recommendable species for intercropping to achieve superior grain and protein yields in an environmentally sustainable manner. To evaluate the effects of intercropping on root distribution in the field, root segments will be measured directly at the soil profile wall using a mobile FTIR spectrometer. By extracting the main root compounds (lipids, proteins, carbohydrates) and recording their FTIR-ATR spectra as references, we will elucidate the chemical basis of species-specific differences.
To predict ecosystem reactions to elevated atmospheric CO2 (eCO2) it is essential to understandthe interactions between plant carbon input, microbial community composition and activity and associated nutrient dynamics. Long-term observations (greater than 13 years) within the Giessen Free Air Carbon dioxide Enrichment (Giessen FACE) study on permanent grassland showed next to an enhanced biomass production an unexpected strong positive feedback effect on ecosystem respiration and nitrous oxide (N2O) production. The overall goal of this study is to understand the long-term effects of eCO2 and carbon input on microbial community composition and activity as well as the associated nitrogen dynamics, N2O production and plant N uptake in the Giessen FACE study on permanent grassland. A combination of 13CO2 pulse labelling with 15N tracing of 15NH4+ and 15NO3- will be carried out in situ. Different fractions of soil organic matter (recalcitrant, labile SOM) and the various mineral N pools in the soil (NH4+, NO3-, NO2-), gross N transformation rates, pool size dependent N2O and N2 emissions as well as N species dependent plant N uptake rates and the origin of the CO2 respiration will be quantified. Microbial analyses will include exploring changes in the composition of microbial communities involved in the turnover of NH4+, NO3-, N2O and N2, i.e. ammonia oxidizing, denitrifying, and microbial communities involved in dissimilatory nitrate reduction to ammonia (DNRA). Stable Isotope Probing (SIP) and mRNA based analyses will be employed to comparably evaluate the long-term effects of eCO2 on the structure and abundance of these communities, while transcripts of these genes will be used to target the fractions of the communities which actively contribute to N transformations.
In the last decades agricultural policy has gained increasingly in complexity. Nowadays it influences the food and agricultural sector from the global market down to the farm level. Widespread research questions, like the impact of the WTO negotiations on the farm structure, most often require comprehensive modeling frameworks. Thus, different types of models are utilized according to their comparative advantages and combined in a strategically useful way to more accurately represent micro and macro aspects of the food and agricultural sector. Consequently, in recent years we have seen an increase in the development and application of model linkages. Given this background, the overall objective of this subproject is a systematic sensitivity analysis of model linkages that gradually involves more and more characteristics of the linkage and the corresponding transfer of results between models. In addition, the project aims to answer the following specific question: How does structural change at the farm level influence aggregate supply and technical progress? Under which conditions is it possible to derive macro-relationships from micro-relationships? How does the aggregation level influence the model results and how can possible problems be overcome? This procedure is used to quantify the effects and to derive conditions for optimal interaction of the connected models. The analysis is based on the general equilibrium model GTAP (Global Trade Analysis Project) and the farm group model FARMIS (Farm Modelling Information System) which are employed in conjunction to analyze the effects of WTO negotiations on the farm level.
Flowering time (FTi) genes play a key role as regulators of complex gene expression networks, and the influence of these networks on other complex systems means that FTi gene expression triggers a cascade of regulatory effects with a broad global effect on plant development. Hence, allelic and expression differences in FTi genes can play a central role in phenotypic variation throughput the plant lifecycle. A prime example for this is found in Brassica napus, a phenotypically and genetically diverse species with enormous variation in vernalisation requirement and flowering traits. The species includes oilseed rape (canola), one of the most important oilseed crops worldwide. Previously we have identified QTL clusters related to plant development, seed yield and heterosis in winter oilseed rape that seem to be conserved in diverse genetic backgrounds. We suspect that these QTL are controlled by global regulatory genes that influence numerous traits at different developmental stages. Interestingly, many of the QTL clusters for yield and biomass heterosis appear to correspond to the positions of meta-QTL for FTi in spring-type and/or winter-type B. napus. Based on the hypothesis that diversity in FTi genes has a key influence on plant development and yield, the aim of this study is a detailed analysis of DNA sequence variation in regulatory FTi genes in B. napus, combined with an investigation of associations between FTi gene haplotypes, developmental traits, yield components and seed yield.
In bog ecosystems, vegetation controls key processes such as the retention of carbon, water and nutrients. In northern hemispherical bogs, a shift from Sphagnum- to vascular plant-dominated vegetation is often traced back to Climate Change and increased anthropogenic nitrogen deposition and coincides with substantially reduced capacities in carbon, water and nutrient retention. In southern Patagonia, bogs dominated by Sphagnum and vascular plants coexist since millennia under similar environmental settings. Thus, South Patagonian bogs may serve as ideal examples for the long-term effect of vascular plant invasion on carbon, water and nutrient balances of bog ecosystems. The contemporary balances of carbon and water of both a bog dominated by Sphagnum and vascular plants are determined by CO2- H2O and CH4 flux measurements and an estimation of lateral water losses as well as losses via dissolved organic and inorganic carbon compounds. The high time resolution of simultaneous eddy covariance measurements of CO2 and H2O in both bog types and the strong interaction between climatic variables and the physiology of bog plants allow for direct comparisons of carbon and water fluxes during cold, warm, dry, wet, cloudy or sunny periods. By the combination with leaf-scale measurements of gas exchange and fluorescence, plant-physiological controls of photosynthesis and transpiration can be identified. Long-term peat accumulation rates will be determined by carbon density and age-depth profiles including a characterization of peat humification characteristics. A reciprocal transplantation experiment with incorporated shading, liming and labeled N addition treatments is conducted to explore driving factors affecting competition between Sphagnum and vascular plants as well as the interactions between CO2-, CH4-, and water fluxes and decisive plant functional traits affecting key processes for carbon sequestration and nutrient cycling. Decomposition rates and driving below ground processes are analyzed with a litter bag field experiment and an incubation experiment in the laboratory.
Chlorinated ethylenes are prevalent groundwater contaminants. Numerous studies have addressed the mechanism of their reductive dehalogenation during biodegradation and reaction with zero-valent iron. However, despite insight with purified enzymes and well-characterized chemical model systems, conclusive evidence has been missing that the same mechanisms do indeed prevail in real-world transformations. While dual kinetic isotope effect measurements can provide such lines of evidence, until now this approach has not been possible for chlorinated ethylenes because an adequate method for continuous flow compound specific chlorine isotope analysis has been missing. This study attempts to close this prevalent research gap by a combination of two complementary approaches. (1) A novel analytical method to measure isotope effects for carbon and chlorine. (2) A carefully chosen set of well-defined model reactants representing distinct dehalogenation mechanisms believed to be important in real-world systems. Isotope trends observed in biotic and abiotic environmental dehalogenation will be compared to these model reactions, and the respective mechanistic hypotheses will be confirmed or discarded. With this hypothesis-driven approach it is our goal to elucidate for the first timdehalogenation reactions.
Boron (B) is an essential microelement for plants. Despite the use of modern fertilization methods, B deficiency still causes losses in agricultural plant production. Even though many positive effects of B on plant growth and physiology have been reported, a large majority of B functions and the regulatory mechanisms controlling the B nutritional status remain unknown. The main objective of this project is to elucidate how the greatly B deficiency-sensitive Brassica crop plants process and regulate their B status during vegetative and reproductive growth. In this context, the project aims at identifying the mode of action of B in mechanisms regulating the B status itself and uncovering those mechanisms contributing to B efficiency in different genotypes. Plant species subjected to investigation will be the agronomically important oilseed and vegetable plant Brassica napus (rapeseed) and its close relative the genetic and molecular model plant Arabidopsis thaliana. Questions addressed within the scope of this project should lead to a detailed understanding of mechanisms controlling B uptake and allocation from the level of the whole plant down to the cellular level. B transport routes and rates will be determined in sink- and source tissues and in developmental periods with a particularly high B demand. A special focus will be on the identification of B transport bottlenecks and the analysis of B deficiency-sensitive transport processes to and within the highly B-demanding reproductive organs. Recent studies in Arabidopsis suggest that Nodulin26-like Intrinsic Proteins (NIPs), which belong to the aquaporin channel protein family, are essential for plant B uptake and distribution. The systematic focus on the molecular and physiological characterization of B. napus NIPs will clarify their role in B transport and will identify novel NIP-associated mechanisms playing key roles in the B response network.To further resolve the mostly unknown impact of the B nutritional status on gene regulation and metabolism, a transcript and metabolite profile of B-sufficient and B-deficient rapeseed plants will be generated. Additionally, an Arabidopsis transcription factor knockout collection (greater 300 lines) will be screened for abnormalities in responses to the B nutritional status. This will identify yet unknown B-responsive genes (transcription factors and their targets) and gene products (enzymes or metabolite variations) playing key roles in signalling pathways and mechanisms regulating the B homeostasis. Boron (in form of boric acid) and arsenite (As) share in all likelihood the same NIP-mediated transport pathways. To assess the consequences of this dual transport pathway the so far unstudied impact of the plants B nutritional status on the accumulation and distribution of As will be investigated in B. napus. Moreover, the current dimension of the As contamination of Brassica-based food products, to which consumers are exposed to, will be analyzed. usw.
Various species of pest insects cause substantial damage to agriculture every year, or transmit deadly diseases to animals and humans. A successful strategy to control pest insect populations is based on the Sterile Insect Technique (SIT), which uses the release of mass-reared, radiation sterilized male insects to cause infertile matings and thus reduce the pest population level. However, irradiation is not applicable to every insect species. Thus, new strategies based on genetic modifications of pest insects have been developed or are currently under investigation.The goal of the proposed research is to improve the development and ecological safety of genetically engineered (GE) insects created for enhanced biological control programs, including the SIT and new strategies based on conditional lethality. A major concern for GE insect release programs is transgene stability, and maintenance of their consistent expression. Transgene loss or intra-genomic movement could result in loss of strain attributes, and may ultimately lead to interspecies movement resulting in ecological risks. To address potential transgene instability, a new transposon vector that allows post-integration immobilization will be tested in the Mediterranean, Mexican and Oriental fruit fly tephritid pest species. In addition, the system will be established in the mosquito species Aedes and Anopheles - carriers of dengue and malaria.Random genomic insertion is also problematic for GE strain development due to genomic position effects that suppress transgene expression, and insertional mutations that negatively affect host fitness and viability. Diminished transgene expression could result in the unintended survival of conditional lethal individuals, or the inability to identify them. To target transgene vectors to defined genomic insertion sites having minimal negative effects on gene expression and host fitness, a recombinase-mediated cassette exchange (RMCE) strategy will be developed that. RMCE will also allow for stabilization of the target site, will be tested in tephritid and mosquito species, and will aid to the development of stabilized target-site strains for conditional lethal biocontrol. This will include a molecular and organismal evaluation of an RNAi-based lethality approach. Lethality based on an RNAi mechanism in the proposed insects would increase the species specificity and having multiple targets for lethality versus one target in existing systems. By seeking to improve transgene expressivity and stabilization of transposon-based vector systems, this proposal specifically addresses issues related to new GE insects by reducing their unintended spread after field release, and by limiting the possibilities for transgene introgression.
In many plant species, FLOWERING LOCUS T and related proteins are the mobile signal that communicates information on photoperiod from the leaves to the shoots, where the transition to flowering is realized. FT expression is tightly controlled at the transcriptional level so that it is restricted to leaves, occurs only in appropriate photoperiods, and integrates ambient temperature and developmental cues, as well as information on biotic and abiotic stress. We previously established that FT transcription in the model plant Arabidopsis thaliana requires proximal promoter cis-elements and a distal enhancer, both evolutionary conserved among Brassicacea species. In addition, FT transcription is blocked prior vernalization in biannual accessions and vernalization-dependency of FT is controlled through a CArG-box located in the first intron that binds the transcriptional repressor FLOWERING LOCUS C (FLC). Chromatin-mediated repression by the Polycomb Group (PcG) pathway is required for photoperiod-dependent FT regulation and participates in FT expression level modulation in response to other cues.In this project, I propose to explore the available sequence data from the 1001 genome project in Arabidopsis to evaluate how often changes in regulatory cis-elements at FT have occurred and how these translate into an adaptive value. Allele-specific FT expression pattern will be measured in F1 hybrids of different accessions in response to varying environmental conditions. FT alleles that show cis-regulatory variation will be further analyzed to pinpoint the causal regulatory changes and study their effect in more detail. The allotetrapolyploid species Brassica napus is a hybrid of two Brassiceae species belonging to the A- and C-type genome, which are in turn mesopolyploid due to a genome triplication that occurred ca. 10x106 years ago. We will determine allele-specific expression of FT paralogs from both genomes of a collection of B. napus accessions. The plants will be grown in the field in changing environmental conditions to maximize the chance to detect expression variation of the paralogs. We will compare the contribution of the founder genomes to the regulation of flowering time and asses variation in this contribution. A particular focus will be to study the impact of chromatin-mediated repression on allele selection in B. napus.
| Origin | Count |
|---|---|
| Bund | 540 |
| Wissenschaft | 8 |
| Type | Count |
|---|---|
| Daten und Messstellen | 7 |
| Förderprogramm | 539 |
| Text | 1 |
| unbekannt | 1 |
| License | Count |
|---|---|
| geschlossen | 1 |
| offen | 547 |
| Language | Count |
|---|---|
| Deutsch | 125 |
| Englisch | 510 |
| Resource type | Count |
|---|---|
| Archiv | 1 |
| Datei | 6 |
| Keine | 440 |
| Webseite | 101 |
| Topic | Count |
|---|---|
| Boden | 481 |
| Lebewesen und Lebensräume | 524 |
| Luft | 435 |
| Mensch und Umwelt | 548 |
| Wasser | 434 |
| Weitere | 548 |