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End date: 2009 × Start date: 2000 × DDC: 570 × Type: Text × WGL Institute: INM ×

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    The analysis of arabidopsis nicotianamine synthase mutants reveals functions for nicotianamine in seed iron loading and iron deficiency responses
    (Rockville, MD : American Society of Plant Biologists, 2009) Fink-Straube, Claudia; Klatte, Marco; Schuler, Mara; Wirtz, Markus; Hell, Rüdiger; Bauer, Petra
    Nicotianamine chelates and transports micronutrient metal ions in plants. It has been speculated that nicotianamine is involved in seed loading with micronutrients. A tomato (Solanum lycopersicum) mutant (chloronerva) and a tobacco (Nicotiana tabacum) transgenic line have been utilized to analyze the effects of nicotianamine loss. These mutants showed early leaf chlorosis and had sterile flowers. Arabidopsis (Arabidopsis thaliana) has four NICOTIANAMINE SYNTHASE (NAS) genes. We constructed two quadruple nas mutants: one had full loss of NAS function, was sterile, and showed a chloronerva-like phenotype (nas4x-2); another mutant, with intermediate phenotype (nas4x-1), developed chlorotic leaves, which became severe upon transition from the vegetative to the reproductive phase and upon iron (Fe) deficiency. Residual nicotianamine levels were sufficient to sustain the life cycle. Therefore, the nas4x-1 mutant enabled us to study late nicotianamine functions. This mutant had no detectable nicotianamine in rosette leaves of the reproductive stage but low nicotianamine levels in vegetative rosette leaves and seeds. Fe accumulated in the rosette leaves, while less Fe was present in flowers and seeds. Leaves, roots, and flowers showed symptoms of Fe deficiency, whereas leaves also showed signs of sufficient Fe supply, as revealed by molecular-physiological analysis. The mutant was not able to fully mobilize Fe to sustain Fe supply of flowers and seeds in the normal way. Thus, nicotianamine is needed for correct supply of seeds with Fe. These results are fundamental for plant manipulation approaches to modify Fe homeostasis regulation through alterations of NAS genes.
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    Fast and sensitive screening of transparent composite materials using polarized light image processing
    (Saarbrücken : Leibniz-Institut für Neue Materialien, 2009) Weiss, Ingrid M.; Heiland, Birgit
    Composite materials of natural origin have remarkable material properties. In order to mimic the various functions of such materials for technical applications, it is necessary to understand the structure and the mechanisms of their formation, a scientific field which is called structural biology. A milestone in the era of structural biology was the application of the polarized light microscope for investigating biological specimens by W. J. Schmidt in 1924. A recent development in polarization technology is the LC-PolScope (Abrio IM™ Imaging System) that has been developed by R. Oldenbourg and his colleagues during the past 20 years. Like conventional polarization microscopy, it probes the local anisotropy of the specimen’s optical properties, such as birefringence or dichroism. Since there is a close relationship between such properties and molecular order in bulk materials, polarization microscopy can be regarded as a submicroscopic technique. The LC-PolScope is especially suitable for investigating biological materials without the need for using contrasting agents such as fluorescent markers. We demonstrated the applicability of this technique for the fast and sensitive screening of biological composite materials. Implications for the characterization of biomineralization phenomena in a quantitative manner are discussed.
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    The structure of mollusc larval shells formed in the presence of the chitin synthase inhibitor Nikkomycin Z
    (London : BioMed Central, 2007) Weiss, Ingrid M.; Schönitzer, Veronika
    Background Chitin self-assembly provides a dynamic extracellular biomineralization interface. The insoluble matrix of larval shells of the marine bivalve mollusc Mytilus galloprovincialis consists of chitinous material that is distributed and structured in relation to characteristic shell features. Mollusc shell chitin is synthesized via a complex transmembrane chitin synthase with an intracellular myosin motor domain. Results Enzymatic mollusc chitin synthesis was investigated in vivo by using the small-molecule drug NikkomycinZ, a structural analogue to the sugar donor substrate UDP-N-acetyl-D-glucosamine (UDP-GlcNAc). The impact on mollusc shell formation was analyzed by binocular microscopy, polarized light video microscopy in vivo, and scanning electron microscopy data obtained from shell material formed in the presence of NikkomycinZ. The partial inhibition of chitin synthesis in vivo during larval development by NikkomycinZ (5 μM – 10 μM) dramatically alters the structure and thus the functionality of the larval shell at various growth fronts, such as the bivalve hinge and the shell's edges. Conclusion Provided that NikkomycinZ mainly affects chitin synthesis in molluscs, the presented data suggest that the mollusc chitin synthase fulfils an important enzymatic role in the coordinated formation of larval bivalve shells. It can be speculated that chitin synthesis bears the potential to contribute via signal transduction pathways to the implementation of hierarchical patterns into chitin mineral-composites such as prismatic, nacre, and crossed-lamellar shell types.