@phdthesis{Koers2013,
  author    = {Koers, Sandra},
  title     = {Die Rolle der S-Typ Anionenkan{\"a}le in der Reaktion von Gerstenschließzellen auf Blumeria graminis f. sp. hordei},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-77335},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2013},
  abstract  = {In ihrer Evolution mussten Pflanzen Strategien entwickeln um sich sowohl gegen Pathogene aus der Luft als auch solche im Boden zu verteidigen. Diese Resistenzmechanismen der Pflanzen zu verstehen ist von h{\"o}chster Wichtigkeit f{\"u}r die moderne Gesellschaft. Die Weltbev{\"o}lkerung w{\"a}chst schnell, was zu der Notwendigkeit f{\"u}hrt, die landwirtschaftlichen Fl{\"a}chen m{\"o}glichst optimal zu nutzen. Ohne die Weiterentwicklung der landwirtschaftlichen Methoden wird eine ausreichende Versorgung mit Grundnahrungsmitteln nicht m{\"o}glich sein. Obwohl nicht viele Daten zu diesem Thema vorliegen, ist es sehr wahrscheinlich, dass ein hoher Prozentsatz der j{\"a}hrlichen Ernteverluste auf Pflanzenkrankheiten zur{\"u}ckzuf{\"u}hren ist (Orke et al. 1994, Pinstrup-Andersen; 2001). Der Ernteverlust ist nicht ausschließlich auf den Tod der infizierten Pflanze zur{\"u}ckzuf{\"u}hren, sondern vielmehr auf die sogenannten Resistenzkosten Walters und Heil; 2007). Um sich gegen das Pathogen zu sch{\"u}tzen m{\"u}ssen Ressourcen genutzt werden, die sonst f{\"u}r die korrekte Entwicklung der Pflanze, sowie der Samen und Fr{\"u}chte verwendet w{\"u}rden. Die pflanzliche Cuticula, welche die Blattoberfl{\"a}che bedeckt, ist die erste Verteidigungslinie gegen pathogene Microorganismen, die durch die Luft verbreitet werden. Um diese Barriere zu umgehen nutzen Bakterien und einige Pilze die Stomata als Eingang in den Apoplasten der Bl{\"a}tter. Dies kann durch die Pflanze allerdings verhindert werden, indem diese Poren geschlossen werden. Diese Schließzellantwort wurde zun{\"a}chst als Teil der Immunantwort auf Bakterien angesehen (Melotto et al. 2006). Nichtsdestotrotz konnte beobachtet werden, dass die Stomata auch w{\"a}hrend der Infektion des Mehltaupilzes schließen, obwohl dieser nicht durch die Stomata in das Blatt eindringen. Daher haben wir Einzelzellstudien an intakten Gerstenpflanzen vorgenommen um zu kl{\"a}ren, wie die Signale erkannt und weitergeleitet werden, die schließlich zum pathogen-induzierten Stomaschluss f{\"u}hren (Koers et al. 2011). Zusammengefasst kann gesagt werden, dass der Stomaschluss ein wichtiger Bestandteil der pflanzlichen Immunantwort ist. Innerhalb dieser Antwort der Stomata auf durch Wind {\"u}bertragene Pathogene, spielt die Aktivierung der S-Typ Anionenkan{\"a}le eine entscheidende Rolle. Es konnte dabei gezeigt werden, dass die Immunantwort die Licht-induzierte Inhibierung dieser Anionenkan{\"a}le außer Kraft setzt. S-Typ Anionenkan{\"a}le sind aber nicht allein in der Pathogenabwehr von Bedeutung, sondern auch in der Reaktion der Pflanzen auf Trockenstress. Es ist jedoch nicht bekannt, in wie weit sich die beiden Signalwege {\"u}berschneiden. Zusammen mit den neuen mutierten Gerstenlinien, werden die in dieser Arbeit beschriebenen Techniken zur Messung von Einzelzellen tiefere Einsichten in das Zusammenspiel zwischen Trockenstress und Pathogenabwehr in Pflanzen erm{\"o}glichen. Die daraus resultierenden Ergebnisse k{\"o}nnen zur Optimierung von Getreide f{\"u}r die moderne Landwirtschaft genutzt werden. Dies wird einer der wichtigsten Ans{\"a}tze sein, um die Menschheit auch in Zukunft mit ausreichend Nahrung versorgen zu k{\"o}nnen.},
  subject      = {Elektrophysiologie},
  language  = {de}
}
@phdthesis{Zabka2008,
  author    = {Zabka, Vanessa},
  title     = {The Plasticity of Barley (Hordeum vulgare) Leaf Wax Characteristics and their Effects on Early Events in the Powdery Mildew Fungus (Blumeria graminis f.sp. hordei): Interactive Adaptations at the Physiological and the Molecular Level},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-26402},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2008},
  abstract  = {In order to test the effects of environmental factors on different characteristics of plant leaf waxes, barley plants (Hordeum vulgare) were abiotically stress treated (exposure to darkness, heavy metal, high salt concentrations and drought), and biotically stressed by the infection with powdery mildew (Blumeria graminis f.sp. hordei; Bgh). Different wax parameters like amount, chemical composition, and micromorphology of epicuticular wax crystals, were investigated. Etiolated leaves of barley showed distinctly reduced wax amounts and modifications in their relative composition. The alterations of these wax parameters might be a result of a developmental delay, which could have been caused by a decreased availability of energy for cellular processes, due to lack of light. Cadmium exposure led to a 1.5-fold increase of wax amount, while chemical composition was unaffected. In drought- and salt-stressed plants, all investigated leaf wax parameters remained unaltered. In each of the abiotic treatments, the microstructure of epicuticular wax crystals, formed as typical platelets, was not modified. Even after 6d infection with powdery mildew (Bgh), neither locally nor systemically enforced modifications of wax features were revealed. The analyzed leave surfaces, resulting from these four abiotic and the biotic treatment (phenotypic approach), were compared to altered leaf surfaces' characteristics of 18 analyzed eceriferum (cer-) wax mutants (genotypic approach). Within the screening, 5 mutants were selected which distinctly differed from the wild-type in wax amount, portions of epi- and intracuticular wax fraction, relative chemical composition, crystal morphology, and surface wettability (hydrophobicity). Apart from quantitative and qualitative effects on the leaf waxes, environmentally enforced modifications in cuticular waxes might be reflected in molecular processes of wax biogenesis. Therefore, a barley wax-microarray was established. 254 genes were selected, which are putatively involved in processes of de novo fatty acid biosynthesis, fatty acid elongation, and modification, and which are supposed to take part in lipid-trafficking between cell compartments, and transport of wax components to the outer cell surface. The regulations within the expression pattern evoked by the respective treatments were correlated with the corresponding analytical wax data, and the observed molecular effects of a 3d powdery mildew infection were compared with succeeding fungal morphogenesis. Etiolation and cadmium exposition pointed to transcriptional modifications in the de novo fatty acid synthesis, and in the screened, transport-related mechanisms, which correlate with respective alterations in surface wax characteristics. Moderate changes in the gene expression pattern, evoked by drought- and salinity-stress, might give hints for evolved adaptations in barley to such common habitat stresses. Theinvasion of powdery mildew into the epidermal host cells was reflected in the regulation of several genes. Beside other functions, these genes take part in pathogen defense, and intracellular component transport, or they encode transcription factors. The different modifications within the molecular responses evoked by the investigated abiotic treatments, and the effects of powdery mildew infection representing a biotic stressor, were compared between the different treatments. In order to test the potential impact of different wax parameters on Bgh, conidia germination and differentiation was comparably investigated on leaf surfaces of abiotically stressed wild-type and cer-mutants, isolated cuticles, and further artificial surfaces. The rates of conidial development were similar on each of the leaf surfaces resulting from the abiotic treatments, while a significant reduction of the germination and differentiation success was revealed for the wax mutant cer-yp.949. Compared to the wild-type, developmental rates on isolated cuticles and extracted leaf waxes of the mutant cer-yp.949 indicated a modified embedding of cuticular waxes, and a possibly changed three-dimensional structure of the cer-yp.949 cuticle, which might explain the reduced conidial developmental rates on leaf surfaces of this particular mutant. Experiments with Bgh conidia on mechanically de-waxed leaf surfaces (selective mechanical removal of the epicuticular leaf waxes with glue-like gum arabic, followed by an extraction of the intracuticular wax portion with chloroform) demonstrated the importance of the wax coverage for the germination and differentiation of the fungal conidia. On all dewaxed leaf surfaces, except those of cer-yp.949, the differentiation success of the germlings was significantly reduced, by about 20\% ("wax-effect"). This result was verified through an artificial system with increased conidia developmental rates on glass slides covered with extracted leaf waxes. Further comparative tests with the major components of barley leaf wax, hexacosanol and hexacosanal, showed that the germination and differentiation of powdery mildew conidia not only depends on the different chemistry, but is also influenced by the respective surface hydrophobicity. Compared to hexacosanol, on hexacosanal coated glass surfaces, higher germination and differentiation rates were achieved, which correlated with increased levels of surface hydrophobicity. Developmental rates of conidia on hydrophobic foils demonstrated that hydrophobicity, as a sole surface factor, may stimulate the conidial germination and differentiation processes. Moreover, the survival of conidia on artificial surfaces is determined by additional surface derived factors, e.g. the availability of water, and a pervadable matrix.},
  subject      = {Mehltau},
  language  = {en}
}