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Accueil du site → Doctorat → Allemagne → 2007 → 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

Bayerischen Julius-Maximilians-Universität Würzburg (2007)

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

Zabka, Vanessa

Titre : 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

Auteur : Zabka, Vanessa

Université de soutenance : Bayerischen Julius-Maximilians-Universität Würzburg

Grade : Doktorgrades 2007

Résumé
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.

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Page publiée le 11 mars 2009, mise à jour le 12 mai 2019