VAAM-Jahrestagung 2011 Karlsruhe, 3.–6. April 2011

FBV003Molecular and chemical characterization of secondarymetabolite gene clusters in Fusarium fujikuroiE.-M. Niehaus*, B. TudzynskiInstitute of Biology and Biotechnology of Plants, Westphalian Wilhelms-University, Münster, GermanyThe filamentous fungus F. fujikuroi is known to produce a variety of severalsecondary metabolites such as the plant hormones gibberellins, polyketidepigments such as bikaverin and fusarubin, and mycotoxins like beauvericin,fusarin C and moniliformin (MON) which cause enormous economicallosses in trade of crops.In order to reduce the health risk of these mycotoxins in food, feed andbiotechnologically produced gibberellin preparations, identification of theinvolved gene clusters is of great importance.The recently sequenced genome of F. fujikuroi contains 17 polyketidesynthases (PKS). So far we know the genes which encode the polyketidesynthases of bikaverin, fusarin C, fumonisin and fusarubin. Currently we areworking on the elucidation of the biosynthetic pathway of fusarin C usingthe deletion mutants of the involved gene cluster which recently have beenidentified in Fusarium ssp. Until now only the hybrid polyketidesynthase/nonribosomal peptide synthetase-encoding gene (PKS/NRPS) hasbeen identified in F. venetatum.Further on the identification of the biosynthetic genes for the mycotoxinMON is of great interest. Up to now none of the MON biosynthetic genes isknown in any Fusarium ssp. Therefore we are generating deletion mutantsfor putative PKS genes in a MON-producing F. fujikuroi strain, because aPKS pathway is suggested in the literature.Besides’ we study the influence of the regulation mechanism for differentpathway genes (the role of nitrogen and pH), as well as the impact of globalregulators on their expression (e.g. velvet, laeA and histone-modifyingenzymes).To investigate products of the remaining PKS with unknown functions theestablishment of a method for LC-MS (comparison of the product spectra ofthe deletion mutants with the wildtype) is on its way.FBV004Preventing Fusarium Head Blight of Wheat and Cob Rotof Maize by Inhibition of Fungal DeoxyhypusineSynthaseA.L. Martinez -Rocha*, M. Woriedh, W. SchäferMolecular Phytopathology and Genetics, Microbiology, Biocenter KleinFlottbek, Hamburg, GermanyUpon posttranslational activation, the eukaryotic initiation factor-5A (eIF-5A) transports a subset of mRNAs out of the nucleus to the ribosomes fortranslation. Activation of the protein is an evolutionary highly conservedprocess which is unique to eIF-5A: the conversion of a lysine to a hypusine.Instrumental for the synthesis of hypusine is the first of two enzymaticreactions mediated by deoxyhypusine synthase (DHS). We show that DHSof wheat and the pathogenic fungus Fusarium graminearum, which causesone of the most destructive crop diseases worldwide, are transcriptionallyupregulated during their pathogenic interaction. Although DHS of wheat,fungus, and human can be equally inhibited by the inhibitor CNI-1493 invitro, application during infection of wheat and maize flowers results instrong inhibition of the pathogen without interference with kerneldevelopment. Our studies provide a novel strategy to selectively inhibitfungal growth, without affecting plant growth. We identified fungal DHS asa target for the development of new inhibitors, for which CNI-1493 mayserve as a lead substance.FBV005The mitogen-activated protein kinase HOG1 in Fusariumgraminearum is involved in osmoregulation, sexualreproduction and virulence.T. Nguyen*, J. Bormann, B. Hadeler, C. Kröger, W. SchäferMolecular Phytopathology and Genetics, Microbiology, Biocenter KleinFlottbek, Hamburg, GermanyFusarium graminearum is an important ascomycetous plant pathogen andthe causal agent of Fusarium head blight disease in small grain cereals andof cob rot disease of maize. Infection with F. graminearum leads to yieldlosses and mycotoxin contamination. Among the mycotoxins produced bythe fungus, the trichothecene deoxynivalenol (DON) was shown to beimportant for virulence in wheat. The trichothecene production is influencedby the osmotic environment. In this regard we analyse the F. graminearumorthologue of the Saccharomyces cerevisiae hog1 mitogen-activated proteinkinase (MAPK). The HOG1 deletion mutants show increased sensitivitytowards osmotic treatments. The mutants show a reduced growth rate onagar plates supplemented with 0.8 M NaCl. On this medium conidialgermination is severely impaired. Germ tubes emerging from conidia areswollen and contain multiple nuclei. Furthermore, sexual reproduction isharmed in the deletion mutants. They completely fail to produce peritheciaand ascospores on wheat nodes and carot agar. The in planta DONproduction is nearly abolished in the deletion mutants. However, weobserved an even higher DON concentration in the deletion mutants whenanalyzed under in vitro induction conditions. The HOG1 deletion mutantsare completely apathogenic towards wheat and maize. Except for the pointinoculatedspikelet, no disease symptoms are detectable. In order to analyzethe infection pattern of the mutants in more detail, we constitutively expressthe fluorescent protein dsRED in these strains and in the wild type. Usingthese strains we are able to monitor the formation of infection structures onthe surface of the spikelet and to follow the infection process in the plant.FBV006Will be presented as poster with the ID FBP045!FBV007Cell wall thickness and composition in the yeastsSaccharomyces cerevisiae and Kluyveromyces lactis adaptto growth conditionsK. Backhaus*, J. HeinischDepartment of Biology, University of Osnabrück, Osnabrück, GermanyThe cell wall is an essential part of fungal cells, which provides protectionagainst adverse environmental conditions and determines cell morphology.In yeasts, it is made up of two layers. The inner one appears electrontransparent in transmission electron microscopy (TEM) and is composed ofβ-1,3-glucan, β-1,6-glucan and a minor amount of chitin. The outer - moreelectron dense - layer consists of mannoproteins. Both, the polysaccharideand the protein composition of the cell wall are constantly remodelled as aresult of normal growth and are also dependent on the environmentalconditions, such as carbon sources or the presence of damaging agents. Thisremodelling is triggered by the cell wall integrity pathway, which detectsperturbances at the cell surface, triggers an intracellular, highly conservedMAPK cascade and leads to proper cellular responses by activation oftranscription factors.We will report on our results regarding a comparison of cell walls from twodifferent ascomycetous yeast species: The baker's yeast S. cerevisiae and themilk yeast K. lactis. Both the cell wall proteome and the overall thickness ofthe cell wall, which corresponds to its polysaccharide composition, vary inresponse to the carbon soure used for growth (i.e. glucose versus ethanol).Another conserved protein kinase complex so far only reported to theregulate carbohydrate metabolism also seems to influence cell wall thicknessand composition in S. cerevisiae. We will present our preliminary data withregard to this regulation.FBV008The AUACCC-binding protein Khd4 regulates cellmorphology and pathogenicity in Ustilago maydisE. Vollmeister*, C. Haag, S. Baumann, M. FeldbrüggeInstitute for Microbiology, Heinrich-Heine-University, Düsseldorf, GermanyIn the plant-pathogen Ustilago maydis evidence is accumulating that posttranscriptionalprocesses play a major role in regulating cell morphology andpathogenicity. Key factors of the post-transcriptional machinery are RNAbindingproteins, which recognize specific motifs within target transcripts toregulate for example translation, localization, or mRNA-stability. We areworking with the RNA-binding protein Khd4 that contains at least five Khomology domains. Deletion of khd4 leads to severe consequences:disturbed cell shape, abnormal cell wall composition, cytokinesis defect, andstrongly reduced pathogenicity. Interestingly, the KH domains 3 and 4,which recognize the motif AUACCC, are required for Khd4 function sincemutations in the conserved structural motif G-X-X-G lead to the khd4spektrum | Tagungsband 2011