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

deletion phenotype. Furthermore, the motif AUACCC is necessary andsufficient for binding and is most likely a regulatory element since itaccumulates in untranslated regions. An independent mRNA expressionprofiling approach revealed that the binding motif is significantly enrichedin transcripts showing altered expression levels in khd4Δ strains. Since thevast majority of potential Khd4 target mRNAs exhibit increased amounts indeletion mutants, Khd4 might promote mRNA instability. Consequently,microscopic studies with the RNA-helicase Dhh1, a component ofprocessing bodies, that are known sites of mRNA degradation, revealed colocalizationof Khd4 and Dhh1. These findings suggest that Khd4 mightfunction in mRNA-stability processes and is important for the posttranscriptionalregulation of cell morphology and pathogenicity in U.maydis.FBV009Molecular basis of photoconidiation in the filamentousfungus Trichoderma atroviride.A. Herrera*, U. Esquivel-Naranjo, M. Hernández-Oñate, E. Ibarra-LacletteNational Laboratory of Genomics for Biodiversity, None, Irapuato, MexicoTrichoderma is a common soil fungus used as a photomorphogenetic modeldue to its ability to conidiate upon exposure to light. In total darkness, T.atroviride grows indefinitely as a mycelium provided that nutrients are notlimiting. However, a brief pulse of blue light given to a radially growingcolony induces synchronous sporulation. Photoconidiation in Trichodermais controlled by the orthologs of the N. crassa white-collar genes (blr1 andblr2), that form the photreceptor complex. Recently, we have applied highthroughputsequencing technology to the study of the Trichodermaatroviride transcriptome. We obtained RNA samples from the wild typestrain grown in the dark or after exposure to a pulse of white or blue-light, aswell as from a photoreceptor mutant (Δblr-1) exposed to white light. Weidentified over 300 light responsive genes, both induced and repressed, themajority of them blr1 dependent. However, there is an important set ofgenes that is induced independently of this photoreceptor. Among the genesidentified there are transcription factors, DNA-repair enzymes, and a setchaperons, including heat shock proteins, suggesting that light is perceivedas a stress signal by Trichoderma. We have obtained gene disruptionmutants of several of the transcription factors, and other key genes. Usingthis strategy we have obtained mutants that do not conidiate in response tolight, as well as mutants that do not require this stimulus to conidiate.FBV010Using codon-improved GFP for imaging gene expressionduring germination and host penetration of Botrytiscinerea conidiaM. Leroch*Plant Pathology Group, University of Kaiserslautern, Kaiserslautern,GermanyMichaela Leroch, Tina Coenen, Dieter Koppenhöfer, Dennis Mernke,Andreas Mosbach, Prisca Schneider, Matthias Hahn. Dept.of Biology,University of Kaiserslautern, P.O. box 3049, 67653 Kaiserslautern,GermanyGermination of spores is a fundamental event in fungal life, represented bythe initiation of growth from a dormant state. In plant pathogens,germination immediately precedes host penetration, and therefore is ofcrucial importance for the success of infection. We have performedtranscriptome studies to follow gene expression changes during germinationand differentiation of Botrytis cinerea conidia. Massive changes in geneexpression were observed already after 1 hour, before germ tube emergence.The genes that were specifically upregulated during germination (1-4 h.p.i.),were found to be enriched in genes encoding secreted proteins, indicating astrong secretory activity during the early stages of development. In a bmp1MAP kinase mutant, which is essential for germination on a hydrophobicsurface and host penetration, upregulation of these genes was not observed.Using a codon-improved version of the egfp gene, strong GFP fluorescencecould be detected for the first time in B. cinerea. Promoter-GFP reporterstrains confirmed germination-specific expression for several germinationgenes. In particular, we found that the expression of several cutinase geneswas regulated both in a developmental and in a substrate (cutin monomers orwaxes) dependent manner. These data indicate a very early molecularcommunication between pathogen and host which starts during or evenbefore germ tube emergence.FBV011Characterization of Small GTPase Complexes and theirEffects on Polar Growth during Infection of ClavicepspurpureaA. Herrmann*, B. Tillmann, M. Bölker, P. TudzynskiDepartment of Biology and Biotechnology of Fungi, Institute for Biologyand Biotechnology of Plants, Münster, GermanyThe biotrophic plant pathogen Claviceps purpurea which infectsmonocotyledonous plants, among them important crops like rye, is aninteresting model organism for research in plant-pathogen interactions. Thestrict polar growth in C. purpurea‘s early infection stages in rye ovaries is ofparticular interest, as the fungus is not recognized as a pathogen possiblydue to its pollen tube-like growth. Small GTPases and their effectors areknown to be involved in polarity. Therefore, the investigation of the effectsof these factors is crucial for a better understanding of polar growth infilamentous fungi.Knockout strains of the small GTPases Rac and Cdc42 and of the p21activated kinase (PAK) Cla4 as a GTPase downstream effector have beengenerated. The deletion strains of the small GTPases showed inversephenotypes with regard to sporulation and growth patterns. In contrast tothat the deletion strain of cla4 greatly resembled the phenotype of the racknockout, thus indicating towards an involvement of Cla4 and Rac in thesame pathway [1, 2]. For a better understanding of the dynamics in theGTPase cycles, the genes of two guanine nucleotide exchange factors(GEFs), Cdc24 and Dock180, which are predicted to be specific for Cdc42or Rac, were identified in the genome. Knockout approaches of these geneshave been started and interaction studies are being carried out. No directinteraction of Cdc24 and Cdc42 could be observed, which indicates the needfor a scaffold protein to allow the reaction between a GTPase and itscorresponding GEF. First hints pointing to an interaction of the scaffoldprotein Bem1 with Cdc24 could be observed in a yeast two hybrid assay,reinforcing this particular hypothesis. As a second candidate, the gene forthe scaffold protein Far1 was identified in the genome and is beinginvestigated to elucidate its role in polar growth and formation of GTPasecomplexes. Furthermore, the sequence of a second PAK, Ste20, which isputatively involved in the Cdc42 pathway, was identified in the genome andis currently being analyzed.The results obtained by these approaches will result in a clearer picture ofcellular processes and complex compositions during infection of C.purpurea and can give useful hints for a better understanding of polargrowth in this fungus.[1] Scheffer, J. et al (2005): Eukaryot Cell 4(7): 1228-38.[2] Rolke, Y. and P. Tudzynski (2008): Mol Microbiol. 68(2):405-23.FBV012Interaction between Streptomycetes and AspergillusnidulansH.-W. Nützmann* 1,2 , V. Schroeckh 1 , K. Scherlach 3 , K. Martin 4 ,C. Hertweck 3,2 , A. Brakhage 1,21 Molecular and Applied Microbiology, Hans Knoll Institute (HKI), Jena,Germany2 Friedrich-Schiller-University, Jena, Germany3 Department of Biomolecular Chemistry, Hans Knoll Institute (HKI), Jena,Germany4 Bio Pilot Plant, Hans Knoll Institute (HKI), Jena, GermanyMicroorganisms as bacteria and fungi produce many important lowmolecularweight molecules that show different biological activities.Genome mining of fungal genomes indicated that their potential to producethese compounds designated secondary metabolites is greatlyunderestimated. However, most of the fungal secondary metabolism geneclusters are silent under laboratory conditions. Therefore, a major challengein this emerging area is to understand the physiological conditions underwhich these compounds are produced. Results in this area will lead to thediscovery of new bioactive compounds and to new insights in fundamentalaspects of communication between microorganisms.To address these questions the important model fungus Aspergillus nidulanswas coincubated with 58 different Streptomycetes. With one particularspecies, a specific interaction was shown. For the first time, usingmicroarray analyses at the molecular level it was demonstrated that thisspektrum | Tagungsband 2011