Program Book - 27th Fungal Genetics Conference

CONCURRENT SESSION ABSTRACTSSecondary metabolism in Botrytis cinerea: the grey and pink sides of a pathogen. M. Viaud 1 , H. Sghyer 1 , J. Schumacher 2 , A. Simon 1 , B. Dalmais 1 , J.M.Pradier 1 . 1) INRA, BIOGER, Av. L. Brétignières, 78850 Grignon, France; 2) Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN47906, USA.Sequencing the genome of the grey mould fungus Botrytis cinerea revealed 40 secondary metabolism (SM) gene clusters corresponding to thebiosynthesis of mostly unknown compounds including polyketides (21), terpenes (11) and non-ribosomal peptides (8). The two identified phytotoxicmetabolites are the polyketide botcinic acid (BOA) and the sesquiterpene botrydial (BOT). Transcriptomic studies previously identified the correspondingBOA and BOT gene clusters. Deletion of the key enzyme BcBOA6 (PolyKetide Synthase) or BcBOT2 (SesquiTerpene Cyclase) encoding genes did not causeany defects, while bcboa6/bcbot2 double mutants were significantly impaired in necrotrophic development on several hosts suggesting that the twocompounds have a redundant function. We are currently investigating how the BOT and BOA gene clusters are regulated: The BOA cluster contains a gene(bcboa13) encoding a C6H6 zinc finger transcription factor (TF). Surprisingly, while bcboa6 mutant has no virulence defect, bcboa13 mutant shows adrastic reduced virulence which is even more pronounced than that of the bcboa6/bcbot2 double mutant lacking both known toxins. A wholetranscriptome analysis of bcboa13 mutant is underway to determine whether other genes apart from those of the BOA cluster are regulated by this TF. Inopposite to the BOA cluster, the BOT cluster does not contain any TF-encoding gene. We therefore set up a Yeast-One-Hybrid library that contains themajority of B. cinerea TFs (393 out of 406) and screened it with the promoter of bcbot2. This led to the identification of a C2H2 TF called BcYOH1.Inactivation of bcyoh1 gene and expression analysis revealed that this TF acts as a global regulator of SM, regulating the expression of genes of the BOT,BOA, and 20 other SM clusters. As in other fungi, the Velvet complex takes part in regulation of light-dependent development and SM in B. cinerea. Geneinactivation of bcvel1, however, does not significantly modify the production of BOA and BOT. Instead, BcVEL1 plays a significant role in the regulation ofoxalic acid (OA) formation and pigmentation: it regulates negatively the synthesis of melanin and positively the synthesis of OA and bikaverin (BIK) anotherpolyketidic pigment that is only produced in rare pink strains of B. cinerea.Is fungal secondary metabolism regulated by competing insects? Annika Regulin 1 , Nancy Keller 2 , Frank Kempken 1 . 1) Department of Botany, Christian-Albrechts University, Kiel, Germany; 2) Department Medical Microbiology and Immunology, Dept of Bacteriology, UW-Madison, USA.Fungi synthesize an astonishing variety of secondary metabolites, some of which belong to the most toxic compounds in the living world. Even thoughlittle is known about the benefit of these metabolites, the ability to regulate the secondary metabolism might be seen as an evolutionary adaptation.Presumably fungi regulate secondary metabolites (e.g. mycotoxin) in response to confrontation with natural competitors like insects to guarantee efficientexploitation of environmental resources (1-3). Admittedly it should be mentioned that secondary metabolites are not the only defence mechanisms offungi (4). In order to enlighten the biological function of these secondary metabolites with reference to chemical defence reactions of insect-fungalinteractions, we utilized complementary approaches of experimental ecology and functional genomic techniques. The vinegar fly Drosophila melanogasterand its natural antagonist Aspergillus nidulans are used as an ecology model system. To analyse fungal up- or down regulated target genes in theinteraction of A. nidulans with Drosophila larvae microarray analysis was performed. This led to the identification of secondary metabolite genes up- ordown-regulated under these conditions. Quantitative RT-PCR was employed to analyze secondary metabolite gene expression at different time points.Fungal single, double and triple mutations of identified up-regulated genes are currently analyzed in confrontation assays to identify potentialmodifications in gene expression and the survival rate of larvae concerning to chemical defense reaction of fungus-insect interaction compared to wildtype. This could reveal insights about the biological function of secondary metabolite genes and clusters such as stc and mdp.(1.) Rohlfs, M., Albert, M., Keller, N. P., and Kempken, F. (2007) Biol Lett 3, 523-25. (2.) Kempken, F., and Rohlfs, M. (2010) Fungal Ecol 3, 107-14. (3.)Rohlfs, M., Trienens, M., Fohgrub, U., and Kempken, F. (2009) in "The Mycota XV. (Anke, T., Ed.), Springer Heidelberg, New York, Tokyo, pp. 131-51 (4.)Kempken, F. (2011) Mol Ecol 20, 2876-77.27th Fungal Genetics Conference | 89