Program Book - 27th Fungal Genetics Conference

CONCURRENT SESSION ABSTRACTSSaturday, March 16 2:00 PM–5:00 PMChapelSecondary MetabolismCo-chairs: Gillian Turgeon and Bettina TudzynskiGenomic profiles of secondary metabolism genes in Cochliobolus pathogens. B. Condon 1* , D. Wu 1 , K. Bushley 3 , I. Grigoriev 2 , C. Elliott 4 , B. Howlett 4 , B. G.Turgeon 1 . 1) Plant Pathology & Plant-Micro Biology, Cornell University, Ithaca, NY; 2) DOE Joint Genome Institute, Walnut Creek, CA; 3) Dept of PlantPathology, Oregon State University, Corvallis OR; 4) School of Botany, University of Melbourne, Melbourne, AU.The genomes of five Cochliobolus heterostrophus strains, two Cochliobolus sativus strains, and three additional Cochliobolus species (Cochliobolusvictoriae, Cochliobolus carbonum, Cochliobolus miyabeanus) were sequenced at the Joint Genome Institute (JGI). These species are notable pathogens ofeconomically important grasses and many produce a signature secondary metabolite host selective toxin, conferring high virulence to a host of a particulargenotype. We catalogued the suites of secondary metabolism genes [focusing on those encoding backbone nonribosomal peptide synthetases (NRPSs) andpolyketide synthases (PKSs)] in these genomes and performed comparative phylogenomic analyses within the Cochliobolus genus and in a kingdom-widecontext. We found that NPS and PKS genes were broadly conserved, disparately conserved, or species-unique. Distribution patterns for conserved ordisparately conserved genes suggest an evolutionary mechanism involving rapid duplication, loss, and recombination of protein domains. Genescategorized as species unique within our dataset often had lone orthologs in phylogenetically distant species. Expanding genomic resources may revealthat ‘signature’ genes, formerly thought to be species-unique are present broadly, but sporadically, in other fungi. These results have strong implicationsfor understanding evolution of genes for host selective toxins and associated virulence.A biosynthetic gene cluster for the antifungal metabolite phomenoic acid in the plant pathogenic fungus, Leptosphaeria maculans. Candace Elliott 1 ,Damien Callahan 2 , Daniel Schwenk 3 , Markus Nett 4 , Dirk Hoffmeister 3 , Barbara Howlett 1 . 1) School of Botany, University of Melbourne, Melbourne,Australia; 2) Metabolomics Australia, School of Botany, The University of Melbourne, Victoria 3010, Australia; 3) Friedrich-Schiller-Universität, DepartmentPharmaceutical Biology at the Hans-Knöll-Institute, Beutenbergstrasse 11a, 07745 Jena, Germany; 4) Leibniz Institute for Natural Product Research andInfection Biology e.V., Hans-Knöll-Institute, Beutenbergstrasse 11a, 07745 Jena, Germany.Phomenoic acid, a long chain aliphatic carboxylic acid, is a major metabolite produced by Leptosphaeria maculans, a fungal pathogen of Brassica napus(canola). Early biosynthetic studies suggested that the methyl group derived from S-adenosylmethionine (SAM), whereas the incorporation pattern of[13C] acetate suggested a polyketidic origin of the linear portion of phomenoic acid (Devys et al., 1984). We have used domain modelling to predict acandidate polyketide synthase (PKS) for phomenoic acid biosynthesis. Of the 15 predicted polyketide synthases (PKS) in the L. maculans genome, sevenwere reducing with the appropriate domains (KS - keto-synthase; AT - acyltransferase; DH - dehydratase; MT- methyltransferase; ER - enoylreductase; KR -ketoreductase; ACP- acyl carrier protein) for the biosynthesis of phomenoic acid. The most highly expressed of these seven genes, PKS2, was silenced to10% of that of wild type levels and the resultant mutant produced 25 times less phomenoic acid than the wild type did, indicating that PKS2 is involved inphomenoic acid biosynthesis. This gene is part of a cluster and nearby genes are co-regulated. A two-fold reduction in the expression of the adjacenttranscriptional regulator C6TF, led to at least a 20-fold reduction in expression of PKS2, as well as of other genes in the cluster (P450, YogA, RTA1 andMFS), but not of the adjacent ChoK or a hypothetical gene (Hyp). This down-regulated mutant also showed a marked reduction in phomenoic acidproduction. Phomenoic acid is toxic towards another canola pathogen Leptosphaeria biglobosa ‘canadensis’, but L. maculans and to a lesser extent thewheat pathogen, Stagonospora nodorum are more tolerant. Phomenoic acid may play a role in allowing L. maculans to outcompete other fungi in itsenvironmental niche.Fusarin C biosynthesis in Fusarium fujikuroi: the fusarin C gene cluster, their function and regulation. Eva-Maria Niehaus 1 , Karin Kleigrewe 2 , PhilippWiemann 1 , Lena Studt 1,2 , Hans-Ulrich Humpf 2 , Bettina Tudzynski 1 . 1) Institute of Plant Biology and Biotechnology, Schlossplatz 8, 48143 Muenster,Germany; 2) Institute of Food Chemistry, Corrensstr. 45, 48149 Muenster, Germany.The filamentous fungus F. fujikuroi is known to produce a variety of structurally diverse secondary metabolites such as the plant hormones gibberellins,pigments and mycotoxins. In order to reduce the health risk of mycotoxins in food, feed and biotechnologically produced gibberellin preparations,identification of mycotoxin biosynthesis genes is of great importance. The recently sequenced genome of F. fujikuroi contains 17 polyketide synthases(PKS). So far only four of them can be linked to specific products: bikaverin, fusarins, fumonisins and fusarubins. The focus of this work is studying thebiosynthesis and regulation of the mutagenic mycotoxin fusarin C by external signals, such as nitrogen availability and pH. Furthermore the involvement ofpotential transcription factors and global regulators such as AreA, AreB, GS, PacC and three members of the velvet-like complex (Vel1, Vel2, Lae1) wereinvestigated. We show that all nine genes are co-expressed under nitrogen sufficient conditions. Chromatin immunoprecipitation (ChIP) experimentsrevealed a high level of H3K9 acetylation under these favorite conditions. By combination of gene deletion and overexpression of the cluster genes and cocultivationof different mutants, we were able to identify the intermediates and finally unraveled the entire fusarin biosynthetic pathway which we arepresenting in a model.27th Fungal Genetics Conference | 87