Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTSIn the tomato pathogen Fusarium oxysporum f. sp. lycopersici, most known effector genes reside on a pathogenicity chromosome that can be exchangedbetween strains through horizontal transfer. Expression of these effector genes is induced upon infection, but the mechanism by which this is regulated isunknown. We noticed that targeted deletion of the effector genes on the pathogenicity chromosome has a particular low rate of succes, when comparedto genes on the core genome. Possibly, the pathogenicity chromosome has a more compact (less accessible) chromatin structure. It has been shown thatrelease of chromatin condensation can be a way to regulate gene expression, for example of secondary metabolite gene clusters in Fusarium [Reyes-Dominguez et al, FGB 2012]. To test whether DNA methylation in F. oxysporum can influence effector expression, knock-outs of HP1 (heterochromatinprotein) and DIM2 (DNA methylase) were tested for expression of the effector gene SIX1. No differences compared to wild-type were observed. Previouslyit was shown that expression of SIX1 requires Sge1, a conserved transcription factor encoded in the core genome. Loss of DNA methylation did, however,also not bypass the requirement of Sge1 for SIX1 expression (in Dhp1Dsge1 and Ddim2Dsge1 double mutants). Both DIM2 and HP1 are not required forpathogenicity of F. oxysporum f.sp. lycopersici, and DNA methylation in this strain in general seems to be very low. To obtain more insight in the regulationof effector gene expression we are currently focussing on the potential targets of the transcription factors encoded on the pathogenicity chromosomeitself.558. Mechanistic investigation of Trichoderma cf. harzianum SQR-T037 mycoparasitism against Fusarium oxysporum f. sp. cubense 4, (banana wiltdisease). Jian Zhang 1,2 , Ruifu Zhang 1,2 , Irina S. Druzhinina 3,4 , Qirong Shen 1,2 . 1) Key Laboratory of Plant Nutrition and Fertilization in Low-Middle Reaches ofthe Yangtze River, Ministry of Agriculture. 210095, Nanjing, China; 2) Jiangsu Key Lab and Engineering Center for Solid Organic Waste Utilization, NanjingAgricultural University, 210095, Nanjing, China; 3) Microbiology Group, Institute of Chemical Engineering, Vienna University of Technology Getreidemarkt9/1665, A-1060 Vienna, Austria; 4) ACIB - Austrian Centre of Industrial Biotechnology, Petersgasse 14, 8010 Graz, Austria.Besides the effective stimulation of banana growth, the wild strain of Trichoderma cf. harzianum SQR-T037 (SQR-T037) is capable to control the soil-bornpathogen Fusarium oxysporum f. sp. cubense 4 (Foc4), the causative agent of banana wild disease . In this work we focused on mechanisms involved in themycoparasitic attack of SQR-T037 on Foc4. In vitro, in dual confrontation assays, SQR-T037 was able to cover (overgrow) the hyphae of Foc4 what resultedin damage of the cell wall of the pray fungus and its death. At early stages of the interactions, when SQR-T037 hyphae started to combat the colony ofFoc4, the droplets of the yellowish exudate putatively secreted by SQR-T037 were observed. The GC-MS analysis identified that the exudate containedalmitic and stearic acids, several hydrolytic enzymes (mainly chitinases and proteases) and essential amount of H 2O 2. It allowed us to assume that thesecompounds play the major role in killing the Foc4. We have detected that hyphae of SQR-T037 indeed accumulated H 2O 2 when it physically made contactwith Foc4 and moreover that H 2O 2 suppressed Foc4 growth. The results of transcriptomics analysis of genes putatively involved in the mycoparasitic attackthrough H 2O 2 or its regulation will be presented.559. Epichloënin A, a unique siderophore of Epichloae endophytes and its role in restricting fungal growth in planta. Natasha Forester 1 , Geoffrey A.Lane 1 , Iain Lamont 2 , Linda J. Johnson 1 . 1) Forage Improvement, AgResearch Limited, Palmerston North, Manawatu, New Zealand; 2) University of Otago,Dunedin, New Zealand.We have previously shown, through characterisation of a non-ribosomal peptide synthetase gene (NRPS), sidN, that the biosynthesis of a novelextracellular ferric iron-chelating siderophore designated as epichloënin A is required for maintaining mutualism of E. festucae with its grass host,perennial ryegrass (Lolium perenne). We have extended our investigation of the role of fungal siderophores in iron homeostasis through thecharacterization of other siderophore biosynthetic genes, including sidA which encodes a putative L-ornithine N5-oxygenase that catalyses the firstenzymatic step in siderophore biosynthesis and sidC, encoding a NRPS siderophore synthetase. Using DsidA, DsidC and DsidN mutants we have discoveredthat E. festucae synthesises two siderophores, epichloënin A that requires SidN and an intracellular siderophore, ferricrocin (FC) that requires SidC;production of both siderophores is totally abolished in DsidA mutants. In contrast to DsidN mutants, DsidC-infected plants showed very little phenotypicconsequences due to loss of FC, and this is likely to be due to functional redundancy of epichloënin A. The levels of iron-bound epichloënin A inside the cellare significantly higher than FC, suggesting that epichloënin A acts both as an extracellular and intracellular siderophore. While investigating the influenceof iron on the siderophore mutants in planta with hydroponically supplied nutrients, we unexpectedly demonstrated that iron exacerbates rather thancomplements the DsidN mutant phenotype. We observed increases in fungal proliferation, production of dense mycelial mats, and increased plantstunting. In infected plants, compared to wild-type (WT), there was also an increased uptake of iron in DsidN cells by reductive iron assimilation. Analysesin culture indicated that in the DsidN mutant more iron was stored (in FC and in vacuoles) than in WT fungi, suggesting that DsidN has increased access toiron relative to WT. However, ultra-structural studies of DsidN hyphae in stunted plants (that were not associated with the host vasculature) suggestedthat DsidN hyphae were often non-viable, implicating resource exhaustion from inappropriate growth and misuse of available iron. We therefore proposethat epichloënin A is a multitasking siderophore specialising in iron sequestration to moderate cellular iron supply.560. Interaction between the saprotrophic fungus Serpula lacrymans and living pine roots. Nils OS Högberg 1 , Anna Rosling 1 , Annegret Kohler 2 , MartinFrancis 2 , Stenlid Jan 1 . 1) Department of Forest Mycology, BioCenter, SLU, Uppsala, Sweden; 2) INRA, Nancy, France.Recently it has been shown, with a Comparative genomic perspective, that brown rot and mycorrhiza fungi have evolved from white rot ancestors. Woodis a composite material composed of lignin, cellulose and hemicellulose. White rot fungi are able to degrade all of these components with a combination ofcarbohydrate active and oxidative enzymes. During the course of evolution brown rot and mycorrhiza have lost most of the genes in these gene families.Nevertheless, brown rot fungi are efficient wood decomposers that degrade cellulose and hemicellulose by means of hydroxyl radical production andremaining carbohydrate active enzymes. The family Boletales includes both brown rot fungi and mycorrhiza and it is tentative to speculate that there hasbeen a parallel evolution of these ecological strategies. Here we test the effect of infecting pine roots with the brown rot fungus Serpula lacrymans. Theinteraction was neutral since plant growth was not stimulated but not reduced either. The fungus formed a mantle around the pine roots but not theHartig net that is typical for ectomycorrhiza. Fungal gene expression was compared with the wood decay transcriptome. 1250 genes were more than twofoldupregulated compared to a glucose medium control. A large proportion of the upregulated genes (62 %) are unknown. Carbohydrate active genesrepresent only 3% of this gene set and genes with oxidoreductase activity, including monoxygenases represent 4% of the upregulated genes. This isconsiderably lower compared to saprotrophic growth on wood where carbohydrate active enzymes accounted for 26% and oxidative enzymes for 19%which dominated the gene expression on wood. Gene expression for genes involved in transportation was about the same, around 10% in this experimentand under wood decomposition. Several genes that indicate an interaction with a host were also upregulated. In conclusion, gene expression wasmarkedly different between a glucose medium, wood decomposition and growth on pine roots. This may be a signal of symbiosis, the effect on pineseedling growth was neutral. Thus we cannot conclude if the interaction is beneficial or negative to the host.561. You turn me on: Pyrenophora tritici-repentis genes differentially regulated early during infection of wheat. V. A. Manning 1 , I. Pandelova 1 , L. M.258