Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTSascarosides, which serve essential functions in regulating nematode development and behavior. Here we show that nematophagous fungi, naturalpredators of soil-dwelling nematodes, can detect and respond to ascarosides. Nematophagous fungi use specialized trapping devices to catch andconsume nematodes, and previous studies demonstrated that most fungal species do not produce traps constitutively but rather initiate trap-formation inresponse to their prey. We found that ascarosides, which are constitutively secreted by many species of soil-dwelling nematodes, represent a conservedmolecular pattern used by nematophagous fungi to detect prey and trigger trap formation. Ascaroside-induced morphogenesis is conserved in severalclosely related species of nematophagous fungi and occurs only under nutrient-deprived condition. Our results demonstrate that microbial predatorseavesdrop on chemical communication among their metazoan prey to regulate morphogenesis, providing a striking example of predator-prey coevolution.We anticipate that these findings will have broader implications for understanding other inter-kingdom interactions involving nematodes, whichare found in almost any ecological niche on Earth.536. Molecular diagnosis to discriminate pathogen and apathogen species of the hybrid Verticillium longisporum on the oilseed crop Brassica napus.Van Tuan Tran, Susanna Braus-Stromeyer, Christian Timpner, Gerhard Braus. Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen,Grisebachstr. 8, 37077 Göttingen, Germany.The cruciferous fungal pathogen Verticillium longisporum represents an allodiploid hybrid with long spores and almost double the amount of nuclearDNA compared to other Verticillium species. V. longisporum evolved at least three times by hybridization. In Europe, virulent A1xD1 and avirulent A1xD3hybrids were isolated from the oilseed crop Brassica napus. Parental A1 or D1 species are yet unknown whereas the D3 lineage represents Verticilliumdahliae. The V. longisporum isolates from Europe or California corresponding to hybrids A1xD1 or A1xD3 were analyzed. Only one single characteristic typeof ribosomal DNA (rDNA) could be assigned to each hybrid lineage. The avirulent A1xD3 isolates carried exclusively D3 rDNA, which corresponds to V.dahliae, whereas the rDNA of the virulent A1xD1 isolates originates from A1. Both hybrid lineages carry distinct isogene pairs of conserved regulatorygenes corresponding to either A1 or D1/D3. D1 and D3 paralogues show high identities but differ in several single nucleotide polymorphisms. Distinctsignatures of the VTA2 regulatory isogene pair allow the identification of V. longisporum hybrids by a single PCR and the separation from haploid speciesas A1 or D1/D3. The combination between the VTA2 marker as a barcode marker and differentiation of the rDNA type represents an attractive diagnostictool to discriminate allodiploid from haploid Verticillia and to distinguish between A1xD1 and A1xD3 hybrids, which differ in their virulence towards B.napus. Furthermore, the VTA2 gene was demonstrated to be a virulence factor that is required for fungal morphogenesis and plant infection.537. Investigating the Pathogenicity of Armillaria. Kathryn Ford 1 , Beatrice Henricot 3 , Kendra Baumgartner 2 , Gary D. Foster 1 , Andy M. Bailey 1 . 1) MolecularPlant Pathology, University of Bristol, Bristol, United Kingdom; 2) USDA-ARS, Plant Pathology, University of California, Davis, CA; 3) Royal HorticulturalSociety, Plant Pathology, Surrey, United Kingdom.Armillaria sp., or 'honey mushroom', is a generalist pathogen of fruit, nut and timber trees in gardens, forests and agricultural systems worldwide,causing Armillaria root disease and resulting in significant yield losses and millions of dollars worth of damage annually. Several questions regarding theinfection mechanisms used by basidiospores, hyphae and rhizomorphs and their subsequent colonisation processes remain unanswered. We established areproducible method of producing fruiting bodies in culture in order to generate basidiospores for use in Agrobacterium-mediated transformation tofacilitate further exploration of Armillaria’s pathogenicity. Results will be presented on the construction and utilisation of various plasmids conferringhygromycin resistance and fluorescent protein expression that have been used to transform A. mellea in order to study the infection mechanisms inherbaceous plants.538. Detoxification of nitric oxide by flavohemoglobin and the denitrification pathway in the maize pathogen Fusarium verticillioides. ThomasBaldwin 1,2 , Anthony Glenn 2 . 1) Plant Pathology Department, Univ of Georgia, Athens, GA; 2) USDA, ARS, R.B. Russell Research Center, Toxicology andMycotoxin Research Unit, , Athens, GA.The ephemeral nitric oxide (NO) is a free radical, highly reactive, environmentally rare, and a potent signaling molecule in organisms across kingdoms oflife. This gaseous small molecule can freely transverse membranes and has been implicated in aspects of pathogenicity both in animal and plant hosts.Fusarium verticillioides is a mycotoxigenic pathogen of maize, notable for its ability to persist as an asymptomatic endophyte. One potential determinantof this lifestyle conversion between overt pathogen and symptomless endophyte may be the regulation of NO. Detoxification of NO is a knownpathogenicity factor for the fungal human pathogen Candida albicans and the bacterial plant pathogen Erwinia chrysanthemi. Both mediate detoxificationby a flavohemoglobin protein (CaYHB1 and HmpX, respectively). BLASTP search of the F. verticillioides genome revealed two putative flavohemoglobinhomologs, denoted FHB1 and FHB2. Microarray analysis revealed a significant induction of FHB2 (13-fold) when the fungus was exposed to exogenous NO.FHB1 had a 2-fold increase. Also noteworthy from the microarray data is the distinct induction of genes within the denitrification pathway, includingdissimilatory nitrate reductase (dNaR, 16-fold increase), dissimilatory nitrite reductase (dNiR, 226-fold), and P450 nitric oxide reductase (P450nor, 27-fold).Flavohemoglobin has been noted as a component of the denitrification pathway, having a role in converting NO to nitrate. Thus, FHB2 is postulated to bethe paralog involved in the F. verticillioides denitrification pathway. Deletion mutants are being created in dNiR, P450nor, FHB1, and FHB2 to furtherevaluate functions of these genes in F. verticillioides. Mutants will be assayed for their endogenous production and regulation of NO, response toexogenous NO, virulence against maize, and mycotoxin production. Elucidating the function of these genes will give insight into the role of NO in F.verticillioides development, maize-fungal interactions, and denitrification, which has previously only been assessed in relation to anaerobic growth.539. Family disintegration: One Fusarium verticillioides beta-lactamase gene at a time. Scott E. Gold, Xiu Lin, Nicole J. Crenshaw, Anthony E. Glenn.Toxicology & Mycotoxin Research, USDA-ARS, Athens, GA.Fusarium verticillioides is a mycotoxigenic fungus found commonly on maize, where it primarily exhibits asymptomatic endophytic growth. The F.verticillioides genome possesses approximately 30 regions that potentially encode beta-lactamase enzymatic domains. These enzymes are classicallyinvolved in bacterial resistance to beta-lactam antibiotics, for example penicillinase. Our attention was drawn to this enzymatic function by the recentfinding that the gene FVEG_08291 is essential for resistance to maize phytoanticipins such as 2-benzoxazolinone (BOA), which possesses a gamma-lactammoiety, the presumed enzymatic target (see poster by Glenn et al.). FVEG_08291 belongs to a subset of these enzymes known as metallo-beta-lactamases.Beta-lactamase enzyme function is not well studied in the fungi, so, in order to further evaluate the roles of these enzymes in F. verticillioides, we are inthe process of deleting the members of their encoding gene family. We assigned directed-research undergraduates each a specific gene, for which theyproduced deletion constructs by DelsGate and/or OSCAR methodology and generated fungal transformants for analysis. Deletion mutants in one of theother metallo-beta-lactamase encoding genes (FVEG_12159) showed a dramatic defective growth phenotype. This observation raises the interestinghypothesis that perhaps this mutant is no longer resistant to a lactam moiety containing compound produced by F. verticillioides itself. Data will bepresented on initial progress with this project.27th Fungal Genetics Conference | 253