Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTS540. A Fungal Metallo-Beta-Lactamase Necessary for Biotransformation of Maize Phytoprotectant Compounds. Anthony E. Glenn, C. Britton Davis,Maurice E. Snook, Scott E. Gold. Toxicology & Mycotoxin Research, USDA-ARS, Athens, GA.Xenobiotic compounds such as phytochemicals, microbial metabolites, and agrochemicals can impact the diversity and frequency of fungal speciesoccurring in agricultural environments. Resistance to xenobiotics may allow plant pathogenic fungi to dominate the overall fungal community, withpotential negative impacts on crop yield and value. The mycotoxigenic Fusarium verticillioides is such a fungus commonly associated with maizeworldwide, often contaminating maize kernels with the fumonisin mycotoxins. The dominance of F. verticillioides as an endophyte may be due in part toits ability to metabolize phytoprotectants produced by maize. The benzoxazinoids and benzoxazolinones are broad spectrum allelopathic, antimicrobial,and anti-herbivory compounds from maize, yet F. verticillioides can rapidly biotransform these phytochemicals into non-toxic metabolites. We haveidentified the genes responsible for the biotransformation process. Two gene clusters were identified that correspond to the previously characterizedFDB1 and FDB2 loci, with both loci being necessary for metabolic tolerance to 2-benzoxazolinone (BOA), one of the maize phytoprotectants. Analysis of thenine ORFs (FVEG_08287 to FVEG_08295) at the FDB1 locus indicated that one of the genes (FVEG_08291) encodes a protein having a metallo-betalactamasedomain, and deletion of the gene in wild-type strain M3125 resulted in the fungus being unable to grow on BOA-amended agar due to aninability to metabolize the compound. Deletion mutants were complemented to wild-type phenotype by transformation with the native allele. Other ORFswere not found to be essential when deleted in M3125. Microarray analysis indicated the metallo-beta-lactamase (FVEG_08291) had a 13-fold induction inresponse to BOA (2-hr incubation), with other genes in the cluster ranging from 3-fold (FVEG_08287) to 42-fold induction (FVEG_08292). Beta-lactamasesare well-known for conferring bacterial resistance to lactam-type antibiotics, but to our knowledge this is the first report of fungal enzymes of this typemetabolizing lactam-like xenobiotics. We are investigating other beta-lactamase encoding genes in F. verticillioides (see poster by Gold et al.) to furtherevaluate their possible role in tolerance to both exogenous as well as endogenous metabolites having lactam-type moieties.541. Nectria haematococca DNase: role in dynamics and localization of pea root infection. D. Huskey, G. Curlango-Rivera, Z. Xiong, H. Van Etten, M.Hawes. University of Arizona, Tucson, AZ.Root tips of pea (Pisum sativum L.) are protected from N. haematococca infection by an extracellular DNA (exDNA)-based trapping process similar to thatoccurring in mammalian defense responses to bacterial and fungal pathogens. N. haematococca spores germinate rapidly in response to root border cellpopulations programmed to export exDNA and antimicrobial proteins as they detach from the root cap. Within 24 h, hyphae and border cells togetherform a mantle which ensheaths the root tip and separates, leaving the root apex uninvaded: >98% of root tips escape infection. When the exDNA isdegraded with DNase added to the root at the time of inoculation, resistance is abolished: 100% of root tips are invaded by proliferating hyphae and rootgrowth ceases within 24 hours. In N. haematococca isolates harboring a conditionally dispensable (CD) chromosome, the process occurs more rapidly thanin CD-minus isolates; a ten-fold increase in spores from CD-minus isolates results in comparable dynamics. Putative DNase-encoding sequences have beendetected on two different CD chromosomes, and direct tests have revealed increased extracellular DNase activity from CD-plus isolates compared with CDminusisolates. The goal of this study is to examine predictions of the hypothesis that CD chromosome encoded DNase activity plays a role in pea rootinfection.542. FvSNF1, a protein kinase of Fusarium virguliforme that affects SDS development in Soybean. K.T. Islam, Ahmad Fakhoury. Plant, Soil and AgSystems, Southern Illinois University, Carbondale, IL.Fusarium virguliforme is a soil-borne pathogen that causes Sudden Death Syndrome (SDS). SDS is one of the top four yield-robbing fungal diseases insoybean resulting in significant economic losses to producers. Despite the importance of SDS, a clear understanding of fungal genetic factors that affectthe development of the disease is still lacking. The aggressiveness of F. virguliforme on infected soybean plants is believed to require the activity of cellwall-degrading enzymes (CWDE). The production of these CWDEs in phytopathogenic fungi is under catabolic repression. In Saccharomyces cerevisiae,catabolic repression is regulated by SNF1 (sucrose non-fermenting 1). To investigate the role of cell wall-degrading enzymes as determinants of F.virguliforme aggressiveness, the F. virguliforme SNF1 homologue FvSNF1 was targeted for disruption. The resulting FvDsnf1 transformant failed to grow ongalactose and grew poorly when arabinose or sucrose where the main carbon source. The mutation did not seem to affect the ability of the fungus to growwith glucose, fructose, maltose, or xylose as the main source of carbon. More importantly, in greenhouse experiments, the FvDsnf1 transformant wasseverely impaired in its ability to cause SDS on challenged soybean plants.543. Functional and molecular analysis of AstA sulfate transporter in pathogenic Fusarium sambucinum with respect to its virulence and ability to infectpotato. Sebastian Pilsyk 1 , Hanna Gawinska-Urbanowicz 2 , Renata Natorff 3 , Marzena Sienko 3 , Joanna S. Kruszewska 1 . 1) Laboratory of Fungal Glycobiology,Institute of Biochemistry and Biophysics, Warsaw, Poland; 2) The Plant Breeding and Acclimatization Institute (IHAR), Bonin, Poland; 3) Department ofGenetics, Institute of Biochemistry and Biophysics, Warsaw, Poland.AstA protein (alternative sulfate transporter) represents a little known type of sulfate trasporter, belonging to an extensive and poorly characterizedfamily of allantoate permeases Dal5. In Aspergillus nidulans the astA gene is under the control of Sulfur Metabolite Repression (SMR). The closesthomologs of astA are frequent in evolutionarily distant fungi belonging to the Pezizomycotina subphylum which exhibit similar plant pathogenicity.Fusarium sp. fungi, like F. sambucinum, contribute to serious devastation of potato crops and increase the cost of cultivation due to the application ofpesticides. Due to the similarity on the metabolic level between pathogenic fungi and the host, there is a problem with efficient plant protection.The aim of this project is elucidation of AstA function upon infection and colonization of potato tubers by the fungal pathogen, Fusarium sambucinumand by its astA deletion mutant. We have observed a high expression level of astA in infected potato tubers and its regulation by SMR as in A. nidulans.The study also involves the identification of amino acid residues crucial for sulfate binding and transportation by the generation of point mutations anduptake analysis. Elucidation of the biological function of AstA will help understanding of fungal pathogenic adaptations upon changes in plant hostmetabolism and definition of a new promising target for a potential fungicide.544. WITHDRAWN545. The adenylate cyclase of the cereal pathogen Fusarium graminearum controls infection structure development, mycotoxin production andvirulence to wheat. Jörg Bormann, Marike Johanne Boenisch, Elena Brückner, Demet Firat, Cathrin Kröger, Birgit Hadeler, Wilhelm Schäfer. MolecularPhytopathology, University Hamburg, Hamburg, Germany.Fusarium graminearum is one of the most devastating pathogens of cereals. Mycotoxins accumulating in infected grains are a serious threat to food andfeed worldwide. Knowledge about the molecular basis of infection and mycotoxin production is still limited. Cyclic 3’,5’-adenosine monophosphate (cAMP)254