Program Book - 27th Fungal Genetics Conference

CONCURRENT SESSION ABSTRACTSInnate Immunity in Fusarium graminearum. Vong shian Simon Ip Cho 1,2 , Gitte Erbs 3 , Thomas Sundelin 3 , Peter Busk 4 , Mari-Anne Newman 3 , Stefan Olsson 1 .1) Genetics and Microbiology, University of Copenhagen, Copenhagen, Denmark; 2) USDA-ARS Cereal Disease Laboratory, University of Minnesota, SaintPaul, MN, USA; 3) Transport Biology, University of Copenhagen, Copenhagen, Denmark; 4) Dept. Biotechnology, Aalborg University, Copenhagen,Denmark.Fungi are often mostly recognized as plant pathogens that cause harm to important economical plants. In nature however, fungi are frequently victims ofbacterial parasitism but little is known about fungal defense mechanisms. The potential existence of fungal innate immunity was studied using Fusariumgraminearum as model organism and bacterial flagellin to mimic the presence of bacteria in an in vitro environment. The presence of flagellin triggered aninitial mitochondrial and cell membrane hyperpolarization which was detected using the florescent dye DiOC 7(3). This was followed by the production ofthe secondary signalling molecule Nitric Oxide (NO), common to innate immunity signalling in other eukaryotes. NO was monitored using the fluorescentdye DAF-FM. NO appears to be produced by an inducible enzyme that is regulated by complex mechanisms but centrally modulated byCalcium/Calmodulin. Inhibition studies suggest the presence of a Nitric Oxide Synthase (NOS), but no typical arginine utilizing NOS was identified withinthe F. graminearum’s genome by homology search. Various genes bearing resemblance to the archetypal NOS, as well as argininosuccinate lyase weredeleted. However, the mutants still produced NO. The presence of alternative pathways contributing towards the production of NO was investigated byadding a variety of potential substrates to challenged cultures. Various reactions were observed suggesting that several pathways are present. Inconclusion, F. graminearum reacts strongly to the presence of the bacterial Microbial Associated Molecular Pattern (MAMP) flagellin with an up-regulationof NO production showing the presence of innate immunity-like responses also in fungi.The Trichoderma reesei polyketide synthase gene pks1 is necessary for yellow-green pigmentation of conidia and is involved in the establishment ofenvironmental fitness. Lea Atanasova 1 , Benjamin P. Knox 2 , Christian P. Kubicek 1 , Scott E. Baker 2 , Irina S. Druzhinina 1 . 1) Microbiology Group, Research AreaBiotechnology and Microbiology, Institute of Chemical Engineering, Vienna University of Technology, 1060 Vienna, Austria; 2) Chemical and BiologicalProcess Development Group, Pacific Northwest National Laboratory, Richland, WA, USA.The economically important genus Trichoderma (Hypocreales, Ascomycota, Dikarya) is well known for its mycotrophic lifestyle and for the broad range ofbiotrophic interactions with plants and animals. Moreover it contains several cosmopolitan species characterized by their outstanding environmentalopportunism. These properties have given rise to the use of several species in agriculture as biopesticides and biofertilizers while T. reesei is applied forproduction of bioenergy-related enzymes. The molecular basis of the opportunistic success of Trichoderma is not yet well understood. While there is someevidence for a role of secreted enzymes and proteins, less is known about a possible role of secondary metabolites. Recently it was predicted that the PKSencoding gene pks1 from T. reesei and its orthologues are most likely responsible for the characteristic yellow-green pigmentation of conidia. To reveal thefull function of the gene we deleted it from the wild-type strain QM 6a what resulted in complete loss of the green coloration of conidia. Theecophysiological profiling of Dpks1 showed that the gene is also involved in multiple functions at different stages of the T. reesei life cycle. Testing theantagonistic antifungal potential of the T. reesei Dpks1 mutant against several host/prey fungi suggested that the loss of pks1 reduced the ability tocombat them by means of both mechanisms: the pre-contact inhibition and direct overgrowth. However the overall analysis of mycoparasitic interactionssuggests that the gene is most likely involved in protection against other fungi rather than in attacking them. Interestingly, we noticed the increasedproduction of volatile compounds by the Dpks1 strains. The phenotype microarrays showed that PKS1 encoding gene restricts T. reesei from conidiation ona number of the best utilized carbon sources but does not influence the sexual development except the alteration of stromata pigmentation. The data fortranscriptional response of genes putatively involved in above mentioned processes will be presented.Semiochemicals and signaling: plant responses to Trichoderma volatile organic compounds. Richard Hung. Plant Biology, Rutgers, The State University ofNew Jersey, New Brunswick, NJ.Volatile organic compounds (VOCs) produced by Trichoderma viride have recently been shown to have plant growth promoting effects on Arabidopsisthaliana. This finding adds a new facet to the multiple methods which fungi in the genus Trichoderma promote plant health and are beneficial to humans.Both above and below ground growth was greater in A. thaliana exposed to naturally produced T. viride VOCs as compared to controls. The average rootmass of control plants was 0.36g and the average mass of VOC exposed plants was 0.77g showing a 113% increase in plant mass. In addition there was a60% increase in chlorophyll concentration (5.5mg/g control, 8.8mg/g test). GCMS analysis of the VOCs produced by T. viride has resulted in 51 identifiedcompounds. Several compounds from the GCMS data were chosen to determine the effects of individual compounds on the health of A. thaliana. Thecompound trans-2-octenol at concentrations of 1ppm caused decreased dry weight (14% less than control) and extended root length (16% longer thancontrol), indicative of stress. At 1 and 10ppm, the compound 2,5-dimethylfuran, which has been reported to be produced by Trichoderma but was notfound in the aforementioned GCMS analysis, caused only visual differences. The exposed A. thaliana had extended stems as compared to controls but noother differences. In summary, the individual compounds of the T. viride volatile profile that were tested, did not promote plant growth.Identification of chemoattractant compounds from tomato root exudate that trigger chemotropism in Fusarium oxysporum. El Ghalid Mennat, DavidTurra, Antonio Di Pietro. Departamento de Genética, Universidad de Córdoba, 14071 Córdoba, Spain.Fusarium oxysporum is a soilborne pathogen that causes vascular wilt disease on a wide range of plant species, including tomato (Solanum lycopersicum).The host signals that trigger fungal infection are currently unknown. A chemotropic response of F. oxysporum towards tomato root exudate was observedusing a plate assay that measures directed growth of fungal germ tubes towards chemoattractants. To purifiy the chemoattractant coumpound(s) fromtomato root exudate, we applied a series of purification methods including extraction with organic and inorganic solvents, fractionation by size exclusionand ion exchange chromatography. The compound(s) showing chemoattractant activity were found in the hydophilic fraction, had a molecular weightbetween 30 and 50 kDa and were sensitive to boiling and treatment with proteinase K, suggesting that they correspond to one or several secreted tomatoproteins. Polyacrylamide gel electrophoresis of the active fraction revealed multiple protein bands of the expected size, two of which displayedchemoattractant activity when eluted from the gel. Identification of the active protein(s) by LC-ESI-MS is currently ongoing. Identification of the secretedchemoattractant(s) from tomato roots will advance our understanding of the molecular events that trigger fungus-root interactions.27th Fungal Genetics Conference | 59