Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTSIndoor fungi are present in a considerable part of the European dwellings and cause cosmetic and structural damage. The presence of indoor fungi posesa potential threat to human health as a result of continuous exposure as they are able to form allergens and mycotoxins. Indoor fungal growth does notexist without the presence and availability of water. Not much is known on the response of fungi to humidity dynamics during different stages of theirdevelopment. Relative humidity (RH) and water activity (aw) are used in many studies for the amount of water available for the fungus. A RH of 80% orhigher is thought to be required for fungal growth to occur. On average the RH is below 50% in normal buildings, suggesting a crucial role of humiditydynamics for fungal growth. In order to study the fungal response to humidity dynamics, two indoor fungal species, Cladosporium halotolerans andPenicillium rubens, were dried in controlled humidity vessels to stop growth and are rehydrated under high humidity conditions after a week. Non-linearSpectral Imaging Microscopy (NSIM) is a non-intrusive method to follow the response of fungal cells under varying relative humidity conditions by lookingat the metabolic activity of separate cells. The different developmental stages of C. halotolerans and P. rubens before and after periods of a certain level ofhumidity are determined by using Cryo Scanning Electron Microscopy (CryoSEM). A different response to humidity dynamics was seen between severaldevelopmental stages and both fungi used. More in depth research will be done on the specific cellular response of the fungi to humidity dynamics.137. Essentiality of Ku70/80 in Ustilago maydis is related to its ability to suppress DNA damage signalling at telomeres. Carmen de Sena-Tomas 1 , EunYoung Yu 2 , Arturo Calzada 3 , William K. Holloman 2 , Neal F. Lue 2 , Jose Perez-Martin 1 . 1) IBFG (CSIC-USAL), Zacarias Gonzalez 3, 37007 Salamanca, Spain; 2)Cornell University Medical College, 1300 York Avenue, 10021 New York; 3) CNB (CSIC), Darwin 3, 28049 Madrid, Spain.Ku heterodimer is formed of two subunits Ku70 and Ku80 that bind with high affinity to DNA ends in a sequence independent manner. Ku has a role inseveral cellular processes including DNA repair, telomere maintenance, transcription and apoptosis. Ku heterodimer is essential in human cells as well as inUstilago maydis, a well-characterized fungal system used in DNA repair studies. We found that depletion of Ku proteins in U. maydis elicits a DNA damageresponse (DDR) at telomeres resulting in a permanent cell cycle arrest, which depends on the activation of the Atr1-Chk1 signalling cascade. Aconsequence of this inappropriate activation is the induction of aberrant homologous recombination at telomeres manifested by the formation ofextrachromosomal telomere circles, telomere lengthening and the accumulation of unpaired telomere C-strand. Abrogation of the DDR response bydeleting either chk1 or atr1 genes alleviates much of these aberrant recombination process suggesting that one of the roles of Ku proteins at telomeres inUstilago maydis is related to the suppression of unscheduled DNA damage signalling at telomeres, in addition to the protection of telomeres.138. Magnaporthe oryzae effectors with putative roles in cell-to-cell movement during biotrophic invasion of rice. Mihwa Yi 1 , Xu Wang 2 , Jung-Youn Lee 2 ,Barbara Valent 1 . 1) Department of Plant Pathology, Kansas State University, Manhattan, Kansas 66506, USA; 2) Department of Plant and Soil Sciences,University of Delaware, Newark, Delaware 19711, USA.Previous studies implicated rice plasmodesmata in two different aspects of rice blast disease caused by the hemibiotrophic ascomycetous fungus,Magnaporthe oryzae. First, effectors that are translocated into the cytoplasm of living rice cells move ahead into uninvaded host plant cells by amechanism that depends on effector protein size and rice cell type. This suggested that these effectors move through plasmodesmata to preparesurrounding host cells for fungal infection. Second, biotrophic invasive hyphae (IH) search for locations to move into neighboring rice cells and theyundergo extreme constriction when crossing the host cell wall. These findings and additional evidence suggested that IH manipulate host pit fieldscontaining plasmodesmata for cell-to-cell movement. Our goals are to test these hypotheses, and to understand the molecular mechanisms responsiblefor cell-to-cell movement in blast disease. We have identified six biotrophy-associated secreted (Bas) proteins that accumulate around IH at the pointwhere they have crossed the rice cell wall to invade neighboring rice cells. We designated these effectors as putative fungal movement proteins (fMPs).When imaged as fluorescently labeled fusion proteins, the fMPs show unique localization patterns at the cell wall crossing points. Functional analysis ofthe fMPs is underway. Precise microscopic characterization with correlative light and electron microscopy (CLEM) and time-course, live-cell imaging isbeing performed to decipher how the fungus manipulates the rice cell wall junction area for effector trafficking and its own cell-to-cell spread. The fMPswill be localized relative to each other and to plasmodesmata-specific fluorescent markers. We will compare the structure and function of riceplasmodesmata in invaded versus non-invaded rice cells. Our results will identify novel host targets exploited by the fungus and related infectionmechanisms at the wall crossing sites to facilitate colonization in planta.139. Functional characterization of autophagy genes Smatg8 and Smatg4 in the homothallic ascomycete Sordaria macrospora. Stefanie Poeggeler,Oliver Voigt. Genetics of Eukaryotic Microorganisms, Georg-August University, Göttingen, Germany.Autophagy is a degradation process involved in various developmental aspects of eukaryotes. However, its involvement in developmental processes ofmulticellular filamentous ascomycetes is largely unknown. Here, we analyzed the impact of the autophagic proteins SmATG8 and SmATG4 on the sexualand vegetative development of the filamentous ascomycete Sordaria macrospora. A yeast complementation assay demonstrated that the S. macrosporaSmatg8 and Smatg4 genes can functionally replace the yeast homologs. By generating homokaryotic deletion mutants, we showed that the S. macrosporaSmATG8 and SmATG4 orthologs were associated with autophagy-dependent processes. Smatg8 and Smatg4 deletions abolished fruiting-body formationand impaired vegetative growth and ascospore germination, but not hyphal fusion. We demonstrated that SmATG4 was capable of processing theSmATG8 precursor. SmATG8 was localized to autophagosomes and SmATG4 was distributed throughout the cytoplasm of S. macrospora. Furthermore, wecould show that Smatg8 and Smatg4 are not only required for nonselective macroautophagy, but for selective macropexophagy as well. Our resultssuggest that in S. macrospora autophagy seems to be an essential and constitutively active process to sustain high energy levels for filamentous growthand multicellular development even under nonstarvation conditions. (Voigt O, Pöggeler S Autophagy genes Smatg8 and Smatg4 are required for fruitingbodydevelopment, vegetative growth and ascospore germination in the filamentous ascomycete Sordaria macrospora. Autophagy. 2012 Oct 12;9(1).[Epub ahead of print]).140. Laser microdissection and transcriptomics of infection cushions formed by Fusarium graminearum. Marike Boenisch 1 , Stefan Scholten 2 , SebastianPiehler 3 , Martin Münsterkötter 3 , Ulrich Güldener 3 , Wilhelm Schäfer 1 . 1) Molecular Phytopathology and Genetics, Biocenter Klein Flottbek, University ofHamburg, Germany; 2) Developmental Biology and Biotechnology, Biocenter Klein Flottbek, University of Hamburg, Germany; 3) Institute of Bioinformaticsand Systems Biology, Helmholtz Zentrum Münich (GmbH), Neuherberg, Germany.The fungal plant pathogen Fusarium graminearum Schwabe (teleomorph Gibberella zeae (Schwein) Petch) is the causal agent of Fusarium head blight(FHB) of small grain cereals and cob rot of maize worldwide. Trichothecene toxins produced by the fungus e.g. nivalenol (NIV) and deoxynivalenol (DON)contaminate cereal products and are harmful to humans, animals, and plants. We demonstrated recently, that F. graminearum forms toxin producinginfection structures during infection of wheat husks, so called infection cushions (Boenisch and Schäfer, 2011). The aims of the presented study were tofurther clarify the penetration mechanism of infection cushions by histological studies and to identify molecular characteristics of infection cushions byexpression analysis. Structural characteristics of infection cushions were visualized by 3D images following laser scanning microscopy. We observed27th Fungal Genetics Conference | 155