Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTSOne such example is PiAvr2, which is located just 231 bp from a class II transposon. The presence of sRNAs mapping to both PiAvr2 and the nearbytransposon indicate that RNA silencing may play a role in regulation of this important effector gene. Over a hundred additional predicted genes werefound to be sRNA hotspots in our data: Crinkler effector genes, arrays of duplicated genes, potentially antisense overlapping transcripts, and genescontaining transposon insertions. Our present task is to reveal the role that sRNAs might play in their regulation.403. Epigenetic control of effector gene expression in the plant pathogen fungus Leptosphaeria maculans. Jessica Soyer, Mennat El Ghalid, Marie-HélèneBalesdent, Thierry Rouxel, Isabelle Fudal. INRA, UR 1290 BIOGER-CPP, Avenue Lucien Brétignière, F-78850 Thiverval-Grignon, France.Plant pathogenic microbes secrete an arsenal of small secreted proteins (SSPs) acting as effectors that modulate host immunity to facilitate infection. InEukaryotic phytopathogens, SSP-encoding genes are often located in particular genomic environments and show waves of concerted expression at diversestages of plant infection. To date, little is known about the regulation of their expression. Leptosphaeria maculans is an ascomycete fungus responsible forthe most devastating disease of oilseed rape (Brassica napus). The sequencing of its genome revealed a bipartite structure alternating gene rich GCisochoresand gene poor AT-isochores made up of mosaics of transposable elements. The AT-isochores encompass one third of the genome and areenriched in putative effector genes that present the same expression pattern (no or a low expression level during in vitro growth and a strong overexpressionduring primary infection). Here, we investigated the involvement of an epigenetic control in the regulation of effector gene expression. For thispurpose, we silenced expression of two key players of heterochromatin remodeling, i.e. HP1 and DIM5, by RNAi and used HP1::GFP as a heterochromatinmarker. Whole genome oligoarrays were done in silenced-HP1 and silenced-DIM5 isolates to analyze the involvement of HP1 and DIM5 on geneexpression according to their function and location. We evaluated the effect of a change of genomic context from AT-isochores to GC-isochores on theexpression of effector genes. Silencing of DIM5 resulted in lack of chromatin condensation. The silencing of HP1 and DIM5 resulted in an over-expressionof pathogenicity-related genes during in vitro growth, with a favored influence on SSP-encoding genes in AT-isochores. The “moving” of effector genescorroborated transcriptomic analysis as it led to a strong overexpression of effector genes during in vitro growth. These data strongly suggest that anepigenetic control represses the expression of effector genes located in AT-isochores during in vitro growth, which is, to our knowledge, the firstdescription of an epigenetic control, relying on HP1 and DIM5, exerted on effector-encoding genes expression. Switch toward pathogenesis lifts thisrepression based on chromatin-structure, rendering promoters of effector genes accessible to specific transcription factors.404. Discovering the link: The NOX-GSA network for sexual development and ascospore germination in Sordaria macrospora. Daniela Dirschnabel,Christian Schäfers, Ines Teichert, Ulrich Kück. General and Molecular Botany, Ruhr-University Bochum, Bochum, Germany.Recently we were successful in establishing a genetic network for sexual development and ascospore germination in the homothallic filamentous fungusSordaria macrospora [1, 2]. Central components of this network are three G-protein alpha subunits (GSA), an adenylat cyclase SAC1, and the transcriptionfactor STE12. The three GSA proteins (GSA1, GSA2 and GSA3) have different roles in developmental processes. GSA1 and GSA2 are important for sexualpropagation and the generation of perithecia, while GSA3 is essential for proper ascospore germination. Interestingly, the phenotypes of mutants lackingfungal NAD(P)H oxidases (NOX) resemble the known Dgsa phenotypes: DnoxA shows an arrest of sexual development and ascospores from a DnoxBmutant fail to germinate. These similarities raised the question, whether the GSA proteins and NOX enzymes are part of identical signaling pathways. Toverify this hypothesis, we generated knockout mutants of both NOX A and B isoforms and their regulator NOXR in S. macrospora. Our hypothesis wasfurther supported by the comparison of these mutants with gsa deletion mutants by measuring hyphal fusion events, quantification of reactive oxygenspecies and ascospore germination. The generation of double mutants and complementation studies with constitutive gsa1 derivatives enabled us topropose an interactive NOX-GSA network for sexual development and ascospore germination. References: 1.Kamerewerd, J., M. Jansson, M. Nowrousian,S. Pöggeler, and U. Kück, Three alpha-subunits of heterotrimeric G proteins and an adenylyl cyclase have distinct roles in fruiting body development in thehomothallic fungus Sordaria macrospora. Genetics, 2008. 180(1): p. 191-206. 2.Engh, I., M. Nowrousian, and U. Kück, Sordaria macrospora, a modelorganism to study fungal cellular development. European journal of cell biology, 2010. 89(12): p. 864-72.405. The bZIP transcription factor Atf1 acts as a global regulator for secondary metabolite production in Fusarium fujikuroi. Sabine E. Albermann,Bettina Tudzynski. IBBP, WWU Muenster, Schlossplatz 8, 48143 Muenster, Germany.The activating transcription factor 1 (Atf1) belongs to the bZIP transcription factor family and is known to have a great impact on stress responsesmediated by the mitogen activated protein kinase (MAPK) cascade in fission yeast. In this pathway, activation of the transcription factor is achieved byphosphorylation via the kinase Sty1. Furthermore, the transcription factor plays a role in sexual and asexual development which was observed for severalfilamentous fungi e.g. in Aspergillus species where it affects conidiospore germination. Atf1 can also act as a virulence factor which was described for itshomologue in the rye pathogen Claviceps purpurea. However, involvement of Atf1 in secondary metabolism was first observed in the grey mould Botrytiscinerea. As Atf1 seems to play a crucial role in different processes, this transcription factor was also investigated in the rice pathogen Fusarium fujikuroi.For this purpose, deletion mutants of atf1 and the Sty1 homologue sak1, the putative kinase for Atf1, were cultivated under varying conditions. HPLCanalysis of the secondary metabolite spectrum revealed a drastic change in the production level of several metabolites. Gibberellic acids, for instance, aredown-regulated up to 50 % in Datf1 compared to the wild-type, whereas the amount of gibberellins in the Dsak mutant is about twice as much as in thewild-type. Furthermore, applied salt stress dramatically enhances mycotoxin production in the Datf1 mutants, while the deletion mutant Dsak1 is not ableto grow at all. Plate assays applying different stressors to the strains revealed involvement of both proteins in the osmotic stress response. However,reactive oxygen species and cell wall damaging agents do not seem to have an impact on their growth. In contrast, reduced protoplast formation wasobserved for Datf1 mutants and even more significantly in Dsak. Therefore, it is very likely, that the cell wall composition and integrity is changed in thesemutants. Summarizing, Atf1 and Sak1 are involved in various processes such as secondary metabolite production, cell wall integrity as well as in stressresponses. The obtained information leads to the conclusion that Sak1 might be the kinase responsible for Atf1 phosphorylation. But there certainly haveto be more factors to be involved in activation of this transcription factor.406. Role of the Vivid ortholog of Fusarium fujikuroi VvdA in carotenoid biosynthesis and development. Marta Castrillo Jimenez, J. Avalos. Genetics,University of Sevilla, Sevilla, Seville, Spain.Fusarium fujikuroi is well known for its ability to produce gibberellins, growth-promoting plant hormones with agricultural applications. Recently, thisspecie has become a model system in the research of other metabolic pathways, including carotenoid biosynthesis. This fungus produces an acidicapocarotenoid, neurosporaxanthin, through the activity of the enzymes encoded by five structural genes, whose expression is induced by light. We areinterested in the molecular basis of this regulation. As usually found in fungi, the F. fujikuroi genome contains genes for WC-1 and WC-2 orthologs. Incontrast to other species with light-induced carotenogenesis, e.g., Neurospora crassa or Phycomyces blakesleeanus, this photoresponse is not impaired innull mutants of the only wc-1-like gene of F. fujikuroi, wcoA. Therefore, we are analyzing the role of other blue-light photoreceptors. Here we described220