Program Book - 27th Fungal Genetics Conference

CONCURRENT SESSION ABSTRACTSRapid evolution of female-biased genes: a novel example from the eukaryotic model organism Neurospora crassa. Hanna Johannesson, Carrie Whittle.Evolutionary Biology, Uppsala University, Uppsala, Sweden.In animals and plants, sex-biased gene expression plays a major role in gene evolution. In particular, reproductive genes with male-biased expressiontend to exhibit rapid protein evolution and reduced codon bias as compared to female-biased or unbiased genes. Minimal data are available for fungi.Here, we demonstrate that sex-biased expression is associated with gene evolution in the filamentous fungus Neurospora crassa, but in contrast toanimals and plants, the rapid evolution occurs for female-biased genes. Based on analyses of >25,000 expressed sequence tags (ESTs) from male (conidial),female (protoperithecial) and vegetative (mycelial) tissues, we show that reproductive genes with female-biased expression exhibit faster proteinevolution and reduced optimal codon usage than male-biased genes and vegetative genes. Furthermore, our data suggest that female-biased genes arealso more apt to experience selective sweeps. The sex-biased expression effects are observable at the species and population level. We argue that therapid molecular evolution of female-biased genes is best explained by sexual selection via female-female competition, but could also result from matechoiceand/or directional natural selection.Self-attraction can not bypass the requirement for two mating type genes during sexual reproduction in Neurospora crassa. Katherine A. Borkovich,Hyojeong Kim, Sara Wright, Gyungsoon Park, Shouqiang Ouyang, Svetlana Krystofova. Plant Pathology and Microbiology, University of California, Riverside,Riverside, CA.The pheromone receptor PRE-2 is highly expressed in male and female reproductive structures of mat a strains in Neurospora crassa. Trichogynes fromDpre-2 mat a protoperithecia do not respond chemotropically to mat A conidia or form mature fruiting bodies or meiotic progeny. Strains with swappedidentity due to heterologous expression of pre-2 or its cognate pheromone ccg-4 behave normally in crosses with opposite mating-type. Coexpression ofpre-2 and ccg-4 in the mat A background leads to self-attraction and development of barren perithecia that lack ascospores. Further perithecialdevelopment is achieved by inactivation of Sad-1, a gene required for meiotic gene silencing in N. crassa. Results from studies using forced heterokaryonsof opposite mating-type strains show that the presence of one receptor and its compatible pheromone is necessary and sufficient for perithecialdevelopment and ascospore production. Taken together, the results demonstrate that although receptors and pheromones control sexual identity, themating-type genes (mat A and mat a) must be in two different nuclei to allow meiosis and sexual sporulation to occur in N. crassa.Fertility in Aspergillus fumigatus and the identification of an additional ‘supermater’ pair. Céline M. O'Gorman 1 , Sameira S. Swilaiman 1 , Janyce A. Sugui 2 ,Kyung J. Kwon-Chung 2 , Paul S. Dyer 1 . 1) School of Biology, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom; 2) MolecularMicrobiology Section, Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health,Bethesda, Maryland, USA.Aspergillus fumigatus is an opportunistic human pathogen that causes a range of allergic and invasive diseases in severely immunocompromisedindividuals, with a very high mortality rate typically in excess of 50%. A functional sexual cycle was discovered in 2009 and a highly fertile ‘supermater’ pair,AFB62 and AfIR928, was later identified from a collection of 50 isolates. Here we describe the results of a larger, worldwide fertility screen and present anadditional ‘supermater’ pair. A set of 126 clinical and environmental A. fumigatus isolates were crossed against two Irish reference strains of each matingtype. A subset of the eight most-fertile strains was then tested in all pairwise combinations. The pairing of isolates 47-169 x 47-154 had consistently highmating efficiency and outcrossing ability after four weeks, therefore it was chosen as an additional ‘supermater’ pair for community use in mating projects.It is important to have alternative tester strains to allow for unexpected mating differences when crossing isolates of diverse genetic origins. This isbecause factors such as heterokaryon incompatibility (het) loci and single nucleotide polymorphisms, can considerably influence sexual compatibility. Theworldwide fertility screen found that approximately 85% of isolates are sexually fertile, indicating that sexual reproduction should be possible in naturewhen suitable environments are present. Next, the plasticity of sexual crossing conditions was tested, to determine whether they could be manipulated toincrease fertility in crosses involving low-fertility strains of interest. A range of environmental and growth conditions were examined, including incubationtemperature, CO 2 level, and oatmeal agar type. Fertility levels were significantly affected by certain parameters. Work is ongoing to integrate these factorsto further optimize fertility in the ‘supermater’ pairs.Sexual reproduction and mating type function in the penicillin producing fungus Penicillium chrysogenum. Julia Böhm 1 , Birgit Hoff 1 , Simon Wolfers 1 ,Céline O'Gorman 2 , Paul Dyer 2 , Stefanie Pöggeler 3 , Ulrich Kück 1 . 1) Christian Doppler Laboratory for Fungal Biotechnology, Ruhr-Universität Bochum,Universitätsstr. 150, 44780 Bochum, Deutschland; 2) School of Biology, University of Nottingham, University Park, Nottingham, NG7 2RD, U.K; 3) AbteilungGenetik eukaryotischer Mikroorganismen, Institut für Mikrobiologie und Genetik, Georg-August Universität Göttingen, 37077 Göttingen, Deutschland.Penicillium chrysogenum is a filamentous fungus of major medical and historical importance, being the original and present day industrial source of theantibiotic penicillin with a world market value of about 600 million € per year. The species has been considered asexual for over 100 years and despiteconcerted efforts it has not been possible to induce sexual reproduction. However, we recently were able to detect mating type loci in different strains,indicating a sexual lifecycle. Isolates, carrying opposite mating types, were found in near-equal proportion in nature and we observed transcriptionalexpression of mating type loci as well as pheromone and pheromone receptor genes [1]. Utilising knowledge of mating-type (MAT) gene organization wenow describe conditions under which a sexual cycle can be induced leading to the production of cleistothecia and meiotic ascospores, which were similarto those described recently for Eupenicillium crustaceum [2]. Evidence of recombination was obtained using both molecular and phenotypic markers. Thenewly identified heterothallic sexual cycle was used for strain development purposes, generating offspring with novel combinations of traits relevant topenicillin production.Furthermore, the MAT1-1-1 mating-type gene, known primarily for a role in governing sexual identity, was also found to control transcription of a widerange of genes including those regulating penicillin production, hyphal morphology and conidial formation, all traits of biotechnological relevance. Forfunctional characterization MAT1-1-1 knockout and overexpression strains were generated and analyzed. These discoveries of a sexual cycle and MATgene function are likely to be of broad relevance for manipulation of other asexual fungi of economic importance.[1] Hoff B, Pöggeler S, Kück U (2008) Eighty years after its discovery, Fleming`s Penicillium strain discloses the secret of its sex. Eukaryot Cell 7: 465-470[2] Pöggeler S, O'Gorman CM, Hoff B, Kück U (2011) Molecular organization of the mating-type loci in the homothallic ascomycete Eupenicilliumcrustaceum. Fungal Biol. 115: 615-624.70