Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTSemerged host-pathogen system provides a rare opportunity to investigate the dynamics of gene evolution by natural selection within and between speciesand on different hosts. Here, we focused on evolution of plant cell wall degrading enzymes (PCWDEs) secreted by the fungus. We found widespreaddifferential transcription among different members of the same gene family, challenging the idea of functional redundancy and suggesting instead thatspecialized enzymatic activity occurs during different stages of the pathogen life-cycle. We also found that natural selection has significantly affected atleast 19 of the 48 identified PCWDEs. The majority of genes showed signatures of purifying selection, typical for the scenario of conserved substrateoptimization. However, six genes showed diversifying selection that could be attributed to either host adaptation or host evasion. This information can beused to determine which genes are the most appropriate targets for subsequent wet lab experimentation to elucidate enzymatic function during relevantphases of the pathogen life cycle.658. Recombination landscape of the plant pathogenic fungus Zymoseptoria tritici (syn. Mycosphaerella graminicola). D. Croll, M. Lendenmann, E.Stewart, M. Zala, B.A. McDonald. ETH Zurich, Zurich, Switzerland.Recombination is a fundamental process driving the evolution of genomes. The rate of recombination influences the level of genetic variation inpopulations and the efficacy of selection. Furthermore, heterogeneity in recombination rates along chromosomes shapes the genetic architecture ofphenotypic traits. Hence, the evolution of virulence and other traits in pathogenic fungi critically depends on the rate of recombination. Despite theimportance of recombination, the rate and homogeneity of recombination in fungal chromosomes is poorly understood. We analyzed 60 progeny from acontrolled sexual cross between two isolates of the wheat pathogen Zymoseptoria tritici (syn. Mycosphaerella graminicola). We genotyped parental strainsusing whole-genome resequencing and we generated progeny genotypes by restriction site-associated DNA sequencing (RADseq). We obtained a total of46’037 single nucleotide polymorphisms (SNP) segregating among the progeny. Based on the physical and genetic map locations of the markers, weshowed that recombination rates were strongly heterogeneous along chromosomes and were influenced by gene density and GC content. We locatedmultiple chromosomal hotspots of recombination that were interspersed by large segments of low recombination rates. Furthermore, we found thatchromosomal regions that were enriched in SNP and indels showed lower recombination rates compared to less diverged regions. The local variation inrecombination rates in Z. tritici may have significant effects on the evolutionary potential of different genomic compartments. Hence, heterogeneity inrecombination rates may play an important role in the evolution of virulence.659. The evolution of Sfp1 mediated, cell size control in Ascomycete fungi. Toni M. Delorey 1 , Jenna M. Pfiffner 1 , Sushmita Roy 2 , Jay Konieczka 1 , Dawn A.Thompson 1 , Aviv Regev 1 . 1) Broad Institute, 7 Cambridge Center, Cambridge, MA 02139; 2) Wisconsin Institute for Discovery (WID), 330 N. Orchard St,Madison, WI 53715.Divergence in gene regulation can play a major role in evolution. We used a phylogenetic framework to measure mRNA profiles in 15 yeast species andreconstruct the evolution of their modular regulatory programs. We found that modules diverge with phylogenetic distance, with prominent regulatorychanges accompanying changes in lifestyle and ploidy. Gene paralogs have significantly contributed to this regulatory divergence. To explore the role oftrans regulator duplication, we examined Sfp1, as gain or loss of the Sfp1 binding site underlied regulatory rewiring of carbon metabolism. In S. cerevisiae,Sfp1, a TOR target, activates transcription of “growth” genes. S. cerevisiae, sfp1D mutants have smaller cells and slower growth, suggesting that thesephenotypes are intertwined. However, we show that duplication of SFP1 in other yeast species has resulted in sub- and neo-functionalization of regulatoryprograms controlling growth rate and cell size. In particular, in S. castellii , the two Sfp1 paralogs have subfunctionalized; one controls cell size while theother controls growth. Therefore, we hypothesize that Sfp1 regulation of ribosome biogenesis underlies growth rate while cell size is mediated by adifferent, unidentified function. To better understand Sfp1-mediated cell size control, we used a two-tiered analysis system of comparing gene expressionand ChIP Seq data to distinguish indirect or direct Sfp1 targets. Expression programs and phenotypes of sfp1D mutants were analyzed in S. cerevisiae, C.glabrata, S. castellii, K. lactis and S. pombe. To identify putative cell size regulators, we examined differentially expressed orthologs in species where sfp1Dmutants had a small size phenotype (S. cerevisiae, C. glabrata and one paralog of S. castellii), and excluded genes involved in ribosomal biogenesis andthose differentially expressed genes in species where sfp1 mutants grew slower but had normal cell size (K. lactis and S. pombe).We found 17 overlappingorthologs including a promising candidate for cell size regulation; the S. cerevisiae ortholog, Ard1, involved in telomeric silencing, and cell cycle control.Finally, we found that Sfp1 binds to the SCH9 promoter in S. cerevisiae and S. paradoxus. Sch9 is a kinase and mutants have reduced cell size. From thesefindings, we present a novel model for cell size regulation.660. Cryptic population subdivision, sympatric coexistence and the genetic basis of local adaptation in Neurospora discreta. Pierre Gladieux, DavidKowbel, Christopher Hann-Soden, John Taylor. Department of Plant and Microbial Biology, University of California, Berkeley, CA.Identifying the genes for ecologically relevant traits is a central challenge in empirical population genetics. Species distributed across strongenvironmental gradients are excellent models to discover and identify the genetic targets of local selection as they are more likely to experience spatiallyheterogeneous selection pressures leading to local adaptation of ecologically important traits. We studied the origin of ecological differentiation in N.discreta phylogenetic species 4 (PS4), a species with a broad latitudinal distribution. We Illumina-sequenced the complete genomes of 52 individualsrepresenting 8 collections sites in Alaska, New Mexico, Washington, California, and Western Europe (average sequencing depth: 52X). Reads were mappedto the N. discreta PS4 reference genomes, and analyses were based on a final set of ca. 1.2 million high-quality SNPs. Phylogenetic analyses identified fourwell-supported clades. Papua New-Guinea individuals formed the most basal clade. Individuals from Alaska and Europe on the one hand, and from NewMexico on the other hand grouped into sister clades, and individuals from California were basal to these two clades. Individuals from Washington, sampledwithin the same site, grouped with either the New Mexico individuals, or the California individuals, indicating the coexistence in sympatry of two divergentpopulations. The observed pattern of population subdivision is being used as a reference to identify genes departing from the genome-wide background,and showing increased divergence consistent with divergent selective pressures, or decreased divergence consistent with gene-flow. Our findingsemphasize the need to continue exploration to uncover divergent populations of Neurospora, and place N. discreta, along with N. crassa, among thehandful of species that have the attributes to serve as outstanding evolutionary and ecological model organisms.661. WITHDRAWN662. Evolutionary genomics of NRPS gene clusters in Beauveria and its allies. J.-G. Han 1 , J. Oh 3 , M.-W. Hyun 2 , B. Shrestha 1 , G.-H. Sung 1 . 1) MushroomResearch Division, Rural Development Administration, Suwon 441-707, Republic of Korea; 2) College of Pharmacy, Chung-Ang University, Seoul 156-756,Republic of Korea; 3) Department of Microbiology and Institute of Basic Sciences, Dankook University, Cheonan 330-714, Republic of Korea.Beauveria is an ascomycetous asexual genus that comprises of 12 species of insect pathogens and linked to its teleomorphic stage of Cordyceps. Amongspecies of Beauveria, Beauveria bassiana is economically important for its use as biological control agent and produces several secondary metabolites suchas beauvericin and bassianolide, which are the causal metabolites of entomopathogenicity. Genes involved in these secondary metabolites are including27th Fungal Genetics Conference | 283