Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTSnonribosomal peptide synthetase (NRPS) that are often physically clustered. To more understand the origins and evolution of these genes, we performedgenome-wide comparative analyses among B. bassiana and its allied species including B. pseudobassiana, B. sungii, Cordyceps militaris, C. pruinosa, Isariatenuipes, and I. farinosa after assembling these genomes. Initially, all the potential gene clusters for secondary metabolites were predicted using byantiSMASH. In B. bassiana, 16 NRPSs and 3 NRPS-PKS hybrid modules were estimated, while in C. militaris, 5 NRPSs and 3 hybrids were found.Interestingly, the presence/absence of NRPSs and PKSs provides a clue in generating their evolutionary hypotheses (e.g., horizontal gene transfer and genefusion). For example, bassianolide synthetase were specifically found in the species referred to Beauveria with the syntenic conservation of genesencoding calreticulin, cyclophilin, DNA replication complex, IdgA domain protein, and phenol 2-monooxygenase. The inferred phylogeny based on theacyltransferase (AT) domain showed that ATs of beauvericin synthetase gene belong to two independent lineages, suggesting that beauvericin synthetaseis a fusion gene which is formed from two previously separated genes. It is also suggested that bassianolide synthetase in Beauveria spp. are possiblyacquired by horizontal gene transfer (HGT) from distantly related fungi.663. Neurospora presents a model for the evolution of mating systems. Christopher Hann-Soden, Pierre Gladieux, John Taylor. Plant and MicrobialBiology, UC Berkeley, Berkeley, CA.The study of plants and animals has yielded a host of theories for the evolution of outbreeding and selfing mating systems, yet these theories have yet tobe extended to microbial organisms, where they might be more easily challenged. Within the genus Neurospora there is evidence of multiple shifts toselfing (homothallic) from outcrossing (heterothallic) ancestral states. However, the most well-studied clade, the members of which produce brightlycolored macroconidia, contains no homothallic members, and there is only one known clade of aconidial heterothallic Neurospora from which homothallicNeurospora could have evolved (Nygren et al. 2011, Glass et al. 1990). We hypothesized that sampling of heterothallic Neurospora has been biased towardmembers that produce brightly colored macroconidia or perithecia in isolation, thereby ignoring aconidial heterothallic species. Collections of crypticheterothallic Neurospora would allow comparison of the evolutionary forces acting on closely related pairs of selfing and outcrossing species. To this end,we have isolated 1 new strain of heterothallic Neurospora and 9 new strains of homothallic Neurospora from soil from two locations in California. Basedon partial sequences of nik-1 (Nygren et al. 2011) we constructed a phylogeny of Neurospora including the new strains. Surprisingly, the new heterothallicNeurospora was found to be almost identical to the only other aconidial, heterothallic Neurospora individuals (Glass et al. 1990), despite over 2,300 km ofseparation. Seven of the eight sequenced homothallic strains were found to be most closely related to Neurospora novoguineensis, but the remainingstrain was more closely related to the aconidial, heterothallic strains. These preliminary results suggest that additional sampling to obtain sufficiently largepopulations of related, aconidial heterothallic and homothallic Neurospora would facilitate studies of the transition from outbreeding to selfing as well asstudies of the genetic basis of the development of macroscopic, brightly colored conidia. References, Glass, N. L., Metzenberg, R. L. & Raju, N. B.Experimental Mycology 14, 274-289 (1990). Nygren, K. et al. Molecular phylogenetics and evolution 59, 649-63 (2011).664. Profiling conditionally dispensable chromosomes of the plant-pathogenic fungus Zymoseptoria tritici (syn. Mycosphaerella graminicola). RonnyKellner 1 , Veronika Schott 1 , Stephan Poppe 1 , Rachel Brem 2 , Eva H. Stukenbrock 1 . 1) Max Planck Institute for Terrestrial Microbiology, Fungal Biodiversity,Karl-von-Frisch-Strasse 10, 35043, Marburg, Germany; 2) University of California, Department for Molecular Cell Biology, 176 Stanley Hall, Berkeley, CA94720-3220, USA.Conditionally dispensable chromosomes (cDCs) are common genomic features in many parasitic ascomycetes. The presence of cDCs entails a highamount of intraspecific genomic variation that is inherited in a non-Mendelian manner. Because genes located on cDCs have in some species been shownto play a role in pathogenicity cDCs may promote rapid adaptive evolution in response to host defenses. With up to eight cDCs the genome of the wheatpathogen Zymoseptoria tritici (syn. Mycosphaerella graminicola) contains by far the largest known proportion of dispensable elements among allascomycetes. In comparison to the core chromosomes, cDCs of Z. tritici are smaller, have on average less and shorter genes with a lower GC content and ahigher amount of paralogous sequences and repetitive elements. Hitherto, the functional relevance of cDCs for Z. tritici remains unclear.In this study we elucidate the relevance of cDCs in Z. tritici by assessing expression profiles during in-planta and axenic growth. Because our RNAseqdataset covers both host and non-host interactions we broaden the perspective of our approach by insights into host-specific expression profiles. In orderto verify the current genome annotation we mapped all RNAseq reads to the genome of Z. tritici and predicted gene transcripts. By combining our resultswith the latest genome annotation we set up a new transcript list, which was used in further analyses. We demonstrate an overall significantly lowertranscription of genes located on cDCs relative to genes located on core chromosomes. In addition, cDCs encode several unique genes that are expressedunder certain conditions. We identify duplicated genes using a blast approach and show differential gene expression between paralogs on cDCs and corechromosomes. To link the transcription of cDC genes to specific stages in the interaction of Z. tritici and wheat we focus on a gene family of three paralogswhere two genes encode secreted proteins. We quantified their expression via qPCR at seven different time points of the interaction. In summary, ourstudy suggests the functional relevance of single cDC genes and the relevance of cDCs for gene innovation and adaptive evolution in Z. tritici.665. Take a walk on the wild side: evolutionary consequences of resistance to apple scab introgressed from a wild host. C. Lemaire 1 , T. Leroy 1 , M. deGracia 2 , C-E. Durel 2 , M. Templeton 3 , J. Bowen 3 , V. Caffier 2 , B. Le Cam 2 . 1) IRHS, University of Angers, Angers, France; 2) IRHS, INRA, Beaucouzé, France; 3)Plant & Food Research, Auckland, New Zealand.Theories on emergence of pathogens are dominated by ecological hypotheses. For instance overcoming of a host resistance gene is often described as aconsequence of the spreading of a mutant that invades resistant hosts from infected susceptible cultivars. However invasion of virulent populations fromwild habitats are often neglected. Though taking into account the occurrence of a preexisting allopatric virulent population greatly impacts conclusionsmade about emergence of new virulence and the nature of barriers to reproduction with the avirulent population. Indeed under allopatric scenario, thesebarriers are not expected to be only adaptive. Here, we intended to decipher the evolutionary history of the European populations of the apple scabpathogen Venturia inaequalis enable to overcome the Rvi6 resistance gene introgressed in Malus x domestica from the crabapple Malus floribunda. Usingmicrosatellite and sequence data in an Approximate Bayesian Calculation (ABC) framework, we demonstrate that virulence corresponding to a newresistance gene introgressed in agrosystems was previously present in the wild within a population that has diverged since several thousands years. Weshow that deployment of the corresponding resistance gene in agrosystems can then act as gateways for virulent populations to invade orchards. At lastwe show that secondary contact followed by mating between invading and resident population can reveal genetic incompatibilities (Dobzhansky-MüllerIncompatibilities) accumulated during divergence between the two populations. These incompatibilities induce hybrid depression by negative epistasis.This study based on state-of-the-art tools of population genomics, phenotyping and genetic mapping is the first to demonstrate the occurrence of intrinsicpost-zygotic barriers in pathogens revealed by a secondary contact. Overall, it points out the risk of generating new “hybrid” populations harbouring newpathogenic traits by introgression of resistance genes in agrosystems by breeders.284