Program Book - 27th Fungal Genetics Conference

CONCURRENT SESSION ABSTRACTSRapid genetic change and plasticity in arbuscular mycorrhizal fungi is caused by a host shift and enhanced by segregation. C. Angelard, I. Sanders.University of Lausanne, Biophore, 1015 Lausanne, Switzerland.Arbuscular mycorrhizal fungi (AMF) are among the most abundant symbionts of plants, improving plant productivity and diversity. They are clonal; a traitassumed to limit adaptability. However, AMF harbour genetically different nuclei. We hypothesized that AMF can respond rapidly to a change ofenvironment through changes in the frequency of nuclei and by making genetically novel offspring. We subjected AMF parents and offspring to a hostshift. We observed genetic changes in all AMF lines. Genetic and phenotypic responses were different among offspring and some displayed higher fitnessthan their parents. Our results demonstrate that AMF rapidly undergo genetic change in response to the environment and that nucleotype frequency playsa role in how they perform in the new environment. Even though clonal, AMF offspring display greater genetic change and plasticity in response to hostshift. Such genetic and phenotypic flexibility is likely to be key to their ecological success.Meiotic Drive: A Single Gene Conferring Killing and Resistance in Fungal Spore Killer. Pierre Grognet 1,2* , Fabienne Malagnac 1,2 , Hervé Lalucque 1,2 , PhilippeSilar 1,2 . 1) Univ Paris Diderot, Sorbonne Paris Cité, Laboratoire Interdisciplinaire des Energies de Demain, 75205 Paris CEDEX 13 France; 2) Univ Paris Sud,Institut de Génétique et Microbiologie, Bât. 400, 91405 Orsay cedex, France.Meiotic drives (MD) are nuclear genetic loci ubiquitous in eukaryotic genomes that cheat the Mendel laws by distorting segregation in their favor. Allknown MD are composed of at least two linked genes, the distorter that acts as a toxin by disrupting the formation of gametes, and the responder thatacts as an antitoxin and protects from the deleterious distorter effects. In fungi, MDs are known as Spore Killers (SK). In the model ascomycete Podosporaanserina, MD has been associated with deleterious effect during ascospore formation of the Het-s prion and in Neurospora crassa a resistance gene(responder) to the Sk-2 and Sk-3 distorters has been identified. MDs are easily studied in P. anserina thanks to the ascus structure as SKs are identified bythe presence of 2-spored asci in crosses between strains. Here, we identify and characterize by targeted deletion in P. anserina Spok1 and Spok2, two MDelements. We show that they are related genes with both spore-killing distorter and spore-protecting responder activities carried out by the same allele,unlike other known MD. These alleles act as autonomous elements and exert their effects in any region of the genome. Moreover, Spok1 acts as aresistance factor to Spok2 killing. As Spok1 and Spok2 belong to a multigene family, these Spore Killer genes represent a novel kind of selfish genes thatproliferate in population through meiotic distortion.Cryptic population subdivision, sympatric coexistence and the genetic basis of local adaptation in Neurospora discreta. Pierre Gladieux, David Kowbel,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.Ecological context in symbioses: when is your enemy also your friend? Georgiana May 1 , Paul Nelson 2 . 1) Dept Ecol, Evol, Behavior,#100, Univ Minnesota,St Paul, MN; 2) EEB graduate program University of Minnesota St. Paul MN.Most plants are rife with fungal symbiotic partners with many of these having little apparent effect on the host's health and fitness. In this work, weexplore the degree to which the outcome of interactions between an endophytic fungus, pathogen and plant host depend on ecological context. Inparticular, we ask whether interactions between the endophyte of maize, Fusarium verticilliodes, with the pathogen Ustilago maydis, depend on hostresistance to the pathogen. In the case of a host susceptible to the pathogen, the two fungal species should meet frequently, and compete over hostresources, potentially driving greater virulence to the host in one or the other fungal species. In the case of a host resistant to the pathogen, theendophyte might be a "bystander" to the pathogen, because the two meet too infrequently to drive their co-evolutionary interaction. We show evidencethat the two fungal species have evolved stronger antagonistic interactions in maize susceptible to the pathogen, and further, that this might beassociated with greater virulence by the pathogen. Results of modeling will also be presented from which we predict longer term evolutionary trajectoriesfor this 3-way interaction.50