Program Book - 27th Fungal Genetics Conference

CONCURRENT SESSION ABSTRACTSFriday, March 15 3:00 PM–6:00 PMHeatherSexual Regulation and Evolution in the FungiCo-chairs: Frances Trail and Nicolas CorradiClonality and sex impact aflatoxigenicity in Aspergillus populations. Ignazio Carbone 1 , Bruce W. Horn 2 , Rodrigo A. Olarte 1 , Geromy G. Moore 3 , Carolyn J.Worthington 1 , James T. Monacell 4,1 , Rakhi Singh 1 , Eric A. Stone 5,4 , Kerstin Hell 6 , Sofia N. Chulze 7 , German Barros 7 , Graeme Wright 8 , Manjunath K. Naik 9 . 1)Department of Plant Pathology, NC State University, Raleigh, NC, USA; 2) National Peanut Research Laboratory, Agricultural Research Service, U.S.Department of Agriculture, Dawson, GA, USA; 3) Southern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, NewOrleans, LA, USA; 4) Bioinformatics Research Center, NC State University, Raleigh, NC, USA; 5) Department of Genetics, NC State University, Raleigh, NC,USA; 6) International Institute of Tropical Agriculture, Cotonou, Republic of Benin; 7) Departamento de Microbiologia e Inmunologia, Universidad Nacionalde Rio Cuarto, Cordoba, Argentina; 8) Department of Primary Industries, Queensland, Kingaroy, Australia; 9) Department of Plant Pathology, College ofAgriculture, Karnataka, India.Species in Aspergillus section Flavi commonly infect agricultural staples such as corn, peanuts, cottonseed, and tree nuts and produce an array ofmycotoxins, the most potent of which are aflatoxins. Aspergillus flavus is the dominant aflatoxin-producing species in the majority of crops. Populations ofaflatoxin-producing fungi may shift in response to: (1) clonal amplification that results from strong directional selection acting on a nontoxin- or toxinproducingtrait; (2) disruptive selection that maintains a balance of extreme toxigenicities and diverse mycotoxin profiles; (3) sexual reproduction thatresults in continuous distributions of toxigenicity; or (4) female fertility/sterility that impacts the frequency of sexual reproduction. Population shifts thatresult in changes in ploidy or nuclear DNA composition (homokaryon versus heterokaryon) may have immediate effects on fitness and the rate ofadaptation in subsequent fungal generations. We found that A. flavus populations with regular rounds of sexual reproduction maintain higher aflatoxinconcentrations than predominantly clonal populations and that the frequency of mating-type genes is directly correlated with the magnitude ofrecombination in the aflatoxin gene cluster. Genetic exchange within the aflatoxin gene cluster occurs via crossing over between divergent lineages inpopulations and between closely related species. During adaptation, specific toxin genotypes may be favored and swept to fixation or be subjected to driftand frequency-dependent selection in nature. Results from mating experiments in the laboratory indicate that fertility differences among lineages may bedriving genetic and functional diversity. Differences in fertility may be the result of female sterility, changes in heterokaryotic state, DNA methylation, orother epigenetic modifications. The extent to which these processes influence aflatoxigenesis is largely unknown, but is critical to understand for bothfundamental and practical applications, such as biological control. Our work shows that a combination of population genetic processes, especiallyasexual/sexual reproduction and fertility differences coupled with ecological factors, may influence aflatoxigenicity in these agriculturally important fungi.Toolkit for sexual reproduction in the genome of Glomus spp; a supposedly ancient asexual lineage. Nicolas Corradi. Department of Biology, Universityof Ottawa, Ottawa, Ontario, Canada.Arbuscular mycorrhizal fungi (AMF) are involved in a critical symbiosis with the roots of most land plants;the mycorrhizal symbiosis. Despite theirimportance for terrestrial ecosystems worldwide, many aspects of AMF evolution and genetics are still poorly understood, resulting in notorious scientificfrustrations and intense debates; especially regarding the genetic structure of their nuclei (heterokaryosis vs homokayosis) and their mode of propagation(long-term clonality vs cryptic sexuality). This will aim address the latter aspect of their biology - i.e. their mode of reproduction - by cataloguing andhighlighting emerging evidence, based on available genome sequence data, for the presence of a cryptic sexual cycle in the AMF . In particular,investigations along available genome and transcriptome data from several AMF species have unravelled the presence of a battery of genes that arecommonly linked with sexually-related processes in other fungal phyla. These include a gene-set required for the initiation and completion of aconventional meiosis, as well as many other genomic regions that are otherwise found to play a pivotal role in fungal partner recognition. The origin,diversity and functional analysis of some of these sexually-related genes in AMF will be discussed.Comparative transcriptomics identifies new genes for perithecium development. Frances Trail 1 , Usha Sikhakolli 1 , Kayla Fellows 1 , Nina Lehr 2 , JeffreyTownsend 2 . 1) Department of Plant Biology, Michigan State Univ, East Lansing, MI; 2) Department of Ecology and Evolutionary Biology, Yale University,New Haven, CT.In recent years, a plethora of genomic sequences have been released for fungal species, accompanied by functional predictions for genes based onprotein sequence comparisons. However, identification of genes involved in particular processes has been extremely slow, and new methodologies foridentifying genes involved in a particular process have not kept pace with the exponential increase in genome sequence availability. We have performedtranscriptional profiling of five species of Neurospora and Fusarium during six stages of perithecium development. We estimated the ancestraltranscriptional shifts during the developmental process among the species and identified genes whose transcription had substantially and significantlyshifted during the evolutionary process. We then examined phenotypes of knockouts of genes whose expression greatly increased in Fusariumgraminearum perithecium development. In numerous cases, gene disruption resulted in substantial changes in perithecium. These genes were notpreviously identified as candidates for function in perithecium development, illustrating the utility of this method for identification of genes associatedwith specific functional processes.27th Fungal Genetics Conference | 69