Program Book - 27th Fungal Genetics Conference

PLENARY SESSION ABSTRACTSThursday, March 14 8:30 AM–12:00 NOONMerrill Hall and ChapelPlenary Session II: Organismic Molecular InteractionsChair: Nick TalbotLarge-scale Biology for Fungal Pathogenicity in Magnaporthe oryzae. Yong-Hwan Lee 1,2 . 1) Department of Agricultural Biotechnology, Seoul NationalUniv, Seoul, 151-921, Korea; 2) Center for Fungal Genetic Resources, and Center for Fungal Pathogenesis, Seoul National University, Seoul 151-921, Korea.Rice blast is a compelling model system for studying host-parasite interactions due to its socioeconomic impact and the availability of both the rice andfungal genomic sequences. In an attempt to understand the molecular mechanisms of rice blast, we have been taking both forward and reverse geneticsapproaches. Our researches using reverse genetics approach focus on identifying and characterizing the genes involved in signal transduction pathwaysleading to appressorium formation, genes encoding transcription factors, and genes that are required for post-penetration stages. For forward geneticsstudies, we carried out a large-scale insertional mutagenesis of the Magnaporthe oryzae strain KJ201 via Agrobacterium tumefaciens-mediatedtransformation, generating over 25,000 mutants. We also developed high throughput phenotype screening system that enables rapid and robust assay ofmutant phenotypes. In addition to our endeavor to functional and comparative genomics, we built a cyber-infrastructure for storage of heterogeneousdata and analysis of such data in multiple contexts. The whole genome sequence information of M. oryzae as well as most of the results from experimentalbiology is housed in our customized database. Our comprehensive and integrative approaches coupled with a web-based Laboratory InformationManagement System would provide a novel platform for systems biology initiatives for fungal pathogenesis.MAPK-mediated control of infectious growth in Fusarium oxysporum. Antonio Di Pietro. Departamento de Genetica, Universidad de Cordoba, 14071Cordoba, Spain.In fungal pathogens, contact with the host triggers a developmental and metabolic transition towards infectious growth. What exactly defines infectiousgrowth and how it is controlled by environmental and host-derived stimuli is not fully understood. We study infectious growth in Fusarium oxysporum, asoilborne fungus that causes vascular wilt disease on a wide range of plant species and opportunistic infections in immunocompromised humans. One ofthe key players in pathogenicity is Fmk1, a conserved mitogen-activated protein kinase (MAPK) that is essential for infection-related processes such aschemotropism, host adhesion, penetration and invasive growth in the plant tissue. Most Fmk1-dependent virulence functions require the homeodomaintranscription factor Ste12, and are repressed in the presence of the preferred nitrogen source ammonium through a mechanism that requires thetransporter MepB and the bZIP factor MeaB. Recent data suggest that ammonium repression is mediated by a shift in extracellular pH, which results inrapid changes in the phosphorylation pattern of different MAPKs. Our current research addresses the mechanisms through which pH controls invasivegrowth of F. oxysporum by reprogramming the activation status of cellular MAPK signalling cascades.Analysis of effector proteins from flax rust and wheat stem rust. Peter Dodds 1 , narayana Upadhyaya 1 , Ann-Maree Catanzariti 2 , Markus Koeck 1 , Adnanenemri 1 , Rohit Mago 1 , Simon Williams 3 , Thomas Ve 3 , Maryam Rafiqi 4 , Wenjie Wu 2 , Adrienne Hardham 2 , David Jones 2 , Jeff Ellis 1 , Bostjan Kobe 3 , Robert Park 5 .1) Plant industry, CSIRO, Canberra, ACT, Australia; 2) Australian National University, Research School of Biology,; 3) University of Queensland, School ofChemistry and Molecular Biosciences; 4) Justus Liebig University, Giessen, Germany; 5) University of Sydney, Camden.Rust fungi cause economically important diseases of cereal crops worldwide, with stem rust caused by the fungus Puccinia graminis tritici one of themost serious diseases in wheat. Because of the ability of the fungus to evolve increased virulence towards previously resistant varieties, continuousbreeding and the identification of new sources of resistance is necessary to keep apace of the threat of rust epidemics. We have been studying how theplant immune system can recognise and respond to rust pathogens using the flax rust model system. Rusts are obligate parasites of plants, and produce aspecialised infection structure called the haustorium which directly penetrates an infected cell and is the main site of nutrient extraction for the fungus. Asuite of disease effector proteins are secreted from haustoria and enter the host cells where they may allow the rust to commandeer host cell biology. It isthese translocated effector proteins that are recognised by host immune receptors, known as resistance (R) proteins. We have been exploring thestructure and function of host-translocated effectors from flax rust and also searching for effector candidates from stem rust that are recgonised by knownwheat R genes.Using genome and transcriptome sequencing we have predicted, carefully curated and analysed the transcription of 400 candidate effectorgenes from the Australian stem rust strain 21-0. To screen for effectors recognized by wheat R genes, we have developed a bacterial Type III SecretionSystem (TTSS)-based delivery assay from the non-pathogen Pseudomonas fluorescens strain Pfo. We are screening candidate effectors on a set of 18wheat cultivars carrying 22 different R genes. Thus far we have identified on effector protein induces a rapid cell death response specifically on a wheatgenotype carrying Sr22. We are also analyzing sequence variation in effector candidates between clonal field isolates that have mutated to overcome theresistance genes that have been deployed in agriculture.27th Fungal Genetics Conference | 23