Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTSlength of the mutant conidia was approximately 25% longer than the wild type. Deletion mutants of ELP3 were sensitive to stress conditions, such as highsaltstress (NaCl and KCl), suggesting a role in adaptation to environmental condition. Virulence on wheat heads was greatly reduced in the ELP3 deletionmutants. These results demonstrate that ELP3 is required for normal sexual and asexual development and ELP3 could be involved in cell size regulation inG. zeae.145. Functional analyses of regulators of G protein signaling (FgRGS) and GzGPA proteins in Gibberella zeae. A.R. Park 1 , A.-R. Cho 1 , J.-A. Seo 2 , K. Min 1 , H.Son 1 , J. Lee 3 , G.J. Choi 4 , J.-C. Kim 4 , Y.-W. Lee 1 . 1) Department of Agricultural Biotechnology and Center for Fungal Pathogenesis, Seoul National University,Seoul 151-921, Republic of Korea; 2) Science and Technology Division, Ministry for Food, Agriculture, Forestry and Fisheries, Gyeonggi-Do 427-712,Republic of Korea; 3) Department of Applied Biology, Dong-A University, Busan 604-714, Republic of Korea; 4) Eco-friendly New Materials Research Group,Research Center for Biobased Chemistry, Division of Convergence Chemistry, Korea Research Institute of Chemical Technology, Daejeon 305-343, Republicof Korea.G protein signaling pathways play key roles in the regulation of fungal development, secondary metabolism, and virulence. Regulators of G proteinsignaling (RGS) proteins make up a highly diverse and multifunctional protein family that plays a critical role in controlling heterotrimeric G proteinsignaling. The genome of the plant pathogenic fungus Gibberella zeae contains seven RGS genes (FgFlbA, FgFlbB, FgRgsA, FgRgsB, FgRgsB2, FgRgsC, andFgGprK). Here we functionally characterized the function of these genes in various cellular processes. Mutant phenotypes were observed for deletionmutants of FgRgsA and FgRgsB in vegetative growth, FgFlbB and FgRgsB in conidia morphology, FgFlbA in conidia production, FgFlbA, FgRgsB, and FgRgsCin sexual development, FgFlbA and FgRgsA in spore germination and mycotoxin production, and FgFlbA, FgRgsA, and FgRgsB in virulence. Furthermore,FgFlbA, FgRgsA, and FgRgsB acted pleiotropically, while FgFlbB and FgRgsC deletion mutants exhibited a specific defect in conidia morphology and sexualdevelopment, respectively. Site-directed Ga subunits mutagenesis and overexpression of the FgFlbA gene revealed that deletion of FgFlbA and dominantactive GzGPA2 mutant, gzgpa2 Q207L , had similar phenotypes in cell wall integrity, perithecia formation, mycotoxin production, and virulence, suggestingthat FgFlbA may regulate asexual/sexual development, mycotoxin biosynthesis, and virulence through GzGPA2-dependent signaling in G. zeae. Especially,GzGPA2 might activate trichothecene production in a FgFlbA-dependent manner.146. A novel gene, GEA1, is required for ascus cell wall development in the ascomycete fungus, Gibberella zeae. H. SON 1 , J. Lee 2 , Y.-W. Lee 1 . 1)Department of Agricultural Biotechnology and Center for Fungal Pathogenesis, Seoul National University, Seoul 151-921, Republic of Korea; 2) Departmentof Applied Biology, Dong-A University, Busan 604-714, Republic of Korea.The ascomycete fungus Gibberella zeae is a devastating plant pathogen for major cereal crops. Ascospores are produced via sexual reproduction andforcibly discharged from mature perithecia, which function as the primary inocula. Perithecium development involves complex cellular processes and isunder polygenic control. In this study, a novel gene, GEA1, was found to be required for ascus wall development in G. zeae. GEA1 deletion mutantsproduced normal-shaped perithecia and ascospores, yet ascospores were observed to precociously germinate inside of perithecium. Moreover, GEA1deletions resulted in abnormal ascus walls that collapsed prior to ascospore discharge. Based on localization of GEA1 to the endoplasmic reticulum (ER),GEA1 may be involved in protein export from the ER to the ascus wall biogenesis. This is the first report to identify a unique gene required for ascus walldevelopment in G. zeae.147. A systems-biology approach to build gene-regulatory network models connecting osmotic stress responses and asexual development in Fusariumgraminearum. A. Thompkins, M. Sexton, S. Atkinson, B. Bass, E. Delancy, J. Rhodes, J. Flaherty. Science and Mathematics, Coker College, Hartsville, SC.Fusarium graminearum is a notorious fungal plant pathogen and causes head blight disease in small grain cereals and ear rot disease in maize. Infectionwith F. graminearum leads to yield losses and mycotoxin contamination. Mycotoxin formation and asexual development are thought to share commonnodes of genetic regulation. However, the regulatory networks connecting salt/osmotic stress to either is limited or undefined. Salt tolerance is a complextrait that remains poorly understood. Very few genes have been identified that are required for salt tolerance in plants, animals, or fungi. To address this,we screened >5,000 insertional mutants of F. graminearum (PH-1) for gain-of-function or loss-of-function phenotypic classes specific to both asexualdevelopment (conidiation) and osmotic stress responses. These screens yielded strains representing all classes and one outlier from each were chosen foradditional analyses. Mutant 9E1 exhibits an “osmotic hyper-tolerant” phenotype when cultured on growth media containing either NaCl or glycerol. Incontrast, mutant 11B1 displays an “osmotic-overly sensitive” phenotype, where growth is severely limited on concentrations of solute that have anegligible effect on growth by control strains. Both 9E1 and 11B1 grow normally on non-osmotically adjusted media and were subsequently chosen fortranscription-profiling experiments. Additionally, mining gene expression data of developmental mutants 8B5 (aconidial) and 8E8 (hyperconidial) haverevealed coordinately expressed, putative candidate regulatory genes. Based on a transcriptomics framework, we applied a bioinformatics approach toidentify shared gene regulatory networks involved in osmotic stress responses and conidiation.This project was supported in part by grants from the National Science Foundation (MCB 0845324), the National Center for Research Resources (5 P20RR016461), and the National Institute of General Medical Sciences (8 P20 GM103499) from the National Institutes of Health.148. Starvation enhances heterokaryon formation between incompatible strains of Fusarium oxysporum. Shermineh Shahi, Martijn Rep. Molecular PlantPathology, Swammerdam Institute for Life Sciences, Amsterdam, Nordholland, Netherlands.Fusarium oxysporum (Fo) is a pathogenic species complex with a broad host range. Comparative genomics revealed lineage-specific (LS) genomic regionsin Fusarium oxysporum f. sp. lycopersici (Fol) that account for more than 25% of the genome. At least two LS chromosomes can be transferred horizontallyto non-pathogenic Fo strains, resulting in acquired pathogenicity in the recipient [1]. Here we want to elucidate the chromosome transfer pathway and themechanisms by which the incompatibility reaction between strains is avoided. It has been suggested that heterokaryon formation is necessary forhorizontal chromosome transfer in Colletotrichum gloeosporioides [2] and that heterokaryon incompatibility is suppressed after conidial anastomosis tube(CAT) fusion [3]. To study nuclear dynamics during formation of heterokaryotic cells in Fo, we observed green or red fluorescent protein labeled nuclei ofFol and a non-pathogenic Fo strains in a vegetatively incompatible interaction.While in rich medium co-cultivation of both strains revealed no heterokaryotic cells, co-cultivation under starvation conditions led to up to ~30%heterokaryotic colonies (red and green nuclei). We were able to distinguish between different types of heterokaryotic conidia. In some cases aftergermination only one of the nuclei was able to propagate, which always originated from the pathogenic strain. In other cases both nuclei were able topropagate and these colonies in turn produced uninucleate conidia (yellow nuclei). Another intriguing finding was that the pathogenic strain used faredbetter under starvation conditions (higher germination and growth rate). We conclude that under starvation condition Fol is the dominant/fitter strain andthat heterokaryon formation in Fo is greatly enhanced, possibly by further suppressing non-self recognition machinery in CATs and/or increased hyphal27th Fungal Genetics Conference | 157