Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTSIllumina genome sequencing and subsequent bulk segregant analysis to identify SNP markers correlated with host-specificity phenotypes.491. Puccinia graminis and Brachypodium distachyon: contrasting profiles of host-pathogen incompatibility. Melania Figueroa 1 , Sergei Filichkin 1 , SeanGordon 2 , Henry Priest 3 , John Vogel 2 , David Garvin 4 , Todd Mockler 3 , William Pfender 1 . 1) Oregon State University, Corvallis, OR; 2) USDA-ARS, WRRC,Albany, CA; 3) Donald Danforth Plant Science Center, St. Louis, MO; 4) USDA-ARS, PSRU, St. Paul, MN.The causal agent of stem rust, Puccinia graminis, is a devastating pathogen that affects the production of cereals and temperate-zone grasses. Someimportant examples of P. graminis and their typical hosts are P. graminis f. sp. tritici (Pg-tr) on wheat and barley, P. graminis f. sp. lolii (Pg-lo) on perennialryegrass and tall fescue, and P. graminis f. sp. phlei-pratensis (Pg-pp) on timothy grass. The biological and evolutionary attributes of Brachypodiumdistachyon have led to its development as a model to study cereals and grasses. To assess the applicability of Brachypodium to investigate non-hostresistance to stem rust, disease severity caused by Pg-tr, Pg-pp and Pg-lo was evaluated across a collection of Brachypodium inbred lines. The differentfungal isolate/Brachypodium line combinations demonstrated significant variation in stem rust resistance and revealed the contrasting pathogenic/virulentcharacteristics among these stem rust isolates. Given the distinct phenotypes obtained when inoculating with Pg-tr, Pg-lo or Pg-pp, Brachypodium lineBd1-1 was selected for further analyses. Histological analysis of the early infection events (first 68 h of infection) indicated that Pg-lo and Pg-pp are moreefficient than Pg-tr in establishing a biotrophic interaction, and that Bd1-1 exhibits pre-haustorial resistance to Pg-tr and post-haustorial resistance to Pg-loand Pg-pp. A comparative transcriptome analysis (RNA-Seq) of the early responses of Bd1-1 to Pg-lo, Pg-pp and Pg-tr was performed. Gene expressionprofiles were determined to capture the transcriptional events in response to 1) appressorium formation (12 hpi, hours post-inoculation), and 2) fungalpenetration (18 hpi) and initial stages of fungal growth in the plant mesophyll for each fungal isolate. The data show distinctive profiles for each fungalisolate/Brachypodium combination. Our results demonstrate a significant transcriptional re-programming that leads to the activation of early plantdefenses associated with quantitative resistance (i.e., phenylpropanoid pathway, cytochrome P450s, and different types of transcription factors).Additionally, several receptor-like proteins and uncharacterized proteins were identified as putative players in pathogen recognition.492. Magnaporthe oryzae has evolved two distinct mechanisms of effector secretion for biotrophic invasion of rice. Martha C. Giraldo 1 , Yasin F. Dagdas 2 ,Yogesh K. Gupta 2 , Thomas A. Mentlak 2,4 , Mihwa Yi 1 , Hiromasa Saitoh 3 , Ryohei Terauchi 3 , Nicholas J. Talbot 2 , Barbara Valent 1 . 1) Plant Pathology, KansasState University, Manhattan, KS. USA; 2) School of Biosciences, University of Exeter, EX4 4QD, UK; 3) Iwate Biotechnology Research Center, Kitakami,Iwate, 024-0003 Japan; 4) Cambridge Consultants Ltd, Cambridge, CB4 0DW, U.K.Pathogens secrete effector proteins into host tissue to suppress immunity and cause disease. Pathogenic bacteria have evolved several distinct secretionsystems to target specific effector proteins during pathogenesis, but it was not previously known if fungal pathogens require different secretorymechanisms. We present evidence that the blast fungus Magnaporthe oryzae possesses distinct secretion systems for delivering effector proteins duringbiotrophic invasion of rice cells. M. oryzae secretes cytoplasmic effectors targeted for delivery inside rice cells and apoplastic effectors targeted to theextracellular space. Cytoplasmic effectors preferentially accumulate in the biotrophic interfacial complex (BIC), a novel in planta structure located besidethe tip of the initially filamentous invasive hypha and then remaining next to the first differentiated bulbous invasive hypha cell. In contrast, apoplasticeffectors remain in the extracellular compartment uniformly surrounding the invasive hypha inside the invaded cell. Disruption of the conventional ER-Golgi secretion pathway by Brefeldin A (BFA) treatment blocked secretion of apoplastic effectors, which were retained in the ER, but not secretion ofcytoplasmic effectors. Fluorescence Recovery After Photobleaching experiments confirmed that cytoplasmic effectors continued to accumulate in BICs inthe presence of BFA. Analysis of mutants showed that the BIC is associated with a novel form of secretion involving exocyst components, Exo70 and Sec5,and the t-SNARE Sso1, which are required for efficient delivery of effectors into plant cells and are critical for pathogenicity. By contrast, effectors whichfunction between the fungal cell wall and plant plasma membrane are secreted from invasive hyphae to the apoplast by the ER-Golgi secretory pathwayconserved in eukaryotes. We propose a model for the distinct secretion systems that the rice blast fungus has evolved to achieve tissue invasion.493. Trichoderma rhizosphere’s competency, endophytism and plant communication: A molecular approach. Artemio Mendoza 1 , Johanna Steyaert 1 ,Natalia Guazzone 1 , Maria Fernanda Nieto-Jacobo 1 , Mark Braithwaite 1 , Robert Lawry 1 , Damian Bienkowski 1 , Christopher Brown 2 , Kirstin MacLean 1 , RobertHill 1 , Alison Stewart 1 . 1) Bio-Protection Research Centre, Lincoln University, Lincoln, New Zealand; 2) Biochemistry Department and Genetics Otago,University of Otago, New Zealand.Establishment of root symbiosis is one the key drivers of biocontrol success for members of the fungal genus Trichoderma. This root symbiosis isdescribed as a two-step process, whereby Trichoderma species colonise the soil surrounding the root (rhizosphere) and then penetrate the root tissue andestablish an endophytic relationship. The ability to colonise and then proliferate over time within the rhizosphere is termed rhizosphere competence (RC).There have been numerous reports of Trichoderma biocontrol strains which persist within the rhizosphere for the growing season of the crop plant. Ourresults strongly suggest that RC is widespread among members of the genus Trichoderma and that RC interactions are strain and host plant specific. Forendophytes and their host plants to maintain a mutualistic relationship requires a constant molecular dialogue between the organisms involved. Forexample, the fungal-derived phytohormone, indole acetic acid (IAA), plays an important role in signalling between Trichoderma and the model plantArabidopsis thaliana. There are however, additional, currently unknown, chemical signals which may be even more important for a positive interactionbetween Trichoderma and plants. By using a soil-maize-Trichoderma as a model system in in situ sterile conditions we are currently analysing the RC andendophytism transcriptomes of two Trichoderma species: T. virens and T. atroviride. Using a combination of bioinformatics, quantitative RT-PCR (for stagespecific genetic markers from Trichoderma) and fluoro-labelled Trichoderma strains we are currently identifying and analysing promising Trichodermacandidates involved in endophytism and RC. A comprehensive panorama of the Trichoderma-soil-plant interaction will be discussed in this conference.494. Ustilago bromivora - Brachypodium distachyon: a novel pathosystem. Franziska Rabe, Regine Kahmann, Armin Djamei. Organismic Interactions, MaxPlanck Institute for Terrestrial Microbiology, Marburg, Germany.The Ustilago maydis - Zea mays pathosystem is a well established model system to investigate basic principles of biotrophic plant-pathogen interactions.However, due to the long generation time, space requirements, and difficulties in transformation of maize studying the plant side is demanding. Recently,it has been shown that the yet uncharacterized smut fungus Ustilago bromivora infects Brachypodium distachyon, a model grass species. Short generationtime, small size, sequenced diploid genome, and accessible reverse genetics make this monocot highly suitable for the analysis of biotrophic interactionswith focus on the pathogen as well as the plant side. The primary goal of this study is therefore the characterization of U. bromivora and the interactionwith its host in order to evaluate the suitability of the U. bromivora - B. distachyon interaction as a new host-pathogen model system.We could show that haploid U. bromivora strains obtained after spore germination can be cultivated and transformed with self-replicating plasmids usedfor U. maydis transformation. A hallmark of smut fungi is that the pathogenic form is the dikaryon which arises after mating of compatible haploids.Haploid cells are produced when diploid spores germinate and undergo meiosis. Usually after germination of a single teliospore, cells with compatible242