Program Book - 27th Fungal Genetics Conference

CONCURRENT SESSION ABSTRACTSFriday, March 15 3:00 PM–6:00 PMMerrill HallPathogenic Signaling via Effector ProteinsCo-chairs: Brett Tyler and Sebastien DuplessisDissecting nuclear immunity using Arabidopsis downy mildew effector as probes. Marie-Cecile Caillaud 1 , Lennart Wirthmueller 1,2 , Shuta Asai 1 , SophiePiquerez 1 , Georgina Fabro 1,3 , Jonathan Jones 1 . 1) The Sainsbury Laboratory, Norwich, United Kingdom; 2) John Innes Centre, Norwich, United Kingdom; 3)Present address: CIQUIBIC-CONICET, Universidad Nacional de Cordoba, Argentina.An important role in plant defence has been attributed to nuclear dynamics, since a growing number of reports reveal that the nuclear localization of keycomponents of plant immunity is essential for disease resistance. Recent studies suggest that effectors may manipulate host transcription or other nuclearprocess for the benefit of the pathogen. However, the specific mechanisms by which these effectors promote susceptibility remain unclear. Theinteraction between Arabidopsis and Hyaloperonospora arabidopsidis (Hpa) has been studied intensively during the past twenty years, and it has becomeone of the most well-understood model systems to help us understand pathogen effector biology and the plant immune system. The recent identificationof 15 nuclear-localized Hpa effectors (HaRxLs) provides a powerful tool to dissect plant nuclear immunity. When stably expressed in planta, nuclear-HaRxLs cause diverse developmental phenotypes which highlight their interferences with fundamental plant regulatory mechanisms. Remarkably, nuclearHaRxLs-plant targets are often transcriptional regulators, which may act in complex with immunity co-factors. Here, we report recent insights into ourunderstanding of the arms race between obligate pathogen and its host.The mutualistic fungus Laccaria bicolor uses the effector protein MiSSP7 to alter host jasmonate signaling and establish symbiosis. Claire Veneault-Fourrey 1 , Jonathan Plett 1,3 , Yohann Daguerre 1 , Aurélie Deveau 1 , Annegret Kohler 1 , Jennifer Morrell-Falvey 2 , Annick Brun 1 , Francis Martin 1 . 1) UMR1136IaM_INRA/UHP, Lorraine Univ / INRA, Lab of Excellence ARBRE, Nancy, France; 2) Oak Ridge National Laboratory, Oak Ridge, TN 37831-6422, USA; 3)Hawkesbury Institute for the Environment, University of Western Sydney, Australia.Roots of most trees form a nutrient-acquiring symbiosis with mutualistic fungi. Mycorrhiza-induced Smal Secreted protein MiSSP7, a fungal effectorprotein necessary for the mutualistic interaction between of the ectomycorrhizal fungus Laccaria bicolor and Populus spp. host trees, is secreted by thefungus in contact with plant tissues and is taken up via endocytosis into plant cells where it localizes to the nucleus and targets plant transcription throughan unknown mechanism Here we demonstrate that MiSSP7 interacts with the jasmonic acid receptorJAZ6 of Populus trichocarpa and that PtJAZ6 interactswith a number of other nuclear localized proteins that likely form a DNA binding complex. MiSSP7 is able to block jasmonic acid signaling in both L. bicolorhost and non-host plants, likely through its interaction with a jasmonate receptor. Loss of MiSSP7 expression in L. bicolor can be complemented bytransgenically varying the transcription of PtJAZ6 or through inhibiting jasmonic acid biosynthesis in poplar roots. We conclude that MiSSP7, in contrast toarbuscular mycorrhizal fungi and pathogenic bacteria that promote jasmonate signaling to colonize host tissues, is a novel effector used to promotemutualism by blocking jasmonic acid signaling. In addition to MiSSP7, L. bicolor expresses other MiSSPs to communicate with its host-plant. In particular,we demonstrate that MiSSP8 an apoplastic effector is required for symbiosis.Plett JM, et al. (2011) Curr Biol . 21:1197-1203.Identification and characterization of an RXLR-like effector family from medically relevant fungi. Shiv D. Kale 1* , Kelly C. Drews 1,2 , Helen R. Clark 1,3 , HuaWise 1,4 , Vincenzo Antignani 1 , Tristan A. Hayes 1,2 , Christopher B. Lawrence 1,2 , Brett M. Tyler 4,5 . 1) Virginia Bioinformatics Institute, Virginia Tech., Blacksburg,VA; 2) Department of Biological Sciences, Virginia Tech., Blacksburg, VA; 3) Department of Biochemistry, Virginia Tech., Blacksburg, VA; 4) Center forGenome Research and Biocomputing, Oregon State University, Corvallis, OR; 5) Department of Botany and Plant Pathology, Oregon State University,Corvallis, OR.Fungal infections have become an increasingly significant problem for immunocompromised individuals, transplant recipients, the elderly, several casesinvolving healthy individuals. There is a significant growth in incidences of morbidity and mortality associated with medically important fungi, specificallyAspergillus species. Aspergillus fumigatus virulence has been attributed to production of pigments, adhesins on the surface of the cell wall, secretedproteases, and mycotoxins. Current treatments consist of oral corticosteroids, antifungal medications, and/or surgery to remove aspergillomas. Many ofthese treatments have substantial shortcomings. Detection and diagnosis is also weighty problem as most clinical tests take weeks for results allowing theinfection to proceed. Appropriately, the paradigm for human fungal interactions has been focused on the host deficiencies mediating virulence ofopportunistic pathogenic fungi. There has been substantial progress in identifying and characterizing secreted proteins (effectors) from bacterial,oomycete, and fungal plant pathogens. A subset of these effector proteins are able to enter host cells and modulate host intracellular functions. Using ourbioinformatics pipeline we have been able to identify a family of secreted proteins from A. fumigatus sharing a conserved N-terminal RXLR-like motif. Wefound this family is expanded amongst primary fungal pathogens. The RXLR and RXLR-like motifs from known intracellular effectors of plant pathogenicand mutualistic oomycetes and fungi have been shown to facilitate effector entry into plant cells via binding external phosphatidylinositol-3-phosphate(PI3P). Here we describe AF2, a candidate effector from A. fumigatus that contains a N-terminal RxLR-like motif. Through the use of confocal microscopyand flow cytometry we show AF2 is rapidly able to enter several primary and immortalized mammalian cell lines. Through the use of isothermal titrationcalorimetry and liposome binding assays we show AF2 has nanomolar binding affinity for PI3P, and does not bind other mono or poly-PIPs that we havetested thus far. Based on our bioinformatics and biochemical analysis we postulate AF2 is a secreted effector protein capable of rapidly translocating intomammalian cells. We will present our latest findings on the physiological relevance of AF2.64