Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTS217. “The vacuole” of Neurospora crassa may be composed of multiple compartments with different structures and functions. Barry J. Bowman 1 , EmmaJean Bowman 1 , Robert Schnittker 2 , Michael Plamann 2 . 1) MCD Biology, University of California, Santa Cruz, CA; 2) Department of Biology, University ofMissouri, Kansas City, KA.The structure of the “vacuole” in Neurospora crassa and other filamentous fungi is highly variable with cell type and position in the hypha. Largespherical vacuoles are typically observed in older hyphal compartments, but approximately 100 microns behind the hyphal tip, vacuolar markers are seenin a dynamic network of thin tubules. At the edge of this network nearest the tip, a few distinct round organelles of relatively uniform size (2-3 microns)have been observed (Bowman et al. Eukaryotic Cell 10:654 ). The function of these round organelles is unknown, although the vacuolar ATPase and avacuolar calcium transporter are strongly localized there. To help identify organelles we have tagged SNARE proteins and Rab GTPases with GFP and RFP.Several of these tagged proteins (sec-22, rab-7, rab-8) appear in the tubular vacuolar network and in the membrane of the round organelles. A uniqueaspect of the round organelles is their association with dynein and dynactin (Sivagurunathan et al. Cytoskeleton, 69:613). In strains with mutations in thetail domain of the dynein heavy chain the dynein is often seen in clumps. This aggregated dynein appears to be tightly associated with (and possibly inside)the round organelles, but not in the tubular vacuolar network. Further analysis of the location of SNARE and Rab proteins may help to identify the functionof the round organelles.218. Comparisons of two wild type A mating type loci and derived self-compatible mutants in the basidiomycete Coprinopsis cinerea. Yidong Yu, MonicaNavarro-Gonzaléz, Ursula Kües. Molecular Wood Biotechnology + Technical Mycology, University of Goettingen, Goettingen, Germany.The A mating type locus in Coprinopsis cinerea controls defined steps in the formation of a dikaryotic mycelium after mating of two compatiblemonokaryons as well as fruiting body formation on the established dikaryon. Usually, three paralogous pairs of divergently transcribed genes for twodistinct types of homeodomain transcription factors (termed HD1 and HD2) are found in the multiple alleles of the A locus. For regulation of sexualdevelopment, heterodimerization of HD1 and HD2 proteins coming from allelic gene pairs is required. In some A loci found in nature, alleles of gene pairsare not complete or one of the two genes have been made inactive. Functional redundancy allows the system still to work as long as an HD1 gene in oneand an HD2 gene in the other allele of one gene pair are operative (Casselton and Kües 2007). Here, we present the structures of two completelysequenced A loci, A42 (this study) and A43 (Stajich et al. 2010). Evidences for gene duplications, deletions and inactivations are found. The loci differ in thenumber of potential gene pairs (five versus three), in genes that have been duplicated in evolution, in genes that have been lost in evolution and in genesthat are still present but have been made inactive. Furthermore, self-compatible mutants of the A loci are found that due to fusions of an HD1 and an HD2gene can carry out sexual reproduction without mating with another compatible strain. The products of the fusion genes can take over the regulatoryfunctions normally executed by heterodimers of HD1 and HD2 proteins that come from different nuclei. In this study, we present a sequenced fusion genefrom a mutant A43 locus. The 5'-half of an HD2 gene was fused in frame to a complete HD1 gene through a linker made up from former promotersequence. An earlier described fusion protein (Kües et al. 1994) similarly contains the 5'-half of an HD2 gene that however was fused to the 3'-half of anHD1 gene. Comparison between the resulting fusion proteins indicates that presence of the HD2 homeodomain and the NLSs (nuclear localization signals)from the HD1 protein are likely essential for the function of the fusion proteins. Other domains required for function in the wild type proteins (such as forheterodimerization) are dispensable for fusion proteins that mediate a self-compatible phenotype.219. Transformation of an NACHT-NTPase gene NWD2 suppresses the pkn1 defect in fruiting body initiation of the Coprinopsis cinerea mutantProto159. Yidong Yu 1 , Pierre-Henri Clergeot 2 , Gwenäel Ruprich-Robert 3 , Markus Aebi 4 , Ursula Kües 1 . 1) Molecular Wood Biotechnology + TechnicalMycology, University of Goettingen, Goettingen, Germany; 2) Department of Botany, Stockholm University, Stockholm, Sweden; 3) Institute of Geneticsand Microbiology, University Paris-Sud, Orsay, France; 4) Institute of Microbiology, ETH Zurich, Zurich, Switzerland.Homokaryon AmutBmut is a self-compatible strain of the mushroom Coprinopsis cinerea which can carry out sexual reproduction without fusing withanother compatible strain. Due to its single nucleus, this strain allows easy induction of mutations in fruiting body formation. One such mutant is the strainProto159, which is defective in the first step of fruiting body initiation (primary hyphal knot formation; pkn1). This mutant has been isolated afterprotoplasting and regeneration of oidia (Granado et al. 1997). It has a reduced growth speed and a reduced rate of oidiation (asexual spore formation)compared to the wild type AmutBmut. In addition, with age, the mycelium of Proto159 produces a dark-brown pigment that diffuses into the medium.This pigmentation is not found in AmutBmut. Proto159 never makes any sclerotium nor initiates formation of any fruiting structure. Complementationtests have been made through transformations with a cosmid bank of the wild type AmutBmut (Bottoli et al. 1999) and the defect has beencomplemented after transformation with the wild type gene NWD2. This gene codes for a NACHT-NTPase (signal transduction protein with a NACHTdomain which is found in animal, fungal and bacterial proteins and named after four different types of P-loop NTPases NAIP, CIITA, HET-E and TP1).However, sequencing of this gene in the mutant Proto159 did not reveal any point mutations, deletions or insertions within this gene. One possibility toexplain the pkn1 defect in mutant Proto159 in connection with the transformation data is that insertion of further copies of gene NWD2 into the genomeof mutant Proto159 has a suppressor effect on the defect in the yet unknown gene pkn1. This situation is reminiscent to findings in Schizophyllumcommune where formation of fruiting bodies has been induced in monokaryons upon transformation with the gene Frt1 (Horton and Raper 1991). GeneFrt1 encodes another type of P-loop NTPase (Horton and Raper 1995) than NWD2. However, the proteins share a novel short motif of amino acid similarityat their C-terminal ends.220. Dynamics of the actin cytoskeleton in Phytophthora infestans. Harold Meijer 1 , Chenlei Hua 1 , Kiki Kots 1,2 , Tijs Ketelaar 2 , Francine Govers 1 . 1) LabPhytopathology, Wageningen University, Wageningen, Netherlands; 2) Lab Cell Biology, Wageningen University, Wageningen, Netherlands.The actin cytoskeleton is conserved among all eukaryotes and plays essential roles during many cellular processes. It forms an internal framework in cellsthat is both dynamic and well organised. The plethora of functions ranges from facilitating cytoplasmic streaming, muscle contraction, formation ofcontractile rings, nuclear segregation, endocytosis and facilitating apical cell expansions. Oomycetes are filamentous organisms that resemble Fungi butare not related to Fungi. The two groups show significant structural, biochemical and genetic differences. One prominent lineage within the class ofoomycetes is the genus Phytophthora. This genus comprises over 100 species that are all devastating plant pathogens threatening agriculture and naturalenvironments. The potato late blight pathogen Phytophthora infestans was responsible for the Irish potato famine and remains a major threat today.Previously the actin organization has been studied in several oomycetes. Next to the common F-actin filaments and cables, cortical F-actin containingpatches or plaques have been observed as in Fungi. However, only a static view was obtained. Here, we use an in vivo actin binding moiety labelled to afluorescent group to investigate the actin cytoskeleton dynamics in hyphae of P. infestans. Our results provide the first visualisation of the dynamicreorganization of the actin cytoskeleton in oomycetes. In the future, this line will provide insight in the role of the actin cytoskeleton during infection.174