Program Book - 27th Fungal Genetics Conference

CONCURRENT SESSION ABSTRACTScannot restrict polarization to a single site. Our results demonstrate how cells optimize symmetry-breaking through coupling between multiple feedbackloops.Cell wall structure and biosynthesis in oomycetes and true fungi: a comparative analysis. Vincent Bulone. Sch Biotech, Royal Inst Biotech (KTH),Stockholm, Sweden.Cell wall polysaccharides play a central role in vital processes like the morphogenesis and growth of eukaryotic micro-organisms. Thus, the enzymesresponsible for their biosynthesis represent potential targets of drugs that can be used to control diseases provoked by pathogenic species. One of themost important features that distinguish oomycetes from true fungi is their specific cell wall composition. The cell wall of oomycetes essentially consists of(1®3)-b-glucans, (1®6)-b-glucans and cellulose whereas chitin, a key cell wall component of fungi, occurs in minute amounts in the walls of some oomycetespecies only. Thus, the cell walls of oomycetes share structural features with both plants [cellulose; (1®3)-b-glucans] and true fungi [(1®3)-b-glucans, (1®6)-b-glucans and chitin in some cases]. However, as opposed to the fungal and plant carbohydrate synthases, the oomycete enzymes exhibit specific domaincompositions that may reflect polyfunctionality. In addition to summarizing the major structural differences between oomycete and fungal cell walls, thispresentation will compare the specific properties of the oomycete carbohydrate synthases with the properties of their fungal and plant counterparts, withparticular emphasis on chitin, cellulose and (1®3)-b-glucan synthases. The significance of the association of these carbohydrate synthases with membranemicrodomains similar to lipid rafts in animal cells will be discussed. In addition, distinguishing structural features within the oomycete class will behighlighted with the description of our recent classification of oomycete cell walls in three different major types. Genomic and proteomic analyses ofselected oomycete and fungal species will be correlated with their cell wall structural features and the corresponding biosynthetic pathways.Cellular morphogenesis of Aspergillus nidulans conidiophores: a systematic survey of protein kinase and phosphatase function. Lakshmi Preethi Yerra,Steven Harris. University of Nebraska-Lincoln, Lincoln, NE.In the filamentous fungus Aspergillus nidulans, the transition from hyphal growth to asexual development is associated with dramatic changes inpatterns of cellular morphogenesis and division. These changes enable the formation of airborne conidiophores that culminate in chains of sporesgenerated by repeated budding of phialides. Our objective is to characterize the regulatory modules that mediate these changes and to determine howthey are integrated with the well-characterized network of transcription factors that regulate conidiation in A. nidulans. Because protein phosphorylationis likely to be a key component of these regulatory modules, we have exploited the availability of A. nidulans post-genomic resources to investigate theroles of protein kinases and phosphatases in developmental morphogenesis. We have used the protein kinase and phosphatase deletion mutant librariesmade available by the Fungal Genetics Stock Center to systematically screen for defects in conidiophore morphology and division patterns. Our initialresults implicate ANID_11101.1 (=yeast Hsl1/Gin4) in phialide morphogenesis, and also reveal the importance of ANID_07104.1 (=yeast Yak1) in themaintenance of cell integrity during asexual development. Additional deletion mutants with reproducible defects have been identified and will bedescribed in detail. We will also summarize initial results from double mutant analyses that attempt to place specific protein kinase deletions within theregulatory network that controls conidiation.Septum formation starts with the establishment of a septal actin tangle (SAT) at future septation sites. Diego Delgado-Álvarez 1 , S. Seiler 2 , S. Bartnicki-García 1 , R. Mouriño-Pérez 1 . 1) CICESE, Ensenada, Mexico; 2) Georg August University, Göttingen, Germany.The machinery responsible for cytokinesis and septum formation is well conserved among eukaryotes. Its main components are actin and myosins, whichform a contractile actomyosin ring (CAR). The constriction of the CAR is coupled to the centripetal growth of plasma membrane and deposition of cell wall.In filamentous fungi, such as Neurospora crassa, cytokinesis in vegetative hyphae is incomplete and results in the formation of a centrally perforatedseptum. We have followed the molecular events that precede formation of septa and constructed a timeline that shows that a tangle of actin filaments isthe first element to conspicuously localize at future septation sites. We named this structure the SAT for septal actin tangle. SAT formation seems to bethe first event in CAR formation and precedes the recruitment of the anillin Bud-4, and the formin Bni-1, known to be essential for septum formation.During the transition from SAT to CAR, tropomyosin is recruited to the actin cables. . Constriction of the CAR occurs simultaneously with membraneinternalization and synthesis of the septal cell wall.Visualization of apical membrane domains in Aspergillus nidulans by Photoactivated Localization Microscopy (PALM). Norio Takeshita 1 , Yuji Ishitsuka 2 ,Yiming Li 2 , Ulrich Nienhaus 2 , Reinhard Fischer 1 . 1) Dept. of Microbiology, Karlsruhe Institute of Technology, Karlsruhe, Germany; 2) Institute for AppliedPhysics, Karlsruhe Institute of Technology.Apical sterol-rich plasma membrane domains (SRDs), which can be viewed using the sterol-binding fluorescent dye filipin, are gaining attention for theirimportant roles in polarized growth of filamentous fungi. The size of SRDs is around a few mm, whereas the size of lipid rafts ranges in general between10-200 nm. In recent years, super-resolution microscope techniques have been improving and breaking the diffraction limit of conventional lightmicroscopy whose resolution limit is 250 nm. In this method, a lateral image resolution as high as 20 nm will be a powerful tool to investigate membranemicrodomains. To investigate deeply the relation of lipid membrane domains and protein localization, the distribution of microdomains in SRDs wereanalyzed by super-resolution microscope technique, Photoactivated Localization Microscopy (PALM). Membrane domains were visualized by each markerprotein tagged with photoconvertible fluorescent protein mEosFP for PALM. Size, number, distribution and dynamics of membrane domains, anddynamics of single molecules were investigated. Time-laps analysis revealed the dynamic behavior of exocytosis.68