Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTSinduced by nonsense mediated decay (NMD) and is required for efficient dissociation of the resulting termination complex. Upf1, a major NMDcomponent, is implicated not only in this but, surprisingly, in all mRNA tagging to date. This led us to propose that deadenylation of mRNA results in an"NMD-like" event, where dissociation of poly(A) binding protein results in recruitment of Upf1 to the mRNA thereby triggering translational repression,clearance of the termination complex and efficient RNA degradation. We will describe our recent findings which relate to the mechanisms that triggermRNA tagging and the downstream events which ultimately repress transcript expression.364. A novel C2H2 type finger transcription factor, MtfA, regulates mycotoxin biosynthesis and development in Aspergillus nidulans . VellaisamyRamamoorthy, Sourabh Dhingra, Sourabha Shantappa, Ana M. Calvo-Byrd. Biological Sciences, Northern Illinois University, Dekalb, IL.Secondary metabolism in the model fungus Aspergillus nidulans is controlled by the global conserved regulator VeA, which also governs morphologicaldifferentiation. Among the secondary metabolites regulated by VeA is the mycotoxin sterigmatocystin (ST), where the presence of VeA is necessary for thebiosynthesis of this carcinogenic compound. We identified revertant mutants (RM) capable of synthesizing ST in the absence of VeA. The point mutation inthe RM7 mutant occurred at the coding region of a gene encoding a novel putative C2H2 zinc finger domain type transcription factor that we denominatedMtfA. As expected, the A. nidulans mtfA gene product localized at nuclei. Deletion of the mtfA gene restored mycotoxin biosynthesis in the absence of veA,but drastically reduced mycotoxin production when mtfA gene expression was altered, by either deletion or overexpression, in the Aspergillus nidulanswild type strain. Our study revealed that mtfA regulates ST production by controlling the expression of the specific ST gene cluster activator aflR.Importantly, mtfA also controls sexual and asexual development in A. nidulans. Deletion of mtfA results in a reduction of conidiation and sexualdevelopment.365. Histidine 704 of the Aspergillus nidulans GATA factor AreA is required for nuclear export. Damien Downes 1 , Brandon Pfannenstiel 1 , CameronHunter 1 , Kendra Siebert 1 , David Clarke 2 , Meryl Davis 2 , Richard Todd 1 . 1) Department of Plant Pathology, Kansas State University, Manhattan, USA; 2)Department of Genetics, University of Melbourne, Melbourne, AUS.In A. nidulans, the GATA transcriptional activator AreA controls the preferential utilization of nitrogen nutrients as well as the response to nitrogenstarvation. During nitrogen starvation AreA accumulates in the nucleus, and a strong increase in target gene expression is observed. Addition of nitrogennutrients to nitrogen starved cells results in rapid translocation of AreA to the cytoplasm and arrest of elevated AreA-dependent gene expression,indicating that regulated nuclear export is the control mechanism for AreA nuclear accumulation. AreA contains a single conserved CrmA-dependentNuclear Export Sequence (NES). We propose that regulated AreA nuclear export is controlled by post-translational modification of residues within the NES.We show that deletion of the AreA NES confers nuclear accumulation. Substitution of individual amino acids within the AreA NES identified a singlehistidine residue, which when mutated to a non-modifiable alanine residue leads to constitutive nuclear accumulation. This suggests that histidinemodification may promote AreA nuclear export. We show that fusion of the AreA NES to the constitutively nuclear protein PrnA confers nucleocytoplasmicdistribution and a proline utilization loss of function phenotype. We have used this phenotype to select mutants affecting AreA-dependent nuclear export.366. Redundant Nuclear Localization Signals Mediate Nuclear Import of the Aspergillus nidulans Transcription Activator of Nitrogen Metabolic GenesAreA. Cameron C. Hunter 1 , Kendra S. Siebert 1 , Damien J. Downes 1 , Koon Ho Wong 2 , Sara Lewis 2 , James A. Fraser 2 , David F Clarke 2 , Michael J. Hynes 2 , MerylA. Davis 2 , Richard B. Todd 1 . 1) Department of Plant Pathology, Kansas State University, Manhattan, KS; 2) Department of Genetics, The University ofMelbourne, Parkville VIC 3010, Australia.The Aspergillus nidulans GATA transcription factor AreA activates transcription of nitrogen metabolic genes. AreA accumulates in the nucleus duringnitrogen starvation but not in the presence of nitrogen sources. AreA contains five putative classical nuclear localization sequences (NLSs) and oneputative non-canonical bipartite NLS. We used two approaches to identify the functional NLSs. First, we constructed epitope-tagged gene replacementareA mutants affected in individual NLSs or combinations of NLSs to identify sequences required for nuclear localization. Deletion of all five classical NLSsdid not affect utilization of nitrogen sources and did not prevent AreA nuclear localization. Mutation of the bipartite NLS conferred inability to utilizealternative nitrogen sources but did not prevent AreA nuclear localization. Combinations of mutations of the six NLSs indicate redundancy among the AreANLSs. Second, we constructed Green Fluorescent Protein (GFP)-AreA NLS fusion genes and introduced them into A. nidulans. The bipartite NLS stronglydirects GFP to the nucleus, one of the classical NLSs weakly directs GFP to the nucleus and the other four classical NLSs collaborate to direct GFP to thenucleus.367. Conditional expression of the phospho-transmitter gene ypdA and the signaling interaction of YpdA with response regulators; SskA and SrrA inAspergillus nidulans. Mayumi Nakayama 1,2 , Yura Midorikawa 1,2 , Akira Yoshimi 2 , Daisuke Hagiwara 2,3 , Keietsu Abe 1,2 . 1) Tohoku University, Sendai, Miyagi,Japan; 2) ABE-project New Industry Hatchery Center (NICHe) Tohoku University, Sendai, Japan; 3) Present address: MMRC, Univ. of Chiba, Chiba Japan.The histidine-to-aspartate (His-Asp) phosphorelay signaling transduction system has been conserved widely in both prokaryotes and eukaryotes. Thesystems typically consist of three types of common signal transducers: His-kinase (HK), a response regulator (RR), and a histidine-containingphosphotransfer intermediate (HPt). Generally, HPt acts as an intermediate between HK and RR and is indispensable for inducing appropriate responses toenvironmental stresses through His-Asp phosphotransfer signaling. In Aspergillus nidulans, we revealed His-Asp phosphorelay signal transducers: HK(NikA), RR (SskA and SrrA), and HPt (YpdA) were essential for the response of high-osmotic and oxidative stresses. Nevertheless the ypdA is the essentialgene, the molecular mechanism underlying the importance of YpdA remains unclear. To identify the function of the YpdA, we constructed A. nidulansmutant in which expression of the ypdA gene is conditionally regulated under the control of the A. nidulans alcA promoter (CypdA strain) and analyzedtheir phenotype. We constructed mutant strain from CypdA by deleting the response regulator gene srrA (CypdA/DsrrA) and sskA (CypdA/DsskA). WhenypdA was downregulated, CypdA showed remarkable growth retardation and formed abnormal hyphae, and CypdA/DsrrA unexpectedly showed moresevere growth retardation than the parent CypdA, in contrast, the growth retardation of CypdA/DsskA partly recovered. It is suggested that the growthretardation of CypdA was only partly suppressed by switching off the HogA pathway. We further constructed a mutant (CypdA/DsrrADsskA) from CypdA bydeleting the two RR genes. Here, we discuss two-component signaling under the inhibitory conditions of signaling between YpdA and response regulators.368. WITHDRAWN369. FigA, a putative member of low-affinity calcium system, is involved in both asexual and sexual differentiation in Aspergillus nidulans. Shizhu Zhang,Hailin Zheng, Nanbiao Long, Sha Wang, Ling Lu. College of life Sciences, Nanjing Normal University, Nanjing, Jiangsu, China.Calcium-mediated signaling pathways are widely employed in eukaryotes and are implicated in the regulation of diverse biological processes. In baker’syeast Saccharomyces cerevisiae, at least two different carrier systems have been identified—a high-affinity calcium influx system (HACS) and a low-affinity210