Fungal Genetics Reports Volume 44 Article 28 Abstracts from the 19th FGC Fungal Genetics Conference Follow this and additional works at: https://newprairiepress.org/fgr This work is licensed under a Creative Commons Attribution-Share Alike 4.0 License. Recommended Citation Fungal Genetics Conference. (1997) "Abstracts from the 19th FGC," Fungal Genetics Reports: Vol. 44, Article 28. https://doi.org/10.4148/1941-4765.1296 This Supplementary Material is brought to you for free and open access by New Prairie Press. It has been accepted for inclusion in Fungal Genetics Reports by an authorized administrator of New Prairie Press. For more information, please contact [email protected]. Abstracts from the 19th FGC Abstract Plenary and poster session abstracts from the 19th Fungal Genetics Conference This supplementary material is available in Fungal Genetics Reports: https://newprairiepress.org/fgr/vol44/iss1/28 : Abstracts from the 19th FGC Plenary Session Abstracts at the 19th Fungal Genetics Conference at Asilomar • Gene Regulation and Metabolism • Cell Biology and Pathogenesis • Evolution and Population Genetics • Sexual/Asexual Reproduction Plenary Session: Gene Regulation and Metabolism (Chair: Claudio Scazzocchio) pH regulation in Aspergillus nidulans . Miguel Angel Penalva, Centro de Investigaciones Biologicas CSIC, Madrid, Spain The zinc-finger transcription factor PacC mediates pH regulation in Aspergillus nidulans and other ascomycetes. The 678-residue PacC primary translation product is inactive in structural gene regulation. Under ambient alkaline pH conditions, a signal provided by the six pal -gene pathway causes an unknown modification in the protein which makes it accessible to a proteolytic processing step. This limited proteolysis eliminates the ~60% residues of PacC at the carboxyl side. The processed protein (~residues 1 - 270) is fully active in structural gene regulation, activating alkaline-expressed genes (through 5'-GCCARG-3' sites) and repressing acid-expressed genes. Thus, the conformational change in PacC resulting from pH signal reception is the pH-sensitive step in the regulatory circuit. The C-terminal moiety of PacC mediates its negative action at least by masking PacC domains involved in transcriptional activation and presumably by preventing nuclear import of the full length protein, but does not appear to impair DNA binding. Point mutations and C-terminal truncations disrupt the interactions between the amino- and carboxyl-terminal moieties of the protein. pacC is itself an alkaline-expressed gene, but its mode of regulation is different from that of alkaline structural genes. Developmental regulation of catalases in Aspergillus nidulans. Rosa E. Navarro, Laura Kawasaki and Jesus Aguirre, Instituto de Fisiologia Celular, Univ Nacional Autonoma de Mexico. A general hypothesis to explain microbial cell differentiation as a response to hyperoxidant states was derived from studies on sporulation in Neurospora crassa. Since catalases are ubiquitous enzymes that are central to cellular antioxidant responses, we have now approached this hypothesis by studying the function and regulation of catalases during A. nidulans asexual sporulation (conidiation). We have found two catalases in this fungus encoded by the catA and catB genes, whose predicted polypeptides are as similar between them, as they are to E. coli HPII catalase. The catA and catB expression is differentially regulated during growth and Published by New Prairie Press, 2017 1 Fungal Genetics Reports, Vol. 44 [1997], Art. 28 development. The catA mRNA and protein appear during sporulation and are accumulated in both, sexual and asexual spores independently of the brlA regulatory gene, in a process that involves transcriptional and translational controls. In contrast, the catB mRNA and protein are very low in spores, accumulate in mature hyphae throughout conidiation and in response to H202 both catalases can offer protection against H20, at different stages of the life cycle. Although the increase in CatB activity and the appearance of CatA during sporulation is consistent with the occurrence of oxidative stress during development, our data indicate the operation of efficient alternative pathways for H202 detoxification. Genetic Regulation of Aspergillus Mycotoxin Biosynthesis. Nancy P. Kellerl and Thomas H. Adams2, lDept. of Plant Pathology and Microbiology, 2Dept. of Biology, Texas A&M University, College Station, TX 77845. Aflatoxin (AF) and sterigmatocystin (ST) are polyketide mycotoxins derived from the same biochemical pathway found in several seed contaminating Aspergillus spp. The AF/ST biosynthesis genes are clustered in a ~60-75 kb DNA segment in all species examined to date. The magnitude of this cluster is well illustrated by the characterization of the A. nidulans ST gene cluster which contains 25 coordinately regulated transcripts most of which encode enzymes with functions required for AF and ST biosynthesis. In each cluster there is a positive-acting pathway specific regulatory gene, aflR, that encodes a sequence-specific DNA binding protein required for cluster gene expression. Regulation of this cluster is complex and involves nutritional factors, pH and life cycle controls. This complexity is illustrated by the fact that the ability of AflR to activate ST/AF gene expression is linked to regulation of asexual sporulation through a requirement for inactivation of an heterotrimeric G protein mediated signal transduction pathway. White collar 1 and White collar 2 are partners in the blue light transduction pathway in Neurospora crassa. Giuseppe Macino, Hartmut Linden, Paola Ballario. Universita "La Sapienza" Roma, Italy. A saturating genetic dissection of "blind" mutants in Neurospora crassa has identified a total of two non-redundant loci (wc1 and wc2 ) each of which is required for blue light perception/signal transduction. Previously, we demonstrated that wc1 is a putative zinc-finger transcription factor able to bind specifically to a light regulated promoter. We have recently demonstrated using mutation analysis and in vitro DNA binding assays that wc2 is the second partner of this two component light signal transduction system and encodes a functional zinc-finger DNA-binding https://newprairiepress.org/fgr/vol44/iss1/28 DOI: 10.4148/1941-4765.1296 2 : Abstracts from the 19th FGC protein with a putative PAS dimerization domain and transcription activation domain. This molecular-genetic dissection of the two components of this light signal transduction system has elucidated a model whereby wc1 and wc2 interact via homologous PAS domains, bind to promoters of light-regulated genes and activate transcription. As such, this study provides the first insight into two interacting partners in blue light signal transduction in any organism and provides the molecular tools with which to dissect this engimatic process. The circadian clock in Neurospora: light resetting of the oscillator and the control of gene expression. Jennifer Loros, Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755. An important property of circadian oscillators is their ability to entrain to the daily light/dark cycle. The clock is a negative feedback loop wherein the frq gene, known component of the clock in Neurospora crassa encodes the FRQ protein which feeds back to turn off the gene, yielding the oscillation in frq transcript and FRQ protein that is the Neurospora clock. Light delivered at any point within the circadian cycle acts rapidly to increase the level of frq transcript. The magnitude of the light-induced increase in frq mRNA and the extent of clock resetting are correlated and the threshold, kinetics and magnitude of this response indicate elevation of the level of frq transcript in the cell is the initial clock-specific even involved in resetting of the clock by light. We are examining the roles of two photo blind strains, band;white collar-1 (bd;wc-1) and white collar-2 ;band;(wc-2 ;bd) in light-resetting of the clock. By Northern analysis we find the transient, light induced accumulation of frq is blocked in bd;wc-1 but not in wc-2;bd . In constant light, frq mRNA remains at high levels in the bd strain, thereby suppressing the frq cycle. This sustained, light driven increase is blocked in both bd;wc strains. Both of the bd;wc strains failed to show a rhythmic phenotype when entrained by either light or temperature steps. In a separate effort aimed at understanding light regulation of rhythmic processes, circadianly expressed genes downstream of the clock, eas (ccg-2 ) and ccg-1, have been examined in a clock null strain and foun not to require a functional clock. Deletion analyses of the eas (ccg-2 ) promoter has localized cis-acting elements mediating clock, light, and developmental control. Primary sequence determinants of a positive activating clock element were found reside in a 45- base pair region close to the TATA box, and spatially distinct from sequence elements governing light regulation. Published by New Prairie Press, 2017 3 Fungal Genetics Reports, Vol. 44 [1997], Art. 28 Plenary Session: Cell Biology and Pathogenesis (Chair: Hans VanEtten) Animal pathogenesis. David. W. Holden, Royal Postgraduate Medical School, London, UK. Systemic fungal infections of humans caused by Candida spp., Aspergillus spp. and Cryptococcus neoformans are increasing in incidence, mainly in patients with impaired immune responses. Patient mortality is high because of difficulties in early diagnosis and the lack of effective and