Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTScomplex, which represses the expression of genes through its interaction with other protein partners, such as the yeast Mig1 repressor, mediator ofcarbon catabolite repression (CCR). The N. crassa CRE-1 is an orthologue of Mig1p and has been reported to regulate a number of genes by binding to theCreA motif 5’-SYGGRG-3’. In this work we investigated if CRE-1 transcription factor regulates glycogen metabolism and whether depends on the RCO-1/RCM-1 complex, the ortologue of the yeast Tup-1/Ssn6. First, we demonstrated that CRE-1 is involved in catabolic repression in N. crassa. Growth of thewild-type strain in VM medium containing xylose + 1 mM 2-deoxyglucose (2-DG) was drastically reduced, while growth in the cre-1 KO was not affected by 2-DG. The cre-1 KO , rco-1 KO and rcm-1 RIP mutant strains showed impaired glycogen accumulation when compared to the wild-type strain, being the higherlevels observed in the cre-1 KO strain. Glycogen accumulated by this mutant strain was much higher than the wild-type strain under both repressed(glucose) and non-repressed (xylose) carbon source, suggesting that the carbon source has no influence in the glycogen accumulated. The DNA motif 5’-SYGGRG-3’ was identified in the promoters of genes encoding for synthesis (gnn, gsn, and gbn) and degradation enzymes (gpn, gdn). Binding of theGST::CRE-1 recombinant protein to the CRE-1 motifs in the gsn and gpn promoters was confirmed by DNA gel shift, indicating that both genes must beregulated by CRE-1. Gene expression was analyzed by qRT-PCR and all genes were differently expressed in the mutant strains, and for some genes, geneexpression correlated well with the levels of glycogen accumulated. ChIP-PCR assay was performed to confirm in vivo CRE-1 binding to the promoters andthe results suggested that the CRE-1, RCO-1 and RCM-1 proteins likely interacted. All results together indicated that the CRE-1 transcription factor acts as arepressor in glycogen regulation, and might require the interaction with RCO-1 and RCM-1 co-repressors. Supported by FAPESP and CNPq.420. Transcriptional Response to Hypoxia in the Dimorphic Fungus Histoplasma capsulatum . Juwen C. DuBois 1,3 , A. George Smulian 2,3 . 1) Pathobiologyand Molecular Medicine Graduate Program, University of Cincinnati, Cincinnati, OH; 2) Infectious Disease Division, University of Cincinnati, Cincinnati, OH;3) Cincinnati VA Medical Center, Cincinnati OH.Background and purpose: The incidence of life-threatening fungal infections has increased because of a rapidly growing population ofimmunocompromised individuals. Histoplasma capsulatum (Hc) is a thermally dimorphic fungal pathogen which causes pulmonary and systemic disease inboth immunocompetent and immunocompromised individuals. All fungal pathogens encounter microenvironmental stresses as they colonize and infectthe mammalian host and their ability to adapt to environmental changes is critical for pathogenicity. While oxygen is essential for the survival of mosteukaryotic organisms, low oxygen availability or hypoxia is one microenvironmental stress that is known to occur during infection. Therefore, we aim todetermine the mechanism by which Hc is able to survive and adapt to hypoxia by determining the significance of its transcriptional response to hypoxia.Methods: Hc yeast cells were cultured to mid-log phase then transferred to normoxic (~21%) or hypoxic conditions (