The Science Seminar Series: april 22, 2010
A COG in the fungal machine: How mutations in two COG proteins affect growth of Aspergillus nidulans
Sara Gremillion1, Darlene Loprete2, and Terry Hill2.
1Department of Biology, Armstrong Atlantic State University, 11935 Abercorn Street, Savannah, GA 31419, USA.
2Departments of Biology and Chemistry, Rhodes College, 2000 N. Parkway, Memphis, TN 38112, USA.
Time: 4:00 -5:00pm
Fungi are a diverse group of organisms that play many roles in nature including decomposers, mutualists and pathogens. Knowledge of how fungi grow will lead to a better understanding of the complexity of these ecologically important organisms. Using the fungus, Aspergillus nidulans, two genetically mutated strains were identified as having abnormal growth when grown at restrictive temperatures. The swoP1 (swollen cell) and podB1 (polarity defective) mutants produce conidia that swell to approximately 1.5 times the normal diameter. Conidia of swoP1 also produce abnormally wide hyphae and establish multiple points of polarity. Genes complementing the mutations of swoP1 and podB1 have genetic sequences homologous to COG4 and COG2, respectively. In mammals and yeast, COG2 and COG4 are part of an eight-protein structure called the COG (conserved oligomeric Golgi) complex associated with retrograde transport within the Golgi apparatus. Evidence from GFP-tagged COG2 indicated a Golgi protein localization. Protein overexpression studies provided evidence of intra-complex interactions between COG2 and COG4 as well as between COG2 and COG3. A promoter replacement strategy of COG2 and COG4 revealed that, when these proteins are produced in low numbers in the cell, fungal growth is only slightly, negatively affected. These studies provide support that the COG complex is an important component of normal fungal growth.