|Ph.D Student||Sherif Ganem|
|Subject||GB, RGS Family Members and the G Protein Signaling Pathway|
of the Maize Pathogenic Fungus Cochliobolus
|Department||Department of Biology||Supervisors||Full Professor Schuster Gadi|
|Full Professor Horwitz Benjamin|
Fungal pathogens perceive and respond to molecules from the plant, triggering pathogenic development. Transduction of these signals may employ heterotrimeric G proteins, and it is thought that protein phosphorylation cascades are also important. We have isolated a G protein b subunit homolog from the maize pathogen Cochliobolus heterostrophus to test its role as a component of the transduction pathways. The new gene,chgb-1, has a deduced amino acid sequence 81% identical to SFAD of the filamentous fungus Aspergillus nidulans and 78% identical to CPGB of Cryphonectria parasitica. Interestingly, the chgb1 protein product shared only 35% identity with the Saccharomyces cerevisiae Gb homologue STE4. Deletion mutants of chgb1 has characteristic colony morphology: poorly developed aerial hyphae and abnormal conidia, invasive growth in agar plates is increased. These chgb1- mutants also fail to form perithecia in crosses with the wild type of the opposite mating type. The ability of chgb1- mutants to infect corn plants is severely reduced. The growth pattern of hyphae on a glass surface is altered from that of the wild type, forming wavy hyphae, but no appressoria. This set of phenotypes differs from that conferred by mutants in SfaD and cpgb1, the only known homologous genes of the filamentous fungus. This finding emphasizes the different use of similar signaling components in filamentous fungus.