title: Targeted disruption of a fungal G-protein beta subunit gene results in increased vegetative growth but reduced virulence.
abstract: Targeted disruption of two G-protein alpha subunit genes in the chestnut blight fungus Cryphonectria parasitica revealed roles for the Gi alpha subunit CPG-1 in fungal reproduction, virulence, and vegetative growth. A second G alpha subunit, CPG-2, was found to be dispensable for these functions. We now report the cloning and targeted disruption of a C. parasitica G-protein beta subunit gene. The deduced amino acid sequence encoded by this gene, designated cpgb-1, was found to share 66.2, 65.9, and 66.7% amino acid identity with G beta homologues from human, Drosophila, and Dictyostelium origins, respectively, but only 39.7% identity with the Saccharomyces cerevisiae G beta homologue STE4 product. Low stringency Southern hybridization failed to detect any related G beta subunit genes in C. parasitica. Targeted disruption of cpgb-1 resulted in several of the changes previously reported to accompany disruption of the C. parasitica Gi alpha subunit gene cpg-1. These included very significant reductions in pigmentation, asexual sporulation, and virulence. In contrast to results obtained for Gi alpha gene disruption, the reduction in virulence resulting from the disruption of a G beta gene was accompanied by increased, rather than decreased, vegetative growth on synthetic medium. The relevance of these results to mechanisms of fungal virulence is considered.
authors.affiliation: Center for Agricultural Biotechnology, University of Maryland Biotechnology Institute, University of Maryland, College Park 20742-4450, USA.
authors.forename: S
authors.initials: S
authors.lastname: Kasahara
authors.forename: D L
authors.initials: DL
authors.lastname: Nuss
mesh_terms: D000595:Amino Acid Sequence; D001203:Ascomycota / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity; D001483:Base Sequence; D003001:Cloning, Molecular; D019204:GTP-Binding Proteins / Q000235:genetics*; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009754:Nuts / Q000382:microbiology; D010935:Plant Diseases / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014197:Trees / Q000382:microbiology; D014774:Virulence / Q000235:genetics
chemical_list: D019204:GTP-Binding Proteins