title: G proteins in Ustilago maydis: transmission of multiple signals?
abstract: In the phytopathogenic fungus Ustilago maydis, cell fusion is governed by a pheromone signalling system. The pheromone receptors belong to the seven transmembrane class that are coupled to heterotrimeric G proteins. We have isolated four genes (gpa1 to gpa4) encoding alpha subunits of G proteins. Gpa1, Gpa2 and Gpa3 have homologues in other fungal species, while Gpa4 is novel. Null mutants in individual genes were viable and only disruption of gpa3 caused a discernible phenotype. gpa3 mutant strains were unable to respond to pheromone and thus were mating-deficient. A constitutively active allele of gpa3 (gpa3(Q206L)) was generated by site-directed mutagenesis. Haploid strains harbouring gpa3(Q206L) were able to mate without pheromone stimulation, indicating that Gpa3 plays an active role in transmission of the pheromone signal. Surprisingly, Gpa3 is also required for pathogenic development, although pheromone signalling is not essential for this process.
authors.affiliation: Institut für Genetik und Mikrobiologie der Universität München, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Regenfelder
authors.forename: T
authors.initials: T
authors.lastname: Spellig
authors.forename: A
authors.initials: A
authors.lastname: Hartmann
authors.forename: S
authors.initials: S
authors.lastname: Lauenstein
authors.forename: M
authors.initials: M
authors.lastname: Bölker
authors.forename: R
authors.initials: R
authors.lastname: Kahmann
mesh_terms: D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000502:physiology; D003001:Cloning, Molecular; D003433:Crosses, Genetic; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D044385:GTP-Binding Protein alpha Subunits; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D019204:GTP-Binding Proteins / Q000235:genetics / Q000502:physiology*; D005800:Genes, Fungal / Q000235:genetics; D020962:Heterotrimeric GTP-Binding Proteins; D020929:Mitogen-Activated Protein Kinase Kinases; D010675:Pheromones; D029701:Saccharomyces cerevisiae Proteins; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000502:physiology*; D014588:Ustilago / Q000235:genetics / Q000502:physiology*
chemical_list: D005656:Fungal Proteins; D044385:GTP-Binding Protein alpha Subunits; C106284:Gpa3 protein, Ustilago maydis; C106283:Gpa4 protein, Ustilago maydis; D010675:Pheromones; D029701:Saccharomyces cerevisiae Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C089988:Fuz7 protein, Ustilago maydis; D020929:Mitogen-Activated Protein Kinase Kinases; D019204:GTP-Binding Proteins; C084293:GPA1 protein, S cerevisiae; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; C083907:Gpa2 protein, S cerevisiae; D020962:Heterotrimeric GTP-Binding Proteins