title: A central role for Ras1 in morphogenesis of the basidiomycete Schizophyllum commune.
abstract: Fungi have been used as model systems to define general processes in eukaryotes, for example, the one gene-one enzyme hypothesis, as well as to study polar growth or pathogenesis. Here, we show a central role for the regulator protein Ras in a mushroom-forming, filamentous basidiomycete linking growth, pheromone signaling, sexual development, and meiosis to different signal transduction pathways. ras1 and Ras-specific gap1 mutants were generated and used to modify the intracellular activation state of the Ras module. Transformants containing constitutive ras1 alleles (ras1(G12V) and ras1(Q61L)), as well as their compatible mating interactions, did show strong phenotypes for growth (associated with Cdc42 signaling) and mating (associated with mitogen-activated protein kinase signaling). Normal fruiting bodies with abnormal spores exhibiting a reduced germination rate were produced by outcrossing of these mutant strains. Homozygous Δgap1 primordia, expected to experience increased Ras signaling, showed overlapping phenotypes with a block in basidium development and meiosis. Investigation of cyclic AMP (cAMP)-dependent protein kinase A indicated that constitutively active ras1, as well as Δgap1 mutant strains, exhibit a strong increase in Tpk activity. Ras1-dependent, cAMP-mediated signal transduction is, in addition to the known signaling pathways, involved in fruiting body formation in Schizophyllum commune. To integrate these analyses of Ras signaling, microarray studies were performed. Mutant strains containing constitutively active Ras1, deletion of RasGap1, or constitutively active Cdc42 were characterized and compared. At the transcriptome level, specific regulation highlighting the phenotypic differences of the mutants is clearly visible.
authors.affiliation: Institute of Microbiology, Friedrich Schiller University, Jena, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Knabe
authors.forename: Elke-Martina
authors.initials: EM
authors.lastname: Jung
authors.forename: Daniela
authors.initials: D
authors.lastname: Freihorst
authors.forename: Florian
authors.initials: F
authors.lastname: Hennicke
authors.forename: J Stephen
authors.initials: JS
authors.lastname: Horton
authors.forename: Erika
authors.initials: E
authors.lastname: Kothe
mesh_terms: D000483:Alleles; D026905:Amino Acid Transport Systems / Q000235:genetics / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D048690:Fruiting Bodies, Fungal / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D015966:Gene Expression Regulation, Fungal; D008540:Meiosis / Q000235:genetics; D009024:Morphogenesis / Q000235:genetics*; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D012567:Schizophyllum / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D012724:Sex Attractants / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction; D013172:Spores, Fungal / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D026905:Amino Acid Transport Systems; D005656:Fungal Proteins; D012724:Sex Attractants; D000242:Cyclic AMP; D020764:cdc42 GTP-Binding Protein; D018631:ras Proteins