title: Regulation of conidiation and adenylyl cyclase levels by the Galpha protein GNA-3 in Neurospora crassa.
abstract: We have identified a new gene encoding the G protein alpha subunit, gna-3, from the filamentous fungus Neurospora crassa. The predicted amino acid sequence of GNA-3 is most similar to the Galpha proteins MOD-D, MAGA, and CPG-2 from the saprophytic fungus Podospora anserina and the pathogenic fungi Magnaporthe grisea and Cryphonectria parasitica, respectively. Deletion of gna-3 leads to shorter aerial hyphae and premature, dense conidiation during growth on solid medium or in standing liquid cultures and to inappropriate conidiation in submerged culture. The conidiation and aerial hypha defects of the Deltagna-3 strain are similar to those of a previously characterized adenylyl cyclase mutant, cr-1. Supplementation with cyclic AMP (cAMP) restores wild-type morphology to Deltagna-3 strains in standing liquid cultures. Solid medium augmented with exogenous cAMP suppresses the premature conidiation defect, but aerial hypha formation is still reduced. Submerged-culture conidiation is refractory to cAMP but is suppressed by peptone. In addition, Deltagna-3 submerged cultures express the glucose-repressible gene, qa-2, to levels greatly exceeding those observed in the wild type under carbon-starved conditions. Deltagna-3 strains exhibit reduced fertility in homozygous crosses during the sexual cycle; exogenous cAMP has no effect on this phenotype. Intracellular steady-state cAMP levels of Deltagna-3 strains are decreased 90% relative to the wild type under a variety of growth conditions. Reduced intracellular cAMP levels in the Deltagna-3 strain correlate with lower adenylyl cyclase activity and protein levels. These results demonstrate that GNA-3 modulates conidiation and adenylyl cyclase levels in N. crassa.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Texas- Houston Medical School, Houston, Texas 77030, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Kays
authors.forename: P S
authors.initials: PS
authors.lastname: Rowley
authors.forename: R A
authors.initials: RA
authors.lastname: Baasiri
authors.forename: K A
authors.initials: KA
authors.lastname: Borkovich
mesh_terms: D000262:Adenylyl Cyclases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D003433:Crosses, Genetic; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology; D005298:Fertility; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D044385:GTP-Binding Protein alpha Subunits; D018390:Gene Targeting; D005800:Genes, Fungal / Q000235:genetics; D006160:Guanosine Triphosphate / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D009492:Neurospora crassa / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D009994:Osmolar Concentration; D010641:Phenotype; D011801:Quinic Acid / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D005656:Fungal Proteins; C414733:GNA-3 protein, Neurospora crassa; D044385:GTP-Binding Protein alpha Subunits; D012333:RNA, Messenger; D011801:Quinic Acid; D006160:Guanosine Triphosphate; D000242:Cyclic AMP; D020962:Heterotrimeric GTP-Binding Proteins; D000262:Adenylyl Cyclases