Overlapping functions for two G protein alpha subunits in Neurospora crassa.
Heterotrimeric G proteins, consisting of alpha, beta and gamma subunits, mediate a variety of signaling pathways in eukaryotes. We have previously identified two genes, gna-1 and gna-2, that encode G protein alpha subunits in the filamentous fungus Neurospora crassa. Mutation of gna-1 results in female infertility and sensitivity to hyperosmotic media. In this study, we investigate the expression and functions of gna-2. Results from Western analysis and measurements of gna-2 promoter-lacZ fusion activity indicate that gna-2 is expressed during the vegetative and sexual cycle of N. crassa in both A and a mating types. Activating mutations predicted to abolish the GTPase activity of GNA-2 cause subtle defects in aerial hyphae formation and conidial germination. Extensive phenotypic analysis of delta gna-2 strains did not reveal abnormalities during vegetative or sexual development. In contrast, deletion of gna-2 in a delta gna-1 strain accentuates the delta gna-1 phenotypes. delta gna-1 delta gna-2 strains have a slower rate of hyphal apical extension than delta gna-1 strains on hyperosmotic media. Moreover, delta gna-1 delta gna-2 mutants have more pronounced defects in female fertility than delta gna-1 strains. We propose that gna-1 and gna-2 have overlapping functions and may constitute a gene family. This is the first report of G protein alpha subunits with overlapping functions in eukaryotic microbes.
Baasiri
R A
RA
Department of Microbiology and Molecular Genetics, University of Texas-Houston Medical School 77030, USA.
Lu
X
X
Rowley
P S
PS
Turner
G E
GE
Borkovich
K A
KA
D004271:DNA, Fungal / Q000032:analysis; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000502:physiology*; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D005800:Genes, Fungal / Q000235:genetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009154:Mutation; D009492:Neurospora crassa / Q000235:genetics / Q000502:physiology*; D012098:Reproduction; D017422:Sequence Analysis, DNA
D004271:DNA, Fungal; D005656:Fungal Proteins; D019204:GTP-Binding Proteins