Overlapping Functions for Two G Protein α Subunits in Neurospora crassa

[摘要] Heterotrimeric G proteins, consisting of α, β and γ subunits, mediate a variety of signaling pathways in eukaryotes. We have previously identified two genes, gna-1 and gna-2 , that encode G protein α 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 Δ gna-2 strains did not reveal abnormalities during vegetative or sexual development. In contrast, deletion of gna-2 in a Δ gna-1 strain accentuates the Δ gna-1 phenotypes. Δ gna-1 Δ gna-2 strains have a slower rate of hyphal apical extension than Δ gna-1 strains on hyperosmotic media. Moreover, Δ gna-1 Δ gna-2 mutants have more pronounced defects in female fertility than Δ 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 α subunits with overlapping functions in eukaryotic microbes.

[学科分类] 医学（综合）