Pseudohyphal differentiation, a filamentous growth form of the budding yeast Saccharomyces cerevisiae, is induced by nitrogen starvation. The mechanisms by which nitrogen limitation regulates this process are currently unknown. We have found that GPA2, one of the two heterotrimeric G protein alpha subunit homologs in yeast, regulates pseudohyphal differentiation. Deltagpa2/Deltagpa2 mutant strains have a defect in pseudohyphal growth. In contrast, a constitutively active allele of GPA2 stimulates filamentation, even on nitrogen-rich media. Moreover, a dominant negative GPA2 allele inhibits filamentation of wild-type strains. Several findings, including epistasis analysis and reporter gene studies, indicate that GPA2 does not regulate the MAP kinase cascade known to regulate filamentous growth. Previous studies have implicated GPA2 in the control of intracellular cAMP levels; we find that expression of the dominant RAS2(Gly19Val) mutant or exogenous cAMP suppresses the Deltagpa2 pseudohyphal defect. cAMP also stimulates filamentation in strains lacking the cAMP phosphodiesterase PDE2, even in the absence of nitrogen starvation. Our findings suggest that GPA2 is an element of the nitrogen sensing machinery that regulates pseudohyphal differentiation by modulating cAMP levels.
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| Gene/Complex | Qualifier | Gene Ontology Term | Annotation Extension | Evidence | Source | Assigned On |
|---|---|---|---|---|---|---|
| GPA2 | involved in | pseudohyphal growth | IMP | SGD | 2013-08-07 | |
| GPA2 | enables | GTPase activity | IMP | SGD | 2013-08-07 |
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| Gene | Phenotype | Experiment Type | Mutant Information | Strain Background | Chemical | Details |
|---|---|---|---|---|---|---|
| GPA2 | colony size: decreased | homozygous diploid | activation Allele: GPA2-2 G132V; constitutively active dominant mutation in GXXGXXG motif | Sigma1278b | ||
| GPA2 | growth in exponential phase: decreased rate | homozygous diploid | activation Allele: GPA2-2 G132V; constitutively active dominant mutation in GXXGXXG motif | Sigma1278b | ||
| GPA2 | pseudohyphal growth: abnormal | homozygous diploid | activation Allele: GPA2-2 | Sigma1278b | 5 mM ammonium sulfate | Details: filamentous growth stimulated under nitrogen rich conditions |
| STE11 | pseudohyphal growth: absent | homozygous diploid | null Allele: ste11-Δ | Sigma1278b | Media: SLAD medium | |
| GPA2 | pseudohyphal growth: decreased | homozygous diploid | null Allele: gpa2-Δ | Sigma1278b | Media: SLAD medium | |
| GPA2 | pseudohyphal growth: decreased | homozygous diploid | dominant negative Allele: GPA2-3 G299A; dominant negative mutation in hinge region | Sigma1278b | Media: SLAD medium Details: inhibits pseudohyphal differentiation in wildtype diploids | |
| PDE2 | pseudohyphal growth: increased | homozygous diploid | null Allele: pde2-Δ | Sigma1278b | 3',5'-cyclic AMP, 5 mM ammonium sulfate | Details: filamentous growth stimulated under nitrogen rich conditions in the presence of cAMP |
| GPA2 | pseudohyphal growth: increased | homozygous diploid | activation Allele: GPA2-2 G132V; constitutively active dominant mutation in GXXGXXG motif | Sigma1278b | Media: SLAD medium |
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| Evidence ID | Analyze ID | Interactor | Interactor Systematic Name | Interactor | Interactor Systematic Name | Allele | Assay | Annotation | Action | Phenotype | SGA score | P-value | Source | Reference | Note |
|---|
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