Vegetative growth signaling in the filamentous fungus Aspergillus nidulans is primarily mediated by the heterotrimeric G protein composed of FadA (Galpha), SfaD (Gbeta) and a presumed Ggamma. Analysis of the A. nidulans genome identified a single gene named gpgA encoding a putative Ggamma subunit. The predicted GpgA protein consists of 90 amino acids showing 72% similarity with yeast Ste18p. Deletion (D) of gpgA resulted in reduced vegetative growth and lowered asexual sporulation. Moreover, despite highly elevated Hülle cell production, the DgpgA mutant was unable to produce sexual fruiting bodies (cleistothecia) in self-fertilization and was severely impaired with cleistothecial development in outcross, indicating that GpgA is required for sexual development. Developmental and morphological defects caused by deletion of flbA encoding an RGS protein controlling FadA-signaling were suppressed by DgpgA, suggesting that GpgA primarily functions in vegetative growth signaling. However, deletion of gpgA could not bypass the need for fluG in asexual sporulation, indicating that GpgA indirectly affects conidiation. We propose that GpgA defines the Ggamma subunit constituting the FadA-SfaD::GpgA heterotrimer, and is required for normal vegetative growth and proper asexual/sexual developmental progression. Effects of deletion of gpgA, sfaD and/or fadA on mRNA levels of remaining G protein subunits are also presented.
Full conference title:
23rd Fungal Genetics Conference
- Fungal Genetics Conference 23rd (2002)