Originally published as Genetics Published Articles Ahead of Print on June 8, 2005.

Genetics, Vol. 171, 81-89, September 2005, Copyright © 2005
doi:10.1534/genetics.105.042796

Multiple Roles of a Heterotrimeric G-Protein {gamma}-Subunit in Governing Growth and Development of Aspergillus nidulans

Jeong-Ah Seo*, Kap-Hoon Han*,1 and Jae-Hyuk Yu*,{dagger},2

* Department of Food Microbiology and Toxicology and Food Research Institute, {dagger} Molecular and Environmental Toxicology Center, University of Wisconsin, Madison, Wisconsin 53706

2 Corresponding author: Department of Food Microbiology and Toxicology, 1925 Willow Dr., Madison, WI 53706-1187.
E-mail: jyu1{at}wisc.edu

Vegetative growth signaling in the filamentous fungus Aspergillus nidulans is primarily mediated by the heterotrimeric G-protein composed of FadA (G{alpha}), SfaD (Gß), and a presumed G{gamma}. Analysis of the A. nidulans genome identified a single gene named gpgA encoding a putative G{gamma}-subunit. The predicted GpgA protein consists of 90 amino acids showing 72% similarity with yeast Ste18p. Deletion ({Delta}) of gpgA resulted in restricted vegetative growth and lowered asexual sporulation. Moreover, similar to the {Delta}sfaD mutant, the {Delta}gpgA mutant was unable to produce sexual fruiting bodies (cleistothecia) in self-fertilization and was severely impaired with cleistothecial development in outcross, indicating that both SfaD and GpgA are required for fruiting body formation. Developmental and morphological defects caused by deletion of flbA encoding an RGS protein negatively controlling FadA-mediated vegetative growth signaling were suppressed by {Delta}gpgA, indicating that GpgA functions in FadA-SfaD-mediated vegetative growth signaling. However, deletion of gpgA could not bypass the need for the early developmental activator FluG in asexual sporulation, suggesting that GpgA functions in a separate signaling pathway. We propose that GpgA is the only A. nidulans G{gamma}-subunit and is required for normal vegetative growth as well as proper asexual and sexual developmental progression.




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