The pga1 gene of Penicillium chrysogenum NRRL 1951 encodes a heterotrimeric G protein alpha subunit that controls growth and development.

The pga1 gene of Penicillium chrysogenum NRRL 1951 has been cloned and shown to participate in the developmental program of this fungus. It encodes a protein showing a high degree of identity to group I alpha subunits of fungal heterotrimeric G proteins, presenting in its sequence all the distinctive characteristics of this group. Northern analysis revealed that pga1 is highly expressed in a constitutive manner in submerged cultures, while its expression changes during development on solid media cultures; it is higher during vegetative growth and decreases significantly at the time of conidiogenesis. Attenuation of pga1 gene expression by antisense RNA, and mutations of pga1 resulting in a constitutively activated (pga1G42R allele) or constitutively inactivated (pga1G203R allele) Pga1 alpha subunit were used to study the function of Pga1 in P. chrysogenum. The phenotype of transformants expressing the antisense construction and the mutant alleles showed substantial morphological differences in colony diameter and conidiation, indicating that Pga1 controls apical extension and negatively regulates conidiogenesis on solid medium, but has no effect on submerged cultures. Pga1 is also functional in Penicillium roqueforti, controlling the same processes.