Evidence for carbon source regulated protein kinase A and protein kinase C signaling in the duplication cycle, polarization and septum formation in Aspergillus nidulans.

The effects of glucose and of a pectic substrate in the duplication cycle, spore polarization and septation of Aspergillus nidulans were tested in poor and rich media. Growth on poor conditions and on sodium polypectate slowed nuclear duplication and reduced the coupling of polarization to mitosis. Coupling of septation to the third mitosis was also reduced by changing growth conditions. When protein kinase A (PKA) and protein kinase C (PKC) activators were added to the media the results suggested a role for PKA in slowing the duplication cycle, while allowing polarization. Addition of a PKC activator to poor media uncoupled the first septum formation from the third mitosis in a carbon source-regulated manner, suggesting a role for PKC in coordinating cell cycle signals, growth and cytokinesis.