Analyzing Protein Kinase C Interactions with Rho4 and Bud3 in the Filamentous Fungus Aspergillus nidulans

Abstract

Cell division in filamentous fungi involves coalescence and subsequent constriction of a contractile actomyosin ring (CAR), as in other fungi and metazoans. In fungi, constriction of the CAR is followed by deposition of cell wall material resulting in a septum. In the model organism, Aspergillus nidulans, many proteins are involved in septation including protein kinase C (PkcA), the formin SepA, the GTPase Rho4, and its guanine nucleotide exchange factor (GEF) called Bud3. In previous work we showed that PkcA both physically and functionally interacts with SepA. The formin SepA belongs to the Diaphanous‐related family of formins that contain an N‐terminal Rho binding domain that upon binding of the appropriate Rho GTPase results in formin activation. In A. nidulans Rho4 is likely the GTPase required for SepA activation. Reports from another group have shown that Rho4 and Bud3 work as a module that is required for septation to occur. The current study focuses on the relationship of the Bud3/Rho4 partnership with PkcA and SepA during polarized growth. Using bimolecular fluorescence complementation (BiFC) and overexpressing PkcA in Bud3‐ and Rho4‐null strains, we examined the relationships between PkcA and Rho4 and PkcA and Bud3. Through BiFC we found that PkcA and Rho4 interact at septation sites. Overexpressing PkcA in a Rho4‐null mutant strain increased colony diameter and improved sporulation. However, PkcA overexpression in a Bud3‐null mutant had no effect on growth and sporulation. These results suggest that there are physical and functional interactions between PkcA and Rho4 that are important in polarized growth.Support or Funding InformationNational Science Foundation Grant 1615192 (Loretta Jackson‐Hayes, PI)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.