Analyzing Protein Kinase C Interactions With Rho‐type GTPases 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, and the GTPase Rho4. The current study focuses on the relationships among PkcA, SepA, and Rho‐type GTPases during septation. PkcA contains two putative N‐terminal Rho binding domains designated HR1A and HR1B. 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. Reports from another group suggest that in A. nidulans Rho4 is likely the GTPase required for SepA activation. In previous work we showed that PkcA both physically and functionally interacts with SepA via one of its three formin homology domains (FH2), and in the sepA1 temperature sensitive mutant (FH2 domain‐L1369S) which is aseptate at elevated temperature, PkcA fails to localize to septation sites at elevated temperature. Here we report via yeast two‐hybrid assay that PkcA interacts with SepA via one of its putative Rho binding domains (HR1A), and that expressing extra copies of pkcA in a rho4‐null mutant increased colony diameter and improved sporulation. PkcA localization to septation sites is reduced in a rhoA mutant while septation is unaffected. The spatiotemporal relationship among PkcA, SepA, Rho4, and RhoA will be further investigated via yeast two‐hybrid, bimolecular complementation assays, and localization of fluorescence labeled proteins in mutant strains.Support or Funding InformationSupport for this work was provided by the National Science Foundation Grant 1615192 (Loretta Jackson‐Hayes, PI).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.