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ion of the plasma membrane. They include two homologous proteins, Pil1 and Lsp1, which colocalize with the transmembrane protein Sur7. In S. cerevisiae the Pkh1/2-Ypk1/2 signaling pathway regulates eisosome assembly and turnover. Recently, the two homo- logues of Pil1/Lsp1, PilA and PilB, were identified in A. nidulans. In A. nidulans wild-type mycelia, punctate structures composed of PilA are present, while PilB is diffused in the cytoplasm. The construction of pilA::gfp and pilB::gfp in the niiA::ypkA background enabled the evaluation of PilA and PilB localization upon ypkA induction and repression. When grown under inducing conditions, as previously observed in the wild-type strain, PilA localized to punctate structures in the cytoplasm, while PilB was diffused throughout the cytoplasm. Upon ypkA repression, there was an increase in the punctate distribution of PilA and PilB throughout the cytoplasm. These results suggest the depletion of YpkA may affect eisosome turnover, increasing the number of structures. Taken together these results imply that ypkA performs an essential role in hyphal morphogenesis and filamentous growth, with the reduction in ypkA expression resulting in deficiencies in polarization related to endocytosis, vesicle transport and the polarized delivery of chitin/lipid to the hyphal apex. A. nidulans YpkA does not Interact with PkhA In S. cerevisiae, Pkh1 activates Ypk1. Thus, as a first step to verify if an A. nidulans Pkh1 homologue interacts with the A. nidulans YpkA, a BLASTp search of the A. nidulans genome 8 Aspergillus Nidulans YPK1 Homologue database using the S. cerevisiae Pkh1 as a query revealed a single ORF with significant similarity. The potential homologue, AN3110, is predicted to be an 813 amino acid with high identity to PkhA. PkhA has a well-defined protein kinase domain. The generation of an 11821021 A. nidulans pkhA null mutant, using an in vivo S. cerevisiae fusion-based approach was unable to generate any primary transformant. Thus a conditional mutant for pkhA was constructed by replacing the endogenous pkhA promoter with the niiA promoter. When the pkhA was repressed, by growing the niiA::pkhA mutant strain in the presence of ammonium tartrate, there was a dramatic ten-fold decrease in the colony diameter. These results strongly indicate that pkhA is also an essential A. nidulans gene. A niiA::pkhA alcA::ypkA double mutant was constructed. When the double mutant was grown on 4% glucose plus ammonium tartrate, representing pkhA and ypkA repressing conditions, radial MedChemExpress 62717-42-4 growth was comparable to the radial growth of the alcA::ypkA mutant strain grown under the same conditions. The alcA::ypkA strain showed a radial diameter similar to that of the double mutant in repressing conditions for niiA promoter and inducing conditions for alcA promoter. The radial diameter of the double mutant was similar during growth on glucose plus sodium nitrate, representing ypkA repression and glucose plus ammonium tartrate, representing pkhA 22440900 repression. Taken together, these results suggested that the ypkA gene is not directly downstream of pkhA or epistatic to pkhA, rather, ypkA and pkhA are genetically independent or in parallel. Ceramides and sphingoid long-chain bases are precursors for more complex sphingolipids and play distinct signaling roles crucial for cell growth and survival. It has been shown that A. nidulans has two ceramide synthases that regulate hyphal morphogenesis and one of them, BarA, is unique to filame

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