title: Involvement of protein kinase C in the suppression of apoptosis and in polarity establishment in Aspergillus nidulans under conditions of heat stress.
abstract: The pkcA gene, which encodes a protein kinase C (PKC) in the filamentous fungus Aspergillus nidulans, is essential for its viability. However, little is known about its functions. To address this issue, we constructed and characterized temperature-sensitive mutants of pkcA. The conidia of these mutants swelled slightly and exhibited apoptotic phenotypes at 42°C. The apoptotic phenotypes were suppressed by an osmotic stabilizer. Under these conditions, the conidia swelled extensively and did not form germ tubes. Moreover, polarized distribution of F-actin was not observed. We then utilized deletion mutants of bckA, an ortholog of Saccharomyces cerevisiae bck1 that encodes a mitogen-activated protein (MAP) kinase kinase kinase and functions downstream of PKC in the cell wall integrity pathway. These mutants exhibited apoptotic phenotypes at 42°C, but they did not show defects in polarity establishment under osmotically stabilized conditions. These results suggest that PkcA plays multiple roles during germination under conditions of heat stress. The first of these roles is the suppression of apoptosis induction, while the other involves polarity establishment. The former depends on the MAP kinase cascade, whereas the latter does not. In addition, repolarization, which was observed after depolarization in the wild-type strain and the bckA deletion mutant under conditions of heat stress, was not observed in the pkcA-ts mutant. This suggests that PkcA also plays role in polarity establishment during hyphal growth independent of the MAP kinase cascade under these conditions.
authors.affiliation: Department of Biotechnology, The University of Tokyo, Tokyo, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Katayama
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Uchida
authors.forename: Akinori
authors.initials: A
authors.lastname: Ohta
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Horiuchi
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology; D001233:Aspergillus nidulans / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D015153:Blotting, Western; D005434:Flow Cytometry; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal / Q000235:genetics / Q000502:physiology; D006358:Hot Temperature; D008856:Microscopy, Fluorescence; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; C072075:BCK1 protein, S cerevisiae; D011493:Protein Kinase C; D020929:Mitogen-Activated Protein Kinase Kinases