title: HwHog1 kinase activity is crucial for survival of Hortaea werneckii in extremely hyperosmolar environments.
abstract: Although suggested, the involvement of the HOG pathway in adaptation processes in extremely halotolerant fungus Hortaea werneckii has never been specifically demonstrated. Here, we show that the H. werneckii HOG pathway is very robust, and that it includes two functionally redundant MAPK homologues, HwHog1A and HwHog1B, that show osmolyte-type-dependent phosphorylation. Inhibition of HwHog1 kinase activity with the ATP analogue BPTIP restricts H. werneckii colony growth at 3.0M NaCl, KCl and sorbitol, most likely due to restricted cell division. On the other hand, HwHog1-regulated transcription of a selected group of genes (HwSTL1, HwGUT2, HwOPI3, HwGDH1, HwUGP1, HwGPD1) is an osmolyte-specific process that is important for induction of gene transcription with high NaCl, for regulation of specific genes with high sorbitol, and has no role in KCl stressed cells. Survival of H. werneckii at moderate NaCl and KCl concentrations is not dependent on HwHog1 activity or the calcineurin pathway, and thus alternative mechanisms must exist. The HOG pathway described here is vital for the extreme osmotolerance of H. werneckii, and its regulation shows important differences from the homologue pathways characterised in other mesophilic and halotolerant fungi.
authors.affiliation: Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Vrazov Trg 2, SI-1000 Ljubljana, Slovenia. Electronic address: anja.kejzar@mf.uni-lj.si.
authors.forename: Anja
authors.initials: A
authors.lastname: Kejžar
authors.affiliation: Department of Chemistry and Molecular Biology, University of Gothenburg, S-405 30 Gothenburg, Sweden. Electronic address: grotli@chem.gu.se.
authors.forename: Morten
authors.initials: M
authors.lastname: Grötli
authors.affiliation: Department of Chemistry and Molecular Biology, University of Gothenburg, S-405 30 Gothenburg, Sweden. Electronic address: markus.tamas@cmb.gu.se.
authors.forename: Markus J
authors.initials: MJ
authors.lastname: Tamás
authors.affiliation: Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Vrazov Trg 2, SI-1000 Ljubljana, Slovenia. Electronic address: ana.plemenitas@mf.uni-lj.si.
authors.forename: Ana
authors.initials: A
authors.lastname: Plemenitaš
authors.affiliation: Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Vrazov Trg 2, SI-1000 Ljubljana, Slovenia; Centre of Excellence for Integrated Approaches in Chemistry and Biology of Proteins (CIPKeBiP), Jamova 39, SI-1000 Ljubljana, Slovenia. Electronic address: metka.lenassi@mf.uni-lj.si.
authors.forename: Metka
authors.initials: M
authors.lastname: Lenassi
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D001203:Ascomycota / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D001483:Base Sequence; D019703:Calcineurin / Q000378:metabolism; D003198:Computer Simulation; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D015966:Gene Expression Regulation, Fungal; D053858:Metabolic Networks and Pathways / Q000235:genetics; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D009994:Osmolar Concentration; D011189:Potassium Chloride / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D013012:Sorbitol / Q000494:pharmacology
chemical_list: D005656:Fungal Proteins; D012965:Sodium Chloride; D013012:Sorbitol; D011189:Potassium Chloride; D020928:Mitogen-Activated Protein Kinases; D019703:Calcineurin
keywords: Calcineurin pathway; HOG pathway; Hog1 inhibitor; Hortaea werneckii; NaCl; Osmotolerance