title: Transport Systems in Halophilic Fungi.
abstract: Fungi that tolerate very high environmental NaCl concentrations are good model systems to study mechanisms that enable them to endure osmotic and salinity stress. The whole genome sequences of six such fungal species have been analysed: Hortaea werneckii, Wallemia ichthyophaga and four Aureobasidium spp.: A. pullulans, A. subglaciale, A. melanogenum and A. namibiae. These fungi show different levels of halotolerance, with the presence of numerous membrane transport systems uncovered here that are believed to maintain physiological intracellular concentrations of alkali metal cations. Despite some differences, the intracellular cation contents of H. werneckii, A. pullulans and W. ichthyophaga remain low even under extreme extracellular salinities, which suggests that these species have efficient cation transport systems. We speculate that cation transporters prevent intracellular accumulation of Na(+), and thus avoid the toxic effects that such Na(+) accumulation would have, while also maintaining the high K(+)/Na(+) ratio that is required for the full functioning of the cell - another crucial task in high-Na(+) environments. This chapter primarily summarises the cation transport systems of these selected fungi, and it also describes other membrane transporters that might be involved in their mechanisms of halotolerance.
authors.affiliation: Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia. 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, Ljubljana, Slovenia.
authors.forename: Tilen
authors.initials: T
authors.lastname: Konte
authors.affiliation: National Institute of Biology, Večna pot 111, SI-1000, Ljubljana, Slovenia.
authors.forename: Cene
authors.initials: C
authors.lastname: Gostinčar
authors.affiliation: Biology Department, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.|Centre of Excellence for Integrated Approaches in Chemistry and Biology of Proteins (CIPKeBiP), Jamova 39, SI-1000, Ljubljana, Slovenia.
authors.forename: Nina Gunde
authors.initials: NG
authors.lastname: Cimerman
mesh_terms: D001487:Basidiomycota / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D017506:H(+)-K(+)-Exchanging ATPase / Q000235:genetics / Q000378:metabolism; D017136:Ion Transport; D009997:Osmotic Pressure; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism; D004718:Saccharomycetales / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D054712:Salinity; D055049:Salt Tolerance; D012965:Sodium Chloride / Q000378:metabolism* / Q000494:pharmacology; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism; D050611:Sodium-Phosphate Cotransporter Proteins, Type III / Q000235:genetics / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological
chemical_list: D005656:Fungal Proteins; D015221:Potassium Channels; D017923:Sodium-Hydrogen Exchangers; D050611:Sodium-Phosphate Cotransporter Proteins, Type III; D012965:Sodium Chloride; D017506:H(+)-K(+)-Exchanging ATPase; D000254:Sodium-Potassium-Exchanging ATPase
keywords: Cation transporters; Extremely halotolerant H. werneckii; Halophilic W. ichthyophaga; Halotolerant Aurobasidium spp.; Mechanisms of halotolerance