title: Overexpression of the potassium channel TPKb in small vacuoles confers osmotic and drought tolerance to rice.
abstract: Potassium (K(+) ) is the most important cationic nutrient for all living organisms. Vacuolar two-pore K(+) (TPK) channels are important players in the regulation of cellular levels of K(+) but have not been characterised in rice. In order to assess the role of OsTPKb, a K(+) selective ion channel predominantly expressed in the tonoplast of small vacuoles, we generated overexpressing (OX) lines using a constitutive promoter and compared their phenotypes with control plants. Relative to control plants, OX lines showed better growth when exposed to low-K(+) or water stress conditions. K(+) uptake was greater in OX lines which may be driven by increased AKT1 and HAK1 activity. The enhanced K(+) uptake led to tissue K(+) levels that were raised in roots and shoots. Furthermore, energy dispersive X-ray (EDX) analyses showed a higher cytoplasm: vacuole K(+) ratio which is likely to contribute to the increased stress tolerance. In all, the data suggest that TPKb can alter the K(+) status of small vacuoles, which is important for general cellular K(+) homeostasis which, in turn, affects stress tolerance.
authors.affiliation: Department of Biology, University of York, York, YO10 5DD, UK.
authors.forename: Izhar
authors.initials: I
authors.lastname: Ahmad
authors.affiliation: Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ, UK.
authors.forename: Jean
authors.initials: J
authors.lastname: Devonshire
authors.affiliation: Department of Biology, University of York, York, YO10 5DD, UK.
authors.forename: Radwa
authors.initials: R
authors.lastname: Mohamed
authors.affiliation: Department of Biology, University of York, York, YO10 5DD, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Schultze
authors.affiliation: Department of Biology, University of York, York, YO10 5DD, UK.
authors.forename: Frans J M
authors.initials: FJ
authors.lastname: Maathuis
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D055864:Droughts; D018506:Gene Expression Regulation, Plant; D018527:Hydroponics; D012275:Oryza / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D009995:Osmosis; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D013052:Spectrometry, X-Ray Emission; D013312:Stress, Physiological / Q000235:genetics; D014617:Vacuoles / Q000378:metabolism*; D014867:Water
chemical_list: D010940:Plant Proteins; D015221:Potassium Channels; D014867:Water; D011188:Potassium
keywords: TPKb; drought; ion channel; osmotic stress; potassium; rice (Oryza sativa); small vacuole