Journal
NEW PHYTOLOGIST
Volume 209, Issue 3, Pages 1040-1048Publisher
WILEY
DOI: 10.1111/nph.13708
Keywords
drought; ion channel; osmotic stress; potassium; rice (Oryza sativa); small vacuole; TPKb
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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.
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