Overexpression of the potassium channel TPK b in small vacuoles confers osmotic and drought tolerance to rice

Summary 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 Os TPK b, 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 AKT 1 and HAK 1 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 TPK b can alter the K + status of small vacuoles, which is important for general cellular K + homeostasis which, in turn, affects stress tolerance.