Expression and Ca²⁺ dependency of plasma membrane K⁺ channels of tobacco suspension cells adapted to salt stress

The expression of plasma membrane K⁺ channels of NaCl-adapted tobacco suspension cells and effects of extracellular Ca²⁺ on plasma membrane K⁺ channels were investigated. Reverse transcription-PCR (RT-PCR) analysis showed that expression of TORK1, which encodes a K⁺ channel, was much lower in NaCl-adapted cells than in NaCl-unadapted cells. The magnitude of the outward K⁺ currents of NaCl-adapted as well as NaCl-unadapted cells decreased with increasing extracellular Ca²⁺ but there is no significant difference in Ca²⁺ dependency of the K ⁺ current. These analyses suggest that reduction of the number of K⁺ channels might cause NaCl adaptation of cells through the decrease of outward K⁺ currents.