Nitric oxide suppresses stomatal opening by inhibiting inward-rectifying Kin+ channels in Arabidopsis guard cells

We explore nitric oxide (NO) effect on K_in⁺ channels in Arabidopsis guard cells. We observed NO inhibited K_in⁺ currents when Ca²⁺ chelator EGTA (Ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid) was not added in the pipette solution; K_in⁺ currents were not sensitive to NO when cytosolic Ca²⁺ was chelated by EGTA. NO inhibited the Arabidopsis stomatal opening, but when EGTA was added in the bath solution, inhibition effect of NO on stomatal opening vanished. Thus, it implies that NO elevates cytosolic Ca²⁺ by activating plasma membrane Ca²⁺ channels firstly, then inactivates K_in⁺ channels, resulting in stomatal opening suppressed subsequently. Supported by the National Natural Science Foundation of China (Grant No. 20701028)