Outward-rectifying potassium channels GORK and SKOR function in regulation of root growth under salt stress in Arabidopsis thaliana

Plants often face high salinity as a significant environmental challenge with roots being the first responders to this stress. Maintaining K⁺/Na⁺ ratio within plant cells is crucial for survival, as the intracellular K⁺ level decreases and the intracellular Na⁺ level increases under saline conditions. However, knowledge about the molecular regulatory mechanisms of K⁺ loss in response to salt stress through outward-rectifying K⁺ channels in plants is largely unknown. In this study, we found that the Arabidopsis double mutant gorkskor, in which the GORK and SKOR genes are disrupted, showed an improved primary root growth under salt stress compared to wild-type (WT) and the gork and skor single-mutant plants. No significant differences in the sensitivity to mannitol stress between the WT and gorkskor mutant were observed. Accumulation of ROS induced by salt stress was reduced in the gorkskor roots. The gorkskor mutant seedlings had significantly higher K⁺ content, lower Na⁺ content, and a greater resultant K⁺/Na⁺ ratio than the WT under salt stress. Moreover, salt-stress-induced elevation of cytosolic free Ca²⁺ concentration was reduced in the gorkskor roots. Taken together, these results suggest that Arabidopsis Shaker-type outward-rectifying K⁺ channels GORK and SKOR may redundantly function in regulation of primary root growth under salt stress and are involved in not only the late-stage response (e.g. K⁺ leakage) but also the early response including ROS production and [Ca²⁺]_cyt elevation.