Isolation and Functional Determination of SKOR Potassium Channel in Purple Osier Willow, Salix purpurea.

Potassium (K⁺) plays key roles in plant growth and development. However, molecular mechanism studies of K⁺ nutrition in forest plants are largely rare. In plants, SKOR gene encodes for the outward rectifying Shaker-type K⁺ channel that is responsible for the long-distance transportation of K⁺ through xylem in roots. In this study, we determined a Shaker-type K⁺ channel gene in purple osier (Salix purpurea), designated as SpuSKOR, and determined its function using a patch clamp electrophysiological system. SpuSKOR was closely clustered with poplar PtrSKOR in the phylogenetic tree. Quantitative real-time PCR (qRT-PCR) analyses demonstrated that SpuSKOR was predominantly expressed in roots, and expression decreased under K⁺ depletion conditions. Patch clamp analysis via HEK293-T cells demonstrated that the activity of the SpuSKOR channel was activated when the cell membrane voltage reached at -10 mV, and the channel activity was enhanced along with the increase of membrane voltage. Outward currents were recorded and induced in response to the decrease of external K⁺ concentration. Our results indicate that SpuSKOR is a typical voltage dependent outwardly rectifying K⁺ channel in purple osier. This study provides theoretical basis for revealing the mechanism of K⁺ transport and distribution in woody plants.