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

Abstract

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.

Genome-Wide Identification and Characterization of the Shaker-Type K+ Channel Genes in Prunus persica (L.) Batsch

“…BLASTP searches against the peach genome database were performed using the full-length sequences of Arabidopsis shaker K + channel proteins as queries. To confirm the existence of the shaker K + channel protein domains (PF00027, PF00520, and PF11834) [ 7 – 9 ], the candidate proteins were analyzed using Pfam ( http://pfam.xfam.org ) and Simple Modular Architecture Research Tool ( http://smart.embl-heidelberg.de/ ). To distinguish the candidate peach shaker K + channel genes, we entitled them in accordance with the order of the corresponding phylogenetic locations.…”

“…The leave, phloem, flower and fruit samples were collected at different developmental stages (DS), as described in our previous reports [ 26 – 28 ]. For stress treatments, Xiahui 6 seedlings were germinated from seeds on MS solid medium and cultured in the incubator of 28°C day 16 h/18°C night 8 h, with a relative humidity of 75%, for 4 weeks, and then treated by K + depletion, 200 μ mol·L −1 ABA, 200 mmol·L −1 NaCl, or 10% (w/v) PEG for 48 h, respectively [ 9 , 29 – 31 ]. The MS medium was used as a control.…”

“…The electrophysiological function of PpSKOR was verified by patch clamping system as described previously [ 9 , 30 ]. The expression plasmid pTracer-CMV3- SKOR was constructed by introducing the PpSKOR gene into the vector of pTracer-CMV3 [ 9 , 30 ].…”

“…The mechanism I system plays a crucial role just when the external K + status is less than 200 μ mol·L −1 , while the mechanism II system plays an important role when the external K + status is more than 1 mmol·L −1 [ 6 , 7 ]. In particular, the long-distance K + distribution and dynamic balance are mainly mediated by 3 categories of K + channels, including shaker-type channels, TPK family channels, and other K + channels, which have been functionally verified via electrophysiological systems [ 2 , 4 , 5 , 8 , 9 ]. Notably, shaker K + channels were the first K + channels identified in plants at the molecular level [ 10 ].…”

“…According to the voltage dependence and K + movement direction, there are 9 shaker-like K + channels in Arabidopsis , including the inward-rectifying K + channels AtKAT1, AtKAT2, AtAKT1, AtAKT5, and AtSPIK, the weak-rectifying K + channel AtAKT2, the outward-rectifying K + channels AtSKOR and AtGORK, and regulatory subunit AtKC1 [ 1 , 8 , 11 – 21 ]. Several members of the shaker K + channel gene family have been cloned and functionally determined by heterologous expression system or electrophysiological system from tomato [ 12 , 13 ], barley [ 14 ], maize [ 15 ], rice [ 16 ], carrot [ 17 ], Ammopoptanthus mongolicus [ 18 ], grape [ 19 – 21 ], strawberry [ 11 ], pear [ 8 ], and osier willow [ 9 ].…”