Bei Q, Luan S
Department of Plant and Microbial Biology, University of California, Berkeley 94720, USA.
Plant J. 1998 Mar;13(6):857-65. doi: 10.1046/j.1365-313x.1998.00084.x.
To express and characterize the function of a plant ion channel gene in plant cells, it is necessary to establish a model system that lacks the endogenous channel activity and can be genetically transformed. Patch-clamp techniques were used to survey voltage-dependent K+ channel activities in different cell types of tobacco plants. Interestingly, mesophyll cells lacked the inward K+ current found in guard cells. A transgene containing the inward K+ channel gene KAT1 from Arabidopsis was constructed and expressed in the mesophyll cells of transgenic tobacco plants. Expression of the KAT1 gene produced a large voltage-dependent inward current across the plasma membrane of mesophyll protoplasts. The KAT1 current was carried by K+ and activated at voltage more negative than -100 mV. This K+ current had a single-channel conductance of 6-10 pS and was highly sensitive to TEA, Cs+ and Ba2+. This study represents the first example in which a plant ion channel gene is functionally expressed and studied in plant cells. Tobacco mesophyll cells will provide a useful model for functional characterization of inward K+ channel genes from higher plants.
为了在植物细胞中表达和表征植物离子通道基因的功能，有必要建立一个缺乏内源性通道活性且可进行遗传转化的模型系统。采用膜片钳技术检测烟草植株不同细胞类型中电压依赖性钾离子通道活性。有趣的是，叶肉细胞缺乏保卫细胞中发现的内向钾离子电流。构建了一个包含来自拟南芥的内向钾离子通道基因KAT1的转基因，并在转基因烟草植株的叶肉细胞中表达。KAT1基因的表达在叶肉原生质体的质膜上产生了一个大的电压依赖性内向电流。KAT1电流由钾离子携带，在电压低于-100 mV时被激活。这种钾离子电流的单通道电导为6-10 pS，对TEA、Cs+和Ba2+高度敏感。这项研究代表了植物离子通道基因在植物细胞中进行功能表达和研究的首个实例。烟草叶肉细胞将为高等植物内向钾离子通道基因的功能表征提供一个有用的模型。
