Arabidopsis thaliana root non-selective cation channels mediate calcium uptake and are involved in growth
Arabidopsis thaliana root non-selective cation channels mediate calcium uptake and are involved in growth
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DOI：
10.1046/j.1365-313x.2002.01467.x
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发表时间：
2002-12-01
期刊：
影响因子：
7.2
通讯作者：
Davies, JM
中科院分区：
文献类型：
--
作者：
Demidchik, V;Bowen, HC;Davies, JM
钙是植物重要的结构和调节营养素。然而，其吸收的根细胞的机制知之甚少。我们发现拟南芥根表皮原生质体中的Ca ~（2+）内流是由电压非依赖性快速激活的Ca ~（2+）可透过的非选择性阳离子通道（NSCCs）介导的。NSCCs的渗透性（P）顺序为：P-Ca（1.00）= P-Ba（0.93）> P-Zn（0.51），P-Ca/ P-Na = 0.19，P-Ca/ P-K = 0.14。它们被奎宁、Gd ~（3+）、La ~（3+）和His修饰剂焦碳酸二乙酯抑制，但不被Ca ~（2+）或K ~+通道拮抗剂维拉帕米和四乙基铵（TEA（+））抑制。在20 mM外部Ca 2+中测量的单通道电导为5.9 pS。钙渗透性NSCCs与超极化激活的Ca 2+通道（HACCs）共存，HACCs在形成全细胞构型后40-60分钟激活。在< -130至-150 mV的电压下激活的HACCs显示出缓慢的激活动力学，并受胞质Ca 2+（[Ca 2 +]（cyt））调节。使用水母发光蛋白表达的植物，观察到膜电位（V-m）和静息[Ca 2 +]（cyt）之间的线性关系，表明NSCCs的参与。完整根Ca-45（2+）内流被Gd 3+（NSCC阻断剂）减少，但对维拉帕米和TEA（+）不敏感。在根伸长区，根净Ca 2+内流（测量Ca 2+选择性振动微电极）和NSCC活性增加相比，成熟的表皮，表明NSCC参与生长。提出了一种基于NSCC和HACC共存的Ca 2+采集系统。在成熟的表皮细胞中，NSCC介导的Ca 2+内流占主导地位，而在[Ca 2 +]（cyt）升高激活HACC的特化根细胞（根毛和伸长区细胞）中，HACC介导的Ca 2+内流占主导地位。
Calcium is a critical structural and regulatory nutrient in plants. However, mechanisms of its uptake by root cells are poorly understood. We have found that Ca2+ influx in Arabidopsis root epidermal protoplasts is mediated by voltage-independent rapidly activating Ca2+- permeable non-selective cation channels (NSCCs). NSCCs showed the following permeability (P) sequence: P-Ca (1.00) = P-Ba (0.93)> P-Zn (0.51), P-Ca/ P-Na = 0.19, P-Ca/ P-K = 0.14. They were inhibited by quinine, Gd3+, La3+ and the His modifier diethylpyrocarbonate, but not by the Ca2+ or K+ channel antagonists, verapamil and tetraethylammonium (TEA(+)). Single channel conductance measured in 20 mM external Ca2+ was 5.9 pS. Calcium-permeable NSCCs co-existed with hyperpolarisation-activated Ca2+ channels (HACCs), which activated 40-60 min after forming the whole-cell configuration. HACCs activated at voltages < -130 to -150 mV, showed slow activation kinetics and were regulated by cytosolic Ca2+ ([Ca2+](cyt)). Using aequorin-expressing plants, a linear relationship between membrane potential (V-m) and resting [Ca2+](cyt) was observed, indicating the involvement of NSCCs. Intact root Ca-45(2+) influx was reduced by Gd3+ (NSCC blocker) but was verapamil and TEA(+) insensitive. In the root elongation zone, both root net Ca2+ influx ( measured by Ca2+-selective vibrating microelectrode) and NSCC activity were increased compared to the mature epidermis, suggesting the involvement of NSCC in growth. A Ca2+ acquisition system based on NSCC and HACC co-existence is proposed. In mature epidermal cells, NSCC-mediated Ca2+ influx dominates whereas in specialised root cells ( root hairs and elongation zone cells) where elevated [Ca2+](cyt) activates HACCs, HACC- mediated Ca2+ influx predominates.