AtCCX3 Is an Arabidopsis Endomembrane H+-Dependent K+ Transporter
AtCCX3 Is an Arabidopsis Endomembrane H+-Dependent K+ Transporter
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DOI：
10.1104/pp.108.118810
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发表时间：
2008-11-01
期刊：
影响因子：
7.4
通讯作者：
Hirschi, Kendal D.
中科院分区：
文献类型：
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作者：
Morris, Jay;Tian, Hui;Hirschi, Kendal D.
拟南芥（Arabidopsis thaliana）阳离子钙交换蛋白（CCXs）最近被确定为阳离子转运蛋白的一个亚家族，然而，没有植物CCXs的功能特征。在这里，我们表明，拟南芥AtCCX 3（At 3g 14070）和AtCCX 4（At 1g 54115）可以抑制酵母突变体在Na+，K+和Mn 2+运输缺陷。我们还报道了表达AtCCX 3的酵母中富含液泡膜的囊泡对Rb-86（+）的高容量摄取。阳离子竞争研究显示过量的Na+、K+和Mn 2+抑制AtCCX 3细胞摄取Rb-86（+）。功能性表位标记的AtCCX 3融合蛋白定位于植物和酵母的内膜。在拟南芥中，AtCCX 3主要在花中表达，而AtCCX 4在整个植物中表达。定量聚合酶链反应表明，AtCCX 3的表达增加与NaCl，KCl和MnCl 2处理的植物。AtCCX 3和AtCCX 4的插入突变株没有表现出明显的生长缺陷;然而，AtCCX 3的过表达导致Na+积累增加和Rb-86（+）转运增加。Rb-86（+）的摄取增加，在富含液泡膜的拟南芥株系中分离，表达由花椰菜花叶病毒35 S启动子驱动的CCX 3。AtCCX 3在烟草（Nicotiana tabacum）中的过表达会导致叶片损伤、生长发育迟缓，并导致大量阳离子的积累。总之，这些研究结果表明，AtCCX 3是一种内膜定位的H+依赖的K+转运蛋白，具有明显的Na+和Mn 2+转运特性，不同于先前表征的植物转运蛋白。
The Arabidopsis (Arabidopsis thaliana) cation calcium exchangers (CCXs) were recently identified as a subfamily of cation transporters; however, no plant CCXs have been functionally characterized. Here, we show that Arabidopsis AtCCX3 (At3g14070) and AtCCX4 (At1g54115) can suppress yeast mutants defective in Na+, K+, and Mn2+ transport. We also report high-capacity uptake of Rb-86(+) in tonoplast-enriched vesicles from yeast expressing AtCCX3. Cation competition studies showed inhibition of Rb-86(+) uptake in AtCCX3 cells by excess Na+, K+, and Mn2+. Functional epitope-tagged AtCCX3 fusion proteins were localized to endomembranes in plants and yeast. In Arabidopsis, AtCCX3 is primarily expressed in flowers, while AtCCX4 is expressed throughout the plant. Quantitative polymerase chain reaction showed that expression of AtCCX3 increased in plants treated with NaCl, KCl, and MnCl2. Insertional mutant lines of AtCCX3 and AtCCX4 displayed no apparent growth defects; however, overexpression of AtCCX3 caused increased Na+ accumulation and increased Rb-86(+) transport. Uptake of Rb-86(+) increased in tonoplast-enriched membranes isolated from Arabidopsis lines expressing CCX3 driven by the cauliflower mosaic virus 35S promoter. Overexpression of AtCCX3 in tobacco (Nicotiana tabacum) produced lesions in the leaves, stunted growth, and resulted in the accumulation of higher levels of numerous cations. In summary, these findings suggest that AtCCX3 is an endomembrane-localized H+-dependent K+ transporter with apparent Na+ and Mn2+ transport properties distinct from those of previously characterized plant transporters.